Inhibition of zygotic DNA repair: transcriptome analysis of the offspring in trout (Oncorhynchus mykiss)

Abstract

Zygotic repair of the paternal genome is a key event after fertilization. Spermatozoa accumulate DNA strand breaks during spermatogenesis and can suffer additional damage by different factors, including cryopreservation. Fertilization with DNA-damaged spermatozoa (DDS) is considered to promote implantation failures and abortions, but also long-term effects on the progeny that could be related with a defective repair. Base excision repair (BER) pathway is considered the most active in zygotic DNA repair, but healthy oocytes contain enzymes for all repairing pathways. In this study, the effects of the inhibition of the BER pathway in the zygote were analyzed on the progeny obtained after fertilization with differentially DDS. Massive gene expression (GE; 61 657 unique probes) was analyzed after hatching using microarrays. Trout oocytes are easily fertilized with DDS and the high prolificacy allows live progeny to be obtained even with a high rate of abortions. Nevertheless, the zygotic inhibition of Poly (ADP-ribose) polymerase, upstream of BER pathway, resulted in 810 differentially expressed genes (DEGs) after hatching. DEGs are related with DNA repair, apoptosis, telomere maintenance, or growth and development, revealing a scenario of impaired DNA damage signalization and repair. Downregulation of the apoptotic cascade was noticed, suggesting a selection of embryos tolerant to residual DNA damage during embryo development. Our results reveal changes in the progeny from defective repairing zygotes including higher malformations rate, weight gain, longer telomeres, and lower caspase 3/7 activity, whose long-term consequences should be analyzed in depth.

Paternal contribution to development: Sperm genetic damage and repair in fish

“…As has been stated above there is a clear link between the alteration of sperm genome or epigenome and the development of fetal disease, the paternal information being a key element during development (Ward 2010;Aitken et al 2014;Fernández-Díez et al 2015;Delbes et al 2010;Wagner et al 2004). Sperm is a mixture of different subpopulations of cells whose ability to fertilize the oocyte depends on a number of factors including membrane integrity, motility pattern, morphology, etc.…”

“…Post-meiotic spermatids have a highly compacted nucleus, limiting the access to the proteins of the DNA repair machinery (Baarends et al 2001;Marchetti et al 2015). In those late steps, sperm DNA is very prone to suffer genetic lesions which can accumulate and can be transmitted to the zygote, making maternal DNA repair mechanisms the responsible to correct the failures after fertilization (Aitken et al 2014;Fernández-Díez et al 2015).…”

“…Increases in DNA fragmentation have been described in rainbow trout sperm at the end of the natural reproductive period Pérez-Cerezales et al 2010;Pérez-Cerezales et al 2011;Fernández-Díez et al 2015) or in sole (S. senegalensis) out of the natural spawning seasons . In addition, the chromatin of the sperm obtained out of season shows a higher susceptibility to cryodamage or to UV irradiation, increasing significantly the fragmentation rate and the number of lesions in specific genes, that is accompanied by a lower reproductive success (increase in the abortion rates and malformed larvae) (Pérez-Cerezales et al 2011;Fernández-Díez et al 2015).…”

“…In addition, the chromatin of the sperm obtained out of season shows a higher susceptibility to cryodamage or to UV irradiation, increasing significantly the fragmentation rate and the number of lesions in specific genes, that is accompanied by a lower reproductive success (increase in the abortion rates and malformed larvae) (Pérez-Cerezales et al 2011;Fernández-Díez et al 2015).…”

“…After fertilization the zygotic mechanisms of DNA repair are activated to correct the failures from paternal origin (Aitken et al 2014;Fernández-Díez et al 2015), supporting early embryonic development until the activation of the zygotic transcription during the ''mid-blastula transition" stage (MBT).…”