ACTL6a Enforces the Epidermal Progenitor State by Suppressing SWI/SNF-Dependent Induction of KLF4

Somatic progenitors suppress differentiation to maintain tissue self-renewal. While epigenetic regulators of DNA and histone modifications can support such repression, a role for nuclear actin-like proteins is unclear. In epidermis, ACTL6a/BAF53A was found enriched in progenitors and down-regulated during differentiation. Conditional ACTL6a deletion abolished epidermal self-renewal and induced terminal differentiation, whereas ectopically expressed ACTL6a suppressed differentiation. Among known activators of epidermal differentiation, KLF4 was found to control 227 genes also regulated by ACTL6a. ACTL6a loss upregulated KLF4 and its target genes, effects that were blocked by KLF4 depletion. Among multiple ACTL6a-interacting epigenetic regulators, the SWI/SNF complex was required for KLF4 activation and differentiation. In progenitors, ACTL6a loss led to enhanced SWI/SNF binding to the promoters of KLF4 and other differentiation genes. ACTL6a thus maintains the undifferentiated progenitor state, in part by suppressing SWI/SNF complex-enabled induction of KLF4.

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Bao X, Tang J, Lopez-Pajares V, Tao S, Qu K, Crabtree GR, Khavari PA