Figure 5. Alternative splicing of Ctnnd1 is regulated by Esrp1/2.

(A) Amino acid sequence alignment of the first 140 residues of CTNND1 protein across human, mouse, and zebrafish. Translation for isoform 1 of CTNND1 begins at methionine 1, while isoform 3 encodes a truncated form that starts translation at methionine 102. Methionine residues at positions 55 and 324 are not conserved across all three species. (B) Detection of esrp1 and ctnnd1 gene expression in zebrafish at 4dpf, demonstrates shared localization of transcripts in the embryonic epithelium. This coronal section includes the ventral Meckel’s cartilage. (C) Detection of murine Ctnnd1 mRNA using isoform-specific base-scope probes in the oral epithelium and tongue mesenchyme. The wildtype sections show that the Ctnnd1 long isoform is present in both epithelial and mesenchymal cells. The Ctnnd1 short isoform is present preferentially in epithelial cells and not in the mesenchymal cells. In the Esrp1/2 DKO mouse, the mesenchymal Ctnnd1 long isoform is detected in epithelial and mesenchymal cells, with loss of the Ctnnd1 short isoform. (D) RT-PCR of the Ctnnd1 long and short isoforms from Py2T cells. (E) Diagrammatic representation of the ESRP-regulated CTNND1 alternative splicing to generate the shorter epithelial isoform.