Abstract
Purpose :
EYS is a major causative gene of autosomal recessive retinitis pigmentosa but is lost in rodents and the understanding of the function(s) is currently very limited. Although, in humans, EYS has been believed to be expressed in retina exclusively, the expressions of its as-yet-unidentified gene fragment in dermal fibroblasts were discovered. In zebrafish, the disruption of the ortholog, eys, led to cone-rod dystrophy, which makes the species an alternative handy valuable animal model. However, little is known about the characteristics of eys gene in photoreceptors. Therefore, the aim of the study was to decipher the EYS transcripts expressed in human dermal fibroblasts and zebrafish retina and get insights into the function(s) of EYS proteins in photoreceptors from the overlapping features.
Methods :
To identify the full-length of the gene fragment, 5’/3’ rapid amplification of cDNA ends (more commonly RACE) was carried out using a primary human fibroblast cell line, HDF-a. In zebrafish, the full coding sequence of eys was cloned from eye, the primary source of retina, and sequenced. Then the conserved and different aspects between the obtained and known transcripts were compared.
Results :
The fragment spanning exon 42-43 was expressed in HDF-a while exon 4-11 was not expressed. By 5’/3’ RACE, two novel 5’ and one known 3’ ends were obtained. One 5’ end was located in the intron between exon 42-43 and the other in exon 37. The former transcript apparently encodes a protein in a different reading frame therefore is different gene but not conserved across species. The latter transcript variant (tv) seemed to encode the last four EGF and two LamG domains but lack a signal sequence and alternative splicing was frequently observed. In zebrafish eye, tv1 was expressed dominantly and there were two important characteristics: an insertion introduces stop codon in the middle portion resulting in the complete loss of the EGF and LamG domains in the second half in its splice variant and 3’ portion is alternatively spliced.
Conclusions :
The novel zebrafish deduced EYS protein lacking the second half resembles human tv2 and tv3. Alternative splicing in the 3’ portion seems the common feature of EYS gene. These results suggest that overall characteristic features of EYS protein(s) in photoreceptors are well conserved across species at least in part.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.