Identities and frequencies of variants in causing primary congenital glaucoma in Pakistan.

PURPOSE

Primary congenital glaucoma (PCG) is a clinically and genetically heterogeneous disease. The present study was undertaken to find the genetic causes of PCG segregating in 36 large consanguineous Pakistani families.

METHODS

Ophthalmic examination including fundoscopy, or slit-lamp microscopy was performed to clinically characterize the PCG phenotype. Genomic nucleotide sequences of the and genes were analyzed with either Sanger or whole exome sequencing. In silico prediction programs were used to assess the pathogenicity of identified alleles. ClustalW alignments were performed to determine evolutionary conservation, and three-dimensional (3D) modeling was performed using HOPE and Phyre2 software.

RESULTS

Among the known loci, mutations in and are the common causes of PCG. Therefore, we analyzed the genomic nucleotide sequences of and , and detected probable pathogenic variants cosegregating with PCG in 14 families. These included the three novel (c.542T>A, c.1436A>G, and c.1325delC) and five known (c.868dupC, c.1168C>T, c.1169G>A, c.1209InsTCATGCCACC, and c.1310C>T) variants in . Two of the novel variants are missense substitutions [p.(Leu181Gln), p.(Gln479Arg)], which replaced evolutionary conserved amino acids, and are predicted to be pathogenic by various in silico programs, while the third variant (c.1325delC) is predicted to cause reading frameshift and premature truncation of the protein. A single mutation, p.(Arg390His), causes PCG in six (~43%) of the 14 mutations harboring families, and thus, is the most common variant in this cohort. Surprisingly, we did not find any pathogenic variants in the families, which further supports the genetic heterogeneity of PCG in the Pakistani population.

CONCLUSIONS

In conclusion, results of the present study enhance our understanding of the genetic basis of PCG, support the notion of a genetic modifier of , and contribute to the development of genetic testing protocols and genetic counseling for PCG in Pakistani families.