Fig. 5.

Genomic structure of teleost β4 genes. A: β4 gene structure, showing alternative splicing at the NH₂ terminus to create β4b transcript variants or β4a transcript variants. In β4b transcripts, exons 1b and 2b splice to exons 3–14, whereas in β4a transcripts, exon 2a splices directly to exons 3–14 (Fig. 2A). The first 3 introns (not drawn to scale) are numbered. Arrows designate locations of RT-PCR primers used in expression studies. B: the percent amino acid identity in exons 3–14 for vertebrate species. C: the size of introns 1, 2, and 3 in β4 genes of several species.