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Stickler syndrome. A mutation in the nonhelical 3' end of type II procollagen gene
N N Ahmad1, J Dimascio, R G Knowlton
1Wills Eye Hospital, Philadelphia, Pa, USA.
Background:
All of the mutations in the type II procollagen (COL2A1) gene that have been identified in families affected with Stickler syndrome have been located primarily in the triple helical region of the gene. We report what we believe is the first premature stop codon in the globular C-propeptide region encoded by the COL2A1 gene, in a family affected with Stickler syndrome.
Design:
Genomic DNA from affected and unaffected family members of this three-generation family was amplified using the polymerase chain reaction. The polymerase chain reaction products were directly sequenced for DNA analysis.
Results:
Direct sequencing showed a single base deletion in exon 50, resulting in a premature stop codon in exon 51 in the globular C-propeptide of COL2A1 gene in all affected members.
Conclusions:
These results implicate premature stop codons as a common cause of Stickler syndrome. The location of this premature stop codon in the far end of the nonhelical 3' end of the gene indicates that a truncated C-propeptide of at least 84 amino acid residues is inadequate for the functional gene product.