DAZL regulates proliferation of human primordial germ cell by direct binding to precursor miRNAs and enhances DICER processing activity

Understanding the molecular and cellular mechanisms of human primordial germ cells (hPGCs) is essential in studying infertility and germ cell tumorigenesis. Many RNA binding proteins (RBPs) and non-coding RNAs are specifically expressed and functional during hPGC developments. However, the roles and regulatory mechanisms of these RBPs and non-coding RNAs, such as microRNAs (miRNAs), in hPGCs remain elusive. In this study, we reported a new regulatory function of DAZL, a germ cellspecific RBP, in miRNA biogenesis and cell proliferation. First, DAZL colocalized with miRNA let-7a in human PGCs and upregulated the levels of over a hundred mature miRNAs, including eight out of nine let-7 family, miR10, and miR199. Purified DAZL directly bound to the loops of precursor miRNAs with sequence specificity of GUU. The binding of DAZL to the precursor miRNA increased the maturation of miRNA by enhancing the cleavage activity of DICER. Furthermore, cell proliferation assay and cell cycle analysis confirmed that DAZL inhibited the proliferation of in vitro PGCs by promoting the maturation of these miRNAs. Evidently, the mature miRNAs upregulated by DAZL silenced cell proliferation regulators including TRIM71. Moreover, DAZL inhibited germline-tumor-cell proliferation and teratoma formation. These results demonstrate that DAZL regulates hPGC proliferation by enhancing miRNA processing. Comparative gene expression profiling analysis of RNA-seq data for WT PGCLCs and oeDAZL PGCLCs and expression profiling analysis of miRNA-seq for WT PGCLCs and its derivatives (shDAZL_4,shDAZL_6).