Fernie B A, Orren A, Würzner R, Jones A M, Potter P C, Lachmann P J, Hobart M J
Molecular Immunopathology Unit, MRC Centre, Cambridge, U.K.
Ann Hum Genet. 1995 Apr;59(2):183-95. doi: 10.1111/j.1469-1809.1995.tb00740.x.
Both complete C6-deficiency (C6Q0) and subtotal C6-deficiency (C6SD) have been described as simple recessive traits and C6SD has been described in combination with subtotal deficiency of the C7 coded at an adjacent locus. The trace of C6 protein found in both C6SD traits is phenotypically indistinguishable, being smaller than normal C6 and having different isoelectric properties. A defect has been found in the C6 gene which plausibly explains the C6SD phenotype, and this defect is also common to both C6SD traits. We present data from seven DNA markers of the C6 and C7 genes which show that although at least four haplotypes are associated with C6Q0, most South African C6Q0 patients carry a common defective haplotype. The most common haplotype associated with C6Q0 has been observed only once among unaffected haplotypes of relatives. In one family, the cases of C6SD share a complete haplotype with both cases of combined deficiency and are probably heterozygous for this condition and complete deficiency of C6. In another family, the C6SD is on a slightly different haplotype and C7 is normally expressed. Thus, the C6 defect is not sufficient on its own to explain the C7 deficiency in the combined deficient haplotype. The haplotype associated with the combined deficiency is found not only in normal control subjects, but also in one case of complete C6 deficiency. In this case the molecular defect seen in combined or C6SD cases is absent.
完全性C6缺乏（C6Q0）和部分性C6缺乏（C6SD）均被描述为简单隐性性状，并且C6SD已被描述为与相邻基因座编码的C7部分缺乏同时出现。在两种C6SD性状中发现的C6蛋白痕迹在表型上无法区分，比正常C6小且具有不同的等电特性。已在C6基因中发现一种缺陷，这可能解释了C6SD表型，并且这种缺陷在两种C6SD性状中也很常见。我们展示了来自C6和C7基因的七个DNA标记的数据，这些数据表明，尽管至少有四种单倍型与C6Q0相关，但大多数南非C6Q0患者携带一种常见的缺陷单倍型。与C6Q0相关的最常见单倍型仅在亲属的未受影响单倍型中观察到一次。在一个家族中，C6SD病例与联合缺乏的两个病例共享一个完整的单倍型，并且可能对此情况和C6的完全缺乏是杂合的。在另一个家族中，C6SD处于略有不同的单倍型，并且C7正常表达。因此，C6缺陷本身不足以解释联合缺陷单倍型中的C7缺乏。与联合缺乏相关的单倍型不仅在正常对照受试者中发现，而且在一例完全性C6缺乏中也发现。在这种情况下，联合或C6SD病例中所见的分子缺陷不存在。
