Ethylnitrosourea-induced apoptosis in primordial germ cells of the rat fetus

In vitro responses to known in vivo genotoxic agents in mouse germ cells

Genotoxic compounds have induced DNA damage in male germ cells and have been associated with adverse clinical outcomes including enhanced risks for maternal, paternal and offspring health. DNA strand breaks represent a great threat to the genomic integrity of germ cells. Such integrity is essential to maintain spermatogenesis and prevent reproduction failure. The Comet assay results revealed that the incubation of isolated germ cells with n-ethyl-n-nitrosourea (ENU), 6-mercaptopurine (6-MP) and methyl methanesulphonate (MMS) led to increase in length of Olive tail moment and % tail DNA when compared with the untreated control cells and these effects were concentration-dependent. All compounds were significantly genotoxic in cultured germ cells. Exposure of isolated germ cells to ENU produced the highest concentration-related increase in both DNA damage and gene expression changes in spermatogonia. Spermatocytes were most sensitive to 6-MP, with DNA damage and gene expression changes while spermatids were particularly susceptible to MMS. Real-time PCR results showed that the mRNA level expression of p53 increased and bcl-2 decreased significantly with the increasing ENU, 6-MP and MMS concentrations in spermatogonia, spermatocytes and spermatids respectively for 24 hr. Both are gene targets for DNA damage response and apoptosis. These observations may help explain the cell alterations caused by ENU, 6-MP and MMS in spermatogonia, spermatocytes and spermatids. Taken together, ENU, 6-MP and MMS induced DNA damage and decreased apoptosis associated gene expression in the germ cells in vitro. Environ. Mol. Mutagen. 58:99-107, 2017. © 2017 Wiley Periodicals, Inc.

Postnatal exposure to N-ethyl-N-nitrosurea disrupts the subventricular zone in adult rodents

N-ethyl-N-nitrosurea (ENU), a type of N-nitrous compound (NOC), has been used as inductor for brain tumours due to its mutagenic effect on the rodent embryo. ENU also affected adult neurogenesis when administered during pregnancy. However, no studies have investigated the effect of ENU when exposured during adulthood. For this purpose, three experimental groups of adult mice were injected with ENU at different doses and killed shortly after exposure. When administered in adult mice, ENU did not form brain tumours but led to a disruption of the subventricular zone (SVZ), an adult neurogenic region. Analyses of the samples revealed a reduction in the numbers of neural progenitors compared with control animals, and morphological changes in ependymal cells. A significant decrease in proliferation was tested in vivo with 5-bromo-2-deoxyuridine administration and confirmed in vitro with a neurosphere assay. Cell death, assessed as active-caspase-3 reactivity, was more prominent in treated animals and cell death-related populations increased in parallel. Two additional groups were maintained for 45 and 120 days after five doses of ENU to study the potential regeneration of the SVZ, but only partial recovery was detected. In conclusion, exposure to ENU alters the organization of the SVZ and causes partial exhaustion of the neurogenic niche. The functional repercussion of these changes remains unknown, but exposure to NOCs implies a potential risk that needs further evaluation.

Quantitative trait loci associated with susceptibility to therapy-related acute murine promyelocytic leukemia in hCG-PML/RARA transgenic mice

Therapy-related acute myelogenous leukemia (t-AML) is an important late adverse effect of alkylator chemotherapy. Susceptibility to t-AML has a genetic component, yet specific genetic variants that influence susceptibility are poorly understood. We analyzed an F(2) intercross (n = 282 mice) between mouse strains resistant or susceptible to t-AML induced by the alkylator ethyl-N-nitrosourea (ENU) to identify genes that regulate t-AML susceptibility. Each mouse carried the hCG-PML/RARA transgene, a well-characterized initiator of myeloid leukemia. In the absence of ENU treatment, transgenic F(2) mice developed leukemia with higher incidence (79.4% vs 12.5%) and at earlier time points (108 days vs 234 days) than mice in the resistant background. ENU treatment of F(2) mice further increased incidence (90.4%) and shortened median survival (171 vs 254 days). We genotyped F(2) mice at 384 informative single nucleotide polymorphisms across the genome and performed quantitative trait locus (QTL) analysis. Thirteen QTLs significantly associated with leukemia-free survival, spleen weight, or white blood cell count were identified on 8 chromosomes. These results suggest that susceptibility to ENU-induced leukemia in mice is a complex trait governed by genes at multiple loci. Improved understanding of genetic risk factors should lead to tailored treatment regimens that reduce risk for patients predisposed to t-AML.

Molecular mechanisms of trophoblast survival: From implantation to birth

Fetal development depends upon a coordinated series of events in both the embryo and in the supporting placenta. The initial event in placentation is appropriate lineage allocation of stem cells followed by the formation of a spheroidal trophoblastic shell surrounding the embryo, facilitating implantation into the uterine stroma and exclusion of oxygenated maternal blood. In mammals, cellular proliferation, differentiation, and death accompany early placental development. Programmed cell death is a critical driving force behind organ sculpturing and eliminating abnormal, misplaced, nonfunctional, or harmful cells in the embryo proper, although very little is known about its physiological function during placental development. This review summarizes current knowledge of the cell death patterns and molecular pathways governing the survival of cells within the blastocyst, with a focus on the trophoblast lineage prior to and after implantation. Particular emphasis is given to human placental development in the context of normal and pathological conditions. As molecular pathways in humans are poorly elucidated, we have also included an overview of pertinent genetic animal models displaying defects in trophoblast survival.