Abstract 1708 CTBP1 Mutation Affects Neuronal Stem Cell Migration

In vertebrates, the C-terminal Binding Protein (CtBP) family consists of two highly related paralogs, CtBP1 and CtBP2. The nuclear isoforms of CtPB1 and CtBP2 function as transcriptional corepressors by targeting various chromatin-modifying enzymes to the promoter region and by interacting with DNA-bound repressors. A de novo recurrent heterozygous missense (c.991C > T) mutation in CtBP1 was discovered in patients with neurodevelopmental defects, including hypotonia, ataxia, and tooth enamel defects, and often associated with cerebellar hypoplasia syndrome. The mutation (R342W) maps within the PXDLS-protein interacting domain. From our previous study, transcriptional profiles of early neurons differentiated from normal and patient-derived induced pluripotent stem cell (iPSC) lines showed that several genes downregulated in patient-derived neurons are involved in neurodevelopment, adhesion, and synaptic activity. We derived isogenic cell lines to eliminate genetic variability that exists between patients. To explore the effect of the CTBP1 mutation, we created isogenic wild-type (WT), heterozygous mutated (1E11), and homozygous mutated (1D7) iPSC lines. We differentiated the cell lines into neurons and analyzed their transcriptome data. In cell lines with CTBP1 homozygous and heterozygous mutation, genes that are involved in neurodevelopment are downregulated, such as adhesion molecules involved in cell-cell interaction, axon growth, and signaling pathways that regulate neurodevelopment. Based on transcriptome data, we hypothesized that isogenic cell lines with CTBP1 mutation will have defective adhesion and migration. We used a neurosphere assay to test the hypothesis and measured the cell migration. Neural stem cells (NSCs) were plated on a non-adherent plate and allowed to form a uniform three-dimensional neurosphere for 48 hours. They were then allowed to attach to a Geltrex-coated surface. The distance of cells migrated from the attached spheroid was measured at various time points. Our preliminary data indicates that neuronal stem cell migration is significantly affected in isogenic cell lines with homozygous and heterozygous mutation compared to wild-type. The DeNardo Education and Research Foundation supported LK.