Investigating the RNA-regulatory activities of the RNA exosome during human motor neuron differentiation

The National Institute of Neurological Disorders and Stroke awarded the University of Southern California $181,891 on January 1, 2026, under the Extramural Research Programs in the Neurosciences and Neurological Disorders program (CFDA 93.853) to investigate the RNA-regulatory activities of the RNA exosome during human motor neuron differentiation.

The research examines how the RNA exosome, a post-transcriptional ribonuclease complex, regulates gene expression during stem cell differentiation into motor neurons. Recessive mutations in RNA exosome subunit genes disproportionately affect neuronal tissues and cause severe neurodevelopmental disorders including pontocerebellar hypoplasia type 1B, characterized by spinal motor neuron defects. The project uses human induced pluripotent stem cells to investigate how RNA exosome function modulates the transcriptome and maintains pluripotent potential in stem cell and progenitor populations, with particular focus on motor neuron differentiation and the unique susceptibility of spinal motor neurons to RNA exosome-mediated post-transcriptional regulation defects.

Work is performed at the University of Southern California in Los Angeles, California, with a period of performance from January 1, 2026, through June 30, 2028. The assistance type is a Project Grant, which supports extramural research exploring fundamental structure and function of the brain and nervous system to reduce the burden of neurological disease.

Abstract

Accurate stem cell differentiation requires precise gene regulation at both the transcriptional and post- transcriptional levels. While the transcriptional activation networks governing cellular differentiation are well characterized, the mechanisms by which post-transcriptional control of gene expression alters the transcriptome to confer cellular identity remain poorly understood. The RNA exosome, an essential and ubiquitous post- transcriptional ribonuclease complex, plays a significant role in cellular differentiation by modulating steady-state level of RNA to maintain the pluripotent potential of stem cell and progenitor populations. Depletion of a single RNA exosome subunit results in precocious differentiation in several cell types, and deletion of any subunit is embryonically lethal. Although the RNA exosome is conserved from yeast to humans and plays essential roles in all cells, recessive mutations in RNA exosome subunit genes disproportionately affect neuronal tissues and give rise to severe neurodevelopmental disorders (ndds). For instance, mutations in the EXOSC3 gene, encoding a structural cap subunit of the RNA exosome, cause pontocerebellar hypoplasia type 1B (PCH1B), a prenatal onset NDD associated with severe spinal motor neuron defects that emerge during embryonic development. Similarly, a mutation in the EXOSC4 gene, which encodes a core subunit of the RNA exosome, was recently linked to a distinct NDD with a comparable spinal motor neuropathy phenotype. These findings suggest that spinal motor neurons are uniquely susceptible to RNA exosome-mediated post-transcriptional regulation defects. However, the RNA exosome has not been studied in human neurons or during neuronal differentiation. To investigate the function of the RNA exosome during neuronal differentiation, i will utilize human induced pluripotent stem cells (hipscs), engineered by my lab via crispr technology, to model RNA exosome- linked motor neuron diseases, including severe PCH1B (EXOSC3-G31A), mild PCH1B (EXOSC3-G191C), and a novel NDD linked to a mutation in EXOSC4 (EXOSC4-L187P). To study the RNA exosome in a disease- relevant context, i will investigate the impact of pathogenic EXOSC3/4 mutations on human spinal motor neuron differentiation using a 2D cell culture method. I hypothesize that disease-linked mutations in EXOSC3/4 alter the function of the RNA exosome during motor neuron differentiation, leading to an accumulation of pathogenic RNA species that cause spinal motor neuropathy. This research will provide a comprehensive analysis of how pathogenic mutations in RNA exosome subunit genes impact post-transcriptional regulation during human neuronal differentiation and provide insight into pathological mechanisms underlying RNA-mediated motor neuropathy.