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CRYAA gene

Overview

Gene (OMIM No.)
Function of gene/protein
  • Protein: crystallin alpha A
  • A major lens component required for the correct assembly of lens intermediate filaments by forming a complex with BFSP1 and BFSP2
  • Highly organized, compact structures that contribute to the refractive index of the lens
  • Interacts with other crystallins help to maintain lens transparency
  • Functions as a molecular chaperone in its oxidized form
Clinical phenotype
(OMIM phenotype no.)
  • Cataract 9, multiple types (#604219)
Inheritance
  • Autosomal recessive
  • Autosomal dominant (more common)
Ocular features
Systemic features
Key investigations
  • Measurement of corneal diameter
  • Anterior segment OCT also helpful in patients with corneal opacities
  • B-scan USS to measure axial length to document microphthalmia and detect any posterior segment abnormalities
  • Electrophysiology
  • TORCH screen
  • MRI brain and orbit
  • Assessment with a pediatrician if suspicious of systemic involvement
Molecular diagnosisNext generation sequencing
  • Targeted gene panels (cataract)
  • Whole exome sequencing
  • Whole genome sequencing
ManagementOcular
Therapies under research
  • None at present
Further information

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Additional information

Apart from cataract, additional ocular abnormalities such as microcornea and MAC have been reported in patients harbouring the following CRYAA variants:

  • Heterozygous p.Arg12Cys (microcornea, MAC and macrocephaly)[3]
  • Heterozygous p.Arg116Cys (microcornea and MAC)[4,5]
  • Heterozygous p.Arg116His (microcornea and/or corneal opacity)[6,7]
  • Homozygous p.Arg54Cys (microcornea)[8]

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References

  1.  Brady JP, Garland D, Duglas-Tabor Y, Robison WG Jr, Groome A, Wawrousek EF. Targeted disruption of the mouse alpha A-crystallin gene induces cataract and cytoplasmic inclusion bodies containing the small heat shock protein alpha B-crystallin. Proc Natl Acad Sci U S A. 1997;94(3):884‐889. doi:10.1073/pnas.94.3.884
  2.  Cobb BA, Petrash JM. Structural and functional changes in the alpha A-crystallin R116C mutant in hereditary cataracts. Biochemistry. 2000;39(51):15791‐15798. doi:10.1021/bi001453j
  3.  Reis LM, Tyler RC, Muheisen S, et al. Whole exome sequencing in dominant cataract identifies a new causative factor, CRYBA2, and a variety of novel alleles in known genes. Hum Genet. 2013;132(7):761-770
  4.  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(3):471‐474. doi:10.1093/hmg/7.3.471
  5.  Beby F, Commeaux C, Bozon M, Denis P, Edery P, Morlé L. New phenotype associated with an Arg116Cys mutation in the CRYAA gene: nuclear cataract, iris coloboma, and microphthalmia. Arch Ophthalmol. 2007;125(2):213-216
  6.  Hansen L, Yao W, Eiberg H, et al. Genetic heterogeneity in microcornea-cataract: five novel mutations in CRYAA, CRYGD, and GJA8. Invest Ophthalmol Vis Sci. 2007;48(9):3937‐3944. doi:10.1167/iovs.07-0013
  7.  Richter L, Flodman P, Barria von-Bischhoffshausen F, et al. Clinical variability of autosomal dominant cataract, microcornea and corneal opacity and novel mutation in the alpha A crystallin gene (CRYAA). Am J Med Genet A. 2008;146A(7):833‐842. doi:10.1002/ajmg.a.32236
  8.  Khan AO, Aldahmesh MA, Meyer B. Recessive congenital total cataract with microcornea and heterozygote carrier signs caused by a novel missense CRYAA mutation (R54C). Am J Ophthalmol. 2007;144(6):949‐952. doi:10.1016/j.ajo.2007.08.005

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Updated on November 30, 2020
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