CHAPTER 6

116 RATIONALE OF THE STUDY: Glycosaminoglycan hyaluronan (HA), composed of repeating dimers of glucuronic acid-N-acetylglucosamine, is a chief component of the extracellular matrices and has a propensity to accumulate at sites of cell division and rapid matrix remodeling [302, 303]. Interaction between HA and its principal multi-structural transmembrame receptor CD44 tends to modulate various fundamental and pathological processes such as embryogenesis, leukocyte homing, cell–cell and cellmatrix communications, and tumor progression and metastases [304, 305]. This family of CD44 proteins are encoded by a single gene composed of 20 exons that spans across a 60 kb region of the human genome on chromosome 11 [306]. The structural and functional polymorphism of this protein is attributed to alternative splicing and post-translational modification events eventually leading to the insertion of variant exons (exons 6–15) into the CD44 standard structure and generating various isoforms of CD44 molecule (12 variants). However, among these variant isoforms, humans lack the v1 isoform due to the presence of an in-frame termination codon in exon 6 [307, 308].