CLINICAL PROFILE AND MOLECULAR ANALYSIS OF HOT SPOT EXONS OF SLC4A11 GENE IN CONGENITAL HEREDITARY ENDOTHELIAL DYSTROPHY CASES PRESENTED AT AL SHIFA TRUST EYE HOSPITAL RAWALPINDI

Abstract

Corneal dystrophies (CDs) are eye disorders that affect cornea of eye and are mostly genetically inherited. These disorders are prevalent across the globe, however, relative incidence of recessively inherited subtypes is higher in populations where consanguinity is customary. Congenital Hereditary Endothelial Dystrophy (CHED) is an autosomal recessive corneal dystrophy that is highly prevalent in Asian territory like India, Saudi Arabia and Pakistan. It can be isolated or can present as one of the feature of Harbyon syndrome. Genetic mutations in solute carrier 4 member 11 (SLC4A11) are reported as a predominant cause of CHED phenotype. SLC4A11 is a trans-membrane transporter in endothelial sheet that strengthen the translucence of cornea by retaining the optimal hydration of corneal stroma. SLC4A11 has total 19 exons which encode 891 amino acids long protein. Present study was conducted to analyze clinical and molecular aspects of CHED phenotype in familial cases visiting Cornea department of A1-Shifa Trust hospital Rawalpindi, Pakistan, during 4 months of sampling from September, 2021 to December, 2021.CHED cases belonging to four families were enrolled after written informed consent. Clinical records were collected and pedigrees were drawn. DNA was extracted from collected blood samples, and a selected CHED affected individual of each family was screened for six hot spot exons (exon 4,5, 14,15,17 and 18) of SLC4A11gene. Our data showed that among all enrolled families, 3 families belonged to Punjab whereas one family belonged to Khyber Pakhtun Khawa (KPK). All families were segregating CHED phenotype in autosomal recessive pattern of inheritance. Affected individuals of all families reported hearing loss confirming Harbyon syndrome. As a result of sequence analysis a total of 10 heterozygous variants i.e. chr20:3214819T>G (in CH28 at exon 4),chr20:3214581C>T (in CH30 at exon 5), chr20:3209034T>C (in CH29 at exon 18),chr20:3208964G>A (in CH29 at exon 18), chr20:3209038G>C (in CH30 at exon 18), chr20:3208952G>T (in CH30 in exon 18), chr20:3209885C>T (in CH30 at exon 15), DRSML QAU Abstract Clinical Profile And Molecular Analysis Of Hot Spot Exons Of SLC4A11 Gene In Congenital Hereditary Endothelial Dystrophy Cases Presented At Al Shifa Trust Eye Hospital Rawalpindi xv chr20:3209834A>C (in CH30 at exon 15), chr20:3209869C>T (in CH31 at exon 15) and chr20:3209860C>A (in CH31 at exon 15) were identified. In silico analysis showed that 3 variants are disease causing and 7 are polymorphisms as predicted by mutation taster. Out of mentioned 10 variant 7 are not reported and 3 are reported. In conclusion only heterozygous disease causing variants were identified, however no homozygous disease causing variant could be detected in analyzed selected exons. Our findings necessitate the screening of remaining exons of SLC4A11 to identify the homozygous disease causing variants segregating with disease causing phenotype in each enrolled family. As 2 different mutations are found in same patient which can be a possibility of compound heterozygosity, but their involvement in disease phenotype will be confirmed after analysis of complete gene as well as segregation analysis using DNA of parents. Genetic counseling was provided to all families to refrain from practicing consanguinity for betterment of upcoming generation