Derek Tai, Center for Genomic Medicine, Massachusetts General Hospital
Conference: Society for Neuroscience 2019, Chicago, IL
Abstract Title: Deciphering the molecular basis of neuronal development deficits in the recurrent genomic disorder
Abstract: Reciprocal copy number variant (CNV) of chromosome 16p11.2 (OMIM 611913) and 15q11.2-13.3 [Prader-Willi syndrome (PWS), OMIM 176270] are the most significant recurrent genomic disorders (RGDs) associated with intellectual disability and autism spectrum disorder. The mechanism of non-allelic homologous recombination (NAHR)-mediated CNV formation involves the mispairing of the flanking segmental duplications, which can result in either the loss or gain of the unique genic segment (600 kb in 16p11.2 RGD; 5.3 Mb in PWS RGD). However, the pathogenic mechanism and the functional relevance of individual genes within RGDs and the combined contributions of multiple genes are not known. To interrogate the region against an isogenic background, we developed a novel CRISPR/Cas9 genome engineering approach to efficiently generate reciprocal CNV that mimics NAHR (Tai et al., Nature Neuroscience, 2016). With the comprehensive cell models and the integrated molecular and computational approaches, we attempt to uncover the molecular basis for abnormal neurodevelopment in disease by recapitulating neuropathology of RGD in derivative neuron models. Our preliminary data and several recent studies have strongly suggested KCTD13 might be one of the drivers of 16p11.2 RGD. We then defined cellular phenotypes, transcriptional signatures, and co-expression modules that are shared with 16p11.2 CNV models, and those that are unique to KCTD13 heterozygous deletion (HET). Our transcriptome profilings and analyses showed that genes regulating cytoskeleton (GO:0005856) and translational initiation (GO:0006413) were significantly altered in the neurons with 16p11.2 CNV. Notably, the SLC17A7 and CAMK2A genes regulating glutamate transport and neuronal plasticity are significantly altered in KCTD13 HET and 16p11.2 CNV neurons. Also, the neurite dynamic experiments revealed increased neurite length in KCTD13 HET and the neurons carrying 16p CNV. Interestingly, KCTD13 HET neurons showed increased neuronal activity but the 16p CNV neurons displayed reduced neuronal activity, suggesting that distinct mechanisms may underlie neurite dynamics and neuronal activity. Regarding the ongoing PWS work, we aim to assess the global molecular effects and consequent transcriptional alterations associated with the disease. These studies will allow us to gain more insights into the relationship of gene expression to phenotype and the pathogenic mechanism underlying the disease. With multidimensional assessment, the causal molecular and cellular mechanisms and divergent and convergent transcriptional signatures in RGDs will be further evaluated.