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Epithelial cell layers need to be tightly regulated to maintain their integrity and correct function. Cell integration into epithelial sheets is now shown to depend on the N-WASP-regulated stabilization of cortical F-actin, which generates distinct patterns of apical–lateral contractility at E-cadherin-based cell–cell junctions.
Emerging data support that RNA methylation plays important roles in RNA processing and metabolism. The methyltransferases Mettl3 and Mettl14 are shown to catalyse N6-methyladenosine (m6A) RNA modification in embryonic stem cells (ESCs). This m6A modification controls RNA metabolism and functions to destabilize mRNAs encoding developmental regulators to help sustain ESC self-renewal.
Meiotic chromosome movement is needed for homologue pairing and synapsis. Watanabe and colleagues identify TERB1 as a protein needed for telomere mobility and attachment to the nuclear envelope, and for telomere enrichment of meiotic cohesin.
Mutations in PINK1 cause early-onset Parkinson’s disease. Martins and colleagues find that the expression levels of genes involved in nucleotide metabolism are upregulated in a Drosophila pink1 mutant, and that this affects neuronal mitochondrial DNA synthesis. They find that enhancing nucleotide synthesis through genetics or pharmacological approaches rescues mitochondrial defects associated with PINK1 mutations.
Yap and colleagues demonstrate that E-cadherin-based cell–cell junctions exhibit distinct patterns of apical and lateral contractility. They show that N-WASP-dependent stabilization of F-actin mediates increased apical junctional tension, and that modulation of intra-junctional tension differences can promote extrusion of cells from monolayers.
Hair follicle stem cells (HFSCs) regenerate hair in response to Wnt signalling. Fuchs and colleagues use a genome-wide survey to discover that Wnt effectors TCF3, TCF4 and Groucho (TLE) coordinately repress Wnt target genes. They find that although β-catenin is dispensable for HSFC viability and proliferation, it is essential to relieve this repression to initiate hair follicle fate during the hair regeneration cycle.
N6-methyladenosine (m6A) is an abundant internal modification of messenger RNA (mRNA) that has been reported recently in thousands of mammalian mRNAs and long non-coding RNAs (lncRNAs). Zhao and colleagues identify two methyltransferases responsible for this modification in mammalian cells, and demonstrate that they are required for embryonic stem cell self-renewal maintenance through an effect of the modification on the degradation of developmental regulator transcripts.
