Defective Glycosaminoglycan Substitution of Decorin in a Patient With Progeroid Syndrome Is a Direct Consequence of Two Point Mutations in the Galactosyltransferase I (�4galT-7) Gene

Abstract

The small dermatan sulfate proteoglycan decorin is involved in the regulation of collagen fibrillogenesis, cell adhesion and migration, and growth factor signaling. In a progeroid patient carrying two point mutations in beta4 galactosyltransferase I (beta4GalT-7) only 50% of the decorin core protein molecules are substituted with glycosaminoglycan chains. We expressed decorin, as well as wild-type and mutant alleles of beta4GalT-7 in galactosyltransferase-deficient CHO618 cells. Decorin was less efficiently substituted with glycosaminoglycan chains upon expression of beta4GalT-7(186D) compared to beta4GalT-7-expressing cells. Decorin from beta4GalT-7-expressing cells displayed increased molecular heterogeneity. Decorin glycosaminoglycan chains were completely susceptible to chondroitinase ABC treatment. Cells expressing beta4GalT-7(206P) did not synthesize the proteoglycanform of decorin. Thus, the beta4GalT-7 mutations directly affect the molecular phenotype of decorin observed in a patient with the progeroid form of Ehlers-Danlos syndrome, which may be a major mechanistic cause for the skin and wound healing defects observed in this patient.