Abstract
Purpose :
The distribution and function of photoreceptors are controlled by multiple genetic and developmental factors. Our goals are to identify the genetic determinants that cause one or more de novo mutations that affect the numbers of photoreceptor types and their function in one of the BXDs—BXD32, using standard linkage and genome-wide association studies (GWAS).
Methods :
We systematically examined BXD32, along with 2 parental controls C57BL/6J (B6) and DBA/2J (D2) by electroretinogram (ERG) assays, immunoblotting (IB), and immunohistochemistry (IHC) using cell type-specific markers. We generated a set of 60 backcross progeny of BXD32 for further evaluation of photoreceptor phenotypes observed in BXD32, followed by evaluation of gene(s) and variants using the mapping module in GeneNetwork.
Results :
BXD32 exhibited a robust reduction in the dark and light-adapted ERG responses starting at postnatal day (P)21 and a complete loss at 1 year. Consistent with ERG findings, IHC analysis of the outer nuclear layer (ONL) thickness and quantification of cones demonstrated a progressive loss of photoreceptors in the BXD32. Genetic mapping of the phenotypes, the thickness of the ONL, and the number of cones in backcross progeny of BXD32 identified significant linkage peaks on Chr 1 and Chr 4, with private homozygous variants associated with candidate gene(s) – RP1, KCNQ5, LIN28A, CASZ1, and CROCC, unique to BXD32, relative to B6 and other BXDs.
Conclusions :
Our study identified photoreceptor phenotypes in BXD32 as having significantly compromised photoreceptor function and cone distribution. Our data show potentially causal gene(s) and genetic variants on chr1 and chr4 associated with ONL thickness and cone numbers in BXD32 comparing B6 and other BXDs suggesting that one or more mutations (de novo) can arise independently. This study should help in elucidating novel mechanistic underpinnings of human retinal diseases by uncovering gene(s) and genetic variants which impact visual function.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.