A Survey of Essential Genome Stability Genes Reveals That Replication Stress Mitigation Is Critical for Peri-Implantation Embryogenesis

Abstract

Murine development demands that pluripotent epiblast stem cells in the periimplantation embryo increase from approximately 120 to 14,000 cells between embryonic days (E) 4.5 and E7.5. This is possible because epiblast stem cells can complete cell cycles in under 3 h in vivo. To ensure conceptus fitness, epiblast cells must undertake this proliferative feat while maintaining genome integrity. How epiblast cells maintain genome health under such an immense proliferation demand remains unclear. To illuminate the contribution of genome stability pathways to early mammalian development we systematically reviewed knockout mouse data from 347 DDR and repair associated genes. Cumulatively, the data indicate that while many DNA repair functions are dispensable in embryogenesis, genes encoding replication stress response and homology directed repair factors are essential specifically during the periimplantation stage of early development. We discuss the significance of these findings in the context of the unique proliferative demands placed on pluripotent epiblast stem cells.

A Critical Role for The COP9 Signalosome Subunit 3 as A Gatekeeper of Genome Integrity in 2-Cell Mouse Embryos

“…The results of our immunological COPS3 inactivation reveal that prior to supporting epiblast survival in the postimplantation embryo, COPS3 accumulates in the oocyte and is required for protecting DNA integrity during the 2-cell stage. Cops3 is thereby recruited to the group of only 10 genes (reviewed in 4 ) which have a lethal mutant phenotype caused by defective DNA repair during the very early phase of development that harbors cellular totipotency. The reassigned function of COPS3 is mediated by an abundant, stable and hitherto overlooked protein deposit, which is present in oocytes in the form of a cortical rim -a cytological theme found also in maternal genes such as those of the subcortical maternal complex (SCMC) 41,42 .…”

“…Exemplarily, of 712 candidate genes screened in a large-scale functional study using RNA interference, only 4 gene interferences resulted in cleavage stage embryo arrest and 20 interferences prevented blastocyst formation 3 . Of 347 genes whose gene ontology (GO) annotations matched the major DNA repair pathways according to the Mouse Genome Informatics Gene Ontology Project (MGI-GO) database, only 10 genes had a lethal knockout phenotype which manifests itself during the totipotent phase or by the blastocyst stage 4 . These small numbers are probably underestimated, due to an earlier accumulation of downstream product (transcript or protein), prior to experimental mutagenesis.…”

An Eye in the Replication Stress Response: Lessons From Tissue-Specific Studies in vivo

“…The DDR is an evolutionarily conserved process that is often believed to operate by universal uniform principles. However, given that different progenitor cells have distinct transcriptional programs, metabolism, microenvironment and face different DNA-damaging insults, the DDR presents cell type- and developmental stage-specific adaptations ( Blanpain et al, 2011 ; Rodrigues et al, 2013 ; Kafer and Cesare, 2020 ). The heterogeneous cellular outcomes of RSR inactivation in retinal and lens progenitor cells leads to the question of why progenitor cells show different sensitivity to RSR inactivation.…”

Epigenetic regulation of replication origin assembly: A role for histone H1 and chromatin remodeling factors

“…Deleterious effects of transcription on DNA replication might be counteracted by several DNA metabolism genes involved in repairing DNA and avoiding DNA replication and transcription conflicts, explaining the embryonically lethal phenotypes following their deletion. [ 125 ] Consistent with transcription's role in perturbing DNA replication, RS often occurs at chromosome loci that contain highly transcribed genes. Among DNA metabolism genes that counteract RS, SSRP1, alone or in the context of the FACT complex, might play a major role.…”