Identification and functional interrogation of neurodevelopmental disease genes at multigene loci

Abstract

The continual discovery of new disease loci through characterization of copy number variants (CNVs) has demonstrated that structural rearrangements play a large role in neurodevelopmental disorders (NDDs). A clear understanding of underlying mechanisms is crucial for NDD treatments. Furthermore, given the reduced penetrance and variable expressivity of these CNVs, creating ways to model this complexity is likewise important for development of effective therapeutics.;In the first part of my thesis, I identified a rare inherited duplication at 19p13.12 in an individual with autism and intellectual disability and in two unaffected family members who are all macrocephalic. Consideration alongside overlapping CNV events in the literature supports a strong relationship between gene dosage at this locus and head size. Using deletion mapping, we narrowed down the critical region to two genes: AKAP8 and AKAP8L. Both are members of the AKAP family, a group already implicated in autism. These findings support the idea that gene dosage at 19p13.12, and AKAP8 and/or AKAP8L in particular, play an important role in modulation of head size and may contribute to NDD risk. Exome sequencing of the case family identified a likely disruptive mutation in TPTE/ PTEN2, a PTEN homologue, which may likewise contribute to both macrocephaly and NDD risk.;In the second part of my thesis, I model the 15g11.2 (BP1-2) deletion, a CNV known to increase risk for epilepsy and schizophrenia, using two cell types. We first examined lymphoblastoid cells from BP1-2 deletion carriers and controls, but found no in differences in multiple cellular and molecular endpoints. We then knocked down CYFIP1, a gene within the BP1-2 locus, in human neural progenitors derived from healthy BP1-2 copy number neutral donors. Transcriptional profiling revealed alteration of cytoskeleton genes, FMRP targets, and postsynaptic density genes in response to CYFIP1 knockdown. Furthermore, schizophrenia and epilepsy genes were overrepresented among dysregulated genes, and the magnitude of these effects differed between lines. Lastly, we showed that phenytoin, an anti-seizure drug, increased levels of CYFIP1 in control NPCs.;Through the strategies described above, we identified and genetically and functionally characterized likely contributory genes within two separate disease-associated loci.