A fourth example suggests that premature termination codons in the COL2A1 gene are a common cause of the Stickler syndrome: analysis of the COL2A1 gene by denaturing gradient gel electrophoresis.

A series of oligonucleotide primers was designed to generate polymerase chain reaction products that contained exons 6 to 49 of the human gene for type II procollagen (COL2A1) and that could be used to detect sequence variations by denaturing gradient gel electrophoresis. To improve the sensitivity of the analysis, GC clamps were introduced into one primer of each pair. The procedure successfully detected 10 neutral single-base variations in the gene. In addition, the procedure detected a single-base deletion in exon 43 that introduced a premature termination codon in exon 44 and caused the Stickler syndrome (arthro-ophthalmopathy) in one family. The mutation is the fourth mutation in the COL2A1 gene shown to cause the Stickler syndrome. The mutation is similar to the first three mutations causing the disease in that they also introduced premature termination signals. Since only one mutation introducing a premature termination codon was found in the course of defining 120 or more mutations in type I and III procollagens, the results suggest that such mutations may have a special relationship to the Stickler syndrome.