Roles of Tet2 in meiosis, fertility and reproductive aging
- PDF / 1,430,457 Bytes
- 8 Pages / 595.276 x 785.197 pts Page_size
- 87 Downloads / 188 Views
Protein & Cell
LETTER
Dear Editor, Ten-eleven translocation (Tet) enzymes play important roles in DNA demethylation involved in various biological processes including stem cell pluripotency and differentiation, and tumorigenesis (Dawlaty et al., 2013; Wu and Zhang, 2017). Tet2 deficiency or mutation leads to severe hematopoietic defects or myeloid malignancies in mice (Delhommeau et al., 2009; Ko et al., 2010; Moran-Crusio et al., 2011). Restoration of TET2 blocks aberrant self-renewal and leukemia progression in patients possessing TET2 mutations (Cimmino et al., 2017). DNA methylationbased biomarkers, or “epigenetic clocks”, link developmental and maintenance processes to biological aging (Horvath and Raj, 2018). Interestingly, age-associated TET2 mutations have been found to drive myeloid dysfunction, cancer and cardiovascular disease (review (Ferrone et al., 2020)). Nevertheless, there has been lack of direct evidence demonstrating that Tet2 mutations or deficiency can actually accelerate aging. Reproductive aging particularly in female germline predates the aging of somatic organs in the body. The ovaries play an important role in maintaining the normal function of the female reproductive system and hormone secretion. Ovarian aging is mainly characterized by a sharp decrease in the number of oocytes and follicles as well as declined oocyte quality. Loss of Tet1 causes meiosis defects in fetal ovaries and in adult testis (Huang et al., 2020; Yamaguchi et al., 2012), and reduces oocyte number (Yamaguchi et al., 2012). Here we show that Tet2 plays multiple roles during meiosis and oocyte development. Moreover, Tet2 deficiency does not affect oocyte number, unlike Tet1 (Yamaguchi et al., 2012), but noticeably delays meiotic progression and reduces oocyte quality and mouse fertility, accelerating age-associated infertility. To study whether Tet2 regulates fertility with age, we employed Tet2-deficient mice generated by deleting exon 3 (See methods). Homozygous mutant mice (Tet2−/−) were generated by crossing the heterozygous mice. The primers were designed to detect three different genotypes (wild-type (WT) Tet2+/+, Tet2+/− and Tet2−/−) (Fig. S1A), and the exon 3 deletion in Tet2−/− female ovaries was also validated by qPCR of mRNA expression (Fig. S1B). Probably Tet2 protein © The Author(s) 2020
level is very low in adult ovary, such that Tet2 protein signal could not be detectable. Thus, we confirmed that Tet2 protein was absent in Tet2−/− blastocysts by immunofluorescence (Fig. S1C). Tet2−/− mice were born at normal Mendelian ratio (Fig. S1D). The 5hmC levels were decreased by immunofluorescence in Tet2-deficient oocytes and granulosa cells (Fig. S1E and S1F). Hence, Tet2 knockout decreases the 5hmC level, as expected. Tet2−/− female mice at young, middle-age and old age (specified in the figure legend) after successful mating with young males exhibited reduced fecundity as shown by smaller litter size, compared with age-matched WT females. The litter size reduced by half when the Tet2−/− mice reached at middle-age, an
Data Loading...
