Conplastic strains for identification of retrograde effects of mitochondrial dna variation on cardiometabolic traits in the spontaneously hypertensive rat

Abstract

Mitochondrial retrograde signaling is a pathway of communication from mitochondria to the nucleus. Recently, natural mitochondrial genome (mtDNA) polymorphisms (haplogroups) received increasing attention in the pathophysiology of human common diseases. However, retrograde effects of mtDNA variants on such traits are difficult to study in humans. The conplastic strains represent key animal models to elucidate regulatory roles of mtDNA haplogroups on defined nuclear genome background. To analyze the relationship between mtDNA variants and cardiometabolic traits, we derived a set of rat conplastic strains (SHR-mtBN, SHR-mtF344 and SHR-mtLEW), harboring all major mtDNA haplotypes present in common inbred strains on the nuclear background of the spontaneously hypertensive rat (SHR). The BN, F344 and LEW mtDNA differ from the SHR in multiple amino acid substitutions in protein coding genes and also in variants of tRNA and rRNA genes. Different mtDNA haplotypes were found to predispose to various sets of cardiometabolic phenotypes which provided evidence for significant retrograde effects of mtDNA in the SHR. In the future, these animals could be used to decipher individual biochemical components involved in the retrograde signaling.

Fig. 1

Derivation of SHR conplastic strains. The nuclear genomes of the mtDNA donor (strain X) and recipient (SHR strain) are indicated in black and white, respectively. The relative increase of recipient nuclear alleles at sequential backcross generations are schematically depicted by different shades of gray. Since the mitochondrial genome is inherited maternally, female offspring are always crossed with males of the SHR recipient strain in each backcross generation to ensure transfer of the donor strain mtDNA onto the SHR recipient strain nuclear genetic background. After 10 backcross generations, nuclear genome of conplastic strain is 99.8 % identical to recipient SHR strain (depicted as white) and harbors mtDNA of donor strain X (BN or F344 or LEW).

Fig. 2

Activity levels of NADH cytochrome c reductase (NCCR, Complex I+III), succinate cytochrome c reductase (SCCR, Complex II+III), cytochrome c oxidase (COX, Complex IV) and citrate synthase (CS) in liver, heart and muscle from the SHR-mt^BN, SHR-mt^LEW and SHR-mt^F344 conplastic strains compared to SHR progenitor strain. All enzyme activities were expressed relative to activity of SHR progenitor strain set at 1. Original raw data were published in Pravenec et al. 2007, Houštěk et al. 2012 and Houštěk et al. 2014. Statistical significance * P<0.05, ** P<0.01, *** P<0.001.

Fig. 3

Echocardiography assessment of fractional shortening in SHR-mt^F344 rats. Baseline as well as maximal values (after dobutamine) are shown.