Mechanism Of Splicing Factor PQBP1 Regulating Striatal Development By Modulating Numb Alternative Splicing

Renpenning syndrome is a kind of X-linked intellectual disability(XLID)caused by mutations in polyglutamine-binding protein 1(PQBP1).The case reports show that more than 86% Renpenning syndrome patients with clinical symptoms of microcephaly,suggesting that PQBP1 mutations cause abnormal brain development.In addition,studies have shown that PQBP1 is widely expressed in brain tissue,suggesting that PQBP1 may be involved in regulating brain development,but the regulatory mechanism is still unclear.When detecting the temporal and spatial expression of PQBP1 in mouse brain tissue,we find that PQBP1 is highly expressed in striatal progenitors during embryonic development,suggesting that PQBP1 may be involved in regulating the development process of the striatum.The striatum is mainly composed of striatal spiny projection neurons(SPNs)originating from the striatal intermediate progenitors(IPs)in the LGE SVZ during the embryonic development.Conditionally deleted Pqbp1 in striatal IPs of the LGE SVZ,we find that deletion of Pqbp1 decreases striatal IPs proliferation and promotes striatal IPs to exit cell cycle in advance and undergoing differentiation,which will result in impaired the striatal IPs pool,decreased striatal SPN neurogenesis during late embryonic development,the striatal area becomes smaller,the mice show the phenotype of microcephaly and abnormal motor function.To explore the molecular mechanism of PQBP1 regulating striatal development,we find that PQBP1 regulating this process through alternative splicing biological event by using immunoprecipitation and mass spectrometry.To further explore the target gene of PQBP1 regulating striatal development,we identify the Numb gene is the target of PQBP1 by using fluorescence activated cell sorting(FACS)and RNA sequencing.We find that PQBP1 promotes Numb pre-mRNA splicing to Numb-9in by directly interacting with Numb pre-mRNA exon 9 in striatal IPs,thereby promoting the self-renewal process.However,deletion of Pqbp1 promotes Numb pre-mRNA splicing to Numb-9ex and promotes the striatal IPs to exit cell cycle in advance and undergoing differentiation.In this study,we find that splicing factor PQBP1 regulates striatal development by balancing the proliferation and differentiation of striatal IPs,and reveal the molecular regulation mechanism,which provides a new theoretical basis for elucidating the pathogenesis of Renpenning syndrome.