Identification of Functional Mutations Associated with Environmental Variance of Litter Size in Rabbits
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Identification of functional mutations associated with environmental variance of litter size in rabbits Cristina Casto-Rebollo, María José Argente, María Luz García, Romi Pena, Noelia Ibáñez-Escriche To cite this version: Cristina Casto-Rebollo, María José Argente, María Luz García, Romi Pena, Noelia Ibáñez-Escriche. Identification of functional mutations associated with environmental variance of litter size in rabbits. Genetics Selection Evolution, BioMed Central, 2020, 52 (1), pp.22. 10.1186/s12711-020-00542-w. hal-02569066 HAL Id: hal-02569066 https://hal.archives-ouvertes.fr/hal-02569066 Submitted on 11 May 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Casto‑Rebollo et al. Genet Sel Evol (2020) 52:22 https://doi.org/10.1186/s12711‑020‑00542‑w Genetics Selection Evolution RESEARCH ARTICLE Open Access Identifcation of functional mutations associated with environmental variance of litter size in rabbits Cristina Casto‑Rebollo1, María José Argente2, María Luz García2, Romi Pena3 and Noelia Ibáñez‑Escriche1* Abstract Background: Environmental variance (VE) is partly under genetic control and has recently been proposed as a measure of resilience. Unravelling the genetic background of the VE of complex traits could help to improve resilience of livestock and stabilize their production across farming systems. The objective of this study was to identify genes and functional mutations associated with variation in VE of litter size (LS) in rabbits. To achieve this, we combined the results of a genome‑wide association study (GWAS) and a whole‑genome sequencing (WGS) analysis using data from two divergently selected rabbit lines for high and low VE of LS. These lines difer in terms of biomarkers of immune response and mortality. Moreover, rabbits with a lower VE of LS were found to be more resilient to infections than animals with a higher VE of LS. Results: By using two GWAS approaches (single‑marker regression and Bayesian multiple‑marker regression), we identifed four genomic regions associated with VE of LS, on chromosomes 3, 7, 10, and 14. We detected 38 genes in the associated genomic regions and, using WGS, we identifed 129 variants in the splicing, UTR, and coding (missense and frameshift efects) regions of 16 of these 38 genes. These genes were related to the immune system, the devel‑ opment of sensory structures, and stress responses. All of these variants (except one) segregated in one of the rabbit lines and were absent (n 91) or fxed in the other one (n 37). The fxed variants were in the HDAC9, ITGB8, MIS18A, ENSOCUG00000021276 and= URB1 genes. We also identifed= a 1‑bp deletion in the 3′UTR region of the HUNK gene that was fxed in the low VE line and absent in the high VE line. Conclusions: This is the frst study that combines GWAS and WGS analyses to study the genetic basis of VE. The new candidate genes and functional mutations identifed in this study suggest that the VE of LS is under the control of functions related to the immune system, stress response, and the nervous system. These fndings could also explain diferences in resilience between rabbits with homogeneous and heterogeneous VE of litter size. Background or VE ). Many studies in various species have provided Understanding the efect of the environment on the phe- statistical evidence that VE is partly under genetic con- notype of farm animals is important to improve responses trol: pigs [1], mice [2], chickens [3], snails (Helix aspersa) to genetic selection. Te environment can afect both the [4] and cattle [5], among others. For instance, the VE can mean of a trait and its variance (environmental variance difer between genotypes under the same environment [6]. Successful divergent selection experiments for VE support these fndings in both livestock and model ani- *Correspondence: [email protected] 1 mals [7–9]. Institute for Animal Science and Technology, Universitat Politècnica de VE València, Valencia, Spain Recently, was proposed as a measure of resilience Full list of author information is available at the end of the article [10], which is the ability of an animal to maintain or © The Author(s) 2020. 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The Creative Commons Public Domain Dedication waiver (http://creat iveco mmons .org/publi cdoma in/ zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. Casto‑Rebollo et al. Genet Sel Evol (2020) 52:22 Page 2 of 9 quickly recover their performance in spite of environ- Phenotype mental perturbations [11, 12]. Previous genome-wide In this study, we investigated genomic regions that were association studies (GWAS) for VE have identifed rele- associated with the VE of LS, which was the selection cri- vant contributions from candidate genes that are related terion in the divergent selection experiment [9]. Te VE to important phases of the infammatory response, such of LS was calculated as the within-doe variance of TNB, as Hsp90 [13, 14], p22-PHOX, GNG11, and GNGT1 [15], after correction of TNB by year-season (47 levels) and which are triggered by tissue damage and the entry of parity-lactation status (3 levels) to avoid the efect of sys- pathogens [16]. In humans, the FTO gene, which afects tematic efects on VE . Te mean estimate of residuals for the variability of body mass index [17], was also found to a doe across parities was used to calculate the VE of LS be associated with sensitivity to infections [18]. All these for a doe, using the minimum quadratic risk estimator: results support the role of the immune system in the n 1 2 detection and response to environmental perturbations VE = (x − x¯) , n + 1 i (1) such as pathogen infections [12]. 1 Unravelling the genetic background of the VE of com- x i plex traits could help to improve resilience of livestock where i is the pre-corrected TNB at parity of a doe and n and stabilize their production across farming systems is the total number of parities of the doe (ranging from V [19]. Te aim of this study was to identify genes and func- 2 to 12). E was calculated by assuming that the addi- tional mutations associated with variation in the VE of tive genetic and permanent efects are approximately the V litter size (LS) in rabbits. We performed a GWAS and a same for each parity of a doe [21]. Te average of the E whole-genome sequencing (WGS) analysis using data of LS was 4.24 (± 3.41), 2.27 (± 1.97) and 3.84 (± 3.69) from two rabbit lines that have been divergently selected for the base population and for the low and high lines, for high and low VE of LS [9]. Tese lines show a remark- respectively. able diference in VE of LS (4.5% of the mean of the base population), as well as diferences in mortality, in bio- Genotypes markers of immune response (plasma cortisol, leukocytes Genomic DNA was isolated from blood sampled from and acute-phase protein levels), and in plasma concen- does using standard procedures. Genotyping was per- trations of cholesterol and triglycerides [20]. Moreover, formed with the 200 K Afymetrix Axiom OrcunSNP VE the line with a low of LS was found to cope better with array (TermoFisher Scientifc). Quality control of geno- environmental stressors such as infections than the line types was performed using the platform Axiom Analy- VE with a high of LS, which suggests that the homogene- sis Suite 3.1 of TermoFisher Scientifc and the PLINK ous line is more resilient. v1.9 software [22]. Animals with a call rate lower than 97% and SNPs with a minor allele frequency lower than 0.05, with missing genotypes higher than 0.05, or with Methods unknown positions on the rabbit reference genome (Ory- Animals Cun v2.0.96) were removed. After quality control, 367 Te rabbits used in this study belong to a divergent selec- animals (1589 parities) and 96,329 SNPs remained in the VE tion experiment for high and low of LS over 12 gen- dataset. Te missing genotypes were imputed with the erations at the University Miguel Hernandez of Elche, Beagle v.4.1 software [23]. Finally, we identifed outliers Spain. Each divergent line had approximately 125 female and checked the population structure by applying a prin- and 25 male parents per generation (for more details see cipal component analysis (PCA) based on the genotypes Blasco et al.