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Cultured human keratinocyte proliferation is either expanding, generating proliferating progeny, or balanced to produce both proliferating and differentiating progeny.p145
The first hours of mammalian embryogenesis are devoted to extensive epigenetic reprogramming. One hallmark is active demethylation of the paternal genome by Tet (ten-eleven translocation) enzymes. However, the process is now shown to be Tet-independent at first, with Tet enzymes only counteracting hitherto underappreciated de novo DNA methylation activity in later zygotic stages.
The control of proteasome-mediated protein degradation is thought to occur mainly at the level of polyubiquitylation of the substrate. However, the proteasome can also be regulated directly, as now demonstrated by a study in which DYRK2-mediated phosphorylation of the 19S subunit Rpt3 is found to increase proteasome activity.
An actin filament coat promotes cargo expulsion from large exocytosing vesicles, but the mechanisms of coat formation and force generation have been poorly characterized. Elegant imaging studies of the Drosophila melanogaster salivary gland now reveal how actin and myosin are recruited, and show that myosin II forms a contractile 'cage' that facilitates exocytosis.
By tracking the division outcomes of thousands of single cells, Jones and colleagues show that primary human keratinocyte proliferation in culture is either expanding, producing proliferating progeny, or balanced, thereby producing proliferating and differentiating progeny.
Nerlov and colleagues show that expression of mKitL by cortical vascular endothelial cells is important for DN1 progenitor maintenance, whereas expression of mKitL by cortical thymic epithelial cells is required for maintaining DN2 progenitor cells.
Nowell et al. report that chronic inflammation of the corneal epithelium activates β-catenin signalling through YAP/TAZ-dependent mechanotransduction, leading to epidermal differentiation on the ocular surface and corneal squamous cell metaplasia.
Rousso et al. describe the dynamics of exocytosis in the Drosophila salivary gland. They show that Dia and Rok regulate the formation of an actomyosin coat around the vesicle, with a contractile myosin II case-like structure driving content release.
Meyer and colleagues use fluorescent biosensors to demonstrate that chemotactic steering and cell polarization are controlled by locally excitable Cdc42 signalling.
Dixon and colleagues and Guo and colleagues find that phosphorylation of the 19S proteasome subunit Rpt3 by DYRK2 increases proteasome activity and promotes cell proliferation, whereas loss of Rpt3 phosphorylation inhibits tumour formation in mice.
Yang and colleagues identify a lncRNA that controls HIF1α signalling to stabilize HIF1α under normoxic conditions, and promotes breast cancer tumorigenesis.
Using ultrasensitive mass spectrometry of wild-type and mutant early mouse zygotes, Hajkova and colleagues show that 5mC loss and 5hmC accumulation are uncoupled during zygotic epigenetic reprogramming.
