Genetic basis of thermal nociceptive sensitivity and brain weight in a BALB/c reduced complexity cross

Abstract

Thermal nociception involves the transmission of temperature-related noxious information from the periphery to the CNS and is a heritable trait that could predict transition to persistent pain. Rodent forward genetics complement human studies by controlling genetic complexity and environmental factors, analysis of end point tissue, and validation of variants on appropriate genetic backgrounds. Reduced complexity crosses between nearly identical inbred substrains with robust trait differences can greatly facilitate unbiased discovery of novel genes and variants. We found BALB/cByJ mice showed enhanced sensitivity on the 53.5°C hot plate and mechanical stimulation in the von Frey test compared to BALB/cJ mice and replicated decreased gross brain weight in BALB/cByJ versus BALB/cJ. We then identified a quantitative trait locus (QTL) on chromosome 13 for hot plate sensitivity (LOD = 10.7; p < 0.001; peak = 56 Mb) and a QTL for brain weight on chromosome 5 (LOD = 8.7; p < 0.001). Expression QTL mapping of brain tissues identified H2afy (56.07 Mb) as the top transcript with the strongest association at the hot plate locus (FDR = 0.0002) and spliceome analysis identified differential exon usage within H2afy associated with the same locus. Whole brain proteomics further supported decreased H2AFY expression could underlie enhanced hot plate sensitivity, and identified ACADS as a candidate for reduced brain weight. To summarize, a BALB/c reduced complexity cross combined with multiple -omics approaches facilitated identification of candidate genes underlying thermal nociception and brain weight. These substrains provide a powerful, reciprocal platform for future validation of candidate variants.

Zhx2 is a candidate gene underlying oxymorphone metabolite brain concentration associated with state-dependent oxycodone reward

“…Interestingly, when analyzed separately by sex we observe that female mice show a significant difference and are driving the observed difference (logFC = 0.37, logOdds = 0.97) as opposed to males who did not reach significance (logFC = 0.17, logOdds = -4.37). Complete data set can be found in Beierle et al, 2022.…”

“…and published procedures (Kirkpatrick & Bryant, 2015) that are summarized above. Immediately after testing for state-dependent CPP on Day 9 (30 min post-OXY), mice were sacrificed and 16 brains were harvested for proteomic analysis as described in Beierle et al, 2022. Briefly, 8 BALB/cJ (2/sex/tx) and 8 BALB/cByJ (2/sex/tx) whole brains were collected, homogenized, fractionated, and MS/MS spectra acquired.…”

“…The J and By substrains differ in several interesting neurobehavioral phenotypes (Dam et al, 2019;Hilakivi & Lister, 1989;Jager et al, 2020;Perincheri et al, 2005;Poyntz et al, 2019;Sittig et al, 2014Sittig et al, , 2014Turner et al, 2008;Velez et al, 2010). Given this phenotypic variation, BALB/c substrains likely harbor readily identifiable causal genetic variants mediating important behavioral traits and we have previously employed a reduced complexity cross in BALB/c substrains to map QTLs, eQTLs, and candidate genes underlying thermal nociception and brain weight (Beierle et al, 2022).…”

“…Large phenotypic variance combined with a drastic reduction in the density of genetic polymorphisms facilitates the identification of causal genes/variants that can readily be validated via gene editing (Mulligan et al, 2019). Reduced complexity crosses have been used between multiple mouse substrains (e.g., C57BL/6, DBA/2, BALB/c) to map the genetic basis of complex phenotypes such as psychostimulant sensitivity, binge-like eating, and thermal nociception (Beierle et al, 2022; Goldberg et al, 2021; Harkness et al, 2015; Kirkpatrick et al, 2017; Kumar et al, 2013; Miner et al, 2017; Reed et al, 2018; Shi et al, 2016).…”

Zhx2 Is a Candidate Gene Underlying Oxymorphone Metabolite Brain Concentration Associated with State-Dependent Oxycodone Reward

“…Large phenotypic variance combined with a drastic reduction in the density of genetic polymorphisms facilitates the identification of causal genes/variants that can readily be validated via gene editing (Mulligan et al, 2019). Reduced complexity crosses have been used between multiple mouse substrains (e.g., C57BL/6, DBA/2, BALB/c) to map the genetic basis of complex phenotypes such as psychostimulant sensitivity, binge-like eating, and thermal nociception (Beierle et al, 2022;Goldberg et al, 2021;Harkness et al, 2015;Kirkpatrick et al, 2017;Kumar et al, 2013;Miner et al, 2017;Reed et al, 2018;Shi et al, 2016).…”