title: Mutations in betaB3-crystallin associated with autosomal recessive cataract in two Pakistani families.
abstract: OBJECTIVE
  To identify the disease locus for autosomal recessive congenital cataracts in consanguineous Pakistani families.
  
  
  METHODS
  Two Pakistani families were ascertained, patients were examined, blood samples were collected, and DNA was isolated. A genome-wide scan was performed using >382 polymorphic microsatellite markers on genomic DNA from affected and unaffected family members. Two-point lod scores were calculated, haplotypes were formed by inspection, and candidate genes were sequenced. Real-time quantitative PCR techniques were used to determine the mRNA levels, and molecular modeling was performed to gain a better understanding of the significance of the disease-causing mutation.
  
  
  RESULTS
  In the genome-wide scan, maximum lod scores of 2.67 and 2.77 for family 60004 and 2.02 and 2.04 for family 60006 were obtained for markers D22S539 and D22S315, respectively. The linked region, 22.7 cM (10 Mb) flanked by markers D22S420 and D22S1163, contains the beta-crystallin gene cluster including the genes CRYBA4, CRYBB1, CRYBB2, and CRYBB3. Sequencing of these genes showed a G-->C transition in exon 6 of CRYBB3 resulting in a p.G165R change in the betaB3-crystallin protein that cosegregates with the disease in both families. Real-time PCR analysis suggested that betaB3-crystallin mRNA levels approximate those of other betagamma-crystallins. Molecular modeling predicted changes in electrostatic potential that would be expected to reduce the stability of the fourth Greek-key motif, and hence the entire protein, dramatically.
  
  
  CONCLUSIONS
  For the first time, a mutation in CRYBB3 is reported in two consanguineous Pakistani families with autosomal recessive congenital cataracts.
authors.affiliation: Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: S Amer
authors.initials: SA
authors.lastname: Riazuddin
authors.forename: Afshan
authors.initials: A
authors.lastname: Yasmeen
authors.forename: Wenliang
authors.initials: W
authors.lastname: Yao
authors.forename: Yuri V
authors.initials: YV
authors.lastname: Sergeev
authors.forename: Qingjiong
authors.initials: Q
authors.lastname: Zhang
authors.forename: Fareeha
authors.initials: F
authors.lastname: Zulfiqar
authors.forename: Assad
authors.initials: A
authors.lastname: Riaz
authors.forename: Sheikh
authors.initials: S
authors.lastname: Riazuddin
authors.forename: J Fielding
authors.initials: JF
authors.lastname: Hejtmancik
mesh_terms: D000595:Amino Acid Sequence; D002386:Cataract / Q000151:congenital / Q000208:ethnology / Q000235:genetics*; D003241:Consanguinity; D003459:Crystallins / Q000235:genetics*; D004252:DNA Mutational Analysis; D005260:Female; D005808:Genes, Recessive; D008040:Genetic Linkage; D005838:Genotype; D006801:Humans; D008126:Lod Score; D008297:Male; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D010154:Pakistan / Q000453:epidemiology; D010375:Pedigree; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D038206:beta-Crystallin B Chain
chemical_list: C103908:CRYBB3 protein, human; D003459:Crystallins; D012333:RNA, Messenger; D038206:beta-Crystallin B Chain