Esrp1-Regulated Splicing of Arhgef11 Isoforms Is Required for Epithelial Tight Junction Integrity

The epithelial-specific splicing regulators Esrp1 and Esrp2 are required for mammalian development, including establishment of epidermal barrier functions. However, the mechanisms by which Esrp ablation causes defects in epithelial barriers remain undefined. We determined that the ablation of Esrp1 and Esrp2 impairs epithelial tight junction (TJ) integrity through loss of the epithelial isoform of Rho GTP exchange factor Arhgef11. Arhgef11 is required for the maintenance of TJs via RhoA activation and myosin light chain (MLC) phosphorylation. Ablation or depletion of Esrp1/2 or Arhgef11 inhibits MLC phosphorylation and only the epithelial Arhgef11 isoform rescues MLC phosphorylation in Arhgef11 KO epithelial cells. Mesenchymal Arhgef11 transcripts contain a C-terminal exon that binds to PAK4 and inhibits RhoA activation byArhgef11. Deletion of the mesenchymal-specific Arhgef11 exon in Esrp1/2 KO epithelial cells using CRISPR/Cas9 restored TJ function, illustrating how splicing alterations can be mechanistically linked to disease phenotypes that result from impaired functions of splicing regulators. [Display omitted] •Ablation of Esrp1 and Esrp2 in mouse epidermis leads to tight junction defects•A switch in splicing of exon 37 in Arhgef11 transcripts produces isoforms that bind Pak4•Inhibition of Arhgef11 by Pak4 causes a reduction in RhoA activation at tight junctions•Restoration of epithelial Arhgef11 isoforms partially rescues tight junction defects Lee et al. identify defects in epithelial tight junctions when the splicing regulators Esrp1 and Esrp2 are ablated in mouse epidermis. A splicing switch in Arhgef11 transcripts partially underlies these defects through inhibition of the mesenchymal isoform of Arhgef11 by Pak4 and a consequent loss of RhoA activation.