Divergent RNA‐binding Proteins, DAZL and VASA, Induce Meiotic Progression in Human Germ Cells Derived in Vitro

Abstract

Our understanding of human germ cell development is limited in large part due to inaccessibility of early human development to molecular genetic analysis. Pluripotent human embryonic stem cells (hESCs) and induced pluripotent stem cells (iPSCs) have been shown to differentiate to cells of all three embryonic germ layers, as well as germ cells in vitro, and thus may provide a model for the study of the genetics and epigenetics of human germline. Here, we examined whether intrinsic germ cell translational, rather than transcriptional, factors might drive germline formation and/or differentiation from human pluripotent stem cells in vitro. We observed that, with overexpression of VASA (DDX4) and/or DAZL (Deleted in Azoospermia Like), both hESCs and iPSCs differentiated to primordial germ cells, and maturation and progression through meiosis was enhanced. These results demonstrate that evolutionarily unrelated and divergent RNA-binding proteins can promote meiotic progression of human-derived germ cells in vitro. These studies describe an in vitro model for exploring specifics of human meiosis, a process that is remarkably susceptible to errors that lead to different infertility-related diseases.

Retinoic Acid Regulates Germ Gene Transcription In Vitro and Spermatogenesis in Testicular Organ Culture

“…This finding is consistent with the reports that vasa is essential for proliferation, differentiation and meiotic progress of germ cells in mouse [66] and human [67]. In mice, it has been reported that RA as well as stem cell factor increases meiotic entry, upregulates expression of meiotic genes stra8 (master regulator of meiosis), dmc1 (early meiotic marker essential for meiotic recombination), bmp6, btg4, dzip1l and phf7, and downregulates expression of stemness genes (pcgf2, pcgf6 and numb) and spermatogonial markers (egr2, pole, ptn, tex16 and zfpm2), which are known to turn off at the onset of meiosis [68].…”

Deleted in Azoospermia-Like Enhances In Vitro Derived Porcine Germ Cell Formation and Meiosis

“…Nevertheless, although we show that somatic cell-derived PGC formation and meiosis are enhanced by the overexpression of DAZL, the efficiency of generating meiotic cells remains very low. Moreover, compared to a study that generated germ cells from human embryonic stem cells overexpressing DAZL [51], the percentage of meiotic cells in our somatic cellderived differentiation system continues to be over one magnitude lower. We speculate that this may be attributed to the possibility that compared to embryonic stem cells, a considerably lower percentage of cells in our somatic stem cell population that have the required potency to enter the germ path, or alternatively, more meiotic key players are missing in our model.…”

“…Future studies aimed at simultaneously introducing multiple factors into our stem cellto-germ cell differentiation system may not only offer an opportunity to understand the key genes and their interactions during germ cell formation and differentiation, but also help to build a more efficient system of generating germ cells in vitro. Interestingly, it was recently reported that overexpression of both VASA and DAZL synergistically increased the percentage of cells positive for the late male germ cell marker ACROSIN that were differentiated from human embryonic stem cells, although their progression to meiosis was not synergistic [51].…”

Generation of male differentiated germ cells from various types of stem cells

“…However, it is unknown about the precise effect of these molecules and how to achieve an efficient differentiation of male gametes from stem cells. In addition, some researchers overexpressed key regulators to regulate the cell lineage decisions to promotes meiosis and the formation of haploid cells in differentiating stem cells (Panula et al 2011, Medrano et al 2012. Nevertheless, the low frequency of haploid cell production suggests that approaches have not yet achieved the best meiotic progression.…”