Posted 24 March 2009

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Attendees/Participants

Amy Arnsten, Yale University
Verain Bader, University of Duesseldorf
Nick Brandon, Wyeth
Sarah Brown, Edinburgh University
Kate Burdick, The Zucker Hillside Hospital-NSLIJHS
Michael Cahill, Northwestern University in Chicago
Ty Cannon, UCLA
Ross Cardarelli, University of Maryland, Baltimore
Becky Carlyle, Edinburgh University
Tom Comery, Wyeth
Angela Epshtein, Schizophrenia Research Forum
Nao Gamo, Yale University
Hugo Geerts, In Silico Biosciences
Christoph Gruenewald, Edinburgh University
Ellen Gruenewald, Edinburgh University
Hakon Heimer Schizophrenia Research Forum
Michy Kelly, Wyeth
Carsten Korth, University of Duesseldorf
Tatiana Lipina, Samuel Lunenfeld Institute at Mount Sinai Hospital, Toronto
Anil Malhotra, The Zucker Hillside Hospital
Karen Marquis, Wyeth
Pat McCaffrey, Schizophrenia Research Forum
Patricio O'Donnell, University of Maryland
Constantinos Paspalas, Yale University
Peter Penzes, Northwestern University, Chicago
Misha Pletnikov, JHU
Amy Ramsey, Duke University
Akira Sawa, Johns Hopkins University
Dani Smith, Johns Hopkins University
David St. Clair, University of Aberdeen
Marquis Vawter, UCI
Min Wang, Yale University
Tracy Young-Pearse, Harvard Medical School, Brigham & Women’s Hospital

Note: Transcript has been edited for clarity and accuracy.

Hakon Heimer
Let's start off by having all the participants in the "room" introduce themselves. Please type your name and affiliation or institution. I'm Hakon Heimer, editor at Schizophrenia Research Forum.

Tyrone Cannon
I'm Ty Cannon, professor of Psychology and Psychiatry at UCLA.

Amy Arnsten
Amy Arnsten and Nao Gamo are sitting in at Yale.

Angela Epshtein
I'm Angela Epshtein, managing editor at Schizophrenia Research Forum.

Becky Carlyle
Hi Everyone, Becky Carlyle, Edinburgh University.

Nick Brandon
Nick Brandon, Head of Schizophrenia Biology, Wyeth.

Karen Marquis
Karen Marquis, Wyeth.

Dani Smith
Hi, Dani Smith at Johns Hopkins.

Becky Carlyle
Hey, Nao!

David St. Clair
I am David St. Clair, University of Aberdeen.

Patricia McCaffrey
Pat McCaffrey, writer for Schizophrenia Research Forum.

Amy Ramsey
I'm from Duke University, but I'll be starting my lab at University of Toronto this summer.

Michael Cahill
Hi, Michael Cahill, Northwestern University in Chicago.

Tracy Young-Pearse
Tracy Young-Pearse, Harvard Medical School, Brigham & Women’s Hospital.

Thomas Comery
Tom Comery, Wyeth.

Hugo Geerts
I am Hugo Geerts, Scientific Liaison Officer at In Silico Biosciences.

Ross A. Cardarelli
I'm Ross Cardarelli, graduate student at the University of Maryland, Baltimore.

Christoph Gruenewald
Christoph Gruenewald (Kirsty Millar's group in Edinburgh).

Amy Arnsten
Hi, Becky!

Peter Penzes
Peter Penzes, assistant professor of Physiology, Northwestern University, Chicago.

Ellen Gruenewald
Hi all; I'm Ellen Gruenewald from Edinburgh University.

Michy Kelly
Michy Kelly, scientist in Nick Brandon's group, Wyeth.

Mikhail Pletnikov
Hi, Misha Pletnikov, JHU.

Hakon Heimer
All, great turnout!

Sarah Brown
Hi, I’m Sarah Brown, third-year Ph.D., Edinburgh University in David Porteous's lab.

Tatiana Lipina
Hi, Sarah!

Sarah Brown
Hi, Tatiana.

Anil Malhotra
Hello, all. Kate Burdick and I are logged on.

Hakon Heimer
Hi, Anil and Kate!

Tatiana Lipina
Hi, I am Tatiana Lipina from Samuel Lunenfeld Institute at Mount Sinai Hospital, Toronto.

Amy Arnsten
Constantinos Paspalas and Min Wang have also joined from Yale (all at my terminal).

Carsten Korth
Hi, I am Carsten Korth from the University of Duesseldorf. Verain Bader, my postdoc, has also joined.

Patricio O’Donnell
Hi, Hakon!! I'm Patricio O'Donnell, at the University of Maryland.

Hakon Heimer
In the informal spirit of this event, I will only mention that Akira is at Johns Hopkins University, Nick is at Wyeth Research in New Jersey, and Ty is at UCLA, and I thank them for bringing us this idea and for their work to prepare the discussion. I'll now turn to Akira, who I believe will orient us on the plans for the discussion.

Akira Sawa
Welcome. Thank you very much for joining this roundtable discussion on DISC1 and schizophrenia today. We will have five agendas: 1) molecular diversity of DISC1; 2) protein interactions around DISC1 and their biological significance; 3) animal models; 4) clinical phenotypes; and 5) therapeutic strategies. The first two topics will be led by Nick Brandon, the third topic by me, fourth by Ty, and the fifth by me. Why don't we start? Nick, can you initiate?

Nick Brandon
Thank you everyone for your comments; there are some very nice, insightful commentaries. The question of isoforms has been an issue in the field and was flagged at the 2006 roundtable, and seemingly we have not made a lot of progress. But, I have been gradually getting more excited about Barbara Lipska’s work, which ended up in a great talk at the ACNP meeting in December 2008. Finally seeing cloned and expressed versions on a gel of human variants of DISC1 was wonderful and clearly could open up this area. In addition, Barbara has shown enrichment of certain short variants in patient brain—amazingly they are not too distinct from the original putative Scottish truncation. This may mean that all the work performed with the truncation could have additional validity. I think we are going to see great advances in this area. Barbara and Joel, if you’re online, could you please comment? Others, please join in.... Okay, we can come back to this when Joel joins. Could others discuss ways to look at this in terms of generalization (e.g., Carsten, you mentioned the oligomers in your comments).

Carsten Korth
Nick, I was emphasizing the significance of post-translational modifications that are not well characterized so far.

Nick Brandon
Carsten, okay, we'll return to this point in a moment.

Amy Ramsey
I agree with Nick that some of the most exciting work has been to show how aberrant DISC1 biology can extend to patients beyond the familial cases.

Nick Brandon
Amy R., I think the generalizability of DISC1 effects is very important. Akira, what are your thoughts here? You saw the same talk at ACNP.

Akira Sawa
As for isoforms, we still need a lot of sincere efforts to find unknown isoforms. Barbara Lipska is doing a good job in this area.

Tatiana Lipina
Nick, here’s a thought about origin of different isoforms: Maybe comparison of different species could be helpful in the evolutionary perspective? What do you think?

Nick Brandon
To the Edinburgh group, regarding Tatiana’s point, what do you think (as you have worked in this area)? Also, who can comment on any new information from work regarding the analysis of the original family? In particular, who can comment on the progress on fusion transcripts or the role of DISC2? These are areas that I think are critically important but have been overlooked.

Becky Carlyle
Nick, the Edinburgh group is working on fusion transcripts right now. The person responsible is unfortunately not in the chat!

Nick Brandon
To all, on to another point regarding isoforms: But what does this mean for rodents? Clearly we need to ascribe actual amino acid identity to the bands we all recognize on our Westerns. What are all those bands? Are they all DISC1? What are the best antibodies to use? There has been some discussion on the use of peptide antibodies vs. fusion proteins. I have been happy with the polyclonals we’ve made, but agree that we need to take a more systematic approach to this analysis. What do others think of their own reagents and the identity of DISC1 forms? How would people like to see DISC1 antisera characterized? Perhaps we can take this offline and work out a plan that we could all share, ensuring that all our reagents have gone through a systematic quality control process.

Akira Sawa
We have studied two major post-translational modifications: SUMOylations and phosphorylations. The former are required for nuclear targeting of some isoforms. Phosphorylation is developmental dependent.

Michy Kelly
Akira, how are you able to determine “some isoforms” are affected by SUMOylations, and which are they?

Akira Sawa
Michy, mass spectrometry.

Marquis Vawter
Nick and Akira, thanks for hosting this discussion. Here’s my question: Are there drugs that alter DISC1 gene and protein expression in brain or cell lines?

Akira Sawa
Mark's point is very important, and can also be addressed in the fifth topic (therapeutic translation).

Nick Brandon
Mark, Barbara Lispka looked at the effects of antipsychotics on DISC1 expression a few years back. I’d need to refresh my understanding of the findings, but I believe she saw changes in rodents.

Amy Ramsey
Nick, I think so, too. I think that APS increased DISC1. When working in mice, I am mainly detecting two isoforms of DISC1: 100 and 70. Are there other meaningful isoforms in mice?

Christoph Gruenewald
Amy R., possible transcripts predict at least five different isoforms (expected protein sizes are 41, 85, 90, 92, and 93 kDa). To my knowledge, these transcripts have not been linked to proteins on WBs.

Nick Brandon
Christoph and Becky, it will be important to make that connection. Are you referring to human or mouse?

Christoph Gruenewald
Nick, I am talking about mouse at the moment.

Akira Sawa
Amy R., even if we see a 100 kDA immunoreactivity in Western blotting, it may represent more than one isoform.

Nick Brandon
Amy R., 100kD and 70kD are likely the most prominent bands on a straight Western. I think we can start to uncover less abundant but likely critical forms when enriching DISC1 using various antisera. What do others see?

Amy Ramsey
Thanks, Nick; that's an interesting observation.

Akira Sawa
Nick's words "various antisera" are important. If we can systematically test all the antibodies among folks and compare, the field will move more systematically forward.

Marquis Vawter
Nick, Akira, and Amy R., you’re right; here’s the quote from Lipska et al.: “We found that atypical antipsychotics, olanzapine and risperidone, in a clinically relevant dose, increased DISC1 expression levels in frontal cortex, while a typical antipsychotic, haloperidol, did not.”

Nick Brandon
One last point from me on this topic: Other forms of DISC1 from a post-translationally modified version to different oligomerized forms of the protein and associated complexes. We heard from Carsten Korth in the pre-meeting discussions regarding oligomers. What do people think are the most fruitful areas to look into here? Phospho-forms, etc., or SUMOylation as Akira has introduced? Carsten, please add your thoughts.

Carsten Korth
Nick, regarding the oligomers, please keep in mind that ultimately the function of DISC1 is executed at the protein level with native proteins. Our studies (and I think your studies as well) with recombinantly expressed DISC1 indicate that DISC1 forms a homomeric complex. It’s clear that anything that interferes with an orderly assembly of this complex disturbs molecular interactions.

David St. Clair
Has anyone looked for glycosylation?

Nick Brandon
David, not recently. I may have done some crazy experiments into this about a decade ago, but the data are probably lost, and I don’t think the data were striking.

Amy Arnsten
Are there differences in isoforms, phosphorylation state (or protein partners), etc., based on developmental state (i.e., perinatal, adolescence, adult)?

Carsten Korth
Amy A., if we take all splice variants, phosphorylation, and possible degradation of DISC1, the electrophoretic migration pattern gets very complex. I see only immunopurification with single-epitope antibodies and then mass spec as a way of determining the exact identity.

Akira Sawa
Carsten, wonderful approach!

Amy Ramsey
Nick, I like your idea of a biochemical assay to address this question of phosphorylation/SUMO. How does DISC1 affect activity of PDE4B? Is phosphorylation involved?

Sarah Brown
Nick, Akira, and Amy R., I’ve looked at clozapine, bupropion, and rolipram, and have seen no change in DISC1 expression in mouse hippocampus. Could it be that only the atypicals alter DISC1?

Amy Ramsey
I haven't tried these experiments myself but would be willing to try!

Akira Sawa
Regarding DISC1 expression by drugs, how about lithium?

Nick Brandon
Sarah, Akira, and Amy R., this is really interesting. It would be worth expanding this out. Are they acute treatments or chronic? On cells or on animals?

Amy Ramsey
Nick, I would try acute treatment first in wild-type animals, and then see if chronic has an effect.

Sarah Brown
Nick, mine was done with one dose (Tatiana is the dosage expert; I can’t remember off the top of my head!) in mouse. I looked at wild-type and the two DISC1 mutants from Steve Clapcote, none of which showed changes in DISC1.

Amy Ramsey
I noticed that cerebellum is quite high in DISC1. And also has D2 receptors. Has anyone else thought about this?

Tatiana Lipina
Akira, in which brain area do you think it’s more relevant to find DISC1 expression changes after drug treatments, e.g., APDs?

Akira Sawa
Tatiana, interesting question. Maybe frontal cortex, especially OFC as well as the hippocampus and thalamus.

Michy Kelly
Akira, is there some reason to expect a limited effect region-wise beyond the regional limitation of where DISC1 is expressed in the first place?

Akira Sawa
Michy, the reason that I limited the regions is because of the expression pattern or role of DISC1 interactors of interest, such as PCM1.

Tatiana Lipina
Akira, those are very interesting findings about PCM1 and BBS4.

Nick Brandon
Okay, I'm going to bring in the next section: We were at the heart of developing the DISC1 interactome—a solid partnership between the bioinformatician (Camargo) and the wet-lab (Brandon). This piece of work highlighted the diversity of possible pathways in which DISC1 could play a critical role. Clearly a systems approach is required to tackle this beast appropriately. On top of the interactions, we have to layer on the context (it’s been said before but I’ll reiterate). By this I mean developmental time periods, subcellular compartments, regional specificity, post-translational modifications, etc. What do people think are the best approaches to slicing up DISC1 biology for maximal efficiency and progress? What are the principal systems we should be working on in the next four to five years?

Amy Ramsey
Nick, I don't think regional specificity holds the best clues to DISC1 function. My hunch is that it’s doing basically the same thing in different brain regions. I am more interested in which of its interactions lead to mental illness.

Nick Brandon
Amy R., are you sure? Data suggest that DISC1 may do different things in the hippocampus vs. PFC in development. Akira, can you add to this?

Amy Ramsey
Nick, no, I’m not sure at all! I’m a novice in this field, and it’s just my hunch that DISC1 has general roles in neuron physiology.

Tatiana Lipina
Nick, I agree with you.

Michy Kelly
Amy R. and Akira, given the evidence implicating cerebellum dysfunction in schizophrenia, I think the cerebellum is likely to be of interest within the context of DISC1.

Hakon Heimer
Michy, could you remind us of what is (are) the major findings in cerebellum vis-à-vis schizophrenia?

Michy Kelly
Hakon, there's been a bit of structural work showing smaller volumes, or correlating volume with symptom severity. There’s also some evidence to suggest cerebellum dysfunction may contribute to aspects of the cognitive dysfunction observed in patients.

Michael Cahill
Is DISC1 highly expressed in inhibitory neurons within the hippocampus and/or frontal cortex?

Akira Sawa
Michael, DISC1 expression is highly expressed more in pyramidal neurons and granule neurons (DG), but there is some expression in interneurons.

Nick Brandon
Michael, we published old data in 2004 in which we identified DISC1 with our D27 antisera in all cell types in the mouse brain (see Schurov et al., 2004).

Akira Sawa
Nick, Tatiana, and Amy R., it’s true that DISC1 behaves differently in the context (regions).

Amy Arnsten
cAMP does different things in the prefrontal cortex than it does in hippocampus; therefore, DISC1 may be having an overall different function by region. And remember that the cerebellum has an extensive noradrenergic input that likely acts via β receptors.

Michy Kelly
Amy A., very good point regarding cAMP's regionally specific effects.

Nick Brandon
Amy A., I have one last comment on the differential effect of cAMP. It’s critical that we incorporate cAMP into our thinking of DISC1. I think we are starting to see that DISC1 and cAMP signaling are inextricably linked with the work of Miles H. and Edinburgh. Miles, any comments here?

Amy Arnsten
I just received a message from Constantinos Paspalas (who is doing EM of monkey prefrontal cortex). He agrees. He sees DISC1 in dendrites and in spines, the latter of which are of pyramidal cells.

Akira Sawa
Regarding the cerebellum, the network of PFC-thalamus-cerebellum is functionally very important, and may be involved in schizophrenia.

Amy Ramsey
Akira, I agree. Aren't smooth eye tracking movements controlled by the cerebellum and disrupted in schizophrenia?

Nick Brandon
One final question for this section: Can anyone online discuss efforts regarding the deep sequencing of DISC1? What’s it starting to look like?

Marquis Vawter
Nick, I think David Porteous is collaborating with CSHL on the question of deep sequencing of DISC1.

Nick Brandon
Amy A., how does the NHP EM compare to the human data published by Kirkpatrick and Akira?

Amy Arnsten
Nick, the human and NHP look very similar. Constantinos has done both. We also have labeling of centrosomes in the monkey PFC tissue.

Michael Cahill
As for DISC1 animal models, most studies have examined adult mice (12 weeks or older) that show several behavioral deficits. Are younger mice (e.g., three weeks) free of behavioral dysfunctions?

Mikhail Pletnikov
Michael, we’re testing developing mice now, and we’re not yet sure what the results could be.

Tyrone Cannon
Michael, we have not tested younger mice behaviorally. They tend to be difficult to test in standard behavioral assays.

Akira Sawa
Taking the information of isoform, protein interactome, and regional specificity into account, how about moving on to the topic of animal models and clinical phenotypes? The former will be led by me, and the latter by Ty. Ty, thanks! Patricio, you have worked in the area of development of the prefrontal cortex. Let us know your thoughts.

Patricio O’Donnell
Akira, you asked about developmental issues in the prefrontal cortex. We should all keep in mind that pyramidal neurons and more notably interneurons continue maturing through adolescence, so it should not be unexpected to see expression changes or modulation differences in adult vs. adolescent or pre-adolescent mice.

Amy Arnsten
cAMP impairs prefrontal working memory function, so loss of DISC1 may worsen prefrontal functions. We are trying to test this now.

Mikhail Pletnikov
Ty, I meant test batteries for developing rodents.

Tyrone Cannon
Mikhail, yes, I think I understood correctly, and I would be interested in knowing what paradigms can be run on developing mice.

Sarah Brown
Mikhail, can I ask how young you are going? Just out of interest, as I would have thought testing young mice would prove to be rather difficult.

Mikhail Pletnikov
Sarah, again one can start with three- to four-day-old mice.

Sarah Brown
Mikhail, sounds interesting. I look forward to the results.

Amy Ramsey
Me, too.

Michy Kelly
Mikhail, Tyrone, Amy R., I've worked with three-week-old mice in behavioral apparati with no issues: open field, PPI/startle, in particular.

Tatiana Lipina
Michy, what were the results in PPI in three-week-old mice? I think the startle reflex is not ready in three-week-old mice.

Michy Kelly
Tatiana, I was able to measure reliable startle and PPI in C57Bl6 mice and CF-1 mice.

Tatiana Lipina
Michy, good. I tested eight-week-old mice in PPI and found no defect in PPI, but startle was already lower in one of our mutants.

Hakon Heimer
Misha and Ty, would olfactory learning paradigms be useful? That's something you can do at that age.

Mikhail Pletnikov
I think so, Hakon.

Tatiana Lipina
Tyrone, Mikhail, and Amy, you can just observe young mice.

Michy Kelly
Mikhail, Tyrone, and Amy, you can also do in-cage observations of social behavior: huddling, nest building, etc.

Tyrone Cannon
Michy and Hakon, yes, those paradigms would be of interest. We've established the clearest links of transgenic DISC1 disruption on spatial working memory and social preference, but I’m not sure about those paradigms in three-week-old mice. But we have studied whether induction of the transgene early vs. later plays a role. Also, for disruption of DISC1-NUDEL binding, clearly early induction is critical for the effects, whereas adult induction is not.

Michy Kelly
Tatiana, I was not referring to results with DISC1 models in particular, but rather generally speaking of the ability to test developing mice.

Hakon Heimer
Misha, if I remember correctly, there's a big body of literature (WG Hall, Blass) on olfactory learning in neonates, but maybe mostly rats.

Patricio O’Donnell
To all, why would one expect behavioral changes in very young mice? If we think DISC1 genetics is important for schizophrenia, a dysfunction in this system would be expected to provide behavioral anomalies after adolescence. And PFC excitation-inhibition balance does mature during that age. So, one can have a dysfunctional circuit due to DISC1-dependent anomalies, but the deficits won’t be expressed until the circuits mature.

Amy Arnsten
Exactly, Patricio! That was why I was asking about changes in DISC1 at adolescence.

Mikhail Pletnikov
Patricio, I think similar to human data, one might be able to find "prodromal" subtle alterations. Our mice with prenatal expression only might indicate this.

Tatiana Lipina
Patricio, yes, you are right about expectations for schizophrenia development.

Michy Kelly
Patricio, would you necessarily expect cognitive/social dysfunction to appear post-adolescence? I thought those features of disease are observed in patients pre-/during adolescence in comparison to the positive symptoms that classically emerge in early adulthood.

Patricio O’Donnell
Michy, sure, one should perhaps expect "positive" symptom-related alterations after adolescence, and perhaps some cognitive prodromal deficits. But if the definition of prodromal status is quite difficult in patients, can we reliably assess it in mice? Perhaps some cognitive tests may reveal alterations as Misha indicated. It would certainly be worth pursuing, but my point is that even if pre-adolescent deficits are found, the full-fledged set of anomalies should be seen after adolescence.

Mikhail Pletnikov
Patricio, yes, you’re right. I was talking more about subtle preceding abnormalities that may be detectable earlier, but this is still at a very preliminary stage of research.

Marquis Vawter
Patricio, premorbid adjustment difficulties occur prior to onset, so it would be consistent to have DISC1 effects in pre-adolescence.

Amy Ramsey
Wouldn't it be lovely to show relatively normal adolescence and abnormal adult behavior in any mouse model?

Akira Sawa
The developmental changes of mouse model behavior are very important when we consider that the study of subjects with prodromal stages is now a hot topic. What do you think, Ty?

Tyrone Cannon
Akira, yes, I agree. Adolescent synaptic pruning is currently seen as a likely mechanism in the onset of psychosis. Are there any good rodent models of this?

Amy Arnsten
Tyrone, we’re looking at stress-induced pruning of spines, and whether these involve cAMP mechanisms.

Tyrone Cannon
Amy A., very interesting. It may be of interest to try out the stress paradigm in mice with and without TG disruption of the cAMP binding domain.

Amy Arnsten
Tyrone, that’s a great idea.

Tatiana Lipina
It would be interesting to estimate step-by-step appearance of schizophrenia and bipolar symptoms by age.

Anil Malhotra
Tatiana, brain structure and functional changes emerge long before psychosis in schizophrenia—less is known about bipolar disorder, but it appears intact until after or close to illness onset.

Mikhail Pletnikov
Tatiana, I agree; we do need a systematic developmental analysis of our mouse models, if that’s what you meant?

Tatiana Lipina
Mikhail, yes.

Hakon Heimer
Ty, I can see that it would be productive to have a live discussion on the prodrome, and what we really know about putative behavioral abnormalities of the prodrome!

Tyrone Cannon
Hakon, Michy et al., yes, while positive symptoms emerge during adolescence, the working memory and LTM deficits are there earlier and are predictive of future psychosis in those at risk. Gray matter decreases more steeply in those prodromal patients who convert compared with those who do not, particularly in dorsal prefrontal.

Nicola Cascella
Ty, please keep in mind the heterogeneity of schizophrenia. There are patients who do not have long prodromal symptoms.

Tyrone Cannon
Nicola, true. I’m referring to data from those who have a clear prodrome, as these are the ones who have been studied systematically with imaging, etc., through the period of risk for onset.

Nick Brandon
Patricio and Ty, how much effort should we put into the younger animals? Perhaps we can discuss offline?

Akira Sawa
In terms of association of DISC1 with environmental stresses, how about the role of the immune system? Associated with intracellular signaling? Synaptic pruning, etc.? This might be a very important topic.

Becky Carlyle
To all, as a reverse question, do we know if stress paradigms applied to animals affect the quantities of the various known DISC1 isoforms?

Amy Arnsten
Great question, Becky. As far as I know, this has not been studied. Akira, Arthur Simen in our group is looking at cytokines, etc., interactions.

Mikhail Pletnikov
Akira, as you know, we have been looking at DISC1-ploy in interactions and have found that immune activation can change the original phenotype in mice.

Akira Sawa
Yes, you have presented several times, which I found many audiences appreciated.

Nick Brandon
Becky and Amy R., we could look at this easily here.

Becky Carlyle
Nick, I'd be very interested to see that.

Amy Ramsey
I like the stress experiment idea; I hope someone does it.

Tyrone Cannon
Amy R., we could discuss collaboration on that experiment with our DISC1-N line.

Tatiana Lipina
Amy R., we do stress experiments as well as Poly I:C, as Mikhail does.

Peter Penzes
Akira, what would be some good environmental stressors/risk factors that are known in humans to increase schizophrenia risk and can also be applied in rodents?

Michy Kelly
Peter, great question!

Tyrone Cannon
Peter, fetal hypoxia is one of the best.

Akira Sawa
Peter, toxoplasma, some viral infection during development.

Amy Arnsten
There are many stress paradigms in rodents; chronic restraint stress is the classic for gray matter changes.

Akira Sawa
Hi, friends, we only have 12 minutes left. Taking everything together, how about starting a discussion about how DISC1 research can contribute to novel discovery of therapeutic strategies? For example, expression change by drugs?

Amy Ramsey
While looking at current APS effects is a good first step, I would love to see someone take on the challenge of developing in vitro assays for DISC1 function, and ultimately look for drugs that affect DISC1 activity. I understand that first we need to nail down which activities are relevant to disease.

Mikhail Pletnikov
Later on, we might consider "ground-breaking" papers that look at the same factors with different mouse models.

Patricio O’Donnell
I feel a bit uneasy about testing effect of drugs on "normal" animals. If we wanted to learn about antipsychotic properties of an agent, a normal subject may not give us much.

Mikhail Pletnikov
Patricio, quite rightly so; that's why new models may give more interesting clues.

Tyrone Cannon
Patricio, I agree. It’s probably more fruitful to target specific DISC1-interacting partner complexes in mutant mice.

Amy Ramsey
Patricio, absolutely. We have several good mutant lines for modeling schizophrenia; we just need some new drugs to test them.

Nick Brandon
All, for drug discovery, everyone looks to PDE4, but it’s been a well-trodden and so far unsuccessful path. We need to look at the pathway, be brave, and look to be innovative.

Akira Sawa
Nick, how about compounds targeting synaptic protein interactions?

Nick Brandon
Akira, it’s a very attractive proposition. We need to know the interactions we want to modulate and develop the appropriate assays. Many companies get nervous at the thought of modulating interactions, but I believe this is changing.

Nick Brandon
During the pre-discussion comments, David Porteous mentioned the point of collaboration with industry and academia. As David has been central in past efforts to work with a company on DISC1, it’s a shame he cannot suggest alternative, perhaps more successful paths forward in which we can work together with the ultimate aim of bringing forward new innovative medicines based on the biology of DISC1 to improve the lives and outcomes of patients.

Amy Arnsten
Nick, most drug studies have tried to develop PDE4 inhibitors, not activators, which is what would "replace" DISC1. We could think of other agents that inhibit cAMP.

Michy Kelly
To all, given the current hypotheses of how DISC1 is dysfunctional in patients, do we think that DISC1 itself would even be a druggable target?

Akira Sawa
Michy, even if DISC1, as an anchoring protein, is not a direct druggable target, there are many interesting DISC1 interactors for the purpose.

Tyrone Cannon
Akira and Michy, yes, and even if not a direct target, the downstream effect (e.g., cytoskeletal development) could be “patched up” via another signaling pathway.

Patricio O’Donnell
Ty and Michy, exactly! This is where mutant mice may provide a fantastic opportunity!!

Sarah Brown
Patricio, agreed, but this is where the mouse models could be very handy.

Nicola Cascella
cAMP is a very interesting point of "attack."

Sarah Brown
As for pathways, some interesting work is going on in Edinburgh just now throwing up possible pathways and interactions that may be viable future targets.

Tatiana Lipina
Sarah, what pathways? cAMP-dependent?

Sarah Brown
Tatiana, as yet I’m still looking into them to work out, namely, which ones are “real.” Validation is ongoing! But I do think cAMP is looking important at the moment from my data.

Akira Sawa
I am slightly negative to target cAMP for schizophrenia, which impairs both HP and PFC. cAMP-targeted drugs for many other brain disorders can be developed, but not for schizophrenia. What do you think, Amy, Nicola, and other friends?

Tatiana Lipina
Akira, exactly; it is not very specific.

Nicola Cascella
There are interesting cancer meds that can be leaders for cytoskeleton.

Amy Ramsey
I don't know, Akira. I would actually be hopeful about cAMP.

Carsten Korth
Nick, why did Wyeth chose DISC1 as a druggable target?

Nick Brandon
Carsten, DISC1 provides an excellent entry point into trying to understand the disease(s). From this we hope that new drug targets and pathways will emerge. The normal comparison is to compare this historically to AD and the APP/presenilin. What AD teaches us is that it takes time to convert biology into commercialized drugs. Ten-plus years of research into the γ-secretase complex has just seen compounds enter Phase 3.

Michy Kelly
Akira et al., I think we have to be careful when considering targeting the cAMP cascade given regional-specificity and negative feedback loops; however, I think if you target the right component with the right regional/subcellular localization, it could work (we'll see).

Peter Penzes
Regarding new drug development, it seems that of the many interactions of DISC1, we should characterize the functions of the ones that are potentially druggable.

Tyrone Cannon
All, on the issue of targeting pathways, can human data on gene-gene or protein interactions be of guidance? I notice that Anil's group and Leena's group have some interesting data on gene-gene interactions in human samples.

Anil Malhotra
Ty, we have published on NDEL-DISC1 interactions, but our current work is focused on PDE4B (notable interaction at the level of genotype but very low MAF)—and FEZ1—I’m not sure NDEL or FEZ will emerge as targets.

Nick Brandon
Akira, the preclinical data with Rolipram is pretty good with both antipsychotic and procognitive effects. It’s just all the unwanted side effects that go with it. Innovation approaches around PDE4 are still possible.

Akira Sawa
Nick, I think DISC1-PDE4 shows great hope, but we need to be much more cautious in data interpretation, especially focusing on regional-specific effects.

Amy Arnsten
Akira, cAMP improves memory consolidation in the hippocampus, so you’re right; it’s not a simple target. It would be best to find molecules that modulate the pathway that are preferentially localized in the prefrontal cortex or hippocampus. We find working memory impairment with Rolipram in our aged monkeys

Michy Kelly
Amy A., that's via PKA?

Amy Arnsten
Michy, we think it is via HCN channel opening.

Amy Arnsten
Tyrone, I would like to e-mail with you about mice after this is finished.

Tyrone Cannon
Amy A., that sounds great.

Akira Sawa
Amy A., please also send e-mails to the JHU folks. The comparison among various animal models of DISC1 should be very important.

Amy Arnsten
Yes indeed, Akira.

Mikhail Pletnikov
Sure thing. We are sending mice to JAX but would be happy to share with anyone interested.

Nick Brandon
We'd like to be involved, too, in these discussions (if we can)!! Michy Kelly in particular from Wyeth.

Hakon Heimer
All, this may be a bit pie in the sky, but as an example of what might be "druggable" in the future with greater knowledge of DISC1 role in development. A paper in Nature Medicine last month showed rescue of an epilepsy phenotype in a developmental migration disorder model—DcX—by postnatal expression of the protein: Manent et al., 2009.

Amy Arnsten
The question of how to rescue DISC1 function in utero and thus spare developmental defects will be the golden challenge.

Carsten Korth
I think what is not so easy with DISC1 is that its lack of expression is associated with disease. That could mean that you may want to substitute its effect on insufficient molecular interactions.

Michy Kelly
Absolutely.

Amy Arnsten
Human cortex migration is completed in utero, so this will be harder in people.

Nick Brandon
Hakon, I know the paper well, and I got very excited by this reversal. There are clearly developmental issues around this piece of work, as you have to treat in utero, but still a giant stride forward!

Nick Brandon
Amy A., hopefully approaches will come to light that do not require such intervention?

Tyrone Cannon
Amy A., we see differences in the developmental relevance of DISC1 disruption based on whether the C-terminal or N-terminal fragment is impaired, the former clearly requiring early induction to see behavioral/histological effects and the latter not requiring this. But I agree the Holy Grail is prenatal/prevention!

Amy Arnsten
Tyrone, that is an important clue.

Tatiana Lipina
Nick, what do you think about DPSYL2 as a drug target?

Nick Brandon
Tatiana, I’m interested; we flagged in our review in 2008 (Wang et al.). We can talk more offline.

Tatiana Lipina
Nick, thank you. Yes, Wang et al. is a very interesting article.

Akira Sawa
This has been a wonderful hour. Hakon and Nico, thanks for coordinating this roundtable discussion for all of our DISC1 folks. This field is a wonderful one shared by many outstanding investigators. I would also like to say thank you very much to Dr. St. Clair, the real pioneer of this field, together with Drs. Blackwood and Muir in Scotland!

Nick Brandon
All, lots of other points were dropped, so it would be great to have follow-up comments added.

Tatiana Lipina
Bye!

David St. Clair
Thanks for inviting me.

Hakon Heimer
Akira, perhaps we should not wait two years for the next roundtable!

Nick Brandon
Hakon, I agree. I think that in 12 months we may see big strides here in a number of avenues: models, cell biology, clinical, so an annual update might not be a bad idea.

Tyrone Cannon
Many thanks to all and especially Hakon and Nico for coordinating, and Akira and Nick for initiating.

David St. Clair
It’s 20 years next year since the original description of family. Maybe should have a meeting in Scotland?

Hakon Heimer
David, I'll come! Never been to Scotland.

Nick Brandon
David, wonderful idea!

David St. Clair
I’ll discuss with the others.

Nick Brandon
Please wait until my green card has arrived as I cannot leave the U.S. until then!

Hakon Heimer
Nick, Akira, Ty, thanks so much for bringing this large group together for the meeting!

Amy Ramsey
Congratulations to all of you who have contributed to making this such an exciting field of research. I enjoyed the discussion.

Amy Arnsten
Thanks for including us!