Fig. 1

Genomic and protein structures of CD44. a The human CD44 gene consists of 20 exons. Those encoding for N-terminal, transmembrane and cytoplasmic domains as well as the exon numbers are shown. Alternative splicing of variable exons, v1-v10 generates CD44 variant isoforms. b The standard CD44 (CD44s) consists of exons 1–5, 16–20. c The variant form, CD44v6 contains the standard exons 1–5, 16–20 and variant exon 11 (v6). d CD44 is a single-pass transmembrane glycoprotein consisting of four functional domains: N-terminal domain, stem region, transmembrane domain and the intracellular cytoplasmic domain. N-terminal domain, the site for HA binding is bound together by three cysteine disulfide cross-links. Alternative splicing occurs at the stem region generating the variant form. The transmembrane domain anchors the molecule in the cytoplasmic membrane, whereas the cytoplasmic region conveys essential functions of CD44. v, variant exon, UTR, untranslated region