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A mutagenesis-derived Lrp5 mouse mutant with abnormal retinal vasculature and low bone mineral density.

ABSTRACT: Familial exudative vitreoretinopathy (FEVR) is caused by mutations in the genes encoding low-density lipoprotein receptor-related protein (LRP5) or its interacting partners, namely frizzled class receptor 4 (FZD4) and norrin cystine knot growth factor (NDP). Mouse models for Lrp5, Fzd4, and Ndp have proven to be important for understanding the retinal pathophysiology underlying FEVR and systemic abnormalities related to defective Wnt signaling. Here, we report a new mouse mutant, tvrm111B, which was identified by electroretinogram (ERG) screening of mice generated in the Jackson Laboratory Translational Vision Research Models (TVRM) mutagenesis program.ERGs were used to examine outer retinal physiology. The retinal vasculature was examined by in vivo retinal imaging, as well as by histology and immunohistochemistry. The tvrm111B locus was identified by genetic mapping of mice generated in a cross to DBA/2J, and subsequent sequencing analysis. Gene expression was examined by real-time PCR of retinal RNA. Bone mineral density (BMD) was examined by peripheral dual-energy X-ray absorptiometry.The tvrm111B allele is inherited as an autosomal recessive trait. Genetic mapping of the decreased ERG b-wave phenotype of tvrm111B mice localized the mutation to a region on chromosome 19 that included Lrp5. Sequencing of Lrp5 identified the insertion of a cytosine (c.4724_4725insC), which is predicted to cause a frameshift that disrupts the last three of five conserved PPPSPxS motifs in the cytoplasmic domain of LRP5, culminating in a premature termination. In addition to a reduced ERG b-wave, Lrp5tvrm111B homozygotes have low BMD and abnormal features of the retinal vasculature that have been reported previously in Lrp5 mutant mice, including persistent hyaloid vessels, leakage on fluorescein angiography, and an absence of the deep retinal capillary bed.The phenotype of the Lrp5tvrm111B mutant includes abnormalities of the retinal vasculature and of BMD. This model may be a useful resource to further our understanding of the biological role of LRP5 and to evaluate experimental therapies for FEVR or other conditions associated with LRP5 dysfunction.

SUBMITTER: Charette JR

PROVIDER: S-EPMC5360454 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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A mutagenesis-derived <i>Lrp5</i> mouse mutant with abnormal retinal vasculature and low bone mineral density.

Charette Jeremy R JR Earp Sarah E SE Bell Brent A BA Ackert-Bicknell Cheryl L CL Godfrey Dana A DA Rao Sujata S Anand-Apte Bela B Nishina Patsy M PM Peachey Neal S NS

Molecular vision 20170318

<h4>Purpose</h4>Familial exudative vitreoretinopathy (FEVR) is caused by mutations in the genes encoding low-density lipoprotein receptor-related protein (LRP5) or its interacting partners, namely frizzled class receptor 4 (FZD4) and norrin cystine knot growth factor (NDP). Mouse models for <i>Lrp5</i>, <i>Fzd4</i>, and <i>Ndp</i> have proven to be important for understanding the retinal pathophysiology underlying FEVR and systemic abnormalities related to defective Wnt signaling. Here, we repor ...[more]

PMID: 28356706

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Project description:BACKGROUND: The low-density lipoprotein receptor-related protein 5 gene (LRP5) was identified to be linked to the variation in BMD in high bone mass pedigrees. Subsequent population-based studies of the association between the LRP5 gene and BMD have yielded conflicting results. The present study was aimed at examining the association between LRP5 gene and BMD by using meta-analysis. METHODS: A systematic electronic search of literature was conducted to identify all published studies in English on the association between LRP5 gene and osteoporosis-related phenotypes, including bone mineral density and fracture. BMD data were summarized from individual studies by LRP5 genotype, and a synthesis of data was performed with random-effects meta-analyses. After excluding studies on animal and review papers, there were 19 studies for the synthesis. Among these studies, 10 studies used the rs3736228 (A1330V) polymorphism and reported BMD values. RESULTS: The 10 eligible studies comprised 16,705 individuals, with the majority being women (n = 8444), aged between 18 - 81 years. The overall distribution of genotype frequencies was: AA, 68%, AV and VV, 32%. However, the genotype frequency varied significantly within as well as between ethnic populations. On random-effects meta-analysis, lumbar spine BMD among individuals with the AA genotype was on average 0.018 (95% confidence interval [CI]: 0.012 to 0.023) g/cm2 higher than those with either AV or VV genotype. Similarly, femoral neck BMD among carriers of the AA genotype was 0.011 (95%CI: 0.004 to 0.017) g/cm2 higher than those without the genotype. While there was no significant heterogeneity in the association between the A1330V polymorphism and lumbar spine BMD (p = 0.55), the association was heterogeneous for femoral neck BMD (p = 0.05). The probability that the difference is greater than one standard deviation was 0.34 for femoral neck BMD and 0.54 for lumbar spine BMD. CONCLUSION: These results suggest that there is a modest effect of the A1330V polymorphism on BMD in the general population, and that the modest association may limit its clinical use.

Project description:Polymorphisms in the LRP5 gene have been associated with bone mineral density (BMD) in men and/or women. However, the functional basis for this association remains obscure. We hypothesized that LRP5 alleles could modulate Wnt signaling and the relationship between physical activity and BMD. This genetic association study was performed in the population-based Framingham Study Offspring Cohort, and included a subset of 1797 unrelated individuals who provided blood samples for DNA and who had BMD measurements of the hip and spine. Ten single-nucleotide polymorphisms (SNPs) spanning the LRP5 gene were genotyped and used for association and interaction analyses with BMD by regression methods. LRP5 haplotypes were transiently co-expressed with Wnt3a, MesD and Dkk1 in HEK293 cells and their activity evaluated by the TCF-Lef reporter assay. Six out of ten SNPs in LRP5 were associated with one or more of the femur or spine BMDs in men or women after adjustment for covariates, and these associations differed between genders. In men< or =age 60 years, 3 SNPs were significantly associated with BMD: rs2306862 on Exon 10 with femoral neck BMD (p=0.01) and Ward's BMD (p=0.01); rs4988321/p. V667M with Ward's BMD (p=0.02); and intronic rs901825 with trochanter BMD (p=0.03). In women, 3 SNPs in intron 2 were significantly associated with BMD: rs4988330 for trochanter (p=0.01) and spine BMD (p=0.003); rs312778 with femoral neck BMD (p=0.05); and rs4988331 with spine BMD (p=0.04). For each additional rare allele, BMD changed by 3-5% in males and 2-4% in females. Moreover, there was a significant interaction between physical activity and rs2306862 in exon 10 (p for interaction=0.02) and rs3736228/p. A1330V in exon 18 (p for interaction=0.05) on spine BMD in men. In both cases, the TT genotype was associated with lower BMD in men with higher physical activity scores, conversely with higher BMD in men with lower physical activity scores. In vitro, TCF-Lef activity in presence of Wnt3a was significantly reduced in cells expressing LRP5 haplotypes carrying the T allele of exon 10 and 18 compared to the wild-type allele, whereas co-expression of Dkk1 completely inhibited Wnt3a response through all LRP5 haplotypes. In summary, genetic variation in exons 10 and 18 of the LRP5 gene modulates Wnt signaling and the relationship between physical activity and BMD in men. These observations suggest that Wnt-LRP5 may play a role in the adaptation of bone to mechanical load in humans, and may explain some gender-related differences in bone mass.

Dataset Information

A mutagenesis-derived Lrp5 mouse mutant with abnormal retinal vasculature and low bone mineral density.

Publications

A mutagenesis-derived <i>Lrp5</i> mouse mutant with abnormal retinal vasculature and low bone mineral density.

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