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Subhabrata Chakrabarti, Meha Kabra, Goutham Pyatla, Sonika Rathi, Anil K Mandal, Sirisha Senthil, Inderjeet Kaur, Rohit C Khanna, Hemant Khanna; Genetic Interactions of Crystallins with Known Primary Congenital Glaucoma Genes. Invest. Ophthalmol. Vis. Sci. 2018;59(9):5148.
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© ARVO (1962-2015); The Authors (2016-present)
Primary congenital glaucoma (PCG) is an autosomal recessive disorder that is largely attributed to mutations in the CYP1B1 gene and to a lesser extent in the LTBP2, TEK, MYOC and FOXC1 genes. Some of the PCG cases develop congenital cataract (CC) post surgically, while it may also co-exist in a few cases. Crystallins are structural proteins in the lens but are also involved in other ocular diseases. Based on these evidences, we aimed to understand their involvement in PCG.
A gene panel with all the eleven crystalline genes (CRYAA, CRYAB, CRYBA1, CRYBA4, CRYBB1, CRYBB2, CRYBB3, CRYGC, CRYGS, CRYGB, CRYGD) that are known to be associated with congenital cataract was designed using the Ion Ampliseq designer. PCG cases that did not harbor homozygous mutations in the known candidate genes (n=323) along with ethnically matched normal controls (n=1157) were screened by deep sequencing on an Ion Proton platform using the Ion Ampliseq chemistry. The raw data was analyzed by GATK and imported to the Ion Reporter software (version 5.2) and aligned to the hg19 sequence for further analysis. Bioinformatic analysis (SIFT, PolyPhen and Grantham) for individual variations and threshold quality scores with a depth of coverage between 100-500X were considered. The potential mutations were further validated by Sanger sequencing (ABI 3130 XL) using BigDye chemistry.
Screening of crystallin genes led to the identification of a 10 novel heterozygous mutations in PCG patients with an overall frequency of 3.71%, of which, eight of them were nonsynonymous changes (p.Gly28Ser [CRYAA], p.Arg22Cys [CRYAB], p.Arg25Trp [CRYBA4], p.Arg214Gln [CRYBB1], p.Ala149Val and p. Glu177Lys [CRYBB3], p.Q13H [CRYGD], p.Pro68Ser [CRYGS] and the rest were potentially abrogating the splice sites (c.40-1G>C [CRYBA4] and c.253-1G>C [CRYGB]). These variations were absent in the controls and rarely found in the ExAC and 1000G databases. Only one patient with the mutation underwent intraocular lens implantation. Interestingly, 6/10 heterozygous crystallin mutations co-occurred with heterozygous mutations in CYP1B1 (3), MYOC (1), LTBP2 (1) and TIE2 (1) indicating a potential digenic inheritance.
The present study implicates the involvement of crystallin genes in PCG, which are being functionally characterized. Our findings expand the spectrum of non-lenticular functions of crystallins in glaucoma pathogenesis.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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