A novel mutation (F71L) in alphaA-crystallin with defective chaperone-like function associated with age-related cataract

Cat-Map: putting cataract on the map

Lens opacities, or cataract(s), may be inherited as a classic Mendelian disorder usually with early-onset or, more commonly, acquired with age as a multi-factorial or complex trait. Many genetic forms of cataract have been described in mice and other animal models. Considerable progress has been made in mapping and identifying the genes and mutations responsible for inherited forms of cataract, and genetic determinants of age-related cataract are beginning to be discovered. To provide a convenient and accurate summary of current information focused on the increasing genetic complexity of Mendelian and age-related cataract we have created an online chromosome map and reference database for cataract in humans and mice (Cat-Map).

Alterations of the 5'untranslated region of SLC16A12 lead to age-related cataract

PURPOSE. Knowledge of genetic factors predisposing to age-related cataract is very limited. The aim of this study was to identify DNA sequences that either lead to or predispose for this disease. METHODS. The candidate gene SLC16A12, which encodes a solute carrier of the monocarboxylate transporter family, was sequenced in 484 patients with cataract (134 with juvenile cataract, 350 with age-related cataract) and 190 control subjects. Expression studies included luciferase reporter assay and RT-PCR experiments. RESULTS. One patient with age-related cataract showed a novel heterozygous mutation (c.-17A>G) in the 5'untranslated region (5'UTR). This mutation is in cis with the minor G-allele of the single nucleotide polymorphism (SNP) rs3740030 (c.-42T/G), also within the 5'UTR. Using a luciferase reporter assay system, a construct with the patient's haplotype caused a significant upregulation of luciferase activity. In comparison, the SNP G-allele alone promoted less activity, but that amount was still significantly higher than the amount of the common T-allele. Analysis of SLC16A12 transcripts in surrogate tissue demonstrated striking allele-specific differences causing 5'UTR heterogeneity with respect to sequence and quantity. These differences in gene expression were mirrored in an allele-specific predisposition to age-related cataract, as determined in a Swiss population (odds ratio approximately 2.2; confidence intervals, 1.23-4.3). CONCLUSIONS. The monocarboxylate transporter SLC16A12 may contribute to age-related cataract. Sequences within the 5'UTR modulate translational efficiency with pathogenic consequences.

Association between gap junction protein-alpha 8 polymorphisms and age-related cataract

GJA8 plays an important role in lens growth and transparency. Therefore, we hypothesized that two single nucleotide polymorphisms (SNPs) in GJA8 might be associated with age-related cataract. We investigated the SNPs rs1495960 and rs9437983 using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and DNA sequencing, in 96 age-related cataract patients, and 208 gender- and age-matched healthy controls. No significant differences between cases and controls were seen in genotype or allele distributions of rs1495960 (P > 0.05). The allele distribution of rs9437983 was different between cases and controls, but no difference was detected in its genotype distribution. Cataract patients had a significantly lower G-G haplotype frequency (4.9% vs. 15.5%, P = 0.0001), and a significantly higher G-A haplotype frequency (45.6% vs. 36.4%, P = 0.030) than controls. Limiting to nuclear cataract cases significantly increased the differences between cases and controls for G-G and G-A haplotypes. These results support that the GJA8 gene may be a novel susceptibility gene for age-related cataracts.