Molecular basis for the progeroid variant of Ehlers-Danlos syndrome - Identification and characterization of two mutations in galactosyltransferase Igene

Progeroid type Ehlers-Danlos (E-D) syndrome was reported to be caused by de fects in galactosyltransferase I (EC 2.4.1.133), which is involved in the s ynthesis of common linkage regions of proteoglycans. Recently, we isolated cDNA of the galactosyltransferase I (XGalT-1) (Okajima, T., Yoshida, K., Ro ndo, T., and Furukawa, H, (1999) J. Biol. Chem. 274, 22915-22918), Therefor e, we analyzed mutations in this gene of a patient with progeroid type E-D syndrome by reverse transcription polymerase chain reaction and direct sequ encing. Two changes of G and T to A and C at 186 and 206, respectively, wer e detected, Then, we determined the genomic DNA sequences encompassing the A186D and L206P mutations, revealing that the unaffected parents and two si blings were heterozygous for either one of the two different mutations and normal, while the patient had both of two different mutant genes. Enzymatic functions of cDNA clones of XGalT-1 containing the individual mutations we re examined, elucidating that L206P clone completely lost the activity, whi le A186D retained similar to 50% or 10% of the activity when analyzed with extracts from cDNA transfectant cells or recombinant soluble enzymes, respe ctively. Moreover, L206P enzyme showed diffuse staining in the cytoplasm of transfectant cells, while the wild type or A186D clones showed Golgi patte rn. These results indicated that the mutations in XGalT-1 were at least one of main molecular basis for progeroid type E-D syndrome.