Lin Hui, Hejtmancik J Fielding, Qi Yanhua
Department of Ophthalmology, the Second Affiliated Hospital, Harbin Medical University, Harbin, China.
Mol Vis. 2007 Sep 30;13:1822-7.
To detect the cataractogenetic mutation for a six-generation family of Chinese origin with autosomal dominant binocular polymorphic cataracts.
A genome wide scan was performed using 382 fluorescent-labeled microsatellite markers. Multiple polymerase chain reaction (PCR) was performed according to the protocols previously described. Two-point linkage analysis was performed with the FASTLINK version of the MLINK in Linkage Program Package. The candidate gene was screened by direct sequencing.
The disease locus was mapped to a 61 cM region on chromosome 12 defined by D12S310 and D12S351 near the major intrinsic protein gene (MIP). The maximum two-point lod score of 5.44 was obtained at marker D12S83 at theta=0.00. Direct sequencing of the encoding region of the candidate gene revealed a novel missense mutation G>A in exon 4 at nucleotide 702, which caused the replacement of arginine to lysine at codon 233 (p.R233K).
The change located in the alpha-helix domain of the COOH-terminus of MIP was determined to be associated with the binocular polymorphic cataract in this study. It suggests that arginine in this domain plays a crucial role in the function of the carboxyl-end of this protein and provides a helpful clue to further studies on completely understanding the physiological significance of MIP and its role in the formation of cataract.
检测一个起源于中国的常染色体显性双眼多形性白内障的六代家族中的致白内障突变。
使用382个荧光标记的微卫星标记进行全基因组扫描。根据先前描述的方案进行多重聚合酶链反应（PCR）。使用连锁程序包中的MLINK的FASTLINK版本进行两点连锁分析。通过直接测序筛选候选基因。
疾病基因座被定位到12号染色体上由主要内在蛋白基因（MIP）附近的D12S310和D12S351定义的61 cM区域。在标记D12S83处，θ=0.00时获得最大两点连锁lod值5.44。候选基因编码区的直接测序显示外显子4中第702位核苷酸处有一个新的错义突变G>A，导致密码子233处的精氨酸被赖氨酸取代（p.R233K）。
本研究确定位于MIP羧基末端α-螺旋结构域的变化与双眼多形性白内障相关。这表明该结构域中的精氨酸在该蛋白羧基末端的功能中起关键作用，并为进一步研究完全理解MIP的生理意义及其在白内障形成中的作用提供了有益线索。
