Transcriptional regulation of neural circuit formation in intellectual disabilities

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Project Summary Intellectual disabilities arise from disruption of normal brain function. ARX is a homeobox transcription factor known to regulate brain development and patterning, which has been shown to cause an X-linked form of intellectual disability and other syndromes associated with neurological deficits. Moreover, several mutations have been identified in this gene, and there is a correlation between the class of mutation and the resulting phenotype. Preliminary data shows that mutations in alr-1/ARX in Caenorhabditis elegans result in defects in GABAergic neuronal differentiation, axon overextension, and synaptogenesis. Thus, the central hypothesis is that different classes of alr-1/ARX variants cause specific syndromes by disrupting specific subsets of alr-1/ARX- regulated gene networks, which in turn affects the formation and function of neural circuits. Using the powerful genetics of the nematode C. elegans as a model and discovery system, alr-1/ARX cellular and molecular function will be dissected to gain mechanistic insight into the role of alr-1/ARX in neural circuit formation and the transcriptional regulation of this process. Additionally, how ARX disease-causing mutations disturb these processes and results in abnormal wiring of the nervous system will be explored. The findings will identify novel candidate genes that may be disrupted in patients with intellectual disabilities and more importantly, the regulatory network responsible. Understanding how their disruption leads to the phenotype is necessary to further elucidate other genes responsible for other unknown cases of ID given that these are likely targets or co-regulators of alr-1/ARX. These findings will establish the ground for the translation of the basic science results to vertebrates and eventually to the bedside. The University of Rochester and its Endocrinology division provide a unique collaborative environment of excellence in basic, clinical and translational research, and is invested in the success of early career scientists. The training plan capitalizes on the applicant’s strong research background and long-standing interest neural circuit formation combined with the mentoring of Dr. Portman. He will obtain training in the transcriptomics field, and master cutting-edge technology in cell-sorting, RNA-sequencing and Cut&Tag-sequencing, while being mentored by leaders in the field. Ultimately, the postdoctoral fellowship will allow the fellow to expand his scientific training and create an independent line of investigation needed for transitioning to an independent physician-scientist career.