Abstract
Retinal degenerative diseases, such as retinitis pigmentosa and Leber congenital amaurosis, are a leading cause of untreatable blindness with substantive impact on the quality of life of affected individuals and their families. Mouse mutants with retinal dystrophies have provided a valuable resource to discover human disease genes and helped uncover pathways critical for photoreceptor function. Here we show that the rd11 mouse mutant and its allelic strain, B6-JR2845, exhibit rapid photoreceptor dysfunction, followed by degeneration of both rods and cones. Using linkage analysis, we mapped the rd11 locus to mouse chromosome 13. We then identified a one-nucleotide insertion (c.420-421insG) in exon 3 of the Lpcat1 gene. Subsequent screening of this gene in the B6-JR2845 strain revealed a seven-nucleotide deletion (c.14-20delGCCGCGG) in exon 1. Both sequence changes are predicted to result in a frame-shift, leading to premature truncation of the lysophosphatidylcholine acyltransferase-1 (LPCAT1) protein. LPCAT1 (also called AYTL2) is a phospholipid biosynthesis/remodeling enzyme that facilitates the conversion of palmitoyl-lysophosphatidylcholine to dipalmitoylphosphatidylcholine (DPPC). The analysis of retinal lipids from rd11 and B6-JR2845 mice showed substantially reduced DPPC levels compared with C57BL/6J control mice, suggesting a causal link to photoreceptor dysfunction. A follow-up screening of LPCAT1 in retinitis pigmentosa and Leber congenital amaurosis patients did not reveal any obvious disease-causing mutations. Previously, LPCAT1 has been suggested to be critical for the production of lung surfactant phospholipids and biosynthesis of platelet-activating factor in noninflammatory remodeling pathway. Our studies add another dimension to an essential role for LPCAT1 in retinal photoreceptor homeostasis.