title: Identification and Functional Analysis of a Novel MIP Gene Mutation Associated with Congenital Cataract in a Chinese Family.
abstract: Congenital cataracts are major cause of visual impairment and blindness in children and previous studies have shown about 1/3 of non-syndromic congenital cataracts are inherited. Major intrinsic protein of the lens (MIP), also known as AQP0, plays a critical role in transparency and development of the lens. To date, more than 10 mutations in MIP have been linked to hereditary cataracts in humans. In this study, we investigated the genetic and functional defects underlying a four-generation Chinese family affected with congenital progressive cortical punctate cataract. Mutation screening of the candidate genes revealed a missense mutation at position 448 (c.448G>C) of MIP, which resulted in the substitution of a conserved aspartic acid with histidine at codon 150 (p.D150H). By linkage and haplotype analysis, we obtained positive multipoint logarithm of odds (LOD) scores at microsatellite markers D12S1632 (Zmax = 1.804 at α = 1.000) and D12S1691 (Zmax = 1.806 at α = 1.000), which flanked the candidate locus. The prediction results of PolyPhen-2 and SIFT indicated that the p.D150H mutation was likely to damage to the structure and function of AQP0. The wild type and p.D150H mutant AQP0 were expressed in HeLa cells separately and the immunofluorescence results showed that the WT-AQP0 distributed at the plasma membrane and in cytoplasm, while AQP0-D150H failed to reach the plasma membrane and was mainly retained in the Golgi apparatus. Moreover, protein levels of AQP0-D150H were significantly lower than those of wide type AQP0 in membrane-enriched lysates when the HEK-293T cells were transfected with the same amount of wild type and mutant plasmids individually. Taken together, our data suggest the p.D150H mutation is a novel disease-causing mutation in MIP, which leads to congenital progressive cortical punctate cataract by impairing the trafficking mechanism of AQP0.
authors.affiliation: Eye Center, Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang Province, China; Zhejiang Provincial Key Laboratory of Ophthalmology, Hangzhou, Zhejiang Province, China.
authors.forename: Xingchao
authors.initials: X
authors.lastname: Shentu
authors.affiliation: Eye Center, Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang Province, China; Zhejiang Provincial Key Laboratory of Ophthalmology, Hangzhou, Zhejiang Province, China.
authors.forename: Qi
authors.initials: Q
authors.lastname: Miao
authors.affiliation: Eye Center, Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang Province, China; Zhejiang Provincial Key Laboratory of Ophthalmology, Hangzhou, Zhejiang Province, China.
authors.forename: Xiajing
authors.initials: X
authors.lastname: Tang
authors.affiliation: Eye Center, Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang Province, China; Zhejiang Provincial Key Laboratory of Ophthalmology, Hangzhou, Zhejiang Province, China.
authors.forename: Houfa
authors.initials: H
authors.lastname: Yin
authors.affiliation: Eye Center, Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang Province, China; Zhejiang Provincial Key Laboratory of Ophthalmology, Hangzhou, Zhejiang Province, China.
authors.forename: Yingying
authors.initials: Y
authors.lastname: Zhao
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics; D020346:Aquaporins / Q000235:genetics*; D044466:Asian People; D001766:Blindness / Q000151:congenital / Q000235:genetics; D002386:Cataract / Q000151:congenital* / Q000235:genetics*; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D002681:China; D005136:Eye Proteins / Q000235:genetics*; D005260:Female; D005455:Fluorescent Antibody Technique; D008040:Genetic Linkage; D057809:HEK293 Cells; D006239:Haplotypes; D006367:HeLa Cells; D006801:Humans; D007908:Lens, Crystalline / Q000378:metabolism*; D008297:Male; D018895:Microsatellite Repeats / Q000235:genetics; D008875:Middle Aged; D020125:Mutation, Missense / Q000235:genetics; D017434:Protein Structure, Tertiary; D021381:Protein Transport / Q000235:genetics; D016415:Sequence Alignment
chemical_list: D020346:Aquaporins; D005136:Eye Proteins; C030328:aquaporin 0