The Mechanism Of PUM Family In Mouse Spermiogenesis And The Establishment Of Pum2 New Mouse Model

During spermiogenesis,the histone-based chromatin will be replaced into highly condensed protamine-based chromatin.However,little is known on the regulation of this process.Here,by studying the function of PUM family in spermatogenesis,we find a posttranscriptional mechanism may be involved in the chromatin structure transformation.Firstly,using purified mouse male germ cells,we confirmed that both PUM1 and PUM2 were expressed in spermatogonia and spermatocytes.Next,we found that male miee lacking both PUM1 and PUM2 in meiotic phase are infertile.And the double knockout(DKO)mice produced sperm not only with no motility,but also with abnormal morphology(about 80%).Transmission electron microscopy(TEM)revealed that round spermatids(RS)in PUM femily knockout(KO)mice underwent asymmetrical acrosome biogenesis and abnormal chromatin remodeling,producing double nuclei cells during spermiogenesis.Protomic analyses showed that HI linker histone variant,H1F0 is highly increased in RS of PUM family KO.Both PUM1 and PUM2 were associated with H1f0 mRNA by RNA Immunoprecipitation(RIP).Further,using dual-luciferase reporter assay system and polysome profile analysis,we found that PUM family suppressed the translation of H1f0 via binding the Pumilio binding element(PBE)in H1f0 3'UTR.Hence PUM family played an essential role in post-meotic spermatid differentiation by regulation of HI linker histone variant,H1f0 mRNA translation.In addition,our lab previously reported Pum2XE772 mouse model produced fusion PUM2 protein,but it remained a concern that the mutant protein might have residual activity.Therefore,we established new Pu12 mouse model(Pum2E67 founder mouse),and confirmed that PWT12E67/E67 is a complete loss of function model.Meantime,we found that Pum2 is required for mouse growth and male fertility but dispensable for female fertility and male gern cell apoptosis.Finally,we built various PUM fenily mouse model for systematic study the biological function of PUM family in the future.