Patey-Mariaud de Serre N, Garfa M, Bessiéres B, Noël L H, Knebelmann B
Department of Pathology, Tumorothéque APHP Necker Hospital, Université Paris Descartes, Inserm U838, Paris, France.
Kidney Int. 2007 Aug;72(4):512-6. doi: 10.1038/sj.ki.5002365. Epub 2007 Jun 6.
Alport syndrome is a collagen type IV disease caused by mutations in the COL4A5 gene with the X-linked form being most prevalent. The resultant alpha5(IV) collagen chain is a component of the glomerular and skin basement membranes (SBMs). Immunofluorescent determination of the alpha5(IV) chain in skin biopsies is the procedure of choice to identify patients. In 30% of patients, however, the mutant protein is still found in the SBM resulting in a normal staining pattern. In order to minimize or eliminate false results, we compared the distribution of the alpha2(IV) chain (another SBM component) and the alpha5(IV) chain by standard double label immunofluorescence (IF) and by confocal laser scanning microscopy. The study was performed on 55 skin biopsies of patients suspected of Alports and five normal control specimens. In normal skin, IF showed the classical linear pattern for both collagens along the basement membrane. Additionally, decreased alpha5(IV) was found in the bottom of the dermal papillary basement membrane. Confocal analysis confirmed the results and show alpha5(IV) focal interruptions. In suspected patients, both techniques showed the same rate of abnormal alpha5(IV) expression: segmental in women and absent in men. Our results show a physiological variation of alpha5(IV) location with focal interruptions and decreased expression in the bottom of the dermal basement membrane. Comparison of alpha5(IV) with alpha2(IV) expression is simple and eliminates technical artifacts.
奥尔波特综合征是一种由COL4A5基因突变引起的IV型胶原疾病，其中X连锁型最为常见。产生的α5（IV）胶原链是肾小球和皮肤基底膜（SBMs）的组成部分。通过免疫荧光法测定皮肤活检组织中的α5（IV）链是识别患者的首选方法。然而，在30%的患者中，仍可在SBM中发现突变蛋白，导致染色模式正常。为了尽量减少或消除假结果，我们通过标准双标记免疫荧光（IF）和共聚焦激光扫描显微镜比较了α2（IV）链（另一种SBM成分）和α5（IV）链的分布。该研究对55例疑似奥尔波特综合征患者的皮肤活检组织和5个正常对照标本进行。在正常皮肤中，IF显示两种胶原蛋白沿基底膜呈经典的线性模式。此外，在真皮乳头基底膜底部发现α5（IV）减少。共聚焦分析证实了结果，并显示α5（IV）有局灶性中断。在疑似患者中，两种技术显示异常α5（IV）表达的发生率相同：女性为节段性，男性则无。我们的结果显示α5（IV）位置存在生理变异，在真皮基底膜底部有局灶性中断和表达减少。比较α5（IV）与α2（IV）的表达简单且可消除技术假象。
