Shiny Titus

Impairment of BRCA1-Related DNA Double-Strand Break Repair Leads to Ovarian Aging in Mice and Humans

DNA double-strand break repair has a central role in oocyte aging. Preserving Fertility Breeds Flexibility Last month, the U.K. Office for National Statistics reported that, in 2010, ~48% of infants were born to mothers 30 years and older, a level not seen since 1946—just after the end of World War II. Delaying childbearing can allow women flexibility with respect to career options. But unlike many somatic tissues, the female germline ages early, with reproductive capacity beginning to diminish after young adulthood. Attempts to stem oocyte aging and preserve fertility will depend on finely characterizing the molecular mechanisms behind the aging process in the female reproductive system. Now, Titus et al. provide evidence for a new mechanism to explain age-related oocyte dysfunction. The authors showed that double-stranded breaks (DSBs) in DNA—which are essential for normal development—accumulate with age and contribute to reproductive aging in mice and women. In single mouse and human oocytes, the expression of DSB repair genes BRCA1, MRE11, RAD51, and ATM declined with age. Thus DSBs likely collect in the oocyte genome because of age-related missteps in DSB repair, which stimulate apoptosis and diminishes ovarian reserve. Indeed, in Brca1-deficient mice, numbers of primordial follicles—immature primary oocytes—were decreased, DSBs were increased, and reproductive capacity was impaired relative to wild-type mice. Using RNA interference in mouse oocytes, the authors showed that inhibition of Brca1, MRE11, RAD51, and, in turn, ATM expression increased DSBs and reduced oocyte survival. The authors then measured serum concentrations of anti-Müllerian hormone—a measure of fertility—in young women with germline BRCA1 mutations versus controls and showed that ovarian reserve was compromised in the latter group. Together, these findings show that the efficiency of DNA DSB repair is a crucial determinant of oocyte loss. The discovery of therapies that target this pathway might help to enhance the duration of ovarian function. The underlying mechanism behind age-induced wastage of the human ovarian follicle reserve is unknown. We identify impaired ATM (ataxia-telangiectasia mutated)–mediated DNA double-strand break (DSB) repair as a cause of aging in mouse and human oocytes. We show that DSBs accumulate in primordial follicles with age. In parallel, expression of key DNA DSB repair genes BRCA1, MRE11, Rad51, and ATM, but not BRCA2, declines in single mouse and human oocytes. In Brca1-deficient mice, reproductive capacity was impaired, primordial follicle counts were lower, and DSBs were increased in remaining follicles with age relative to wild-type mice. Furthermore, oocyte-specific knockdown of Brca1, MRE11, Rad51, and ATM expression increased DSBs and reduced survival, whereas Brca1 overexpression enhanced both parameters. Likewise, ovarian reserve was impaired in young women with germline BRCA1 mutations compared to controls as determined by serum concentrations of anti-Müllerian hormone. These data implicate DNA DSB repair efficiency as an important determinant of oocyte aging in women.

Profiling of E-cadherin, β-catenin and Ca2+ in embryo–uterine interactions at implantation

Establishment of early pregnancy is promoted by a complex network of signalling molecules that mediate cell‐to‐cell and cell‐to‐extracellular matrix communications between the receptive endometrium and the invasive trophectoderm. In this study, we have attempted to evaluate the expression profiles of cadherin and catenin during embryo implantation in the mouse. Western blotting studies along with immunocytochemical analysis revealed that E‐cadherin is expressed rather ubiquitously in the uterine epithelial cells, distinct enrichment is observed on the apical membrane in the endometrium of peri‐implantation uterus specifically at the implantation sites and not at the inter‐implanation sites. β‐Catenin also is upregulated and is specifically restricted to apical membrane of epithelial cells of implantation sites. Progesterone induced expression of E‐cadherin and 17β‐estradiol regulated the expression of catenin in implantation‐delayed uteri. Interestingly, estradiol imparted negative modulation on cadherin expression when co‐administered with progesterone. On the contrary, trophoblast exhibits a striking down regulation of cadherin, catenin and Ca2+ at peri implanting stage. These observations suggest that the trophoblasts exhibited an invasive phenotype while the endometrial epithelium displayed an adhesive phenotype during the window of implantation. Thus, embryo implantation presents an instance where two interacting surfaces showed mutually complementing interaction phenotypes.

BRCA Mutations, DNA Repair Deficiency and Ovarian Aging

ABSTRACT Oocyte aging has a significant impact on reproductive outcomes both quantitatively and qualitatively. However, the molecular mechanisms underlying the age-related decline in reproductive success have not been fully addressed. BRCA is known to be involved in homologous DNA recombination and plays an essential role in double-strand DNA break repair. Given the growing body of laboratory and clinical evidence, we performed a systematic review on the current understanding of the role of DNA repair in human reproduction. We find that BRCA mutations negatively affect ovarian reserve based on convincing evidence from in vitro and in vivo results and prospective studies. Because decline in the function of the intact gene occurs at an earlier age, women with BRCA1 mutations exhibit accelerated ovarian aging, unlike those with BRCA2 mutations. However, because of the still robust function of the intact allele in younger women and because of the masking of most severe cases by prophylactic oophorectomy or cancer, it is less likely one would see an effect of BRCA mutations on fertility until later in reproductive age. The impact of BRCA2 mutations on reproductive function may be less visible because of the delayed decline in the function of normal BRCA2 allele. BRCA1 function and ataxia-telangiectasia-mutated (ATM)-mediated DNA repair may also be important in the pathogenesis of age-induced increase in aneuploidy. BRCA1 is required for meiotic spindle assembly, and cohesion function between sister chromatids is also regulated by ATM family member proteins. Taken together, these findings strongly suggest the implication of BRCA and DNA repair malfunction in ovarian aging.

Age-Related Decline in DNA Repair Function Explains Diminished Ovarian Reserve, Earlier Menopause, and Possible Oocyte Vulnerability to Chemotherapy in Women With BRCA Mutations

United States are projected to increase by 27% based on population changes alone; if the cost of the initial and terminal years of care increase by 2% annually, this estimate increases to 39%. There are growing concerns among many—ranging from patients and their families to providers to payers and to policymakers—regarding these trends, their sustainability, and their ramifications. The high cost of newer anticancer drugs is certainly a contributor, but there are many other cost drivers as well. To effectively and durably address these cost issues will require attention to many factors and a comprehensive approach. Battley et al provide suggestions that offer potential costsaving opportunities. These savings may not require an actual decrease in the drug unit price. That being said, the spirit of their comments clearly highlights the need for a more value-based system in determining the cost of cancer drugs, as noted in the article by Kantarjian et al and the accompanying editorial. In addition, we congratulate Battley et al as oncologists looking to be part of the solution, the importance of which was emphasized in the editorial, and we encourage other oncologists to do the same.

STAT3 and MCL-1 associate to cause a mesenchymal epithelial transition

ABSTRACT Embryo implantation is effected by a myriad of signaling cascades acting on the embryo–endometrium axis. Here we show, by using MALDI TOF analysis, far-western analysis and colocalization and co-transfection studies, that STAT3 and MCL-1 are interacting partners during embryo implantation. We show in vitro that the interaction between the two endogenous proteins is strongly regulated by estrogen and progesterone. Implantation, pregnancy and embryogenesis are distinct from any other process in the body, with extensive, but controlled, proliferation, cell migration, apoptosis, cell invasion and differentiation. Cellular plasticity is vital during the early stages of development for morphogenesis and organ homeostasis, effecting the epithelial to mesenchymal transition (EMT) and, the reverse process, mesenchymal to epithelial transition (MET). STAT3 functionally associates with MCL-1 in the mammalian breast cancer cell line MCF7 that overexpresses STAT3 and MCL-1, which leads to an increased rate of apoptosis and decreased cellular invasion, disrupting the EMT. Association of MCL-1 with STAT3 modulates the normal, anti-apoptotic, activity of MCL-1, resulting in pro-apoptotic effects. Studying the impact of the association of STAT3 with MCL-1 on MET could lead to an enhanced understanding of pregnancy and infertility, and also metastatic tumors.

Murine uterine decidualization is a novel function of autoimmune regulator-beyond immune tolerance.

Autoimmune polyendocrinopathy, candidiasis, and ectodermal dystrophy (APECED, APS‐1) patients characterized by Aire (autoimmune regulator) mutations and Aire homozygous knockouts (Aire−/−) exhibit infertility. It is not clear as to what contributes to infertility in the above.

Ovarian Aging in Women With BRCA Germline Mutations

Context Recent clinical and laboratory studies suggested that women with BRCA mutations have lower ovarian reserve and their primordial follicle oocytes may be more prone to DNA damage; however, direct proof is lacking. Objective To determine whether women with germline BRCA mutations have reduced primordial follicle reserve and increased oocyte DNA damage. Design A comparative laboratory study of ovarian tissue obtained from unaffected BRCA mutation carriers (BMCs) vs age-matched organ donor cadavers. Setting Two academic centers. Patients or Other Participants Of the 230 ovarian specimens from BMCs, 18 met the study inclusion criteria. Healthy ovaries from 12 organ donor cadavers served as controls. Intervention Histology and immunohistochemical analysis on paraffin-embedded ovarian sections. Main Outcome Measure(s) Primordial follicle density and the percentage of DNA double-strand break (DSB)-positive primordial follicle oocytes. Results Ovaries from BMCs had significantly lower primordial follicle densities than those of controls (11.2 ± 2.0 vs 44.2 ± 6.2 follicles/mm3; P = 0.0002). BRCA mutations were associated with increased DNA DSBs in primordial follicle oocytes (62% ± 5.2% vs 36% ± 3.4%; P = 0.0005). In subgroup analyses, both BRCA1 and BRCA2 mutations were associated with lower primordial follicle density (P = 0.0001 and 0.0030, respectively), and BRCA1 mutations were associated with higher DNA DSBs (P = 0.0003) than controls. The rates of follicle decline (R2 = 0.74; P = 0.0001) and DNA DSB accumulation (R2 = 0.70; P = 0.0001) appeared to be accelerated, particularly in primordial follicle oocytes of BMCs over age 30 years. Conclusions We provide direct evidence of diminished ovarian reserve as well as accelerated primordial follicle loss and oocyte DNA damage in women with BRCA mutations. These findings may further our understanding of ovarian aging, and be useful when counseling BMCs.

Impaired DNA Repair as a Mechanism for Oocyte Aging: Is It Epigenetically Determined?

DNA damage is one of the most common insults that challenge all cells, and more so in resting cell-like oocytes. Increased DNA damage in aged oocyte has been shown to negatively impact the reproductive outcomes. The underlying molecular mechanism is still not completely comprehended, but based on the literature, this decline in the aging oocyte is attributed to impaired DNA repair and epigenetic modifications of these genes with increasing age. In this review, we discuss these molecular alterations and the epigenetic modifications in the DNA double strand break repair gene expressions as a mechanism of oocyte aging.