Zhang, j. | bioRxiv Science

bioRxiv2020

DNA Methylation Reprogramming during Sex Determination and Transition in Zebrafish

It is a mystery about sex determination and sexual plasticity in species without sex chromosomes. DNA methylation is a prevalent epigenetic modification in vertebrates, which has been shown to involve in the regulation of gene expression and embryo development. However, it remains unclear about how DNA methylation regulates sexual development. To elucidate it, we used zebrafish to investigate DNA methylation reprogramming during juvenile germ cell development and adult female-to-male sex transition. We revealed that primordial germ cells (PGCs) undergo significant DNA methylation reprogramming during germline development and set to an oocyte/ovary-like pattern at 9 days post fertilization (9 dpf). When blocking DNMTs activity in juveniles after 9 dpf, the zebrafish preferably develops into females. We also show that Tet3 involves in PGC development. Notably, we find that DNA methylome reprogramming during adult zebrafish sex transition is similar to the reprogramming during the sex differentiation from 9 dpf PGCs to sperm. Furthermore, inhibiting DNMTs activity can prevent the female-to-male sex transition, suggesting that methylation reprogramming is required for zebrafish sex transition. In summary, DNA methylation plays important roles in zebrafish germline development and sexual plasticity.

developmental biology↗

bioRxiv2020

The effects of human umbilical cord mesenchymal stem cell transplantation on female fertility preservation in mice

Female fertility is the capacity to produce oocytes and achieve fertilization and pregnancy, and these outcomes are impaired by age, diseases, environment and social pressure. However, there is no effective therapy that preserves female reproductive ability. Mesenchymal stromal cells (MSCs) can exhibit multidirectional differentiation potential, and they have gained great attention as a tool for preserving female fertility. Therefore, this study uses human umbilical cords-MSCs (Huc-MSCs) to preserve and restore fertility in aging female mice and chemotherapy-damaged mice through the rescue of ovarian function and the reconstruction of the fallopian tubes and uterus. In our study, 2 mouse models were generated: aging mice (37 weeks old) and chemotherapy-damaged mice. Then, we injected Huc-MSCs into mice through the tail vein. After treatment, the effect of MSCs on the ovary, fallopian tubes and uterus was evaluated by analyzing gonadal hormone levels and by performing morphological analysis and statistical analysis. The levels of E2 and FSH exhibited a significant recovery after HUC-MSC transplantation both in aging mice and mice treated with chemotherapy. Huc-MSC treatment also increased the numbers of primordial, developing and preovulatory follicles in the ovaries of mice. Meanwhile, MSCs have been shown to rescue the morphology of the fallopian tubes and uterus through mechanisms such as regenerating the cilia in fallopian tubes and reforming glands and chorionic villi in the uterus. Therefore, it is suggested that Huc-MSCs may represent an effective potential treatment for preserving female fertility through recovery from chemotherapy damage and rescuing female reproductive organs from the effects of aging.

cell biology↗