Mutations in the zebrafish ortholog of HCFC1 reveal a critical function in neural precursor function

Mutations in the HCFC1 transcriptional co‐factor cause cblX syndrome, an X‐linked disorder characterized by defects in cobalamin metabolism, intractable epilepsy, microcephaly, intellectual disability, movement disorders, and craniofacial abnormalities. Intractable epilepsy and neurological impairment are two of most severe phenotypes associated with cblX syndrome, however we do not understand the cellular and molecular mechanisms underlying these phenotypes in vivo . The human and mouse orthologs of HCFC1 are located on the X‐chromosome and deletion of the murine HCFC1 gene is subject to compensatory mechanisms, which have limited our ability to understand the function of HCFC1 during early brain development. To circumvent the limitations associated with rodent model systems, we created a stable germline mutation in the zebrafish HCFC1 ortholog, hcfc1a , using CRISPR/Cas9 genome editing. We identified three independent germline alleles in the hcfc1a gene, two of which result in a premature stop codon and a third that results in substitution of two amino acids within the kelch protein interaction domain. In vitro evidence suggests that perturbations in HCFC1 expression affect the number and differentiation of neural precursors. Thus, we analyzed the number of neural precursors and post‐mitotic neurons in hcfc1a mutant embryos. Mutation of hcfc1a resulted in an age dependent statistically significant increase in the number of neural precursors in specific brain regions. In addition, cell cycle analyses demonstrated a critical function of hcfc1a in the transition from S‐phase to G2/M phase. Together, our results provide evidence that HCFC1 plays an important role in the production, maintenance, proliferation, and/or differentiation of neural precursors during early vertebrate development. These data suggest a potential mechanism by which mutations in HCFC1 cause neurological deficits. Support or Funding Information Research reported in this poster was supported by the National Institute Of General Medical Science of the National Institutes of Health under the linked Award Numbers RL5GM118969, TL4GM118971, and UL1GM118970. the content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .