Bcl-x and Bax regulate mouse primordial germ cell survival and apoptosis during embryogenesis.
ABSTRACT Restricted germ cell loss through apoptosis is initiated in the fetal gonad around embryonic day 13.5 (E13.5) as part of normal germ cell development. The mechanism of this germ cell attrition is unknown. We show that Bcl-x plays a crucial role in maintaining the survival of mouse germ cells during gonadogenesis. A bcl-x hypomorphic mouse was generated through the introduction of a neomycin (neo) gene into the promoter of the bcl-x gene by homologous recombination. Mice that contained two copies of the hypomorphic allele had severe reproductive defects attributed to compromised germ cell development. Males with two mutant alleles lacked spermatogonia and were sterile; females showed a severely reduced population of primordial and primary follicles and exhibited greatly impaired fertility. Primordial germ cells (PGCs) in bcl-x hypomorph mice migrated to the genital ridge by E12.5 but were depleted by E15.5, a time when Bcl-x and Bax were present. Two additional bcl-x transcripts were identified in fetal germ cells more than 300 bp upstream of previously reported start sites. Insertion of a neo cassette led to a down-regulation of the bcl-x gene at E12.5 in the hypomorph. Bax was detected by immunohistochemistry in germ cells from bcl-x hypomorph and control testes at E12.5 and E13.5. Bcl-x function was restored, and animals of both genders were fertile after removal of the neo selection cassette using Cre-mediated recombination. Alternatively, the loss of Bcl-x function in the hypomorph was corrected by the deletion of both copies of the bax gene, resulting in a restoration of germ cell survival. These findings demonstrate that the balance of Bcl-x and Bax control PGC survival and apoptosis.
SourceAvailable from: Paul J. Turek[Show abstract] [Hide abstract]
ABSTRACT: Historically, spontaneous deletions and insertions have provided means to probe germline developmental genetics in Drosophila, mouse and other species. Here, induced pluripotent stem cell (iPSC) lines were derived from infertile men with deletions that encompass three Y chromosome azoospermia factor (AZF) regions and are associated with production of few or no sperm but normal somatic development. AZF-deleted iPSC lines were compromised in germ cell development in vitro. Undifferentiated iPSCs transplanted directly into murine seminiferous tubules differentiated extensively to germ-cell-like cells (GCLCs) that localized near the basement membrane, demonstrated morphology indistinguishable from fetal germ cells, and expressed germ-cell-specific proteins diagnostic of primordial germ cells. Alternatively, all iPSCs that exited tubules formed primitive tumors. iPSCs with AZF deletions produced significantly fewer GCLCs in vivo with distinct defects in gene expression. Findings indicate that xenotransplantation of human iPSCs directs germ cell differentiation in a manner dependent on donor genetic status.Cell Reports 04/2014; DOI:10.1016/j.celrep.2014.03.067 · 7.21 Impact Factor
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ABSTRACT: Since the cloning of the bcl-2 gene in 1985, considerable progress has been made in elucidating the function of Bcl-2 and related proteins in controlling apoptosis. Although much of this work initially relied on the ectopic expression of bcl-2 gene family members in cell lines in vitro, a number of genetically manipulated mice have been generated to better understand the in vivo significance of specific family members to organ development and homeostasis. Of the many tissues that exhibit apoptosis at some point during fetal or postnatal life, the female gonads arguably possess one of the highest and most protracted incidences of apoptosis, associated with development and maturation of the germ line. Moreover, female germ cells (oocytes) are, for as-yet poorly understood reasons, extremely vulnerable to a host of pathological insults, such as anti-cancer therapies, that ultimately cause premature ovarian failure and infertility due to accelerated oocyte death. Accordingly, efforts to understand the occurrence and regulation of apoptosis in the ovary are of considerable importance from both biological and clinical perspectives. This review will highlight what is known of apoptosis in the female gonads, and the role that Bcl-2 family members play in regulating this process.Biochimica et Biophysica Acta (BBA) - Molecular Cell Research 03/2004; 1644(2-3):205-210. DOI:10.1016/S0167-4889(03)00185-X · 5.30 Impact Factor
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ABSTRACT: Maternal malnutrition during pregnancy may give rise to female offspring with disrupted ovary functions in adult age. Neonatal ovary development predisposes adult ovary function, yet the effect of maternal nutrition on the neonatal ovary has not been described. Therefore, here we show the impact of maternal protein restriction on the expression of folliculogenic and steroidogenic genes, their regulatory microRNAs and promoter DNA methylation in the ovary of neonatal piglets. Sows were fed either standard-protein (SP, 15% crude protein) or low-protein (LP, 7.5% crude protein) diets throughout gestation. Female piglets born to LP sows showed significantly decreased ovary weight relative to body weight (p<0.05) at birth, which was accompanied with an increased serum estradiol level (p<0.05). The LP piglets demonstrated higher ratio of bcl-2 associated X protein/B cell lymphoma/leukemia-2 mRNA (p<0.01), which was associated with up-regulated mRNA expression of bone morphogenic protein 4 (BMP4) (p<0.05) and proliferating cell nuclear antigen (PCNA) (p<0.05). The steroidogenic gene, cytochrome P450 aromatase (CYP19A1) was significantly down-regulated (p<0.05) in LP piglets. The alterations in ovarian gene expression were associated with a significant down-regulation of follicle-stimulating hormone receptor mRNA expression (p<0.05) in LP piglets. Moreover, three microRNAs, including miR-423-5p targeting both CYP19A1 and PCNA, miR-378 targeting CYP19A1 and miR-210 targeting BMP4, were significantly down-regulated (p<0.05) in the ovary of LP piglets. These results suggest that microRNAs are involved in mediating the effect of maternal protein restriction on ovarian function through regulating the expression of folliculogenic and steroidogenic genes in newborn piglets.Asian Australasian Journal of Animal Sciences 12/2014; 27(12):1695-704. DOI:10.5713/ajas.2014.14335 · 0.56 Impact Factor