Congenital cataracts are one of the leading causes of visual impairment and blindness in children, and genetic factors play an important role in their development. This study aimed to identify the genetic defects associated with autosomal dominant congenital progressive punctate cataracts in a Chinese family and to explore the potential pathogenesis. Detailed family history and clinical data were recorded, and all the family members’ blood samples were collected for DNA extraction. Linkage analysis was performed by microsatellite markers that are associated with punctate cataracts, and logarithm (base 10) of odds (LOD) scores were calculated using the LINKAGE program. Positive two-point LOD scores were obtained at markers D12S1622 (Zmax = 2.71 at θ = 0.0), D12S1724 (Zmax = 2.71 at θ = 0.0), and D12S90 (Zmax = 2.71 at θ = 0.0), which flank the major intrinsic protein of lens fiber (MIP) gene on chromosomal region 12q13. Direct sequencing of the encoding region of the MIP gene revealed a novel mutation (G>D) in exon 4 at nucleotide 644, which caused a substitution of glycine to aspartic acid at codon 215 (p.G215D) for the MIP protein. The mutation cosegregated with all patients with congenital progressive punctate cataracts, but it was absent in the healthy members. Bioinformatics analysis predicted that the mutation affects the function of the MIP protein. The wild type (WT) and G215D mutant of MIP were transfected with green fluorescent protein (GFP) into Hela cells separately, and it was found that the G215D mutant was aberrantly located in the cytoplasm instead of in the plasma membrane. In summary, our study presented genetic and functional evidence linking the new MIP mutation of G215D to autosomal dominant congenital cataracts, which adds to the list of MIP mutations linked to congenital progressive punctate cataracts.
Citation: Ding X, Zhou N, Lin H, Chen J, Zhao C, Zhou G, et al. (2014) A Novel MIP Gene Mutation Analysis in a Chinese Family Affected with Congenital Progressive Punctate Cataract. PLoS ONE 9(7): e102733. https://doi.org/10.1371/journal.pone.0102733
Editor: Edathara Abraham, University of Arkansas for Medical Sciences, United States of America
Received: May 20, 2014; Accepted: June 23, 2014; Published: July 17, 2014
Copyright: © 2014 Ding et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: The authors confirm that all data underlying the findings are fully available without restriction. All relevant data are within the paper and its Supporting Information files.
Funding: This work was supported by the National Natural Science Foundation of China [grant number 81341026]. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: The authors have declared that no competing interests exist.
Congenital cataracts, one of the most common causes of visual impairment, are responsible for approximately 10–30% of blindness cases in children . Genetic factors play an important role in the development of congenital cataracts, and hereditary congenital cataracts are inherited primarily in an autosomal dominant pattern. The identified genes involved in congenital cataracts include ten crystalline genes (αA-crystallin [CRYAA] , αB-crystallin [CRYAB] , βA1-crystallin [CRYBA1] , βA4-crystallin [CRYBA4] , βB1-crystallin [CRYBB1] , βB2-crystallin [CRYBB2] , βB3-crystallin [CRYBB3] , γC-crystallin [CRYGC] , γD-crystallin [CRYGD] , and γS-crystallin [CRYGS] ), two cytoskeletal protein genes (beaded filament structural protein 2, phakinin [BFSP2]  and beaded filament structural protein 1, filensin [BFSP1] ), three transcription factor genes (heat shock transcription factor 4 [HSF4] , Maf-like protein [MAF] , and paired-like homeodomain 3 [PITX3] ), glucosaminyl (N-acetyl) transferase 2 (GCNT2) , chromatin-modifying protein-4B (CHMP4B) , transmembrane protein 114 (TMEM114) , and four membrane transport protein genes (major intrinsic protein of lens fiber [MIP] , lens intrinsic membrane protein 2 gene [LIM2] , gap junction protein [alpha 8, GJA8] , and gap junction protein [alpha 3, GJA3] ). Congenital cataracts are characterized by high genetic heterogeneity and clinical heterogeneity. For example, a mutation in CRYBB2 and CRYGD can cause CCA; in addition, MIP (also known as AQP0), CRYBA1, and GJA3 are related to congenital cataracts with punctate opacities.
MIP is expressed in the ocular lens, contributes to over 50% of the total membrane proteins in the lens fiber cell, and plays a role in maintaining lens transparency . Mutations in the MIP gene have been linked to hereditary cataracts in humans and knockout mouse models –, which further highlight the important role of MIP in maintaining lens transparency. To date, 11 mutations of MIP have been shown to be associated with congenital cataracts (c.97C>T [p.R33C] , c.401A>G [p.E134G] , c.413C>G [p.T138R] , c.530A>G [p.Y177C] , c.559C>T [p.R187C] , c.698G>A [p.R233K] , c.2 T>C [p.Met1] , c.494G>A [p.G165D] , IVS-1G>A [p.V203fs] , c.638delG [p.G213VfsX46] , and c.337C>T [p.R113X] ).
In the present study, we identified that the p.G215D mutation of MIP was linked to congenital progressive punctate cataracts in a three-generation Chinese family (Figures 1 and 2). All family members with the G215D mutant of MIP have punctate cataracts, and the opacity degree of the lens increases with increasing age. Therefore, the aim of this study was to clone and express the G215D mutant of MIP and compare its properties with those of the normal or wild-type (WT) MIP.
A three-generation pedigree with 16 members is shown. Squares and circles indicate males and females, respectively. Shaded shapes indicate affected individuals. The arrow indicates the proband.
After explaining the nature and possible consequences of the study, written informed consents were obtained from subjects including the guardians on behalf of the minors enrolled. All experiments were approved by the Institutional Review Board of Harbin Medical University (Harbin, China) and were conducted according to the principles in the Declaration of Helsinki.
Patient ascertainment and genomic DNA preparation
A three-generation Chinese Han family with congenital progressive punctate cataracts from Shenzhen province was identified as shown in Figure 1. All members of the pedigree were given complete ophthalmologic examinations and did not have any other eye disease. One hundred healthy persons were recruited as the normal controls. After informed consent, 5 ml of venous blood from each subject was collected in a BD Vacutainer (BD, San Jose, CA) containing EDTA. Genomic DNA was extracted by QIAamp DNA Blood Mini Kits (QIAGEN Science, Germantown, MD).
Genotyping and linkage analysis
Fluorescently labeled microsatellite markers, which have been reported to be associated with punctate cataracts, were used for the linkage analysis. Two-point linkage analysis was performed with MLINK from the LINKAGE program package. The disease locus was specified to be an autosomal dominant trait, with a disease allele frequency of 0.0001. The allele frequencies of the markers are considered to be equally distributed.
The coding exons and the flanking regions of the candidate gene were amplified by polymerase chain reaction (PCR) with the primers listed in Table 1. The sequencing was carried out with an ABI 3130XL Genetic Analyzer (Applied Biosystems, Foster City, CA), and the results were analyzed using Chromas (version 1.0) software.
The WT and mutant MIP protein sequences were analyzed with the PolyPhen tool to predict whether the amino acid substitution affects the structure and function of the protein. The amino acid sequences of MIP from several different species were obtained from NCBI GenBank, and conservation analysis was performed by CLC Main Workbench Software (Aarhus, Denmark). The hydrophobic properties of the mutant and WT amino acid sequences were analyzed by Misc Protein Analysis software, respectively.
The expression vector for G215D mutant of MIP was constructed by using site-directed mutagenesis with the following primers: sense primer 5′-GGAGGGGGTCTGGACAGCCTCCTGTAC-3′; antisense primer 5′-GTACAGGAGGCTGTCCAGACCCCCTCC-3′. Mutation was confirmed through DNA sequencing. pGFP-WT and pGFP-G215D resultant plasmids were constructed to create GFP-MIP fusion proteins, the open reading frames of WT and G215D mutant of MIP were amplified by PCR with the following primers: sense primer 5′-AGT ACC TCG AGA TGT GGG AAC TGC GAT CAG C-3′; antisense primer 5′-CTA CGA AGC TTC AGG GCC TGG GTG TTC AGT T-3′. Products were then cloned into Xho I and Hind III digested pGFP-N1 vector.
Cell culture and transfection
Human cervical cancer (Hela) cells were maintaining in Dulbecco’s modification of Eagle’s medium (DMEM) supplemented with 10% fetal bovine serum (FBS), 100 mg/ml penicillin and 100 mg/ml streptomycin in a humidified atmosphere containing 5% CO2 at 37°C. Transfection was carried out using Lipofectamine 2000 (Invitrogen Corporation, Carlsbad, CA, USA).
Expression and subcellular localization
Hela cells were plated in 6-well plates 24 h prior to transfection at approximately 60% confluency. According to the manufacturer’s protocols, GFP-MIP expression constructs containing WT and G215D mutant were transfected using Lipofectamine 2000, separately. The empty vector pGFP-N1 was transfected as a control. 48 hours after transfection, the cells were analyzed by fluorescence microscopy.
Western blot analysis
After transfected with MIP-WT or MIP-G215D plasmids separately, HEK 293t cells were harvested and lysed in lysis buffer (50 mM Tris-HCl, 1% NP40, 150 mM NaCl, 1 mM EDTA and 1 mM PMSF) for 30 min at 4 uC. Total proteins were extracted and separated by 12% SDS/PAGE gels, and then transferred to PVDF membranes, separately. The membranes were incubated with antibodies of anti-β-actin (Cell Signaling Technology, Inc, USA) and anti-GFP (Abcam, Inc, Cambridge, MA). The signals were visualized by using the chemiluminescent substrate method with the SuperSignal West Pico kit. (Pierce Co, Rockford, USA).
Nine family members (I:2, II:1, II:3, II:5, II:7, III:1, III:2, III:3, and III:4) were diagnosed as having congenital progressive punctate cataracts, and they had no other ocular or systemic abnormalities (Figure 1). Progressive punctate cataracts were exhibited fully in these patients (Figure 2). Among them, three had undergone cataract surgery. By linkage and haplotype analysis, we obtained positive two-point logarithm (base 10) of odds (LOD) scores with markers at 12q13. Table 2 shows the linkage analysis results of markers D12S1622 (Zmax = 2.71 at θ = 0.0), D12S1724 (Zmax = 2.71 at θ = 0.0), and D12S90 (Zmax = 2.71 at θ = 0.0). The haplotype analysis showed complete cosegregation in all nine patients (Figure 3).
Eight markers close to MIP were used. The disease haplotype (represented by the black bar) cosegregated with all affected family members from marker D12S1622 to D12S83 but was not shared with unaffected members.
Direct sequencing revealed a heterozygous change, G>A, at position 644 (c.644G>A) of the MIP gene, which leads to the substitution of a glycine in the WT to an aspartic acid at codon 215 (p.G215D). Glycine is highly conserved across various species, as determined from the NCBI database. This mutation cosegregated well with all affected individuals and was not found in unaffected family members or in the 100 unrelated normal controls (Figure 4).
(A) Partial nucleotide sequence of MIP from a patient of the family. The sequence in patients showed a heterozygous G>A conversion, resulting in a substitution of glycine to aspartic acid at codon 215. (B) The healthy members of the family and 100 control subjects lacked this nucleotide change. (C) Phylogenetic conservation analysis. The alignment of the MIP sequence with the corresponding segments of diverse species is shown. Glycine 215 was highly conserved in MIP proteins from several species.
PolyPhen analysis demonstrated that the substitution at position 215 of MIP from glycine to aspartic acid scored 0.811, which meant that this mutation is predicted to be “possibly damaging”. In comparison with the WT-MIP protein, it is obvious that the mutant has a lower hydrophobicity in this region (Figure 5).
The substitution region on the MIP protein is boxed. It is obvious that the mutant has a lower hydrophobicity in this region compared with the WT.
We tested the subcellular location of WT-MIP and G215D-MIP after transient transfection of Hela cells by fluorescence microscopy. As shown in Figure 6, the empty vector pGFP-N1 was located in both the nucleus and cytoplasm, while the expressed WT-MIP was located in the plasma membrane. In contrast, G215D-MIP was aberrantly located in the cytoplasm, indicating that the G215D mutation prevented its localization in the plasma membrane, accurately.
Localizations of WT and G215D-MIP proteins in transfected Hela cells were viewed by fluorescence microscopy. (A) The empty vector pGFP-n1 was located in both the nucleus and cytoplasm. (B) The expressed WT-MIP was located in the plasma membrane. (C) The G215D-MIP was aberrantly located in the cytoplasm.
Western blot analysis revealed that WT-MIP and G215D-MIP had similar protein levels in western blot analysis of the cell lysates (Figure 7), indicating that mutation did not result in the expression or instability of the protein.
In the present study, a novel mutation of the MIP gene was identified in exon 4 at nucleotide 644, which caused a substitution of glycine to aspartic acid at codon 215 (p.G215D) in a Chinese family with congenital progressive punctate cataracts. The G215D MIP mutant was found to cosegregate with the disease phenotype in the family and was not present in unaffected family members or in 100 normal controls.
The MIP gene, also known as the MIP26 or AQP0 gene, encodes a 263-amino acid peptide. AQP0 is abundant and contributes to over 50% of total membrane fiber proteins . As water pores confer rapid movements of water across plasma membranes, AQP0 is considered to be essential for the lens microcirculation system and the maintenance of lens transparency , . It has been widely reported that mutations of MIP in humans and mice are involved in the induction of cataracts –.
As aquaporin, MIP has a unique structure with six transmembrane bilayerspanning domains (H1–H6), three extracellular loops (A, C, and E), two intracellular loops (B and D), and the NH2- and COOH-terminal intracellular domains. To the best of our knowledge, this is the third mutation of the MIP gene in transmembrane bilayer-spanning domains (H6) and the first substitution mutation in H6 that can cause autosomal dominant congenital cataracts. The first mutation in H6 of MIP (C.638delG) was reported to be associated with polymorphic cataracts in 2006 , and the second mutation of MIP (IVS-1G>A) was found to be associated with nuclear “snail-like” cataracts in 2009 . The functional consequences of the 638G deletion have been identified, showing that the mutant protein was located in the endoplasmic reticulum and induced cellular cytotoxicity . Similarly, Prior studies of mutant MIP proteins have shown a loss of water permeability function and impaired trafficking in expression systems , . Our findings were consistent with the results of Senthil Kumar et al , who identified the G165D MIP mutation and confirmed that this mutant was involved in congenital lamellar cataracts in a South Indian family. In addition, the expression of MIP and G165D-MIP in Xenopus oocytes and Hela cells suggested that substitution of the conserved glycine residue leads to improper trafficking of AQP0 and destruction of water channel function.
In summary, the current study presented genetic and functional evidence linking a new mutation of MIP (G215D) to autosomal dominant congenital cataracts. Our results showed that G215D-MIP had a lower hydrophobicity and was aberrantly located in the cytoplasm of Hela cells, while WT-MIP was mainly detected in the plasma membrane. We speculate that G215D-MIP would be unable to exert channel functions. Since AQP0 has several functions and plays an adhesive molecule role in the lens, it is likely that, besides channel functions, G215D-MIP would be unable to exert many other functions. Further studies, such as research on protein aggregation in solution and animal models, are needed in order to provide insights into the molecular consequence of this mutation.
The authors are grateful to all patients, the family, and normal volunteers for their participation in this research.
Conceived and designed the experiments: XCD NZ YHQ. Performed the experiments: XCD NZ CYZ GKZ. Analyzed the data: XCD JJC HL. Contributed reagents/materials/analysis tools: XCD NZ YHQ JFH. Contributed to the writing of the manuscript: XCD NZ.
- 1. Li FF, Zhu SQ, Wang SZ, Gao C, Huang SZ, et al. (2008) Nonsense mutation in the CRYBB2 gene causing autosomal dominant progressive polymorphic congenital coronary cataracts. Mol Vis 14: 750–5.
- 2. Su D, Guo Y, Li Q, Guan L, Zhu S, et al. (2012) A novel mutation in CRYAA is associated with autosomal dominant suture cataracts in a Chinese family. Mol Vis 18: 3057–63.
- 3. Chen Q, Ma J, Yan M, Mothobi ME, Liu Y, et al. (2009) A novel mutation in CRYAB associated with autosomal dominant congenital nuclear cataract in a Chinese family. Mol Vis 15: 1359–65.
- 4. Qi Y, Jia H, Huang S, Lin H, Gu J, et al. (2004) A deletion mutation in the betaA1/A3 crystallin gene (CRYBA1/A3) is associated with autosomal dominant congenital nuclear cataract in a Chinese family. Hum Genet 114: 192–7.
- 5. Billingsley G, Santhiya ST, Paterson AD, Ogata K, Wodak S, et al. (2006) CRYBA4 a novel human cataract gene is also involved in microphthalmia. Am J Hum Genet 79: 702–9.
- 6. Mackay DS, Boskovska OB, Knopf HLS, Lampi KJ, Shiels A (2002) A nonsense mutation in CRYBB1 associated with autosomal dominant cataract linked to human chromosome 22q. Am J Hum Genet 71: 1216–21.
- 7. Weisschuh N, Aisenbrey S, Wissinger B, Riess A (2002) Identification of a novel CRYBB2 missense mutation causing congenital autosomal dominant cataract. Mol Vis 18: 174–80.
- 8. Riazuddin SA, Yasmeen A, Yao W, Sergeev YV, Zhang Q, et al. (2005) Mutations in beta-B3-crystallin associated with autosomal recessive cataract in two Pakistani families. Invest Ophthalmol Vis Sci 46: 2100–6.
- 9. Li XQ, Cai HC, Zhou SY, Yang JH, Xi YB, et al. (2002) A novel mutation impairing the tertiary structure and stability of γC-crystallin (CRYGC) leads to cataract formation in humans and zebrafish lens. Hum Mutat 33(2): 391–401.
- 10. Vanita V, Singh D (2002) A missense mutation in CRYGD linked with autosomal dominant congenital cataract of aculeiform type. Mol Cell Biochem 368(1–2): 167–72.
- 11. Sun H, Ma Z, Li Y, Liu B, Li Z, et al. (2002) Gamma-S crystallin gene (CRYGS) mutation causes dominant progressive cortical cataract in humans. J Med Genet 42: 706–10.
- 12. Conley YP, Erturk D, Keverline A, Mah TS, Keravala A, et al. (2000) A juvenile-onset progressive cataract locus on chromosome 3q21-q22 is associated with a missense mutation in the beaded filament structural protein-2. Am J Hum Genet 66: 1426–31.
- 13. Ramachandran RD, Perumalsamy V, Hejtmancik JF (2000) Autosomal recessive juvenile onset cataract associated with mutation in BFSP1.. Hum Genet 121: 475–82.
- 14. Bu L, Jin Y, Shi Y, Chu R, Ban A, et al. (2002) Mutant DNA-binding domain of HSF4 is associated with autosomal dominant lamellar and Marner cataract. Nat Genet 31: 276–8.
- 15. Hansen L, Eiberg H, Rosenberg T (2007) Novel MAF mutation in a family with congenital cataract-microcornea syndrome. Mol Vis 13: 2019–22.
- 16. Berry V, Francis PJ, Prescott Q, Waseem NH, Moore AT, et al. (2007) A novel 1-bp deletion in PITX3 causing congenital posterior polar cataract. Mol Vis 17: 1249–53.
- 17. Yu LC, Tu YC, Chang CY, Lin M (2001) Molecular basis of the adult phenotype and the gene responsible for the expression of the human blood group I antigen. Blood 98: 3840–5.
- 18. Shiels A, Bennett TM, Knopf HLS, Yamada K, Yoshiura K, et al. (2007) CHMP4B a novel gene for autosomal dominant cataracts linked to chromosome 20q. Am J Hum Genet 81: 596–606.
- 19. Jamieson RV, Farrar N, Stewart K, Perveen R, Mihelec M, et al. (2007) Characterization of a familial t(16,22) balanced translocation associated with congenital cataract leads to identification of a novel gene TMEM114 expressed in the lens and disrupted by the translocation. Hum Mutat 28: 968–77.
- 20. Senthil Kumar G, Kyle JW, Minogue PJ, Dinesh Kumar K, Vasantha K, et al. (2013) An MIP/AQP0 mutation with impaired trafficking and function underlies an autosomal dominant congenital lamellarcataract. Exp Eye Res 110: 136–41.
- 21. Pras E, Levy-Nissenbaum E, Bakhan T, Lahat H, Assia E, et al. (2002) A missense mutation in the LIM2 gene is associated with autosomal recessive presenile cataract in an inbred Iraqi Jewish family. Am J Hum Genet 70: 1363–7.
- 22. Su D, Yang Z, Li Q, Guan L, Zhang H, et al. (2013) Identification and functional analysis of GJA8 mutation in a Chinese family with autosomal dominant perinuclear cataracts. PLoS One 8(3): e59926.
- 23. Zhou D, Ji H, Wei Z, Guo L, Li Y, et al. (2013) A novel insertional mutation in the connexin 46 (gap junction alpha 3) gene associated with autosomal dominant congenital cataract in a Chinese family. Mol Vis 19: 789–95.
- 24. Alcalá J, Lieska N, Maisel H (1975) Protein composition of bovine lens cortical fiber cell membranes. Exp Eye Res 6: 581–95.
- 25. Yibo Yu, Yinhui Yu, Peiqing Chen, Jinyu Li, Yanan Zhu, et al. (2014) A novel MIP gene mutation associated with autosomal dominant congenital cataracts in a Chinese family. BMC Medical Genetics 15: 6.
- 26. Zeng L, Liu W, Feng W, Wang X, Dang H, et al. (2013) A novel donor splice-site mutation of major intrinsic protein gene associated with congenital cataract in a Chinese family. Mol Vis 19: 2244–9.
- 27. Watanabe K, Wada K, Ohashi T, Okubo S, Takekuma K, et al. (2012) A 5-bp insertion in Mip causes recessive congenital cataract in KFRS4/Kyo rats. PLoS One 7(11): e50737.
- 28. Gu F, Zhai H, Li D, Zhao L, Li C, et al. (2007) A novel mutation in major intrinsic protein of the lens gene (MIP) underlies autosomal dominant cataract in a Chinese family. Mol Vis 13: 1651–6.
- 29. Berry V, Francis P, Kaushal S, Moore A, Bhattacharya S (2000) Missense mutations in MIP underlie autosomal dominant polymorphic and lamellar cataracts linked to 12q. Nat Genet 25: 15–7.
- 30. Yang G, Zhang G, Wu Q, Zhao J (2011) A novel mutation in the MIP gene is associated with autosomal dominant congenital nuclear cataract in a Chinese family. Mol Vis 17: 1320–3.
- 31. Wang KJ, Li SS, Yun B, Ma WX, Jiang TG, et al. (2011) A novel mutation in MIP associated with congenital nuclear cataract in a Chinese family. Mol Vis 17: 70–7.
- 32. Lin H, Hejtmancik JF, Qi Y (2007) A substitution of arginine to lysine at the COOH-terminus of MIP caused a different binocular phenotype in a congenital cataract family. Mol Vis 13: 1822–7.
- 33. Xiao X, Li W, Wang P, Li L, Li S, et al. (2011) Cerulean cataract mapped to 12q13 and associated with a novel initiation codon mutation in MIP. Mol Vis 17: 2049–55.
- 34. Senthil Kumar G, Kyle JW, Minogue PJ, Dinesh Kumar K, Vasantha K, et al. (2013) An MIP/AQP0 mutation with impaired trafficking and function underlies an autosomal dominant congenital lamellar cataract. Exp Eye Res 110: 136–41.
- 35. Jiang J, Jin C, Wang W, Tang X, Shentu X, et al. (2009) Identification of a novel splice-site mutation in MIP in a Chinese congenital cataract family. Mol Vis 15: 38–44.
- 36. Varadaraj K, Kumari SS, Patil R, Wax MB, Mathias RT (2008) Functional characterization of a human aquaporin 0 mutation that leads to a congenital dominant lens cataract. Exp Eye Res 87: 9–21.
- 37. Alcala J, Lieska N, Maisel H (1975) Protein composition of bovine lens cortical fiber cell membranes. Exp Eye Res 6: 581–95.
- 38. Kumari SS, Varadaraj K (2009) AQP0 performs cell-to-cell adhesion. Biochem Biophys Res Commun 390: 1034–9.
- 39. Gonen T, Cheng Y, Kistler J, Walz T (2004) Aquaporin-0 membrane junctions form upon proteolytic cleavage. J Mol Biol 342: 1337–45.
- 40. Kai Jie Wang, Sha Sha Li, Bo Yun, Wen Xian Ma, Tian Ge Jiang, et al. (2011) A novel mutation in MIP associated with congenital nuclear cataract in a Chinese family. Mol Vis 17: 70–7.
- 41. Yang G, Zhang G, Wu Q, Zhao J (2011) A novel mutation in the MIP gene is associated with autosomal dominant congenital nuclearcataract in a Chinese family. Mol Vis 17: 1320–3.
- 42. Watanabe K, Wada K, Ohashi T, Okubo S, Takekuma K, et al. (2012) A 5-bp insertion in Mip causes recessive congenital cataract in KFRS4/Kyo rats. PLoS One 7(11): e50737.
- 43. Senthil Kumar G, Kyle JW, Minogue PJ, Dinesh Kumar K, Vasantha K, et al. (2013) An MIP/AQP0 mutation with impaired trafficking and function underlies an autosomal dominant congenital lamellarcataract. Exp Eye Res 110: 136–41.
- 44. Sindhu Kumari S, Varadaraj K (2014)Intact and N- or C- terminal end truncated AQP0 function as open water channels and cell-to-cell adhesion proteins: End truncation could be a prelude for adjusting the refractive index of the lens to prevent spherical aberration. Biochim Biophys Acta S0304-4165(14)00159-7.