Abstract
Purpose: :
The zebrafish (Danio rerio) has become a valuable model organism for the genetic analysis of patterning and development of the vertebrate embryo including the visual system. We have undertaken a large-scale genetics screen to identify mutations that alter photoreceptor cell number and mosaic pattern in free-swimming larvae and adult zebrafish. The locus lots-of-rods-junior (ljr) was identified in a screen of chemically mutagenized zebrafish. The goals of this study are to further characterize the ljr mutant phenotype and molecularly identify the mutant gene.
Methods: :
To characterize the photoreceptor phenotype, the number and distribution of the cones, rods, and retinal cells in wild-type and ljr mutant larvae were analyzed in inmmunolabeled retinal sections. Cell cycle was studied by phospho-histone 3 (PH3) immunolabeling and BrdU incorporation in mutants and wild-types. Chromosome linkage was assigned using SSLP markers. The high-resolution mapping was performed by generating additional polymorphic markers in the mutation interval. Cell autonomy was tested by generating genetic chimeras by blastula cell transplants.
Results: :
ljr
Conclusions: :
This study demonstrates the power of screening for alterations in photoreceptor patterning to identify genes related to photoreceptor development. lrj is the second locus identified in zebrafish, after lor, which demonstrate an alteration in the photoreceptor cell number without cell death. Future investigations will comprise the fine mapping to identify the loci mutated in ljr.
Keywords: photoreceptors • genetics • retinal development