January 2000
Volume 41, Issue 1
Free
Lens  |   January 2000
Genetic Heterogeneity of the Coppock-like Cataract: A Mutation in CRYBB2 on Chromosome 22q11.2
Author Affiliations
  • Dan Gill
    From the Eye Research Institute of Canada and the
  • Robert Klose
    From the Eye Research Institute of Canada and the
  • Francis L. Munier
    Hôpital Ophthalmique Jules Gonin, Unité de Génétique Moléculaire, Division de Génétique Médicale,
    Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland.
  • Michelle McFadden
    From the Eye Research Institute of Canada and the
  • Megan Priston
    From the Eye Research Institute of Canada and the
  • Gail Billingsley
    From the Eye Research Institute of Canada and the
  • Nicolas Ducrey
    Hôpital Ophthalmique Jules Gonin, Unité de Génétique Moléculaire, Division de Génétique Médicale,
  • Daniel F. Schorderet
    Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland.
  • Elise Héon
    From the Eye Research Institute of Canada and the
    Department of Ophthalmology, University of Toronto; the
    Hospital for Sick Children Research Institute, Toronto, Canada; and
Investigative Ophthalmology & Visual Science January 2000, Vol.41, 159-165. doi:
  • Views
  • PDF
  • Share
  • Tools
    • Alerts
      ×
      This feature is available to authenticated users only.
      Sign In or Create an Account ×
    • Get Citation

      Dan Gill, Robert Klose, Francis L. Munier, Michelle McFadden, Megan Priston, Gail Billingsley, Nicolas Ducrey, Daniel F. Schorderet, Elise Héon; Genetic Heterogeneity of the Coppock-like Cataract: A Mutation in CRYBB2 on Chromosome 22q11.2. Invest. Ophthalmol. Vis. Sci. 2000;41(1):159-165.

      Download citation file:


      © ARVO (1962-2015); The Authors (2016-present)

      ×
  • Supplements
Abstract

purpose. To identify the genetic defect for the Coppock-like cataract (CCL) affecting a Swiss family, which defect was unlinked to the chromosome 2q33-35 CCL locus.

methods. A large family was characterized for linkage analysis by slit lamp examination or by the review of drawings made before cataract extraction. The affection status was attributed before genotyping, and the genotyping was masked to the affection status. Two-point and multipoint linkage analyses were performed using the MLINK and the LINKMAP components of the LINKAGE program package (ver. 5.1), respectively. Mutational analysis of candidate genes was performed by a combination of direct cycle sequencing and an amplification refractory mutation system assay.

results. Ten individuals were affected with the CCL phenotype. The disease was autosomal dominant and appeared to be fully penetrant. A new CCL locus was identified on chromosome 22q11.2 within a 11.67-cM interval (maximum lod score [Zmax] = 4.14; θ = 0). Mutational analysis of the CRYBB2 candidate gene identified a disease-causing mutation in exon 6. This sequence change was identical with that previously described to be associated with the cerulean cataract, a clinically distinct entity.

conclusions. The CCL phenotype is genetically heterogeneous with a second gene on chromosome 22q11.2, CRYBB2. The CCL and the cerulean cataract are two distinct clinical entities associated with the same genetic defect. This work provides evidence for a modifier factor that influences cataract formation and that remains to be identified.

Despite the great advances in the clinical management of cataracts and the better understanding of lens structure and function, cataract remains a leading cause of blindness worldwide, 1 and the world incidence is increasing as a consequence of the aging population. 2 The mechanisms of lens opacification remain poorly understood; however, studies suggest that a Mendelian factor is likely to play a major role in the most common age-related cataracts. 3 4 Congenital cataracts are one of the most common major eye disorders in infants, and their frequent autosomal dominant inheritance represents a tool to identify cataract-related genetic defects. Genetic factors have been identified in animals and humans, but the combination of the genetic heterogeneity of the disease, and the intra- and interfamilial variable expression have been a hurdle to the progression of genetic studies. 5 To date, more than 14 candidate loci have been identified and seven cataract-related genes characterized. 6 7 8 9 10 11 12 The molecular characterization of different phenotypes is important for the identification of the various elements involved in lens opacification. 
The Coppock cataract was first described by Nettleship in 1906 and refers to a congenital pulverulent disc-like opacity involving the embryonal and fetal nucleus with many tiny white dots in the lamellar portion of the lens. 13 It is usually bilateral and dominantly inherited. The Coppock cataract was mapped to chromosome 1q by linkage to the Duffy blood group 14 and a mutation recently identified in GJA8, a member of the connexin genes family. 10 A morphologically similar cataract, now referred to as the Coppock-like cataract (CCL), was linked to theγ -crystallin cluster on chromosome 2q33-35 15 16 and a disease-causing mutation recently identified in CRYGC. 12  
A four-generation family affected with CCL was studied in an attempt to identify the genetic defect associated with this cataract phenotype. 
Methods
Clinical Evaluation
This study was approved by the Ethics Committee of the Faculty of Medicine of the University of Lausanne, Switzerland, and was conducted according to the tenets of the Declaration of Helsinki. All participants were examined. The phenotypes were characterized by direct examination when possible as well as through the examination of photographs and drawings obtained from physicians who had examined patients before the removal of cataracts. The disease status was determined before genotyping on the basis of the clinical examination and not by history alone. 
For the purpose of the linkage study, patients were considered to be affected when they had had central pulverulent and/or zonular pulverulent lens changes. Because the youngest age at diagnosis was 1 year and those affected were all symptomatic by the age of 30, those who did not show the presence of the characteristic lens opacity by adulthood were considered “unaffected.” 
Genotyping
After informed consent, blood samples were obtained from family members (affected and unaffected) and spouses. DNA was prepared from whole blood using a nonorganic procedure. 17 Genotyping was performed by investigators masked to the patients’ disease status. Genetic maps used for the selection of short tandem repeat polymorphisms were obtained from the literature, those characterized by the Cooperative Human Linkage Center (CHLC), 18 Généthon, 19 and others available through the Internet such as, Marshfield and The Genome Database. Primers were obtained from Research Genetics (screening set 6A; Huntsville, AL), ACGT, or Dalton (Toronto, Ontario, Canada). A fluorescent dye label was incorporated on the 5′ end of one of the primers, and the amplification products were electrophoresed using automated sequencers (ALF; Pharmacia, Piscataway, NJ) and analyzed using the Fragment Manager software (Pharmacia). The amplification protocol has been described previously. 20  
The order of the markers used at the 22q11.2-11.3 locus, proximal to distal, and their intermarker distances (in centimorgans [cM]) were determined from genome database genetic maps (www.marshmed.org/genetics/maps and www.chlc.org) and were as follows (parentheses denote that intermarker distance is unknown): D22S420 - 4.2 - D22S427 - 5.3 - (D22S264) - D22S425 - 0.9 - D22S446 - 2.0 - D22S303 - 1.9 - D22S257 - 0.4 - D22S1685 - 1.2 - (D22S301) - D22S1174, D22S156, TOP1P2 - (D22S431) - 2.1 - CRYBB2 - (D22S258 - D22S351) - 3.3 - D22S1167 - 2.7 - D22S1144 - 0.5 - D22S1163 - 0.5 - D22S689, D22S275 - 1.1 - D22S273 - 1.6 - D22S280 - 0.54 - D22S1158 -0.5 - D22S685. 
Linkage Analysis
Cyrillic (ver. 2.1.3) (Cherwell Scientific Publishing, Oxford, UK) was used for data management and pedigree drawing. Two-point linkage analysis between a cataract phenotype and the genotype information used the MLINK component of LINKAGE (ver. 5.1). 21 Multipoint analysis used the LINKMAP support program of LINKAGE. A 3-lod-unit support interval was used to ensure a high degree of confidence in locus placement for the multipoint analysis. Full penetrance was assumed, and a disease-gene frequency of 0.0001 was used for the disease locus. 
For data given in Table 1 , the allele frequencies were assumed to be equal for each marker, because the true population allele frequencies for each marker could not be reliably estimated because of the small number of spouses and Swiss control subjects available. To show that this assumption would not significantly affect our linkage results, lod scores were recalculated using allele frequencies of 0.01 to 0.5 for the“ affected” allele of the most tightly linked markers (CRYBB2, D22S1174, D22S1167) and the Zmax remained unchanged. 
Mutational Analysis of CRYBB2 Exon 6
Mutational analysis of CRYBB2, a strong candidate gene, began with exon 6, because this exon was associated with cataracts in human 6 and mouse. 22 For screening of exon 6, from affected and unaffected unrelated individuals, we used direct cycle sequencing after polymerase chain reaction (PCR) amplification of DdeI restriction enzyme–digested genomic DNA. 
DdeI Restriction Endonuclease Digestion.
CRYBB2 and CRYBB2P1 are highly homologous. To ensure specific PCR amplification of CRYBB2 exon 6, genomic DNA was initially restriction endonuclease digested with DdeI, which was unique to the exon 6 homologous region of the CRYBB2 pseudogene and disrupted its amplification. Four hundred nanograms of genomic DNA was digested overnight at 37°C, in a 10-μl volume with 3 units of DdeI (New England Biolabs, Beverly, MA). 
Amplification of CRYBB2 Exon 6.
PCR amplification conditions were as follows: 100 ng of DdeI-digested genomic DNA, 1.5 mM MgCl2, PCR buffer (GeneAmp II; Perkin-Elmer, Norwalk, CT), 5% dimethyl sulfoxide (DMSO), 1 unit DNA polymerase (AmpliTaq, Perkin–Elmer), 200 μM of each dNTP, and 50 ng of each exon 6 primer 6 in a final PCR reaction volume of 20 μl. Hot-start addition of DNA polymerase, after an initial 3-minute denaturation (94°C), was followed by 35 cycles of 30 seconds at 94°C, 35 seconds at 58°C, and 40 seconds at 72°C and was completed with an 8-minute extension at 72°C, by using a thermocycler (Robocycler Gradient 96; Stratagene; LaJolla, CA). 
Direct Sequencing of CRYBB2 Exon 6.
The column-purified (QIAquick PCR Purification Kit; Qiagen, Basel, Switzerland) PCR products (final volume of 20 μl) containing exon 6 were sequenced on a automated DNA sequencing unit (MicroGene Blaster; Visible Genetics, Toronto, Canada) using nested Cy5.5-labeled primers (forward, 5′GCCTCTCTCTCTGTCTGCTTC-3′; reverse, 5′-TTGGAGGTCTGGAGGGTTC-3′) and a cycle-sequencing core kit (US79610, Thermo Sequenase; Visible Genetics). The sequencing reactions, which included 2 μl template, 10% DMSO, and 1 picomole primer, were performed for 35 cycles (35 seconds at 94°C, 35 seconds at 56°C, and 1 minute at 70°C) after an initial denaturation step (94°C for 3 minutes) and a final 6-minute 70°C extension. Sequence variants were analyzed in both directions. 
Amplification Refractory Mutation System Assay.
All family members and controls were screened for the proposed disease-causing mutation through an amplification refractory mutation system (ARMS) assay. 23 To ensure CRYBB2 specificity, 25 ng of genomic DNA was digested with 2 units DdeI in 5 μl total volume, as previously described. The mutation-specific ARMS primer, 5′-CTGCAGGTGGGTTGGTTACT-3′, was specific to the C-to-T transition at base pair 14 of exon 6 and, to increase specificity, had an internal nucleotide (in bold) that did not match either the normal or mutant allele. This primer was paired with the exon 6 reverse PCR primer. Primers for the short tandem repeat polymorphism marker D1S1663 (409–425 bp) were included in each reaction as a positive control for PCR. After DdeI digestion, the whole mixture was incorporated into a 20-μl PCR reaction containing PCR buffer (GeneAmp II), 5% DMSO, 200 μM of each dNTP, 50 ng of each primer, and 1 unit of DNA polymerase (AmpliTaq). Reactions were performed on a thermocycler (PTC-100; MJ Research; Watertown, MA) with an initial denaturation of 2 minutes at 94°C, followed by 36 cycles of 30 seconds at 94°C, 30 seconds at 61°C, 35 seconds at 72°C, and a final 8-minute extension at 72°C. Products were electrophoresed on 1% agarose gel stained with ethidium bromide and then visualized by UV transillumination. Affected individuals had a 400-bp control band and a 220-bp mutation-specific band, whereas unaffected individuals had only the 400-bp internal control band. 
Results
Clinical Findings
A four-generation Swiss family from the canton of Vaud was identified with 13 individuals affected with a CCL (Fig. 1) . After informed consent, 16 individuals with a family history of autosomal dominant CCL and 4 spouses were examined and included in this study. Ten of these 16 individuals were affected with the CCL phenotype, and none of the spouses showed sign of the disease. Male to male transmission of the disease phenotype confirmed the autosomal dominant mode of inheritance. The penetrance appeared to be complete, and the cataracts were bilateral and symmetrical. 
This cataract was characterized by a pulverulent opacification of the embryonal nucleus, giving a gray disc appearance associated with zonular opacities to a variable degree (Fig. 2) . Although the progressive nature of this cataract has not been clearly documented, a steady decrease in the visual acuity starting in the teens and a premature nuclear sclerosis were observed. Visual impairment was usually first noticed in the teenaged years, and most affected individuals required cataract surgery in their 40s to improve their visual function. 
Linkage Analysis
Candidate loci related to congenital cataracts, and particularly the crystallin gene loci, were initially screened with at least three highly polymorphic short tandem repeat polymorphism markers per locus. 20 The Coppock and Coppock-like loci were analyzed first and excluded genetically (data not shown). Significant linkage was found with markers of the CRYBB2 locus at the 22q11.2-q13.1 region. Two-point maximum likelihood data for markers of this region are summarized in Table 1 . The highest observed lod score was 4.14 (θ = 0) with marker CRYBB2, an intragenic polymorphism. 
Critical recombination events defined an initial disease-gene interval of 11.67 cM between markers D22S303 and D22S1144 (Fig. 1) . Multipoint analysis supported the same disease-gene interval (11.67 cM) (Fig. 3) . The centromeric recombination event involved a 32-year-old unaffected individual (III:2). However, in this family the youngest affected individual was 1 year of age, and all affected individuals were symptomatic by the age of 30, which suggests that III:2 most likely was not a carrier of the disease-gene mutation. 
Several candidate genes such as those encoding for the α- or theβ -crystallin proteins (CRYB; B1, B2, B3, A4, and B2 pseudogene) and several other important genes for cell metabolism and differentiation (UFD1L, CAMKB, KCNNB) were of particular interest. 
Candidate Gene Analysis
Direct cycle sequencing of CRYBB2 exons 1 to 6 identified a 14C→T mutation in exon 6 (Fig. 4A ). This mutation creates a stop codon that truncates theβ B2-crystallin polypeptide by 51 residues. This change cosegregated with the disease phenotype (Fig. 4B) and was not seen in 115 control subjects of various ethnic backgrounds and 39 unrelated individuals affected with congenital cataract. The same mutation was observed in one unrelated patient affected with cerulean cataracts. The remainder of the coding sequence and the promoter region of CRYBB2 (base pairs 66,014–66,649, GDB accession number 299916) failed to show any significant sequence change. 
Discussion
This study provides the first evidence of genetic heterogeneity of the Coppock-like phenotype and the identification of CRYBB2 as the second disease-gene (CCL2) on chromosome 22q11.2-12.2. The phenotypes associated with the two CCL loci are indistinguishable from the initial drawings by Nettleship of the Coppock cataract mapped to chromosome 1, 13 14 which emphasizes the confusion derived from the current classification of lens opacities. Referring to the genetic heterogeneity of the phenotype of combined embryonal and lamellar pulverulent opacities may be more appropriate. 
Even though the hereditary aspects of cataracts have been recognized for nearly a century, the molecular information on the disease remains relatively scarce, with only seven human cataract genes identified, five of which are crystallin genes. 6 7 8 9 10 11 12 The crystallins constitute more than 90% of the soluble proteins in the eye and are critical to lens function, fulfilling a structural role for transparency and refraction. 24 25 In man, there are three classes of crystallins, the γ (CRYG), β (CRYB), and α (CRYA), that are distinguished as a result of their chromatographic properties. In the human lens, α-crystallin constitutes 40% of the crystallins,β -crystallin 35%, and γ-crystallin 25%. 26 The structural stability of crystallins is important. They have to last a lifetime, because the lens cells lose their nuclei and cells are never shed. 27  
The β-crystallins family contains seven protein chains (three CRYBB and four CRYBA). The gene structure of the β-crystallins is very similar, suggesting that they may have been derived from a sequence of a single ancestor. 28 29 CRYBB1, BB2, BB3, and BA4, all map to chromosome 22q11.2-13.1, 29 30 31 whereas the gene for BA1/BA3 maps to chromosome 17q11.2-q12, 32 33 and CRYBA2 to chromosome 2q33-35. 34 The β-crystallins appear in the lens as heterogeneous dimers (βL) to octamers (βH). The most distinct feature for individual β-crystallin molecules is located in their N- and C-terminal arms. In addition to sequence variations, the N-terminal arms differ significantly in length. 35 This tail appears to be responsible for protein–protein interactions within the lens. 36 Different β-crystallin proteins are found in both prenatal and postnatal developing lens and their interaction with each other, as well as with other lens proteins, are postulated to be key in maintenance of lens transparency. 37 38 The CRYBB2 gene was of high interest in our work, because it was mapped to our disease interval, it was present in the postnatal lens, and it is also presumed to play a key role in maintenance of lens transparency. 6 Furthermore, mutations in theβ B2-crystallin gene were associated with a “cerulean cataract phenotype” in human 6 and with the Philly mouse cataract. 22 39  
The C-to-T chain termination mutation observed in CRYBB2 exon 6 of patients affected with CCL is identical with that observed in patients with cerulean cataracts. This mutation results in an in-frame stop codon at nucleotide 14 that causes 51 amino acids to be truncated from the C-terminal end of the CRYBB2 protein. 
The absolute role of crystallin protein in the maintenance of lens transparency is not clear. The result of a truncated CRYBB2 in human expression is speculated from a mouse cataract model and experimental work performed on altered CRYBB2. 36 38 Because exon 6 encodes for the extension of the C-terminal arm, the mutation hereby described, truncating 51 amino acids from the C-terminal end of CRYBB2, could well result in an inability of the protein to anchor itself in an octomer structure, impeding its role in higher aggregation. 40 Improper ability of the altered CRYBB2 protein to aggregate in an orderly fashion could result in an insoluble protein that precipitates as a result of misfolding and improper interactions. 
The cerulean cataract is clinically distinct from the CCL, being characterized by coarser punctate lens opacities that may have a bluish hue involving the more superficial layers of the nucleus.44 Explanations for the observation of two different phenotypes with the same mutation could relate to the influence of a modifier gene yet to be identified or to sequence variations that could influence CRYBB2 expression. Regulatory elements have been identified in the promoter region of the rat and observed to influence the expression of CRYBB2 in lens cells. 42 However, the homologous regions were sequenced in affected individuals, and no significant sequence variations were observed. Other surrounding crystallins are being analyzed. 
Although we understand some aspects of lens structure and function, the series of events leading to lens opacification remain unclear. Further identification of cataract-related genetic defects, as well as factors that modulate their variable expression, will contribute to better understanding of the process of lens opacification. 
 
Table 1.
 
Two-Point Linkage Data for the Coppock-like Cataract and Markers of the 22q11.2 Region
Table 1.
 
Two-Point Linkage Data for the Coppock-like Cataract and Markers of the 22q11.2 Region
Markers IMD (cM) Recombination Fraction (θ) θmax Zmax
0.00 0.05 0.10 0.20 0.30 0.40
D22S427 −0.26 −0.18 −0.13 −0.06 −0.02 −0.005 0.50 0.00
5.3
D22S425 −∞ 1.15 1.22 1.05 0.75 0.40 0.10 1.22
2.9
D22S303 −∞ 0.71 0.78 0.60 0.29 0.06 0.09 0.78
2.3
D22S1685 2.80 2.65 2.45 1.92 1.29 0.59 0.00 2.80
1.2
D22S1174 3.91 3.58 3.23 2.46 1.61 0.69 0.00 3.91
0
D22S156 2.94 2.71 2.46 1.91 1.29 0.60 0.00 2.94
0
TOP1P2 2.71 2.46 2.20 1.65 1.02 0.39 0.00 2.71
2.2
CRYBB2 4.14 3.78 3.41 2.61 1.70 0.73 0.00 4.14
3.3
D22S1167 3.61 3.30 2.97 2.62 1.48 0.65 0.00 3.61
2.7
D22S1144 −∞ 0.19 0.35 0.34 0.19 0.05 0.14 0.38
0.5
D22S1163 −∞ 1.59 1.63 1.35 0.89 0.36 0.08 1.64
0.5
D22S275 −∞ 2.30 2.27 1.86 1.24 0.51 0.06 2.32
1.1
D22S273 −∞ −0.04 0.17 0.26 0.18 0.06 0.19 0.26
1.6
D22S280 −∞ −0.51 0.15 0.55 0.50 0.24 0.23 0.56
Figure 1.
 
Pedigree of family studied with haplotype for selected markers relevant to recombinant breakpoints on chromosome 22q11.2. Filled symbols denote affected status. The affected haplotype is indicated by the filled box; the critical crossovers defining the proximal and distal boundaries of the CCL2 candidate region involve individuals III:2 and IV:4, placing the disease locus between the markers D22S303 and D22S1144.
Figure 1.
 
Pedigree of family studied with haplotype for selected markers relevant to recombinant breakpoints on chromosome 22q11.2. Filled symbols denote affected status. The affected haplotype is indicated by the filled box; the critical crossovers defining the proximal and distal boundaries of the CCL2 candidate region involve individuals III:2 and IV:4, placing the disease locus between the markers D22S303 and D22S1144.
Figure 2.
 
(A) Slit lamp photography of an individual (III-12, 30 years old) affected with CCL. Left: front view, Right: slit view of the lens and cornea. (B) Intrafamilial phenotype variability observed in the family studied. This was derived from a combination of drawings, photographs, and examinations.
Figure 2.
 
(A) Slit lamp photography of an individual (III-12, 30 years old) affected with CCL. Left: front view, Right: slit view of the lens and cornea. (B) Intrafamilial phenotype variability observed in the family studied. This was derived from a combination of drawings, photographs, and examinations.
Figure 3.
 
Multipoint linkage analysis between the cataract locus and chromosome 22q11.2 microsatellite markers, with a peak lod score of 4.08, 0.5 cM distal to D22S1167.
Figure 3.
 
Multipoint linkage analysis between the cataract locus and chromosome 22q11.2 microsatellite markers, with a peak lod score of 4.08, 0.5 cM distal to D22S1167.
Figure 4.
 
Mutation analysis of CRYBB2 exon 6. (A) Normal and heterozygous affected DNA (individual IV-1) sequence (sense strand) showing the C-to-T transition at base 14 of exon 6 that changes glutamine (CAG) to an in-frame stop codon. (B) ARMS assay showing cosegregation of the C14T mutation with the CCL phenotype for part of the family. Mutation-specific amplification of a 220-bp PCR product (primer 5′-CTGCAGGTGGGTTGGTTACT-3′) is seen in affected individuals only. Primers for the short tandem repeat polymorphism marker D1S1663 (409–425 bp) were included in each reaction as a positive control for PCR. Individuals are identified as in Figure 1 . One hundred-base-pair ladder is in the outside lanes.
Figure 4.
 
Mutation analysis of CRYBB2 exon 6. (A) Normal and heterozygous affected DNA (individual IV-1) sequence (sense strand) showing the C-to-T transition at base 14 of exon 6 that changes glutamine (CAG) to an in-frame stop codon. (B) ARMS assay showing cosegregation of the C14T mutation with the CCL phenotype for part of the family. Mutation-specific amplification of a 220-bp PCR product (primer 5′-CTGCAGGTGGGTTGGTTACT-3′) is seen in affected individuals only. Primers for the short tandem repeat polymorphism marker D1S1663 (409–425 bp) were included in each reaction as a positive control for PCR. Individuals are identified as in Figure 1 . One hundred-base-pair ladder is in the outside lanes.
The authors thank the families for their enthusiastic participation. 
Thylefors B, Négrel A, Pararajasegaram R, Dadzie K. Global data on blindness. Bull World Health Organ. 1995;73:115–121. [PubMed]
Arnold J. Global cataract blindness: the unmet challenge. Br J Ophthalmol. 1998;82:593–596. [CrossRef] [PubMed]
Heiba IM, Elston RC, Klein BEK, Klein R. Sibling correlations and segregation analysis of age-related maculopathy: the Beaver Dam Eye Study. Genet Epidemiol. 1994;11:51–67. [CrossRef] [PubMed]
Heiba IM, Elston RC, Klein BE, Klein R. Evidence for a major gene for cortical cataract. Invest Ophthalmol Vis Sci. 1995;36:227–235. [PubMed]
Scott M, Heijtmancik J, Wozencraft L, Reuter L, Parks M, Kaiser–Kupfer M. Autosomal dominant congenital cataract. Ophthalmology. 1994;101:866–871. [CrossRef] [PubMed]
Litt M, Carrero VR, LaMorticella DM, et al. Autosomal dominant cerulean cataract is associated with a chain termination mutation in the human beta-crystallin gene CRYBB2. Hum Mol Genet. 1997;6:665–668. [CrossRef] [PubMed]
Kannabiran C, Rogan P, Olmos L, et al. Autosomal dominant zonular cataract with sutural opacities is associated with a splice mutation in the beta A3/A1-crystallin gene. Mol Vis. 1998;4:21–31. [PubMed]
Litt M, Kramer P, LaMorticella DM, Murphey W, Lovrien EW, Weleber RG. Autosomal dominant congenital cataract associated with a missense mutation in the human alpha crystallin gene CRYAA. Hum Mol Genet. 1998;7:471–474. [CrossRef] [PubMed]
Mumford A, Vulliamy T, Lindsay J, Watson A. A hereditary hyperferritinemia-cataract syndrome: two novel mutations in the L-ferritin iron-responsive element. Blood. 1998;6:665–668.
Shiels A, Mackay D, Ionides A, Berry V, Moore A, Bhattacharya S. A missense mutation in the human connexin50 gene (GJA8) underlies autosomal dominant “zonular pulverulent” cataract, on chromosome 1q. Am J Hum Genet. 1998;62:526–532. [CrossRef] [PubMed]
Stephan D, Gillanders E, Vanderveen D, et al. Progressive juvenile-onset punctate cataracts caused by mutation of the gammaD-crystallin gene. Proc Natl Acad Sci USA. 1999;96:1008–1012. [CrossRef] [PubMed]
Héon E, Priston M, Schorderet DF, et al. The γ-Crystallins and human cataract: A puzzle made clearer. Am J Hum Genet. 1999;65:1261–1267. [CrossRef] [PubMed]
Nettleship E, Ogilvie F. A peculiar form of hereditary congenital cataract. Trans Ophthalmol Soc UK. 1906;26:191.
Renwick J, Lawler S. Probable linkage between a congenital cataract locus and the Duffy blood group locus. Ann Hum Genet. 1963;27:67–84. [CrossRef] [PubMed]
Lubsen N, Renwick J, Tsui L-C, Breitman M, Schoenmackers J. A locus of a human hereditary cataract is closely linked to the gamma-crystallin gene family. Proc Natl Acad Sci USA. 1987;84:489–492. [CrossRef] [PubMed]
Brakenhoff R, Henskens H, van Rossum M, Lubsen N, Schoenmakers G. Activation of the gamma E-crystallin pseudogene in the human hereditary Coppock-like cataract. Hum Mol Genet. 1994;3:279–283. [CrossRef] [PubMed]
Miller S, Dykes D, Polesky H. A simple salting out procedure for extracting DNA from human nucleated cells. Nucleic Acids Res. 1988;16:1215. [CrossRef] [PubMed]
Murray J, Buetow K, Weber J, et al. A comprehensive human linkage map with centimorgan density: Cooperative Human Linkage Center. Science. 1994;265:2049–2054. [CrossRef] [PubMed]
Gyapay G, Morissette J, Vignal A, et al. The 1993–94 Généthon human genetic linkage map. Nat Genet. 1994;7:246–339. [CrossRef] [PubMed]
Héon E, Liu S, Billingsley G, et al. Gene localization for aculeiform cataract, on chromosome 2q33-35. Am J Hum Genet. 1998;63:921–926. [CrossRef] [PubMed]
Lathrop G, Lalouel J. Easy calculations of lod scores and genetic risk on small computers. Am J Hum Genet. 1984;36:460–465. [PubMed]
Kador P, Fukui H, Fukushi S, Jernigan H, Kinoshita J. Philly mouse: A new model of hereditary cataract. Exp Eye Res. 1980;30:59–68. [CrossRef] [PubMed]
Newton C, Graham A, Heptinsall I, Powell S, Summers C, Kalsheker N. Analysis of any point mutation in DNA. The amplification refractory mutation system (ARMS). Nucleic Acids Res. 1989;17:2503–2515. [CrossRef] [PubMed]
Delaye M, Tardieu A. Short-range order of crystallin proteins accounts for eye lens transparency. Nature. 1983;302:415–417. [CrossRef] [PubMed]
Wistow G, Piatigorsky J. Lens crystallins: the evolution and expression of proteins for a highly specialized tissue. Annu Rev Biochem. 1988;57:479–504. [CrossRef] [PubMed]
Hejtmancik JF. The genetics of cataract: our vision becomes clearer (editorial). Am J Hum Genet. 1998;62:520–525. [CrossRef] [PubMed]
Harding J, Crabe M. The lens: development, proteins, metabolism and cataract. Davson H eds. The Eye. 1984; 3rd ed. 207–492. Academic Press London.
Piatigorsky J. Gene expression and genetic engineering in the lens. Friedwald lecture. Invest Ophthalmol Vis Sci. 1987;28:9–28. [PubMed]
Van Rens G, de Jong W, Bloemendal H. A superfamily in the mammalian eye lens: the beta/gamma-crystallins. Mol Biol Rep. 1992;16:1–10. [CrossRef] [PubMed]
Sparkes R, Hogg D, Gorin M, et al. Assignment of a second human beta-crystallin gene (CRYB2) to 22q11.2-q12.2 (Abstract). Cytogenet Cell Genet. 1987;46:696.
Hulsebos T, Bijlsman E, Geurts van Kessel A, Brakenhoff R, Westerveld A. Direct assignment of human beta B2 and beta B3 crystallin genes to 22q11.2-q12: markers for neurofibromatosis 2. Cytogenet Cell Genet. 1991;56:171–175. [PubMed]
Law M, Cai G-Y, Hartz J, et al. Localization of a beta-crystallin gene, the Hu beta A3/A1 (gene symbol CRYB1) to the long arm of chromosome 17. Cytogenet Cell Genet. 1986;42:202–207. [CrossRef] [PubMed]
Sparkes R, Mohandas T, Heinzman C, Gorin M, Zollman S, Horwitz J. Assignment of beta-crystallin gene to 17 cen-q23. Hum Genet. 1986;74:133–136. [CrossRef] [PubMed]
Hulsebos TJ, Cerosaletti KM, Fournier RE, et al. Identification of the human beta-A2 crystallin gene (CRYBA2): localization of the gene on human chromosome 2 and of the homologous gene on mouse chromosome 1. Genomics. 1995;28:543–548. [CrossRef] [PubMed]
Lubsen N, Aarts H, Schoenmakers J. The evolution of lenticular proteins: the beta- and gamma-crystallin super gene family. Prog Biophys Mol Biol. 1988;51:47–76. [CrossRef] [PubMed]
Norledge B, Trinkl S, Jaenicke R, Slingsby C. The X-ray structure of a mutant eye lens beta B2-crystallin with truncated sequence extensions. Protein Sci. 1997;6:1612–1620. [CrossRef] [PubMed]
Bax B, Lapatto R, Nalini V, et al. X-ray analysis of bB2-crystallin and evolution of oligomeric lens proteins. Nature. 1990;347:776–780. [CrossRef] [PubMed]
Russell P, Chambers C. Interaction of an altered beta-crystallin with other proteins in the Philly mouse lens. Exp Eye Res. 1990;50:683–687. [CrossRef] [PubMed]
Carper D, Shinohara T, Piatigorsky J, Kinoshita J. Deficiency of functional messenger RNA for a developmentally regulated b-crystallin polypeptide in a hereditary cataract. Science. 1982;217:463–464. [CrossRef] [PubMed]
Cooper PG, Carver J, Truscott J. H-NMR spectroscopy of bovine lens β-crystallin: The role of the βB2-crystallin C-terminal extension in aggregation. Eur J Biochem. 1993;213:321–328. [CrossRef] [PubMed]
Francois J. Varieties of congenital cataracts. Congenital Cataracts. 1963;164–165. Royal Van Gorcum Assen.
Dirks R, Kraft H, Van Genesen S, et al. The cooperation between two silencers creates an enhancer element that controls both the lens-preferred and the differentiation stage-specific expression of the rat betaB2-crystallin gene. Eur J Biochem. 1996;239:23–32. [CrossRef] [PubMed]
Figure 1.
 
Pedigree of family studied with haplotype for selected markers relevant to recombinant breakpoints on chromosome 22q11.2. Filled symbols denote affected status. The affected haplotype is indicated by the filled box; the critical crossovers defining the proximal and distal boundaries of the CCL2 candidate region involve individuals III:2 and IV:4, placing the disease locus between the markers D22S303 and D22S1144.
Figure 1.
 
Pedigree of family studied with haplotype for selected markers relevant to recombinant breakpoints on chromosome 22q11.2. Filled symbols denote affected status. The affected haplotype is indicated by the filled box; the critical crossovers defining the proximal and distal boundaries of the CCL2 candidate region involve individuals III:2 and IV:4, placing the disease locus between the markers D22S303 and D22S1144.
Figure 2.
 
(A) Slit lamp photography of an individual (III-12, 30 years old) affected with CCL. Left: front view, Right: slit view of the lens and cornea. (B) Intrafamilial phenotype variability observed in the family studied. This was derived from a combination of drawings, photographs, and examinations.
Figure 2.
 
(A) Slit lamp photography of an individual (III-12, 30 years old) affected with CCL. Left: front view, Right: slit view of the lens and cornea. (B) Intrafamilial phenotype variability observed in the family studied. This was derived from a combination of drawings, photographs, and examinations.
Figure 3.
 
Multipoint linkage analysis between the cataract locus and chromosome 22q11.2 microsatellite markers, with a peak lod score of 4.08, 0.5 cM distal to D22S1167.
Figure 3.
 
Multipoint linkage analysis between the cataract locus and chromosome 22q11.2 microsatellite markers, with a peak lod score of 4.08, 0.5 cM distal to D22S1167.
Figure 4.
 
Mutation analysis of CRYBB2 exon 6. (A) Normal and heterozygous affected DNA (individual IV-1) sequence (sense strand) showing the C-to-T transition at base 14 of exon 6 that changes glutamine (CAG) to an in-frame stop codon. (B) ARMS assay showing cosegregation of the C14T mutation with the CCL phenotype for part of the family. Mutation-specific amplification of a 220-bp PCR product (primer 5′-CTGCAGGTGGGTTGGTTACT-3′) is seen in affected individuals only. Primers for the short tandem repeat polymorphism marker D1S1663 (409–425 bp) were included in each reaction as a positive control for PCR. Individuals are identified as in Figure 1 . One hundred-base-pair ladder is in the outside lanes.
Figure 4.
 
Mutation analysis of CRYBB2 exon 6. (A) Normal and heterozygous affected DNA (individual IV-1) sequence (sense strand) showing the C-to-T transition at base 14 of exon 6 that changes glutamine (CAG) to an in-frame stop codon. (B) ARMS assay showing cosegregation of the C14T mutation with the CCL phenotype for part of the family. Mutation-specific amplification of a 220-bp PCR product (primer 5′-CTGCAGGTGGGTTGGTTACT-3′) is seen in affected individuals only. Primers for the short tandem repeat polymorphism marker D1S1663 (409–425 bp) were included in each reaction as a positive control for PCR. Individuals are identified as in Figure 1 . One hundred-base-pair ladder is in the outside lanes.
Table 1.
 
Two-Point Linkage Data for the Coppock-like Cataract and Markers of the 22q11.2 Region
Table 1.
 
Two-Point Linkage Data for the Coppock-like Cataract and Markers of the 22q11.2 Region
Markers IMD (cM) Recombination Fraction (θ) θmax Zmax
0.00 0.05 0.10 0.20 0.30 0.40
D22S427 −0.26 −0.18 −0.13 −0.06 −0.02 −0.005 0.50 0.00
5.3
D22S425 −∞ 1.15 1.22 1.05 0.75 0.40 0.10 1.22
2.9
D22S303 −∞ 0.71 0.78 0.60 0.29 0.06 0.09 0.78
2.3
D22S1685 2.80 2.65 2.45 1.92 1.29 0.59 0.00 2.80
1.2
D22S1174 3.91 3.58 3.23 2.46 1.61 0.69 0.00 3.91
0
D22S156 2.94 2.71 2.46 1.91 1.29 0.60 0.00 2.94
0
TOP1P2 2.71 2.46 2.20 1.65 1.02 0.39 0.00 2.71
2.2
CRYBB2 4.14 3.78 3.41 2.61 1.70 0.73 0.00 4.14
3.3
D22S1167 3.61 3.30 2.97 2.62 1.48 0.65 0.00 3.61
2.7
D22S1144 −∞ 0.19 0.35 0.34 0.19 0.05 0.14 0.38
0.5
D22S1163 −∞ 1.59 1.63 1.35 0.89 0.36 0.08 1.64
0.5
D22S275 −∞ 2.30 2.27 1.86 1.24 0.51 0.06 2.32
1.1
D22S273 −∞ −0.04 0.17 0.26 0.18 0.06 0.19 0.26
1.6
D22S280 −∞ −0.51 0.15 0.55 0.50 0.24 0.23 0.56
×
×

This PDF is available to Subscribers Only

Sign in or purchase a subscription to access this content. ×

You must be signed into an individual account to use this feature.

×