COL2A1 and Stickler syndrome: In patients with Stickler syndrome, the majority of mutations in the COL2A1 gene that lead to a premature termination codon trigger the nonsense-mediated mRNA decay (NMD) mechanism, ultimately causing haploinsufficiency of the COL2A1 gene and thereby affecting collagen synthesis (Richards et al., 2000b; Freddi et al., 2000).