Sasaki S, Zhou B, Fan W W, Kim Y, Barker D F, Denison J C, Atkin C L, Gregory M C, Zhou J, Segal Y, Sado Y, Ninomiya Y, Michael A F, Kashtan C E
Department of Pediatrics, University of Minnesota Medical School, Minneapolis 55455, USA.
Matrix Biol. 1998 Aug;17(4):279-91. doi: 10.1016/s0945-053x(98)90081-6.
COL4A5 mutations causing X-linked Alport syndrome (XLAS) are frequently associated with absence of the alpha3, alpha4,alpha5 and alpha6 chains of type IV collagen from basement membranes and increased amounts of the alpha1(IV) and alpha2(IV) chains in glomerular basement membrane. Although many COL4A5 mutations have been described in XLAS, the mechanisms by which these mutations influence the basement membrane appearance of chains other than alpha5(IV) remain poorly understood. In this study, we used dermal fibroblasts from eight normal individuals and nine males with XLAS to test the hypotheses that COL4A5 mutations increase transcription of COL4A1 and suppress transcription of COL4A6. Ribonuclease protection assays revealed that alpha1(IV), alpha5(IV) and alpha6(IV) transcripts were expressed in cultures of dermal fibroblasts. The mRNA levels for alpha1(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 alpha1(IV) mRNA levels. No differences in steady-state mRNA levels for alpha6(IV) were found when XLAS fibroblasts were compared with controls, even though little or no alpha6(IV) protein was detectable at the dermal-epidermal junction by immunofluorescence study. This finding suggests that post-transcriptional events account for the absence of alpha6(IV) in the Alport dermal-epidermal junction.
导致X连锁遗传性肾炎（XLAS）的COL4A5突变常与基底膜中IV型胶原的α3、α4、α5和α6链缺失以及肾小球基底膜中α1（IV）和α2（IV）链数量增加有关。尽管XLAS中已描述了许多COL4A5突变，但这些突变影响除α5（IV）以外的其他链在基底膜上表现的机制仍知之甚少。在本研究中，我们使用来自8名正常个体和9名XLAS男性患者的皮肤成纤维细胞，来检验COL4A5突变会增加COL4A1转录并抑制COL4A6转录的假设。核糖核酸酶保护试验表明，α1（IV）、α5（IV）和α6（IV）转录本在皮肤成纤维细胞培养物中表达。与对照组相比，9名XLAS患者中有8名患者的α1（IV）mRNA水平未升高；1名COL4A5大片段缺失的患者显示α1（IV）mRNA水平显著升高。当将XLAS成纤维细胞与对照组进行比较时，未发现α6（IV）的稳态mRNA水平存在差异，尽管通过免疫荧光研究在真皮 - 表皮交界处几乎检测不到或检测不到α6（IV）蛋白。这一发现表明，转录后事件是导致Alport综合征患者真皮 - 表皮交界处缺乏α6（IV）的原因。
