Novel mutations in RDH5 cause fundus albipunctatus in two consanguineous Pakistani families.
OBJECTIVE
To identify the underlying genetic causes of fundus albipunctatus (FA), a rare form of congenital stationary night blindness that is characterized by the presence of white dots in the midperiphery of the retina and delayed dark adaptation, in Pakistan.


METHODS
Two families with FA were identified by fundus examination, and genome-wide single nucleotide polymorphism genotyping was performed for two individuals from family A and six individuals from family B. Genotyping data were subsequently used to identify the identical homozygous regions present in the affected individuals of both families using the online homozygosity mapping tool Homozygosity Mapper. Candidate genes selected from the homozygous regions were sequenced.


RESULTS
Three identical homozygous regions were identified in affected persons of family A (on chromosomes 8, 10, and 12), whereas a single shared homozygous region on chromosome 12 was found in family B. In both families, the homozygous region on chromosome 12 harbored the retinol dehydrogenase 5 (RDH5) gene, in which mutations are known to be causative of FA. RDH5 sequence analysis revealed a novel five base pair deletion, c.913_917delGTGCT (p.Val305Hisfs*29), in family A, and a novel missense mutation, c.758T>G (p.Met253Arg), in family B.


CONCLUSIONS
We identified two novel disease-causing RDH5 mutations in Pakistani families with FA, which will improve diagnosis and genetic counseling, and may even lead to treatment of this disease in these families.
Department of Biosciences, Faculty of Science, COMSATS Institute of Information Technology, Islamabad, Pakistan.
Muhammad
M
Ajmal
Muhammad Imran
MI
Khan
Kornelia
K
Neveling
Yar Muhammad
YM
Khan
Syeda Hafiza Benish
SH
Ali
Waqas
W
Ahmed
Muhammad Safdar
MS
Iqbal
Maleeha
M
Azam
Anneke I
AI
den Hollander
Rob W J
RW
Collin
Raheel
R
Qamar
Frans P M
FP
Cremers
D000293:Adolescent; D000328:Adult; D000429:Alcohol Oxidoreductases / Q000235:genetics*; D044466:Asian People / Q000235:genetics*; D001483:Base Sequence; D002648:Child; D002881:Chromosomes, Human, Pair 12 / Q000235:genetics*; D003241:Consanguinity; D015785:Eye Diseases, Hereditary; D005260:Female; D005654:Fundus Oculi; D040181:Genetic Diseases, X-Linked; D055106:Genome-Wide Association Study; D005838:Genotype; D006720:Homozygote; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D020125:Mutation, Missense / Q000235:genetics*; D009216:Myopia / Q000235:genetics*; D009755:Night Blindness / Q000235:genetics*; D010154:Pakistan; D010375:Pedigree; D020641:Polymorphism, Single Nucleotide; D017384:Sequence Deletion / Q000235:genetics*
D000429:Alcohol Oxidoreductases; C105846:retinol dehydrogenase 5