Poster abstracts

Poster number 31 submitted by Shaokun Li

CLP1 R140H mutation disrupts alternative polyadenylation in a neurodegenerative disorder - PCH10

Shaokun Li (Department of Neurosciences, Case Western Reserve University), Ashleigh Schaffer (Department of Molecular and Medical Genetics, Oregon Health & Science University)

Abstract:
CLP1, together with PCF11, consists of mammalian pre-mRNA cleavage complex II (CFIIm). The R140H mutation in CLP1 causes the pontocerebellar Hypoplasia subtype 10 (PCH10), which is a monogenic neurodegenerative disorder. Our prior work found that motor neurons derived from PCH10 patient iPSCs prefer using longer mRNA isoforms compared to control groups, while CLP1KO motor neurons prefer using shorter mRNA isoforms, which made us hypothesize that CLP1R140H possesses gain-of-function properties. To test this hypothesis, we overexpressed CLP1/CLP1R140H in H9 hESCs of motor neuron differentiation process. We found that in motor neurons derived from H9 hESCs: i) both CLP1 and CLP1R140H overexpression contribute to mRNA 3’UTR lengthening in motor neuron progenitors (MNPs). ii) CLP1 but not CLP1R140H overexpression contributes to mRNA 3’UTR shortening in mature motor neurons (MNs) but not MNPs. iii) CLP1 and CLP1R140H overexpression later than MNP stage do not alter gene expression. Based on these observations, we predict that CLP1 overexpression contributes to APA in a cell type specific manner – generating long mRNA isoforms in motor neuron progenitors and short mRNA isoforms in mature motor neurons. CLP1R140H retains its mRNA processing function in MNPs but not in MNs, resulting in motor neuron degeneration in PCH10 patients. Our next questions to address are: i) What are the protein and RNA interactomes of CLP1/CLP1R140H? ii) What are the primary targets of CLP1/CLP1R140H in MNPs and MNs and how do they drive the PCH10 disease progression? Ultimately, this study will not only elucidate the mechanism of pathogenicity of PCH10 disease but also provide profound insight into the mechanism by which the cleavage site is selected from multiple possible elements.

Keywords: alternative polyadenylation, neurodegenerative disorders, motor neurons