Bruce, A. W. | Search bioRxiv

bioRxiv2019

Wwc2 is a novel mitotic/meiotic cell-cycle regulator and cell fate related gene, during preimplantation mouse embryo development and oogenesis

Formation of a mature and hatching mouse blastocyst marks the end of the preimplantation development, whereby regulated cell cleavages culminate in the formation of three distinct lineages. We report dysregulated expression of Wwc2, an ill-characterised paralog of the Hippo-signalling activator Kibra/Wwc1, is specifically associated with cell autonomous deficits in embryo cell number and cell division abnormalities, typified by imbalanced daughter cell chromatin segregation. Division phenotypes are also observed during mouse oocyte meiotic maturation, as Wwc2 dysregulation blocks progression to the fertilisation competent stage of meiosis II metaphase arrest, characterised by spindle defects and failed Aurora-A kinase (AURKA) activation. Such cell division defects, each occurring in the absence of centrosomes, are fully reversible by expression of recombinant HA-epitope tagged WWC2, restoring activated oocyte AURKA levels. Additionally, clonal dysregulation implicates Wwc2 in maintaining the pluripotent late blastocyst stage epiblast lineage. Thus, Wwc2 is a novel regulator of meiotic and early mitotic cell divisions, and mouse blastocyst cell-fate.

developmental biology↗

bioRxiv2019

p38-mitogen activated kinases mediate a developmental regulatory response to amino acid depletion and associated oxidative stress in mouse blastocyst embryos

Maternal starvation coincident with preimplantation development has profound consequences for placental-foetal development, with various identified pathologies persisting/manifest in adulthood; the Developmental Origin of Health and Disease (DOHaD) hypothesis/model. Despite evidence describing DOHaD-related incidence, supporting mechanistic and molecular data relating to preimplantation embryos themselves are comparatively meagre. We recently identified the classically recognised stress-related p38-mitogen activated kinases (p38-MAPK) as regulating formation of the extraembryonic primitive endoderm (PrE) lineage within mouse blastocyst inner cell mass (ICM). Thus, we wanted to assay if PrE differentiation is sensitive to amino acid availability, in a manner regulated by p38-MAPK. Although blastocysts appropriately mature, without developmental/morphological or cell fate defects, irrespective of amino acid supplementation status, we found the extent of p38-MAPK inhibition induced phenotypes was more severe in the absence of amino acid supplementation. Specifically, both PrE and epiblast (EPI) ICM progenitor populations remained unspecified and there were fewer cells and smaller blastocyst cavities. Such phenotypes could be ameliorated, to resemble those observed in groups supplemented with amino acids, by addition of the anti-oxidant NAC (N-acetyl-cysteine), although PrE differentiation deficits remained. Therefore, p38-MAPK performs a hitherto unrecognised homeostatic early developmental regulatory role (in addition to direct specification of PrE), by buffering blastocyst cell number and ICM cell lineage specification (relating to EPI) in response to amino acid availability, partly by counteracting induced oxidative stress; with clear implications for the DOHaD model.

developmental biology↗