| Summary: | 碩士 === 國立臺灣大學 === 解剖學暨細胞生物學研究所 === 105 === The integration of retrotransposons into genomes plays an important role in evolution and make up about half of mammalian genome. Without tight and finely tuned regulation to repress these “jumping genes”, retrotransposons may wreak havoc and disrupt normal gene expression, especially in germ cells. Aberrant derepression of retrotransposons is associated with germ cell developmental defects. Promyelocytic leukemia zinc finger (PLZF), expressed mainly in germ cells in testes, is known to have a crucial role in spermatogenesis through self-renewal and differentiation regulation to prevent the depletion of spermatogonial stem cells (SCCs). In this study, we used Plzflu/lu mutant and wild type mouse to explore the roles of PLZF in modulating retrotransposons in testes.
First, through bioinformatics and RT-qPCR analysis, I saw that PLZF binds to the DNA sequences of repeat elements in cultured SSCs and in 8 dpp testes of Plzflu/lu, retrotransposons, LINE1 and IAP, displayed a deregulation in expression when compared to that of wild type littermates, concluding that PLZF is necessary to regulate retrotransposon in testes. Moreover, based on the preliminary data from our lab, PLZF interacts with MILI and MAEL in 4 weeks SSC enriched THY1+ cells. However, in 8dpp whole testes, I was only able to confirm the interaction between PLZF and MILI. Since MILI plays an important role in piRNA pathways, which include the repression of retrotransposons after epigenetic reprogramming during germ cell development to maintain the integrity of germ cell genome, I hypothesize that PLZF partially modulates retrotransposons through piRNA pathways. However, my small RNA sequencing results from 8 dpp testes of Plzflu/lu and their counterpart wild type littermates did not reveal major differences on the piRNA production, characteristics and specific retrotransposon subfamily associated piRNA candidates.
All in all, we and others demonstrated that PLZF has many levels of modulation in testes, essential for germline maintenance and spermatogenesis, and may modulate transposable elements through transcriptional gene silencing and/or through post-transcriptional gene silencing by affecting retrotransposon mRNA stability. The lack of significant difference in piRNA biogenesis may imply that MILI-PLZF interaction modulates MILI’s function independent of piRNA pathway, beyond transposable element modulation which may further suggest PLZF’s function in translational control in germ cells to repress retrotransposons and potentially other transcripts.
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