Figure 3.

Alternative splicing for the human CD44 locus and its protein products. (A) The genomic structure for the human CD44 locus. It has 10 constant exons (exons 1–5 and 15–19) shown in tan that encode the extracellular, transmembrane, and cytoplasmic tail sequences and 10 variable exons for the extracellular domain (shown in silver). (B) Protein structures for the standard (CD44s) and variant CD44 (CD44v) proteins. CD44v has insertion of amino acid sequences between those encoded by exons 5 and 15 (exons 5a–14). The exon 5a (=exon v1) is not expressed in human tissues.