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The DISC1 Switch in Neurodevelopment

22 April 2011. Disrupted in schizophrenia 1 (DISC1), a major susceptibility factor for schizophrenia and other mental disorders, acts as a switch between neuronal proliferation and migration during brain development, according to a study appearing online April 6 in Nature. Led by Akira Sawa of Johns Hopkins University School of Medicine in Baltimore, Maryland, the study finds that the phosphorylation state of DISC1 flips the switch: when unphosphorylated at a certain site, DISC1 promotes neuron birth through Wnt signaling, and when phosphorylated, DISC1 aggregates with centrosomal proteins, which are instrumental for getting new neurons to move on to their proper locations in the brain.

The study unites previous findings of a role for DISC1 in both proliferation and migration. Reduced neuronal proliferation by neural progenitors has been reported in mice with a DISC1 mutation modeled after the translocation found in the Scottish family that originally led researchers to DISC1 (Shen et al., 2008), and DISC1 promotes new neuron birth through Wnt signaling—a pathway involved in the proliferation of a number of cell types (see SRF related news story). In addition, Sawa and his team have shown that DISC1 binds to Bardet-Biedel syndrome (BBS) proteins and recruits them to the centrosome, an event that readies new neurons for migration (see SRF related news story).

The new work illustrates how DISC1 can work through distinct pathways during the course of brain development. Combined with another study that explores the neuroanatomical consequences of point mutations to DISC1 from Albert Wong at the University of Toronto in Canada, these findings support the idea that DISC1 is critical for proper neurodevelopment, and that problems with the protein could leave a brain predisposed to mental illness.

Focus on phosphorylation
Suspecting that a phosphorylation-mediated modification could regulate whether DISC1 spurred proliferation or migration, first author Koko Ishizuka and colleagues began by simply asking whether human DISC1 protein could be phosphorylated. Indeed, it could, at three different sites, two of which were conserved in mouse DISC1: serine 170 (S170) and serine 58 (S58). Using site-directed mutagenesis, the researchers developed a "phospho-dead" version of the protein that was incapable of being phosphorylated at the S170 site, or a "phospho-mimic" that was constitutively phosphorylated at this site. They found that the phospho-dead DISC1 protein did not bind as well to BBS1 and BBS4 proteins as wild-type DISC1 did under conditions that safeguard phosphorylation. In contrast, the phospho-mimic DISC1 readily bound to BBS1, and in mouse cortical neurons, this resulted in correct localization of BBS1 to the centrosome. Mutations to the S58 site did not affect this interaction, suggesting that phosphorylation specifically at the S170 site is critical for migration.

On the other hand, DISC1 needed to be unphosphorylated at S170 to promote Wnt pathway signaling and spur cell proliferation. When DISC1 levels were knocked down in a non-neural cell line that reports Wnt pathway activity, the phospho-dead DISC1 could rescue Wnt signaling, but not the phospho-mimic DISC1 (as read out by β-catenin and cyclin D1 activity, downstream events in the Wnt pathway). An in vivo version of this experiment using in utero gene transfer in mice to introduce Wnt signaling constructs and RNAi to knock down endogenous DISC1 found the same requirement for unphosphorylated DISC1 to revive Wnt pathway activity in neurons.

Field test in the developing brain
These results suggest that, once phosphorylated at S170, DISC1 switches its role from proliferation to migration, and prompted the researchers to look for evidence of such a change in the developing mouse brain. Using an antibody that recognizes DISC1 only when it is phosphorylated at S170, they found higher antibody staining levels at E18, when migration is prominent, than at E14, when proliferation predominates. This staining was not found in the birthplace of new neurons, but rather in regions where only migrating neurons pass through.

Next, the researchers used co-immunoprecipitation to ask which proteins in mouse brain extracts normally bind to phosphorylated DISC1 at different time points in development. Between E14, when cell birth abounds, and E18, when migration is afoot, they found an increase in the amount of BBS1 protein bound by phosphorylated DISC1, and a similar sized decrease in the amount of bound glycogen synthase kinase 3β (GSK3β)—a key player in Wnt signaling. This same pattern emerged when progenitor cells and post-mitotic neurons were isolated from mouse brain, with post-mitotic neurons exhibiting increased levels of phosphorylated DISC1 at S170, increased BBS1 binding, and decreased affinity for GSK3β compared to progenitor cells.

Finally, when they knocked down DISC1 in embryos using in utero gene transfer, Ishizuka and colleagues could rescue proliferation at E13 by co-injecting phospho-dead or wild-type DISC1, whereas phospho-mimic DISC1 did not work. Conversely, co-injecting the phospho-mimic or wild-type DISC1 at E15 rescued migration, returning the number of migrating cells to normal, but the phospho-dead DISC1 did not. Based on their results, the authors propose that DISC1 unphosphorylated at S170 binds tightly to GSK3β to promote cell proliferation. Later in this model, when DISC1 is somehow phosphorylated at this site, DISC1 dissociates from GSK3β and shuttles BBS1 to the centrosome, triggering migration.

Point mutations point to neurodevelopment
This dual role for DISC1 is reinforced by Wong's study, appearing on March 2 in the Journal of Neuroscience, which explores how two missense point mutations—Q31L and L100P—of DISC1 in mice alter brain anatomy. Though not modeled after human disease-related variants, the two point mutations result in behaviors reminiscent of either depression or schizophrenia (see SRF related news story). In both mutant mouse lines, first author Frankie Lee and colleagues examined the cortex and found decreases in neuron number and neurogenesis—indicators of disturbed proliferation—as well as altered neuron distributions, suggesting that neurons were not migrating correctly compared to wild-type littermate controls. The neurons themselves had shorter dendrites and decreased spine densities than did neurons from wild-type mice, which suggest defects in connectivity. Despite the different behaviors in the two mouse lines, their neuroanatomical findings were largely similar and mimic some of the findings from postmortem brain tissue from individuals with schizophrenia, such as decreased neuron and spine densities.

Together, the new studies present a nuanced view of DISC1 function, with slight changes to DISC1, such as phosphorylation state having significant and widespread consequences in the brain. This calls for careful examination of even subtle modifications of DISC1—not just the major disruption that put it on the radar in the first place—to fully understand DISC1 function in health and in mental illness.—Michele Solis.

References:
Ishizuka K, Kamiya A, Oh EC, Kanki H, Seshadri S, Robinson JF, Murdoch H, Dunlop AJ, Kubo KI, Furukori K, Huang B, Zeledon M, Hayashi-Takagi A, Okano H, Nakajima K, Houslay MD, Katsanis N, Sawa A. DISC1-dependent switch from progenitor proliferation to migration in the developing cortex. Nature. 2011 Apr 6. Abstract

Lee FH, Fadel MP, Preston-Maher K, Cordes SP, Clapcote SJ, Price DJ, Roder JC, Wong AH. Disc1 point mutations in mice affect development of the cerebral cortex. J Neurosci. 2011 Mar 2;31(9):3197-206. Abstract

Comments on News and Primary Papers


Primary Papers: Disc1 point mutations in mice affect development of the cerebral cortex.

Comment by:  Atsushi Kamiya
Submitted 2 May 2011
Posted 2 May 2011

In this paper, Lee et al. characterized DISC1 mutant mice, animals with ENU-induced mutation of Q31L and L100P, by systematic histological examinations. These animals had been previously reported to show behavioral abnormalities relevant to major mental disorders, such as schizophrenia and major depression, by Roder and Clapcote (Clapcote et al., 2007). The authors found decreased cell proliferation, altered neuronal distribution, as well as impaired dendritic growth and reduction of spine density in pyramidal neurons, all phenotypes observed in the cerebral cortex. As the authors described, these abnormal cellular architectures had been previously reported in the other DISC1 animal models, including studies using RNAi approaches (Kamiya et al., 2005; Li et al., 2007; Kvajo et al., 2008; Pletnikov et al., 2008; Shen et al., 2008; Mao et al., 2009; Hayashi-Takagi et al., 2010; Niwa et al., 2010). An important question arising is whether all DISC1 functions in such cellular events are implicated in disease processes or some specific functional aspects are critical. This is a tremendously difficult question, because the molecular disposition of DISC1 is complex, as reflected by multiple isoforms at both mRNA and protein levels (Nakata et al., 2009; Ishizuka et al., 2006). Nonetheless, biological functions of DISC1 are currently being explored without waiting for the complete identification of DISC1 isoforms, resulting in the identification of multiple roles of DISC1 with many protein interactors in various functional contexts. Further investigations with advanced genetic engineering techniques, which allow researchers to dissect region and cell type-specific DISC1 functions in a temporal manner, might allow us to more clearly elucidate DISC1 functions relevant to psychiatric disorders.

References:

Clapcote SJ, Lipina TV, Millar JK, Mackie S, Christie S, Ogawa F, Lerch JP, Trimble K, Uchiyama M, Sakuraba Y, Kaneda H, Shiroishi T, Houslay MD, Henkelman RM, Sled JG, Gondo Y, Porteous DJ, Roder JC. Behavioral phenotypes of Disc1 missense mutations in mice. Neuron. 2007 May 3;54(3):387-402. Abstract

Kamiya A, Kubo K, Tomoda T, Takaki M, Youn R, Ozeki Y, Sawamura N, Park U, Kudo C, Okawa M, Ross CA, Hatten ME, Nakajima K, Sawa A. A schizophrenia-associated mutation of DISC1 perturbs cerebral cortex development. Nat Cell Biol. 2005 Dec;7(12):1167-78. Epub 2005 Nov 20. Erratum in: Nat Cell Biol. 2006 Jan;8(1):100. Abstract

Li W, Zhou Y, Jentsch JD, Brown RA, Tian X, Ehninger D, Hennah W, Peltonen L, Lönnqvist J, Huttunen MO, Kaprio J, Trachtenberg JT, Silva AJ, Cannon TD. Specific developmental disruption of disrupted-in-schizophrenia-1 function results in schizophrenia-related phenotypes in mice. Proc Natl Acad Sci U S A. 2007 Nov 13;104(46):18280-5. Epub 2007 Nov 2. Abstract

Kvajo M, McKellar H, Arguello PA, Drew LJ, Moore H, MacDermott AB, Karayiorgou M, Gogos JA. A mutation in mouse Disc1 that models a schizophrenia risk allele leads to specific alterations in neuronal architecture and cognition. Proc Natl Acad Sci U S A. 2008 May 13;105(19):7076-81. Epub 2008 May 5. Abstract

Pletnikov MV, Ayhan Y, Nikolskaia O, Xu Y, Ovanesov MV, Huang H, Mori S, Moran TH, Ross CA. Mol Psychiatry. 2008 Feb;13(2):173-86, 115. Inducible expression of mutant human DISC1 in mice is associated with brain and behavioral abnormalities reminiscent of schizophrenia. Epub 2007 Sep 11. Abstract

Shen S, Lang B, Nakamoto C, Zhang F, Pu J, Kuan SL, Chatzi C, He S, Mackie I, Brandon NJ, Marquis KL, Day M, Hurko O, McCaig CD, Riedel G, St Clair D. Schizophrenia-related neural and behavioral phenotypes in transgenic mice expressing truncated Disc1. J Neurosci. 2008 Oct 22;28(43):10893-904. Abstract

Mao Y, Ge X, Frank CL, Madison JM, Koehler AN, Doud MK, Tassa C, Berry EM, Soda T, Singh KK, Biechele T, Petryshen TL, Moon RT, Haggarty SJ, Tsai LH. Disrupted in schizophrenia 1 regulates neuronal progenitor proliferation via modulation of GSK3beta/beta-catenin signaling. Cell. 2009 Mar 20;136(6):1017-31. Abstract

Hayashi-Takagi A, Takaki M, Graziane N, Seshadri S, Murdoch H, Dunlop AJ, Makino Y, Seshadri AJ, Ishizuka K, Srivastava DP, Xie Z, Baraban JM, Houslay MD, Tomoda T, Brandon NJ, Kamiya A, Yan Z, Penzes P, Sawa A. Disrupted-in-Schizophrenia 1 (DISC1) regulates spines of the glutamate synapse via Rac1. Nat Neurosci. 2010 Mar;13(3):327-32. Epub 2010 Feb 7. Abstract

Niwa M, Kamiya A, Murai R, Kubo K, Gruber AJ, Tomita K, Lu L, Tomisato S, Jaaro-Peled H, Seshadri S, Hiyama H, Huang B, Kohda K, Noda Y, O'Donnell P, Nakajima K, Sawa A, Nabeshima T. Knockdown of DISC1 by in utero gene transfer disturbs postnatal dopaminergic maturation in the frontal cortex and leads to adult behavioral deficits. Neuron. 2010 Feb 25;65(4):480-9. Abstract

Nakata K, Lipska BK, Hyde TM, Ye T, Newburn EN, Morita Y, Vakkalanka R, Barenboim M, Sei Y, Weinberger DR, Kleinman JE. DISC1 splice variants are upregulated in schizophrenia and associated with risk polymorphisms. Proc Natl Acad Sci U S A. 2009 Sep 15;106(37):15873-8. Epub 2009 Sep 2. Abstract

Ishizuka K, Paek M, Kamiya A, Sawa A. A review of Disrupted-In-Schizophrenia-1 (DISC1): neurodevelopment, cognition, and mental conditions. Biol Psychiatry. 2006 Jun 15;59(12):1189-97. Abstract

View all comments by Atsushi KamiyaComment by:  Albert H. C. Wong
Submitted 13 May 2011
Posted 13 May 2011

This recent and important paper by Sawa's group adds another layer to the complex story of DISC1 function in neurodevelopment. Their findings clarify and integrate two streams of research implicating DISC1 in both neuron proliferation and migration. The identification of the S170 phosphorylation site also raises the exciting possibility that pharmacological strategies targeted at this phosphorylation-dependent switch might be useful in correcting or preventing mental illness-related problems with brain development. It would be interesting in this context to explore whether disease-associated DISC1 gene variants in humans affect DISC1 phosphorylation, and the subsequent balance between neuron proliferation and migration.

I agree with Atsushi Kamiya that further work is needed to understand which of the many effects of DISC1 perturbation are specific to human psychiatric disease phenotypes. Again, from a treatment perspective, it is vital to know which cellular abnormality underlies the most debilitating symptoms so that new treatments can be screened for effects on these specific abnormalities. Another recent paper from our group reinforces this point (Lee et al., 2011). We found that genetic inactivation of GSK3α restored dendritic spine deficits in DISC1 L100P mutant mice, in parallel with amelioration of behavioral abnormalities as previously reported (Lipina et al., 2011). However, other abnormalities in dendrite morphology caused by the DISC1 L100P mutation were not corrected by GSK3α inactivation.

References:

Lee FH, Kaidanovich-Beilin O, Roder JC, Woodgett JR, Wong AH. Genetic inactivation of GSK3α rescues spine deficits in Disc1-L100P mutant mice, Schizophrenia Research. 2011;Apr 16. Abstract

Lipina TV, Kaidanovich-Beilin O, Patel S, Wang M, Clapcote SJ, Liu F, Woodgett JR, Roder JC. Genetic and pharmacological evidence for schizophrenia-related Disc1 interaction with GSK-3. Synapse. 2011;65:234-248. Abstract

View all comments by Albert H. C. Wong

Comments on Related News


Related News: New Spin on DISC1—Mouse Mutation Impairs Behavior

Comment by:  Akira Sawa, SRF Advisor
Submitted 8 May 2007
Posted 8 May 2007

This is outstanding work reporting DISC1 genetically engineered mice. Thus far, one type of DISC1 mutant mouse has been reported, by Gogos and colleagues (Koike et al., 2006).

There are two remarkable points in this work. First, of most importance, John Roder and Steve Clapcote have been very successful in using mice with ENU-induced mutations for their questions. Due to the complexity of the DISC1 gene and isoforms, several groups, including ours, have tried but not succeeded in generating knockout mice. However, Roder and Clapcote found alternative mice that could be used in testing our main hypothesis. I believe that the majority of the success in this work is on this particular point. Indeed, to explore animal models for other susceptibility genes for major mental illnesses, this approach should be considered.

Second, it is very interesting that different mutations in the same gene display different types of phenotypes. I appreciate the excellence in the extensive behavioral assays in this work.

Although we need to wait for any molecular and mechanistic analyses of these mice in the future, this work provides us outstanding methodologies in studying major mental conditions. I anticipate that four to five papers will come out in this year that report various types of DISC1 genetically engineered mice. Neutral comparison of all the DISC1 mice from different groups will provide important insights for DISC1 and its role in major mental conditions.

View all comments by Akira Sawa

Related News: New Spin on DISC1—Mouse Mutation Impairs Behavior

Comment by:  Christopher Ross
Submitted 8 May 2007
Posted 8 May 2007

This paper demonstrates that mutations in DISC1 can alter mouse behavior, brain structure, and biochemistry, consistent with the idea that DISC1 is related to major psychiatric disorders. This is already an important result. But more strikingly, the authors’ interpretation is that one mutation (L100P) causes a phenotype similar to schizophrenia, while the other mutation (Q31L) results in a phenotype similar to affective disorder.

There are a number of caveats that need to be considered. No patients with equivalent mutations have been identified. The behavioral tests have only a hypothesized or empiric relevance to behavior in the human illnesses. DISC1 itself, while a very strong candidate gene, is still not fully validated, and the best evidence for its role in schizophrenia still arises from the single large pedigree in Scotland.

Despite these caveats, I believe this paper is potentially a major advance. The authors’ interpretations are provocative, and could have far-reaching implications for understanding of the biological bases of psychiatric diseases. The models provide strong support for further study of DISC1. DISC1 has numerous very interesting interacting proteins and thus may provide an entry into pathogenic pathways for psychiatric diseases. We have suggested that interactors at the centrosome, involved with neuronal development, may be especially relevant to schizophrenia, while interactors at the synapse, or related to signal transduction, may be especially relevant to affective disorder (Ross et al., 2006). The beginnings of an allelic series of DISC1 mutations will presage more detailed genotype-phenotype studies in a variety of mouse models, with potential relevance to both schizophrenia and affective disorder.

View all comments by Christopher Ross

Related News: New Spin on DISC1—Mouse Mutation Impairs Behavior

Comment by:  Nick Brandon (Disclosure)
Submitted 8 May 2007
Posted 8 May 2007

Mutant Mice Bring Further Excitement to the DISC1-PDE4 Arena
DISC1 continues to ride a wave of optimism as we look for real breakthroughs in the molecular events underlying major psychiatric disorders including schizophrenia, bipolar, and depression. In 2005, its fortunes became entwined with those of the phosphodiesterase PDE4B as they were shown to functionally and physically interact (Millar et al., 2005). Evidence linking PDE4B to depression has been known for some time, but in the wake of the DISC1 finding, its link to schizophrenia has hardened (Siuciak et al., 2007; Menniti et al., 2006; Pickard et al., 2007).

The Roder and Porteous labs have come together to produce a fantastic paper describing two ENU mutant mice lines with specific mutations in the N-terminus of DISC1. Luck was on their side as the mutations seem to have a direct impact on the interaction with the PDE4B. Furthermore, the two lines look to have distinct phenotypes—one a little schizophrenic, the other depressive. It is known from the clinical and genetic data that DISC1 is associated with schizophrenia, bipolar, and MDD, so this mouse dichotomy is very intriguing.

The mutant line Q31L is claimed to have a “depressive-like” phenotype. This comes from behavioral experiments including a range of assays looking at depressive-like behaviors where this strain had severe deficits, treatable with the dual serotonin-noradrenaline reuptake inhibitor (SNRI) bupropion, commonly prescribed for depression. Together these findings could just as easily be linked to the negative symptoms of schizophrenia. Furthermore, Q31L also shows modest deficits in two sensory processing paradigms (latent inhibition and pre-pulse inhibition), for which antipsychotics had no impact, and a working memory deficit, so this strain has characteristics of all the three key domains of schizophrenia. The pharmacology gets more interesting when these animals are dosed with rolipram (PDE4 inhibitor, raises cAMP levels) and look to be resistant to its effects. At the protein level, while it effects no changes in absolute levels of DISC1 and PDE4B, it leads to a 50 percent reduction in PDE4 activity. This information connects together nicely with the rolipram resistance, and thus the authors suggest that elevated cAMP might explain the behaviors observed, but they unfortunately do not show any cAMP levels in these animals. The paper also reports a decreased binding of the mutant form of DISC1 with PDE4B in overexpressed systems; coupled with the decreased PDE activity, this is in slight contradiction to the original Millar paper (Millar et al., 2005), but as the authors explain, the complexity of the DISC1-PDE4 molecular partnership could easily explain this. From my perspective, the lack of data to date on DISC1-PDE4 brain complexes is a major weak point of this story—this needs to be addressed as we move forward. This will also allow us to understand better the role of different DISC1 isoforms.

L100P is the “schizophrenic” brother of Q31P and has severe deficits in two sensory processing paradigms (latent inhibition and pre-pulse inhibition) which is reversed by typical and atypical antipsychotic and rolipram. Rolipram is able to modulate the behavior as PDE4 activity levels are at a wild-type level. Again, it shows decreased levels of DISC1-PDE4 binding.

Together, these two lines, along with the Gogos mice and a further bank of DISC1 mice which we should expect to see in the next year, puts the field in a position where we are now able to start to dissect out the clearly complex biological functions of DISC1. But as I indicated earlier, we need more information on relevant DISC1 isoforms. We know from the DISC1 interactome that there are many exciting partnerships to develop, but we may not have the fortune of an ENU screen to pull out mice with specific effects on an interaction. The differences in the behavior and pharmacology of these two strains is striking. In combination with the impact on PDE4-DISC1 binding and PDE4 activity, it highlights how much still needs to be understood for this interaction alone. More immediately, the mice show clearly that specific DISC1 mutations may give rise to specific clinical end-points and open up DISC1 pharmacogenomics as a real possibility.

View all comments by Nick Brandon

Related News: DISC1: A Matter of Life or Death for Neural Progenitors

Comment by:  Khaled Rahman
Submitted 26 March 2009
Posted 26 March 2009

Mao and colleagues present an impressive body of work implicating GSK3β/β-catenin signaling in the function of Disc1. However, several key experimental controls are missing that detract from the impact of their study, and it is unclear whether this function of Disc1 among its many others is the critical link between the t(1;11) translocation and psychopathology in the Scottish family.

The results of Mao et al. suggest that acute knockdown of Disc1 in embryonic brain causes premature exit from the proliferative cell cycle and premature differentiation into neurons. In fact, they observe fewer GFP+ cells in the VZ/SVZ and greater GFP+ cells within the cortical plate. This is in contrast to the study by Kamiya et al. (2005), in which they find that knocking down Disc1 caused greater retention of cells in the VZ/SVZ and fewer in the cortical plate, suggesting retarded migration. Although the timing of electroporation (E13 vs. E14.5) and examination (E15 vs. P2) differed between the two studies, these results are not easily reconciled.

The authors also suggest that they can rescue the deficits in proliferation by overexpressing human wild-type DISC1, stabilizing β-catenin expression, or inhibiting GSK3β activity, and thus conclude that Disc1 is acting through this pathway. This conclusion, however, rests on an error in logic. If increasing X causes an increase in Y, and decreasing Z causes a decrease in Y, this does not mean that X and Z are operating via the same mechanism. In fact, overexpressing WT-DISC1, stabilizing β-catenin, or inhibiting GSK3β activity all increase proliferation in control cells. Thus, the fact that these manipulations also work in progenitors with Disc1 silenced only tells us that these effects are independent or downstream of Disc1. What are needed are studies that show a differential sensitivity of Disc1-silenced cells to manipulations of β-catenin or GSK3β. In other words, is there a shift in the dose response curves? This is what is to be expected given that Mao et al. show changes in β-catenin levels and changes in the phosphorylation of GSK3β substrates in Disc1 silenced cells.

Furthermore, it is surprising that a restricted silencing of Disc1 in the adult dentate gyrus produces changes in affective behaviors, when total ablation of dentate neurogenesis in the adult produces little effects on depression-related behaviors (Santarelli et al., 2003; Airen et al., 2007). The fact that inhibiting GSK3β increases proliferation in both control and Disc1 knockdown animals to a similar degree suggests that the “rescue” of any behavioral deficits is independent of the drug’s effects on proliferation. Correlating measures of proliferation with behavioral performance would help address this issue.

How this study will lead to new or improved therapeutic interventions is also an open question. Lithium is well known for its mood-stabilizing properties, and this study may point to better, more efficient ways to address these symptoms. However, it is also known that lithium does little for, if not worsens, cognitive symptoms in patients (Pachet and Wisniewski, 2003), and it is this symptom domain that is in dire need of drug development.

It is also important to keep in mind that acute silencing of Disc1 in a restricted set of cells will not necessarily recapitulate the pathogenetic process of a disease-associated mutation. It remains to be seen if similar results are obtained in animal models of the Disc1 mutation (Clapcote et al., 2007; Hikida et al., 2007; Li et al., 2007).

References:

Kamiya A, Kubo K, Tomoda T, Takaki M, Youn R, Ozeki Y, Sawamura N, Park U, Kudo C, Okawa M, Ross CA, Hatten ME, Nakajima K, Sawa A. A schizophrenia-associated mutation of DISC1 perturbs cerebral cortex development. Nat Cell Biol. 2005 Dec 1;7(12):1167-78. Abstract

Santarelli, L. et al. Requirement of hippocampal neurogenesis for the behavioral effects of antidepressants. Science 301, 805–809 (2003). Abstract

Airan, R.D. et al. High-speed imaging reveals neurophysiological links to behavior in an animal model of depression. Science 317, 819-23 (2007). Abstract

Pachet AK, Wisniewski AM. The effects of lithium on cognition: an updated review. Psychopharmacology (Berl). 2003 Nov;170(3):225-34. Review. Abstract

Clapcote SJ, Lipina TV, Millar JK, Mackie S, Christie S, et al. (2007) Behavioral phenotypes of Disc1 missense mutations in mice. Neuron 54: 387–402. Abstract

Hikida T, Jaaro-Peled H, Seshadri S, Oishi K, Hookway C, et al. (2007) Dominant-negative DISC1 transgenic mice display schizophrenia-associated phenotypes detected by measures translatable to humans. Proc Natl Acad Sci U S A 104: 14501–14506. Abstract

Li W, Zhou Y, Jentsch JD, Brown RA, Tian X, et al. (2007) Specific developmental disruption of disrupted-in-schizophrenia-1 function results in schizophrenia-related phenotypes in mice. Proc Natl Acad Sci U S A 104: 18280–18285. Abstract

View all comments by Khaled Rahman

Related News: DISC1: A Matter of Life or Death for Neural Progenitors

Comment by:  Simon Lovestone
Submitted 27 March 2009
Posted 27 March 2009

This is an intriguing paper that builds on a growing body of evidence implicating wnt regulation of GSK3 signaling in psychotic illness (Lovestone et al., 2007).

It is interesting that the authors report that binding of DISC1 to GSK3 results in no change in the inhibitory Ser9 phosphorylation site of GSK3 but a change in Y216 activation site and that this resulted in effects on some but not all GSK3 substrates. This poses a challenge both in terms of understanding the role of GSK3 signaling in schizophrenia and other psychotic disorders and in drug discovery.

The authors cite some of the other evidence for regulation of GSK3 signaling in psychosis, including, for example, the evidence for a role of AKT signaling alteration in schizophrenia and lithium, an inhibitor of GSK3, as a treatment for bipolar disorder. But in both cases, AKT (Cross et al., 1995) and lithium (Jope, 2003), the effect on GSK3 is predominantly via Ser9 phosphorylation and not via Y216. The unstated implication is at least two, possibly three, mechanisms for regulation of GSK3 are all involved in psychotic illness—the auto-phosphorylation at Y216, the exogenous signal transduction regulated Ser9 site inhibition and, if the association of schizophrenia with the wnt inhibitor DKK4 we reported is true (Proitsi et al., 2008), also via the wnt signaling effects on disruption of the macromolecular complex that brings GSK3 together with β-catenin. On the one hand, this might be taken as positive evidence of a role for GSK3 in psychosis—all of its regulatory mechanisms have been implicated; therefore, the case is stronger. On the other hand, GSK3 lies at the intersection point of very many signaling pathways and so is likely to be implicated in many disorders (as it is), and the fact that in cellular and animal models related to psychosis there is no consistent effect on the enzyme is troublesome.

From a drug discovery perspective, those with GSK3 inhibitors in the pipeline will be watching this space carefully. However, it is worth noting that Mao et al. find very selective effects of DISC1 on GSK3 substrates. Despite convincing evidence of an increase in Y216 phosphorylation, which one would expect to increase activity of GSK3 against all substrates, the authors find no evidence of effects on phosphorylation of the GSK3 substrates Ngn2 or C/EBPα. This is somewhat puzzling and merits further attention, especially as in vitro direct binding of a DISC1 fragment to GSK3 inhibited the action of GSK3 on a range of substrates. Might there be more to the direct interaction of DISC1 with GSK3 than a regulation of Y216 autophosphorylation and activation? If, however, GSK3 regulation turns out to be part of the mechanism of schizophrenia or bipolar disorder, then identifying which of the substrates and which of the many activities of GSK3, including on plasticity and hence cognition (Peineau et al., 2007; Hooper et al., 2007), are important in disease will become the critical task.

References:

Lovestone S, Killick R, Di Forti M, Murray R. Schizophrenia as a GSK-3 dysregulation disorder. Trends Neurosci. 2007 Apr 1 ; 30(4):142-9. Abstract

Cross DA, Alessi DR, Cohen P, Andjelkovich M, Hemmings BA. Inhibition of glycogen synthase kinase-3 by insulin mediated by protein kinase B. Nature . 1995 Dec 21-28 ; 378(6559):785-9. Abstract

Jope RS. Lithium and GSK-3: one inhibitor, two inhibitory actions, multiple outcomes. Trends Pharmacol Sci . 2003 Sep 1 ; 24(9):441-3. Abstract

Proitsi P, Li T, Hamilton G, Di Forti M, Collier D, Killick R, Chen R, Sham P, Murray R, Powell J, Lovestone S. Positional pathway screen of wnt signaling genes in schizophrenia: association with DKK4. Biol Psychiatry . 2008 Jan 1 ; 63(1):13-6. Abstract

Peineau S, Taghibiglou C, Bradley C, Wong TP, Liu L, Lu J, Lo E, Wu D, Saule E, Bouschet T, Matthews P, Isaac JT, Bortolotto ZA, Wang YT, Collingridge GL. LTP inhibits LTD in the hippocampus via regulation of GSK3beta. Neuron . 2007 Mar 1 ; 53(5):703-17. Abstract

Hooper C, Markevich V, Plattner F, Killick R, Schofield E, Engel T, Hernandez F, Anderton B, Rosenblum K, Bliss T, Cooke SF, Avila J, Lucas JJ, Giese KP, Stephenson J, Lovestone S. Glycogen synthase kinase-3 inhibition is integral to long-term potentiation. Eur J Neurosci . 2007 Jan 1 ; 25(1):81-6. Abstract

View all comments by Simon Lovestone

Related News: DISC1: A Matter of Life or Death for Neural Progenitors

Comment by:  Nick Brandon (Disclosure)
Submitted 27 March 2009
Posted 30 March 2009
  I recommend the Primary Papers

Li-huei Tsai and colleagues have identified another pathway in which the candidate gene DISC1 looks to have a critical regulatory role, namely the wnt signaling pathway, in progenitor cell proliferation. In recent years we have seen that DISC1 has a vital role at the centrosome (Kamiya et al., 2005), in cAMP signaling (Millar et al., 2005), and in multiple steps of adult hippocampal neurogenesis (Duan et al., 2007). They have shown a pivotal role for DISC1 in neural progenitor cell proliferation through regulation of GSK3 signaling using a spectacular combination of cellular and in utero manipulations with shRNAs and GSK3 inhibitor compounds. These findings clearly implicate DISC1 in another “druggable” pathway but at this stage do not really identify new approach/targets, except perhaps to confirm that manipulating adult neurogenesis and the wnt pathway holds much potential hope for therapeutics. Perhaps understanding the mechanism of inhibition of GSK3 by DISC1 in more detail might reveal more novel approaches or encourage more innovative work around this pathway. In addition, I have read the other comment (by Rahman), and though I agree that this work still leaves many questions to be answered, the paper is much more significant and likely reconcilable with previous papers than appreciated. The commentary from Lovestone was very insightful and brings up additional gaps and issues with the present work. Additional experimentation I am sure will tease out more key facets of the DISC1-wnt interaction in the near future.

There are many avenues now to proceed with this work. In particular, from the DISC1-centric view, a GSK3 binding site on DISC1 overlaps with one of the critical core PDE4 binding site. Mao et al. show that residues 211 to 225 are a core part of a GSK3 binding site. Previously, Miles Houslay had shown very elegantly that residues 191-230 form a common binding site (known as common site 1) for both PDE4B and 4D families (Murdoch et al., 2007). It will be important to understand the relationship between GSK3 and PDE4 related signaling in reference to the activity of DISC1 starting at whether a trimolecular complex among DISC1-PDE4-GSK3 can form. Then it will be critical to understand the regulatory interplay among these molecules. For example, it is known that PKA can regulate GSK3 activity (Torii et al., 2008) and the interaction between DISC1 and PDE4, while both GSK3 and PKA can phosphorylate β-catenin (Taurin et al., 2006). The output of these relationships on progenitor proliferation will further deepen insights into the role of DISC1 complexes in neuronal processes. This type of situation is not really surprising for a molecule (DISC1) which has been shown to interact with >100 proteins (Camargo et al., 2007). The context of these interactions in both normal development and disease is likely to be critical to allow understanding of its complete functional repertoire.

Another area where these new findings need to be exploited is in the study of additional animal models. Though the two behavioral endpoint models used in the paper (amphetamine hyperactivity and forced swim test) provide a tantalizing glimpse of the behavioral importance of the complex, it would be critical to look in additional models relevant for schizophrenia and mood disorders. Furthermore, it will be very interesting to look at the effects of GSK3β inhibitors in some of the DISC1 animal models already available and to see if they can reverse all or a subset of reported behaviors. In reviewing a summary of the phenotypes available to date (Shen et al., 2008) there is clearly a number of lines which share the properties with mice injected with DISC1 shRNA into the dentate gyrus and would be of value to look at.

A very exciting paper which I am sure will drive additional research into understanding the role of DISC1 in psychiatry and hopefully encourage drug discovery efforts around this molecular pathway (Wang et al., 2008).

References:

1. Kamiya A, Kubo K, Tomoda T, Takaki M, Youn R, Ozeki Y, Sawamura N, Park U, Kudo C, Okawa M, Ross CA, Hatten ME, Nakajima K, Sawa A. A schizophrenia-associated mutation of DISC1 perturbs cerebral cortex development. Nat Cell Biol . 2005 Dec 1 ; 7(12):1167-78. Abstract

2. Millar JK, Pickard BS, Mackie S, James R, Christie S, Buchanan SR, Malloy MP, Chubb JE, Huston E, Baillie GS, Thomson PA, Hill EV, Brandon NJ, Rain JC, Camargo LM, Whiting PJ, Houslay MD, Blackwood DH, Muir WJ, Porteous DJ. DISC1 and PDE4B are interacting genetic factors in schizophrenia that regulate cAMP signaling. Science . 2005 Nov 18 ; 310(5751):1187-91. Abstract

3. Duan X, Chang JH, Ge S, Faulkner RL, Kim JY, Kitabatake Y, Liu XB, Yang CH, Jordan JD, Ma DK, Liu CY, Ganesan S, Cheng HJ, Ming GL, Lu B, Song H. Disrupted-In-Schizophrenia 1 regulates integration of newly generated neurons in the adult brain. Cell . 2007 Sep 21 ; 130(6):1146-58. Abstract

4. Murdoch H, Mackie S, Collins DM, Hill EV, Bolger GB, Klussmann E, Porteous DJ, Millar JK, Houslay MD. Isoform-selective susceptibility of DISC1/phosphodiesterase-4 complexes to dissociation by elevated intracellular cAMP levels. J Neurosci . 2007 Aug 29 ; 27(35):9513-24. Abstract

5. Torii K, Nishizawa K, Kawasaki A, Yamashita Y, Katada M, Ito M, Nishimoto I, Terashita K, Aiso S, Matsuoka M. Anti-apoptotic action of Wnt5a in dermal fibroblasts is mediated by the PKA signaling pathways. Cell Signal . 2008 Jul 1 ; 20(7):1256-66. Abstract

6. Taurin S, Sandbo N, Qin Y, Browning D, Dulin NO. Phosphorylation of beta-catenin by cyclic AMP-dependent protein kinase. J Biol Chem . 2006 Apr 14 ; 281(15):9971-6. Abstract

7. Camargo LM, Collura V, Rain JC, Mizuguchi K, Hermjakob H, Kerrien S, Bonnert TP, Whiting PJ, Brandon NJ. Disrupted in Schizophrenia 1 Interactome: evidence for the close connectivity of risk genes and a potential synaptic basis for schizophrenia. Mol Psychiatry . 2007 Jan 1 ; 12(1):74-86. Abstract

8. Shen S, Lang B, Nakamoto C, Zhang F, Pu J, Kuan SL, Chatzi C, He S, Mackie I, Brandon NJ, Marquis KL, Day M, Hurko O, McCaig CD, Riedel G, St Clair D. Schizophrenia-related neural and behavioral phenotypes in transgenic mice expressing truncated Disc1. J Neurosci . 2008 Oct 22 ; 28(43):10893-904. Abstract

9. Wang Q, Jaaro-Peled H, Sawa A, Brandon NJ. How has DISC1 enabled drug discovery? Mol Cell Neurosci . 2008 Feb 1 ; 37(2):187-95. Abstract

View all comments by Nick Brandon

Related News: DISC1: A Matter of Life or Death for Neural Progenitors

Comment by:  Akira Sawa, SRF Advisor
Submitted 8 April 2009
Posted 8 April 2009

Mao and colleagues’ present outstanding work sheds light on a novel function of DISC1. Because DISC1 is a multifunctional protein, the addition of new functions is not surprising. Thus, for the past several years, the field has focused on how DISC1 can have distinct functions in different cell contexts (for example, progenitor cells vs. postmitotic neurons, or developing cortex vs. adult dentate gyrus). In addition to Mao and colleagues, I understand that several groups, including ours, have obtained preliminary, unpublished evidence that DISC1 regulates progenitor cell proliferation, at least in part via GSK3β. Thus, I am very supportive of this new observation.

If there might be a missing point in this paper, it is unclear whether suppression of GSK3β occurs in several different biological contexts in brain in vivo. In other words, it is uncertain whether DISC1’s actions on GSK3β are constitutive or context-dependent. How can we reconcile differential roles for DISC1 in progenitor cells in contrast to postmitotic neurons? We have already obtained a preliminary promising answer to this question, which is currently being validated very intensively. These two phenotypes (progenitor cell control and postmitotic migration) may compensate for each other in cortical development; thus, overall cortical pathology looks milder in adults, at least in our preliminary unpublished data using DISC1 knockout mice. We are not sure how this novel function of DISC1 may account for the pathology of Scottish cases. Although I have great respect for the Scottish pioneers of DISC1 study, such as St. Clair, Blackwood, and Muir (I believe that the St. Clair et al., 1990 Lancet paper is one of the best publications in psychiatry), now is the time to pay more and more attention to the question of the molecular pathway(s) involving DISC1 in general schizophrenia (see 2009 SRF roundtable discussion). Unlike the role of APP in Alzheimer’s disease, DISC1 is not a key biological target in general schizophrenia, instead being an entry point to explore much more important targets for schizophrenia. There may be no more need to stick to DISC1 itself in the unique Scottish cases in schizophrenia research. In sum, although there may still be key missing points in this study, I wish to congratulate the authors on their outstanding work.

References:

St Clair D, Blackwood D, Muir W, Carothers A, Walker M, Spowart G, Gosden C, Evans HJ. Association within a family of a balanced autosomal translocation with major mental illness. Lancet . 1990 Jul 7 ; 336(8706):13-6. Abstract

View all comments by Akira Sawa