Identification of a 2 Mb Human Ortholog of Drosophila eyes shut/spacemaker that Is Mutated in Patients with Retinitis Pigmentosa

• Published in: American journal of human genetics Vol. 83; no. 5; pp. 594 - 603
• Main Authors: Collin, Rob W.J., Littink, Karin W., Klevering, B. Jeroen, van den Born, L. Ingeborgh, Koenekoop, Robert K., Zonneveld, Marijke N., Blokland, Ellen A.W., Strom, Tim M., Hoyng, Carel B., den Hollander, Anneke I., Cremers, Frans P.M.
• Format: Journal Article
• Language: English
• Published: Chicago, IL Elsevier Inc 01-11-2008; University of Chicago Press; Elsevier
• Subjects: Amino Acid Sequence; Amino Acid Substitution; Animals; Biological and medical sciences; Case-Control Studies; Chromosome Mapping; Chromosomes, Human, Pair 6; Codon, Nonsense; DNA Mutational Analysis; Drosophila; Drosophila - genetics; Drosophila Proteins - genetics; Electroretinography; Exons; Eye Proteins - genetics; Female; Frameshift Mutation; Fundamental and applied biological sciences. Psychology; General aspects. Genetic counseling; Genes, Recessive; Genetics of eukaryotes. Biological and molecular evolution; Homozygote; Humans; Male; Medical genetics; Medical sciences; Molecular and cellular biology; Molecular Sequence Data; Mutation; Ophthalmology; Pedigree; Polymorphism, Single Nucleotide; Protein Structure, Tertiary; Retinitis Pigmentosa - genetics; Retinopathies; RNA, Messenger - metabolism; Sequence Homology, Amino Acid; Siblings; Human; Retinopathy; Retinitis pigmentosa; Insecta; Patient; Identification; Drosophilidae; Genetic disease; Eye; Eye disease; Arthropoda; Genetics; Invertebrata; Drosophila melanogaster; Diptera
• ISSN: 0002-9297; 1537-6605
• DOI: 10.1016/j.ajhg.2008.10.014

In patients with autosomal-recessive retinitis pigmentosa (arRP), homozygosity mapping was performed for detection of regions harboring genes that might be causative for RP. In one affected sib pair, a shared homozygous region of 5.0 Mb was identified on chromosome 6, within the RP25 locus. One of the genes residing in this interval was the retina-expressed gene EGFL11. Several genes resembling EGFL11 were predicted just centromeric of EGFL11. Extensive long-range RT-PCR, combined with 5′- and 3′- RACE analysis, resulted in the identification of a 10-kb transcript, starting with the annotated exons of EGFL11 and spanning 44 exons and 2 Mb of genomic DNA. The transcript is predicted to encode a 3165-aa extracellular protein containing 28 EGF-like and five laminin A G-like domains. Interestingly, the second part of the protein was found to be the human ortholog of Drosophila eyes shut (eys), also known as spacemaker, a protein essential for photoreceptor morphology. Mutation analysis in the sib pair homozygous at RP25 revealed a nonsense mutation (p.Tyr3156X) segregating with RP. The same mutation was identified homozygously in three arRP siblings of an unrelated family. A frame-shift mutation (pPro2238ProfsX16) was found in an isolated RP patient. In conclusion, we identified a gene, coined eyes shut homolog (EYS), consisting of EGFL11 and the human ortholog of Drosophila eys, which is mutated in patients with arRP. With a size of 2 Mb, it is one of the largest human genes, and it is by far the largest retinal dystrophy gene. The discovery of EYS might shed light on a critical component of photoreceptor morphogenesis.