Paternal cyclophosphamide treatment causes postimplantation loss via inner cell mass-specific cell death

Paternal exposure to cyclophosphamide dysregulates the gene activation program in rat preimplantation embryos

Although there has been progress in determining the mechanisms by which maternal toxicant exposure affects progeny, there is little information on the actions of drugs administered to the father. We investigated the effects of pre-conceptional paternal exposure to cyclophosphamide, an anti-cancer agent, on embryonic gene activation in the rat. The male pronucleus was formed earlier in embryos sired by cyclophosphamide-treated male rats than in those sired by controls; early male pronucleus formation was followed by alterations in the gene activation program. BrUTP incorporation into RNA and Sp1 transcription factor immunostaining were increased and spread over both cytoplasmic and nuclear compartments in 2-cell embryos sired by cyclophosphamide-treated males compared to controls. Total RNA synthesis was constant in 1-8 cell embryos sired by drug-treated fathers, while in control embryos RNA synthesis increased four-fold to peak at the 4-cell stage. In 2-cell embryos sired by drug-treated males, the relative abundance of candidate imprinted genes was elevated significantly above control; a peak in the expression of these genes was not observed until the 8-cell stage in control embryos. Thus, paternal drug exposure temporally and spatially dysregulated rat zygotic gene activation, altering the developmental clock.

Lead: male-mediated effects on reproduction and development in the rat

The present study was designed to determine the effect of relatively low levels of lead acetate (25 and 250 ppm) exposure on fertility and offspring viability in male Sprague-Dawley rats. Protein synthesis in 2-cell embryos was monitored by [35S] methionine labeling and two-dimensional SDS gel electrophoresis. Fertility was reduced in males with blood lead levels in the range 27-60 microg/dL. Lead was found to affect initial genomic expression in embryos fathered by male rats with blood lead levels as low as 15-23 microg/dL. Dose-dependent increases were seen in an unidentified set of proteins with a relative molecular weight of approximately 70 kDa (Mr). These results indicate that male-mediated effects of lead may be observed in the 2-cell embryo. The alteration observed in embryonic gene expression with paternal lead exposure may be useful for studying the role of the paternal contribution to the activation of the embryonic genome and protein synthesis in the early embryo.

Paternal exposures: impact on reproductive and developmental outcome. An overview

Experimental and epidemiologic investigations document the adverse consequences of an array of paternal exposures on the development of subsequent offspring. Male-mediated abnormalities have been reported after exposure to therapeutic and recreational drugs, to chemicals in the workplace and environment and to ionizing radiation. The impact on progeny outcome includes: an increase in congenital malformations, spontaneous abortions, fetal resorptions; low birth weight; increase in childhood cancers; developmental, neurobehavioral, neuroendocrine, neurochemical abnormalities; effects in F2 generation progeny. Fertility is often unaffected. The comparative influence of genetic, epigenetic and nongenetic mechanisms in the etiology of paternally-mediated adverse outcomes is unknown. There is no a priori reason to assume that male-mediated effects are limited to the agents studied to date. The broad spectrum of alterations recorded after exposure to a variety of unrelated agents suggests the need for a more focused effort and multidisciplinary exploration of the potential impact of the male parent on reproductive outcome.

Gene expression in pre-implantation mammalian embryos

The pre-implantation mammalian embryo is initially under the control of maternal informational macromolecules that are accumulated during oogenesis. Subsequently, the genetic program of development becomes dependent upon new transcription derived from activation of the embryonic genome. Several embryonic transcripts including those that encode growth factors, cell junction components and plasma membrane ion transporters are required for normal progression of the embryo to the blastocyst stage. The pattern of genes expressed and the overall program of development is subject to the influences of genomic imprinting as well as external influences encountered by the embryo within the maternal reproductive tract.