Genotypic spectrum and phenotype correlations of ABCA4-associated disease in patients of south Asian descent.
Variants in the ABCA4 gene are the most common cause of juvenile-onset blindness affecting close to 1 in 10 000 people worldwide. Disease severity varies largely according to genotype, which can be specific to ethnic and racial groups. Here we investigate the spectrum of ABCA4 variation and its phenotypic expression in 38 patients of South Asian descent, notably from India, Pakistan, Bangladesh and Sri Lanka. Sequencing of all exons and flanking intronic sequences of ABCA4 revealed disease-causing variants in all patients: 3 in 2.6%, 2 in 81.6% and 1 in 15.8%. Altogether, 36 distinct variants were identified, including 9 previously not described. The most frequent variant c.5882G>A, p.(G1961E) was found in half the patients, the highest ever reported in a single study cohort. The South Asian founder variant c.859-9T>C was identified along with other founder variants ascribed to Danish, Chinese, Mexican and African patients. Patients carrying c.5882G>A, p.(G1961E) exhibited a consistently confined disease phenotype, normal quantitative autofluorescence (qAF) levels and preserved full-field ERG (ffERG) while c.859-9T>C resulted in widespread disease, significantly elevated qAF and reduced to non-detectable ffERG. South Asian patients present with a relatively unique ABCA4 profile comprised of various ethnic founder variants resulting in two or three major retinal phenotypes.
Department of Ophthalmology, Columbia University, New York, NY, USA.
Winston
W
Lee
Department of Ophthalmology, Columbia University, New York, NY, USA.
Kaspar
K
Schuerch
Department of Ophthalmology, Columbia University, New York, NY, USA.
Jana
J
Zernant
The Pangere Center for Inherited Retinal Diseases, The Chicago Lighthouse, Chicago, IL, USA.
Frederick T
FT
Collison
Department of Ophthalmology, Columbia University, New York, NY, USA.
Srilaxmi
S
Bearelly
The Pangere Center for Inherited Retinal Diseases, The Chicago Lighthouse, Chicago, IL, USA.
Gerald A
GA
Fishman
Department of Ophthalmology, Columbia University, New York, NY, USA.|Department of Pathology & Cell Biology, Columbia University, New York, NY, USA.
Stephen H
SH
Tsang
Department of Ophthalmology, Columbia University, New York, NY, USA.|Department of Pathology & Cell Biology, Columbia University, New York, NY, USA.
Janet R
JR
Sparrow
Department of Ophthalmology, Columbia University, New York, NY, USA.|Department of Pathology & Cell Biology, Columbia University, New York, NY, USA.
Rando
R
Allikmets
D018528:ATP-Binding Cassette Transporters / Q000235:genetics*; D000293:Adolescent; D000328:Adult; D001459:Bangladesh; D005091:Exons; D015785:Eye Diseases, Hereditary / Q000208:ethnology / Q000235:genetics* / Q000473:pathology; D005260:Female; D018703:Founder Effect; D005838:Genotype; D006801:Humans; D007194:India; D008268:Macular Degeneration / Q000208:ethnology / Q000235:genetics* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D010154:Pakistan; D010641:Phenotype; D020641:Polymorphism, Single Nucleotide; D013188:Sri Lanka
C056475:ABCA4 protein, human; D018528:ATP-Binding Cassette Transporters