Kristen BrennandAssociate Professor, Department of Genetics and Genomic Sciences, Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai

Presentation Title: Using Stem Cells to Explore the Genetics Underlying Neuropsychiatric Disease

Schizophrenia (SZ) is a debilitating psychiatric disorder for which the complex genetic mechanisms underlying the disease state remain unclear. Whereas highly penetrant variants have proven well-suited to human induced pluripotent stem cell (hiPSC)-based models, the power of hiPSC-based studies to resolve the much smaller effects of common variants within the size of cohorts that can be realistically assembled remains uncertain. Overall, we consider the successes and limitations in applying hiPSC-based models to study the impact of rare and common variants in SZ risk. First, we evaluated the impact of patient-specific NRXN1+/- deletions in hiPSC-neurons, observing greater than two-fold reduction of half of the wildtype NRXN1α isoforms and detecting dozens of novel isoforms expressed from the mutant allele; reduced neuronal activity in patient hiPSC-neurons was ameliorated by overexpression of individual control isoforms in a genotype-dependent manner, whereas individual mutant isoforms decreased neuronal activity levels in control hiPSC-neurons. Second, by integrating CRISPR-mediated gene editing, activation and repression technologies to study one putative causal SZ SNP (FURIN rs4702) and four top-ranked SZ-eQTL genes (FURIN, SNAP91, TSNARE1, CLCN3), our hiPSC-based neuronal platform resolved uncovered an unexpected synergistic effect between SZ-eQTL genes that converges on synaptic function and links the rare and common variant genes implicated in psychiatric disease risk, one which may represent a generalizable phenomenon occurring more widely in complex genetic disorders.

We predict a growing convergence between hiPSC and post-mortem studies as both approaches expand to larger cohort sizes. We demonstrate a systematic and scalable strategy to interpret and evaluate the growing number of SZ-associated variants and genes across neural cell types and genetic backgrounds. Altogether, our objective is to dissect the genetic origins of SZ while developing a precision medicine approach to screen for novel therapeutics with which to prevent or reverse disease course.

David R. Hampson, Ph.D.

University of Toronto, Dept. of Pharmaceutical Sciences, University of Toronto, Dept. of Pharmaceutical Sciences

Title: Developing Adeno-associated Viruses for Treating Fragile X Syndrome and Dravet Syndrome

Fragile X Syndrome is caused by an expanded repeat in the FMR1 gene.  It is one of the most common known genetic causes of autism and cognitive impairment.  Dravet Syndrome, also known as Severe Myoclonic Epilepsy of Infancy, is a genetic disorder characterized by sudden unexpected death in epilepsy (SUDEP), febrile seizures, and autism-like behaviors.  Most cases of Dravet Syndrome are caused by loss-of-function mutations in the SCN1A gene encoding a voltage-gated sodium channel that mediates action potentials in some neurons.  Both of these genetic disorders are in need of more effective treatments.

 Our laboratory is working towards developing viral vector-mediated gene therapy treatments for these conditions.  This work entails the use of adeno-associated viral (AAV) vectors and mouse and rat animal models.  A major advantage of viral vectors is the ability to selectively target recombinant proteins to specific brain cell populations by using cell-type specific gene promotors or enhancers.  For example, successful targeting of inhibitory neurons releasing GABA could be useful in Dravet Syndrome.  Increased cell-type specificity reduces unwanted expression in off-target cells, minimizing the chance of overexpression, liver toxicity and immune responses.  Another advantage is long-term protein expression (months to years) after a single injection.  Our initial approaches to AAV gene therapy for Fragile X and Dravet Syndrome demonstrated partial phenotypic correction; current work in our lab is capitalizing on our experience with both AAV vectors and with the mouse and rat animal models, with the goal of moving the ball forward towards the development of more effective vectors and treatment strategies.

Alysson R. Muotri, Ph.D.

Professor, Director of the Stem Cell Program, Institute for Genomic Medicine, University of San Diego

Presentation Title: Development of Oscillatory Waves on Cortical Organoids for Developmental and Evolutionary Studies

Structural and transcriptional changes during early brain maturation follow fixed developmental programs defined by genetics. However, whether this is true for functional network activity remains unknown, primarily due to experimental inaccessibility of the initial stages of the living human brain. We developed cortical organoids that spontaneously display periodic and regular oscillatory network events that are dependent on glutamatergic and GABAergic signaling. These nested oscillations exhibit cross-frequency coupling, proposed to coordinate neuronal computation and communication. As evidence of potential network maturation, oscillatory activity subsequently transitioned to more spatiotemporally irregular patterns, capturing features observed in preterm human electroencephalography (EEG). These results show that the development of structured network activity in the human neocortex may follow stable genetic programming, even in the absence of external or subcortical inputs. Our approach provides novel opportunities for investigating and manipulating the role of network activity in the developing human cortex. Applications for neurodevelopmental disorders and brain evolution will be discussed.

Matthew Porteus, M.D., Ph.D.

Matthew Porteus, M.D., Ph.D. Professor, Stanford University

Title: Engineering Stem Cells by Genome Editing to Treat Neurodegenerative Diseases

Genome editing provides a precise method to change the nucleotide sequence of a cell. It can be used to create mutations in specific genes, change single nucleotide variants or triplet repeats in specific genes, or add new genes to cells, including stem cells.  Each of these approaches could be used to create safer and more effective cell based therapies for this broad class of diseases. My research program has focused primarily on combining genome editing with the principles of synthetic biology to create safer and possibly effective therapies for neurodegenerative diseases. This includes creating novel safety switches to allow control of cell based therapies and engineering cells to secrete therapeutic proteins to compensate for missing proteins in other cells or to accelerate regeneration in damaged tissues.