Identification of a spontaneous mutation in Adiponectin receptor 1 in a complement factor H knockout mouse

Abstract

Purpose : A subset of mice in our Cfh knockout (Cfh^-/-) colony exhibited rapid retinal degeneration, suggesting a spontaneous mutation occurred on mouse chromosome 1 (Chr 1). The retinal phenotype was similar to that in AdipoR1 knockout (AdipoR1^-/-) mice, whose gene is located near the Cfh locus on Chr 1. We attempted to determine if a mutation in AdipoR1 occurred on the Cfh^-/- background.

Methods : We performed an allele complementation test with a cross between a Cfh^-/- mouse with retinal degeneration and an AdipoR1^-/- mouse with retinal degeneration. RNA-seq, in situ hybridization, immunohistochemistry and protein analysis were used to profile Cfh^-/- and AdipoR1^-/- mice.

Results : About 50% of Cfh^-/- mice exhibited retinal degeneration. Cfh^-/- mice, regardless of retinal phenotype, demonstrated elevated complement activation in the eye compared to littermate controls. All offspring from the complementation test exhibited retinal degeneration, implying that AdipoR1 mutant alleles were responsible for the retinal degeneration. AdipoR1 protein, normally present in the RPE apical microvilli, was notably absent in Cfh^-/- mice with retinal degeneration. Cfh^-/- mice with normal retinal anatomy expressed AdipoR1 protein and were comparable to littermates[QY1] . Adipor1 mRNA expression levels were comparable across the colony as measured by RNAscope and RNA-seq. Analysis of AdipoR1 mRNA sequence revealed a transversion at position c.841 C>T in the Adipor1 gene concordant with mice exhibiting retinal degeneration. Further breeding identified mutant AdipoR1 mRNA in two Cfh^+/- mice and one Cfh^+/+ mice with early onset retinal degeneration, implying a recent cross over on Chr 1. This missense mutation results in a proline to serine conversion (P281S) in the fifth transmembrane domain of AdipoR1 and is predicted to be detrimental to the AdipoR1 protein.

Conclusions : The spontaneous mutation in the AdipoR1 gene results in early onset retinal degeneration in a subset of our Cfh^-/- mouse colony. Elevated complement activity in the eye does not appear to affect the course of retinal degeneration, as gene signatures are comparable across all mice with retinal degeneration, regardless of Cfh genotype.

This is a 2021 ARVO Annual Meeting abstract.