Chromatin Interaction Changes during the iPSC-NPC Model to Facilitate the Study of Biologically Significant Genes Involved in Differentiation

RFX4 is an intrinsic factor for neuronal differentiation through induction of proneural genes POU3F2 and NEUROD1

Proneural genes play a crucial role in neuronal differentiation. However, our understanding of the regulatory mechanisms governing proneural genes during neuronal differentiation remains limited. RFX4, identified as a candidate regulator of proneural genes, has been reported to be associated with the development of neuropsychiatric disorders. To uncover the regulatory relationship, we utilized a combination of multi-omics data, including ATAC-seq, ChIP-seq, Hi-C, and RNA-seq, to identify RFX4 as an upstream regulator of proneural genes. We further validated the role of RFX4 using an in vitro model of neuronal differentiation with RFX4 knock-in and a CRISPR-Cas9 knock-out system. As a result, we found that RFX4 directly interacts with the promoters of POU3F2 and NEUROD1. Transcriptomic analysis revealed a set of genes associated with neuronal development, which are highly implicated in the development of neuropsychiatric disorders, including schizophrenia. Notably, ectopic expression of RFX4 can drive human embryonic stem cells toward a neuronal fate. Our results strongly indicate that RFX4 serves as a direct upstream regulator of proneural genes, a role that is essential for normal neuronal development. Impairments in RFX4 function could potentially be related to the development of various neuropsychiatric disorders. However, understanding the precise mechanisms by which the RFX4 gene influences the onset of neuropsychiatric disorders requires further investigation through human genetic studies.

Rare Does Not Mean Worthless: How Rare Diseases Have Shaped Neurodevelopment Research in the NGS Era

The advent of next-generation sequencing (NGS) is heavily changing both the diagnosis of human conditions and basic biological research. It is now possible to dig deep inside the genome of hundreds of thousands or even millions of people and find both common and rare genomic variants and to perform detailed phenotypic characterizations of both physiological organs and experimental models. Recent years have seen the introduction of multiple techniques using NGS to profile transcription, DNA and chromatin modifications, protein binding, etc., that are now allowing us to profile cells in bulk or even at a single-cell level. Although rare and ultra-rare diseases only affect a few people, each of these diseases represent scholarly cases from which a great deal can be learned about the pathological and physiological function of genes, pathways, and mechanisms. Therefore, for rare diseases, state-of-the-art investigations using NGS have double valence: their genomic cause (new variants) and the characterize the underlining the mechanisms associated with them (discovery of gene function) can be found. In a non-exhaustive manner, this review will outline the main usage of NGS-based techniques for the diagnosis and characterization of neurodevelopmental disorders (NDDs), under whose umbrella many rare and ultra-rare diseases fall.