Multiple groups within the Seaver Center make use of national registers to identify causes of risk for psychiatric disorders. The Buxbaum lab, in collaboration with Sven Sandin, focuses primarily on Swedish health registers and has used such registers to identify risk factors for autism and for OCD. In addition, the Buxbaum lab uses the register information to collect DNA samples from affected individuals, using an epidemiological framework. All samples are genotyped and sequenced and used for gene discovery (for example, in collaboration with the ASC, see above) and the associated medical information is used for genotype-phenotype correlations. The autism study is called PAGES, which is an acronym for ‘Population-Based Autism Genetics and Environment Study.’ The OCD study is led by Dorothy Grice and is called EGOS, for ‘Epidemiology and Genetics of Obsessive-compulsive disorder and chronic tic disorders in Sweden’.

Because of their pluripotency and ability to differentiate into neural cell types, induced pluripotent stem cells (iPSCs) derived from patients represent an experimental system of choice for the study of complex neuropsychiatric disorders. To determine the impact of ADNP, DDX3X, FOXP1, and SHANK3 mutations on neuronal mechanisms and pathways, we are generating iPSCs from blood samples collected from patients and their siblings (as a control) and are reprogramming them into neural progenitor cells (NPCs) and differentiating them into mature neurons. These cells can be used to mimic the pathology of the disorder and to thoroughly understand the physiology of neuronal populations that would otherwise not be accessible for investigation. Similarly, we are collecting blood samples from patients with idiopathic autism. The work on iPSC, NPC and induced neurons for these 4 rare disorders is being carried out in close collaboration with Nan Yang and Ana Kostic.

Another strategy used in our laboratory consists of creating and phenotyping a series of isogenic lines using gene-targeting methods in healthy control cells. Matt Lalli, an Instructor in the group, has selected over 100 genes associated with ASD from our genetic analyses to be investigated.

Both patient-derived cells and engineered cells are tested through a battery of high-throughput phenotypic and molecular assays at both the progenitor and mature neuron stage designed to assess genome wide expression changes and a range of phenotypes including cell replication, survival, migration, connectivity, electrophysiological properties, dendritic arborization and synaptic structure. This work will provide insight into the neuronal pathways disrupted in ASD and, ultimately, those cell lines will provide a unique platform for drug discovery, allowing high-throughput screening of large compounds libraries for their effect on modulating the human neural phenotype of ASD.

In collaboration with Kristen Brennand and the New York Stem Cell Foundation, we are using robotic methods to reprogram and differentiate over 100 fibroblast samples, half from individuals with schizophrenia and half from control individuals. Schizophrenia is a chronic, severe and disabling brain disorder that affects an estimated 1 in 100 persons. Though its key symptoms generally appear late in adolescence, schizophrenia is a neurodevelopmental condition with a strong genetic component and heritability estimated to be as high as 80%. While there have been improvements in the understanding of the biological systems implicated in the pathogenesis and pathophysiology of schizophrenia, progress has been slow and limited both by the difficulty in obtaining relevant tissues from patients and the inadequacy of animal models to deal with the level of genetic complexity involved in this disease. To date, most of the molecular and cellular studies of schizophrenia have been performed on postmortem tissues or on genetically defined mouse models that do not fully recapitulate the human genetic risk or neural phenotype. The rapid advances in iPSC methodology provide new opportunities to overcome some of the obstacles inherent to the modeling of neurodevelopmental diseases.

We are applying revolutionary robotic methods to generate pluripotent stem cells from a large cohort of patients and carefully matched controls. We will then use this sample, as well as two existing samples of iPSCs with child onset schizophrenia and/ or known, rare, highly penetrant genetic lesions, to generate both excitatory (glutamatergic) and inhibitory (GABAergic) neurons. This will create the first large scale, highly standardized library of iPSC and neurons derived from patients with schizophrenia. Subsequently, we are performing gene expression profiling on the schizophrenia and control neurons and using innovative systems biological analyses to identify dysregulated pathways in schizophrenia and key molecular drivers that underlie these pathway changes. These key molecular drivers represent potentially high-impact targets for drug development. Altogether, the completion of the aims will provide new insight into the neuronal pathways disrupted in schizophrenia, and identify potential drug targets.

Our work in schizophrenia is enhanced by our collaboration with the CommonMind Consortium. The CommonMind Consortium is a public-private partnership bringing together area knowledge, large scale and well-curated brain sample collections, data management and analysis expertise. The consortium has a goal to generate and analyze large-scale genomic data from human subjects with neuropsychiatric disease and to make these data and the associated analytical results broadly available to qualified investigators. The consortium is generating multiple data modalities (e.g. RNA and DNA sequencing, genotyping, epigenetics) across multiple brain regions from individuals with schizophrenia, bipolar disorder, and unaffected controls on a collection of more than 1,000 individuals. Buxbaum is a Founding Member of the Consortium and his lab carries out innovative analyses of the data, including a recent study on RNA editing in brain-expressed transcripts. In this study, Michael Breen, now an Assistant Professor at the Seaver Center demonstrated that editing QTLs account for some of the genetic findings made in schizophrenia.

The Buxbaum lab has generated and characterized over a dozen genetically modified rodent models for autism, schizophrenia and other psychiatric disorders. Many of the ongoing studies focus on the four genes that are noted above, specifically, ADNP, DDX3X, FOXP1, and SHANK3. The work on Shank3 is being taken forward by Hala Harony-Nicolas while the work on DDX3X is being taken forward by Silvia De Rubeis, both Assistant Professors in the Seaver Center. The Buxbaum and Kostic labs are collaborating on creating or ascertaining mouse models with disruptions in ADNP or FOXP1 and characterizing all four models for translatable biomarkers, such as chronic EEG and activity monitoring, that might be useful in as checkpoints in drug development.

Individuals with mutations in ADNP, DDX3X, FOXP1, or SHANK3 are being brought into the the Seaver Autism Center for deep, prospective phenotyping by the clinical team. The Buxbaum lab collaborates on these studies, collecting and analyzing biospecimens, including cells for iPSC and characterizing additional molecular markers. All the faculty working on the relevant animal models compare phenotypes with the human studies and search for translatable biomarkers, as noted above. The Buxbaum lab is very active in the integrative looks at these four genes, from biochemistry, to iPSC, to animal models, to clinical findings. Several of these integrative analyses have led to new clinical trials with these rare disorders, including testing IGF-1 and oxytocin in individuals with SHANK3 mutations.