EYS, encoding an ortholog of Drosophila spacemaker, is mutated in autosomal recessive retinitis pigmentosa

Abstract

Using a positional cloning approach supported by comparative genomics, we have identified a previously unreported gene, EYS, at the RP25 locus on chromosome 6q12 commonly mutated in autosomal recessive retinitis pigmentosa. Spanning over 2 Mb, this is the largest eye-specific gene identified so far. EYS is independently disrupted in four other mammalian lineages, including that of rodents, but is well conserved from Drosophila to man and is likely to have a role in the modeling of retinal architecture.

Figure 1

RP25 gene structure and domain architecture. (a) Chromosomal region at 6q12. (b) Schematic representation of the genes and microsatellite markers flanking the RP25 gene. (c) Previously predicted genes overlapping RP25. (d) The 43 exons comprising the RP25 gene with the initiation (ATG) and stop codon (TAA) marked within exons 4 and 43, respectively; mutations are indicated in red and the asterisk at exon 29 marks the 1,238-bp segment missing from the human reference assembly. (e) Domain architecture of human SPAM and its Drosophila spam ortholog.

Figure 2

Expression pattern and immunolocalization of spam. (a) EYS (SPAM) expression in different tissues is shown in the upper panel with a specific 1.8-kb product in the retina and in Y79 photoreceptor-like cells. ARPE19 is a retinal pigment epithelial cell line. A 400-bp fragment representing the gene PGM1, which is ubiquitously expressed in all tissues and cell lines, is shown as an amplification control in the lower panel. (b) Subcellular localization of spam to the outer segment of mature porcine retina using antibody to spam (green) and antibody to rhodopsin (red). The overlay shows the localization of spam in the same region as rhodopsin (yellow) in the outer segment of the photoreceptor cell layer.