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Mol Vis. 2007 Sep 30;13:1822-7.

A substitution of arginine to lysine at the COOH-terminus of MIP caused a different binocular phenotype in a congenital cataract family.

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Department of Ophthalmology, the Second Affiliated Hospital, Harbin Medical University, Harbin, China.



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.

[Indexed for MEDLINE]

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