Loss of KANSL3 leads to defective inner cell mass and early embryonic lethality.

e-Lysine acetylation is a prominent histone mark found at transcriptionally active loci. Among many lysine acetyl transferases, nonspecific lethal complex (NSL) members are known to mediate the modification of histone H4. In addition to histone modifications, the KAT8 regulatory complex subunit 3 gene (Kansl3), a core member of NSL complex, has been shown to be involved in several other cellular processes such as mitosis and mitochondrial activity. Although functional studies have been performed on NSL complex members, none of the four core proteins, including Kansl3, have been studied during early mouse development. Here we show that homozygous knockout Kansl3 embryos are lethal at peri-implantation stages, failing to hatch out of the zona pellucida. When the zona pellucida is removed in vitro, Kansl3 null embryos form an abnormal outgrowth with significantly disrupted inner cell mass (ICM) morphology. We document lineage-specific defects at the blastocyst stage with significantly reduced ICM cell number but no difference in trophectoderm cell numbers. Both epiblast and primitive endoderm lineages are altered with reduced cell numbers in null mutants. These results show that Kansl3 is indispensable during early mouse embryonic development and with defects in both ICM and trophectoderm lineages.

The missense mutation C667F in murine ß-dystroglycan causes embryonic lethality, myopathy and blood-brain barrier destabilization.

Dystroglycan (DG) is an extracellular matrix receptor consisting of an α- and a ß-DG subunit encoded by the DAG1 gene. The homozygous mutation (c.2006G>T, p.Cys669Phe) in ß-DG causes muscle-eye-brain disease with multicystic leukodystrophy in humans. In a mouse model of this primary dystroglycanopathy, approximately two-thirds of homozygous embryos fail to develop to term. Mutant mice that are born undergo a normal postnatal development but show a late-onset myopathy with partially penetrant histopathological changes and an impaired performance on an activity wheel. Their brains and eyes are structurally normal, but the localization of mutant ß-DG is altered in the glial perivascular end-feet, resulting in a perturbed protein composition of the blood-brain and blood-retina barrier. In addition, α- and ß-DG protein levels are significantly reduced in muscle and brain of mutant mice. Owing to the partially penetrant developmental phenotype of the C669F ß-DG mice, they represent a novel and highly valuable mouse model with which to study the molecular effects of ß-DG functional alterations both during embryogenesis and in mature muscle, brain and eye, and to gain insight into the pathogenesis of primary dystroglycanopathies.

Depletion of Ppp6c in hematopoietic and vascular endothelial cells causes embryonic lethality and decreased hematopoietic potential.

Protein phosphatase 6 (PP6) is a serine/threonine (Ser/Thr) protein phosphatase, and its catalytic subunit is Ppp6c. PP6 forms the PP2A subfamily with PP2A and PP4. The diverse phenotypes observed following small interfering RNA (siRNA)-based knockdown of Ppp6c in cultured mammalian cells suggest that PP6 plays roles in cell growth and DNA repair. There is also evidence that PP6 regulates nuclear factor kappa B (NF-κB) signaling and mitogen-activated protein kinases and inactivates transforming growth factor-ß-activated kinase 1 (TAK1). Loss of Ppp6c causes several abnormalities, including those of T cell and regulatory T cell function, neurogenesis, oogenesis, and spermatogenesis. PP2A has been reported to play an important role in erythropoiesis. However, the roles of PP6 in other hematopoietic cells have not been investigated. We generated Ppp6cfl/fl;Tie2-Cre (Ppp6cTKO) mice, in which Ppp6c was specifically deleted in hematopoietic and vascular endothelial cells. Ppp6cTKO mice displayed embryonic lethality. Ppp6c deficiency increased the number of dead cells and decreased the percentages of erythroid and monocytic cells during fetal hematopoiesis. By contrast, the number of Lin-Sca-1+c-Kit+ cells, which give rise to all hematopoietic cells, was slightly increased, but their colony-forming cell activity was markedly decreased. Ppp6c deficiency also increased phosphorylation of extracellular signal-regulated kinase 1/2 and c-Jun amino (N)-terminal kinase in fetal liver hematopoietic cells.