Fig. 1.

COL2A1 spliced isoforms and the effect of exon 2 splice site mutation on pre-mRNA alternative splicing. Panel A shows all potential alternative splicing events involving COL2A1 exon 2 described to date (McAlinden et al., 2008). Panel B shows the composition of the human COL2A1 mini-gene containing full-length exons 1, 2 and 3 and intervening introns 1 and 2. The position of the 3′ splice site (3′ss) and 5′ splice site (5′ss) of exon 2 are indicated. Asterisk denotes the exon-intron junction at the 5′ss where uppercase nucleotides represent exonic sequence and lowercase nucleotides represent intronic sequence with respect to the IIA splicing event. The position of both the IIA and IID splice sites are shown by the arrows. The underlined four nucleotides denote the intronic splice site sequence that was mutated (bold, italic) to create the consensus 5′ss sequence present in the COL2A1^+ex2 mini-gene. Panel C shows autoradiograph images of cDNA products derived from splicing of wild type or mutant mini-genes in cell lines HEK-293 (293), MC615, TC28 and RCS. The position of IIA/IID and IIB products are indicated. Double arrow represents a slower-migrating band formed by heteroduplex formation of mismatched IIA and IID cDNA strands (Claus et al., 2010; McAlinden et al., 2008). Note disappearance of this band as a result of the IIA splice site mutation which disrupts the IID exon-intron splice site.