Genetic modifiers of retinal degeneration in the rd3 mouse.
ABSTRACT In previous studies of light-induced (LRD) and age-related (ageRD) retinal degeneration (RD) between the BALB/cByJ (BALB) and B6(Cg)-Tyr(c-2J)/J (B6a) albino mouse strains, RD-modifying quantitative trait loci (QTLs) were identified. After breeding BALB- and B6a-rd3/rd3 congenic strains and finding significant differences in RD, an F1 intercross to determine rd3 QTLs that influence this inherited RD was performed.
N10, F2 BALB- and B6a-rd3/rd3 strains were measured for retinal outer nuclear layer (ONL) thickness from 5 to 12 weeks of age. Since 10 weeks showed significant differences in the ONL, F2 progeny from an F1 intercross were measured for ONL thickness. F2 DNAs were genotyped for SNPs by the Center for Inherited Disease Research. Correlation of genotype with phenotype was made with Map Manager QTX.
One hundred forty-eight SNPs approximately 10 cM apart were typed in the F2 progeny and analyzed. Significant QTLs were identified on chromosomes (Chrs) 17, 8, 14, and 6 (B6a alleles protective) and two on Chr 5 (BALB alleles protective). Suggestive QTLs were found as well. For the strongest QTLs, follow-up SNPs were analyzed to narrow the critical intervals. Additional studies demonstrated that rd3 disease is exacerbated by light but not protected by the absence of rhodopsin regeneration.
QTLs were identified that modulate rd3-RD. These overlapped some QTLs from previous ageRD and LRD studies. The presence of some of the same QTLs in several studies suggests partial commonality in RD pathways. Identifying natural gene/alleles that modify RDs opens avenues of study that may lead to therapies for RD diseases.
Article: A QTL on distal chromosome 3 that influences the severity of light-induced damage to mouse photoreceptors.[show abstract] [hide abstract]
ABSTRACT: C57BL/6J-c(2J) (c2J) albino mice showed much less damage to their photoreceptors after exposure to prolonged light than BALB/c mice and seven other albino strains tested. There were no gender differences, and preliminary studies suggested that the c2J relative protective effect was a complex trait. A genome-wide scan using dinucleotide repeat markers was carried out for the analysis of 194 progeny of the backcross (c2J x BALB/c)F(1) x c2J and the thickness of the outer nuclear layer (ONL) of the retina was the quantitative trait reflecting retinal damage. Our results revealed a strong and highly significant quantitative trait locus (QTL) on mouse Chromosome (Chr) 3 that contributes almost 50% of the c2J protective effect, and three other very weak but significant QTLs on Chrs 9, 12, and 14. Interestingly, the Chrs 9 and 12 QTLs corresponded to relative susceptibility alleles in c2J (or relative protection alleles in BALB/c), the opposite of the relative protective effect of the QTLs on Chrs 3 and 14. We mapped the Rpe65 gene to the apex of the Chr 3 QTL (LOD score = 19.3). Northern analysis showed no difference in retinal expression of Rpe65 message between c2J and BALB/c mice. However, sequencing of the Rpe65 message revealed a single base change in codon 450, predicting a methionine in c2J and a leucine in BALB/c. When the retinas of aging BALB/c and c2J mice reared in normal cyclic light were compared, the BALB/c retinas showed a small but significant loss of photoreceptor cells, while the c2J retinas did not. Finding light damage-modifying genes in the mouse may open avenues of study for understanding age-related macular degeneration and other retinal degenerations, since light exposures may contribute to the course of these diseases.Mammalian Genome 07/2000; 11(6):422-7. · 2.89 Impact Factor
Article: A novel de novo frameshift mutation of RPGR ORF15 is associated with X-linked retinitis pigmentosa in a Chinese family.[show abstract] [hide abstract]
ABSTRACT: To identify the genetic basis of disease in a Chinese family with retinitis pigmentosa (RP). Linkage analysis was performed for 15 family members in the RP family using microsatellite markers flanking candidate genetic loci for known autosomal dominant RP (adRP) and markers covering the entire X chromosome by every 10 cM. To screen for a mutation causing RP, PCR and DNA sequence analyses of the complete coding region (including ORF15) and exon-intron boundaries of the retinitis pigmentosa GTPase regulator (RPGR) gene associated with X-linked RP (xlRP) were carried out for the proband in the RP family. After the mutation was identified, direct DNA sequence analysis was preformed for all 15 family members and 101 controls to determine whether the mutation co-segregated with RP in the family and whether it was present or absent in the controls. Linkage analysis excluded all known adRP loci. However, positive linkage was identified with two markers on the X chromosome, DXS993 and DXS1068, where the RPGR gene is located. Direct DNA sequence analysis revealed a hemizygous mutation, g.ORF15+1166delA (c.2919delA), in affected males. The deletion results in a frameshift leading to early termination of RPGR. The g.ORF15+1166delA mutation arose de novo and co-segregated with all male patients, but was not present in normal family members and 101 controls. The clinical features of the mutation carriers showed intrafamilial variability. The novel g.ORF15+1166delA mutation of RPGR causes X-linked RP in a four generation Chinese family. The deletion arose de novo. An interesting feature of mutation g.ORF15+1166delA is that it was associated with RP in all hemizygous males and four of five heterozygous female carriers in the Chinese family. These results revealed the broader xlRP genotypic and phenotypic spectrum of RPGR mutations.Molecular vision 02/2007; 13:1548-54. · 2.20 Impact Factor