DIDEOXYFINGERPRINTING (DDF) ANALYSIS OF THE TYPE-X COLLAGEN GENE (COL10A1) AND IDENTIFICATION OF A NOVEL MUTATION (S671P) IN A KINDRED WITHSCHMID METAPHYSEAL CHONDRODYSPLASIA

Schmid metaphyseal chondrodysplasia (SMCD; MIM 156500) is an autosomal dominant disorder of the skeleton that is manifested in early childho od by short stature, coxa vara, and a waddling gait. Patients with SMC D have mutations in the gene that codes for the alpha-1 chain of colla gen X (COL10A1); however, mutation analysis of this gene is hampered b y its size. We studied a family with SMCD: the mother, a 36-year-old w oman with a height of 149 cm, had mild bilateral coxa vara. Her two so ns presented with short stature, bowed legs, and coxa vara in early ch ildhood. DNA was extracted from peripheral lymphocytes from the three patients and subjected to PCR amplification by COL10A1 gene-specific p rimers. In addition to single-strand conformational polymorphism (SSCP ) analysis of the COL10A1 gene, we used a novel method, dideoxy finger printing (ddF). The genetic defect in this family was found to be a pr eviously unreported missense mutation (T-to-C transition) at nucleotid e 2011. This change resulted in a Ser-to-Pro substitution at position 671 of the carboxy-terminus of the COL10A1 protein. In addition, the t wo boys, but not the mother, were found to carry a trinucleotide (CCC) deletion at position 2048 of the 3' untranslated region, a polymorphi sm of the COL10A1 gene, We conclude that ddF can be used in the analys is of the COL10A1 gene along with SSCP. The S671P substitution is nove l, but located in the same region with the other reported COL10A1 muta tions, con firming type X collagen as the locus for this disease.