Proper neurodevelopment requires an intricate series of gene regulatory interactions, mediated by activity of key neural transcription factors. POU3F2, a neural-specific POU-domain transcription factor, has proven critical for the proper distribution of specific neuronal fates, including layer II-III cortical neurons and hypothalamic neurons of the supraoptic and paraventricular nuclei. In humans, heterozygous loss-of-function and missense mutations in POU3F2 have been linked to neurodevelopmental defects. Additionally, POU3F2 has been identified as a candidate risk gene for neuropsychiatric disorders such as bipolar disorder and schizophrenia.
While these studies have underscored the importance of proper POU3F2 activity during neurodevelopment, little is known about its molecular function or downstream effectors. To elucidate the POU3F2-dependent regulatory network, we generated loss-of-function mutations in POU3F2 in two independent human induced pluripotent stem cell (iPSC) lines, which were differentiated into neural progenitor cells (NPCs). RNA-sequencing of POU3F2WT and POU3F2MUT NPCs identified downregulation of Wnt pathway inhibitors as a central hallmark in POU3F2MUT NPCs, validated by a Wnt reporter assay demonstrating increased canonical Wnt responsiveness in POU3F2MUT NPCs.
Further analysis of POU3F2MUT NPCs demonstrated robust downregulation of SOX13, a canonical Wnt pathway inhibitor and putative transcriptional target of POU3F2, across multiple differentiations. From these data, we hypothesize that POU3F2 activates transcription of SOX13, which in turn inhibits the Wnt signaling pathway. We plan to further examine POU3F2-mediated regulation of the Wnt signaling pathway and its role in the etiology of neurodevelopmental disorders in future work, using both iPSC-derived cellular models and mouse models.