EXPRESSION OF MESSENGER-RNA FOR TYPE-IV COLLAGEN ALPHA-1, ALPHA-5 ANDALPHA-6 CHAINS BY CULTURED DERMAL FIBROBLASTS FROM PATIENTS WITH X-LINKED ALPORT-SYNDROME

COL4A5 mutations causing X-linked Alport syndrome (XLAS) are frequentl y associated with absence of the alpha 3, alpha 4, alpha 5 and alpha 6 chains of type IV collagen from basement membranes and increased amou nts of the alpha 1(IV) and alpha 2(IV) chains in glomerular basement m embrane. Although many COL4A5 mutations have been described in XLAS, t he mechanisms by which these mutations influence the basement membrane appearance of chains other than alpha 5(IV) remain poorly understood. In this study, we used dermal fibroblasts from eight normal individua ls and nine males with XLAS to test the hypotheses that COL4A5 mutatio ns increase transcription of COL4A1 and suppress transcription of COL4 A6. Ribonuclease protection assays revealed that alpha 1(IV), alpha 5( IV) and alpha 6(IV) transcripts were expressed in cultures of dermal f ibroblasts. The mRNA levels for alpha 1(IV) in eight of nine patients with XLAS were not increased compared to controls; one patient with a large COL4A5 deletion showed significant elevation of alpha 1(IV) mRNA levels. No differences in steady-state mRNA levels for alpha 6(IV) we re found when XLAS fibroblasts were compared with controls, even thoug h little or no alpha 6(IV) protein was detectable at the dermal-epider mal junction by immunofluorescence study. This finding suggests that p ost-transcriptional events account for the absence of alpha 6(IV) in t he Alport dermal-epidermal junction.