Three inquiries into the origin of Manchado de Jabugo pigs

Ponencia publicada en ITEA, vol.104El origen de la población Manchado de Jabugo se atribuye a cruces realizados en el siglo XIX entre cerdos Ibéricos negros y colorados. Se supone que animales de razas Large White y Berkshire contribuyeron además a fundar esta población, que ha permanecido aislada durante décadas en algunos pueblos de la Sierra de Aracena. El objetivo de este trabajo fue rastrear posibles huellas genéticas de las variedades y razas fundadoras en la población actual, conservada por la Diputación de Huelva. El ADN mitocondrial de animales Manchado de Jabugo y Large White presenta secuencias coincidentes tanto para la región de control D-loop, como para los genes Cyt b, ATPasa8, ATPasa6 y NADH5. La mutación IGF2 g.3072G>A, ocurrida en un cromosoma asiático, se detecta en la población Manchado, y está presente asimismo en Large White y Berkshire. Ello concuerda con la posible contribución fundacional de ambas razas británicas, en las que se introdujeron genes de origen asiático a partir del siglo XVIII. Finalmente, esta población presenta cuatro alelos del gen MC1R. El alelo MC1R*3 es característico de la variedad negra de cerdo Ibérico y del Large White. Los alelos MC1R*6 y MC1R*7 de la variedad colorada, y el primero también del Berkshire. La presencia del alelo MC1R*4, característico de la raza Duroc indica una contribución más reciente de esta otra raza foránea al germoplasma del Manchado de Jabugo.Animals born at the end of the XIX century from crosses between Red and Black Iberian pigs were the main founders of the black spotted population named Manchado de Jabugo. Pigs of the Large White and Berkshire breeds had also contributed to the foundation of this population, which was isolated for several decades in some villages of Huelva. Our objective was to verify the possible genetic traces of founder varieties and breeds in this population, preserved by the Diputación de Huelva. The mitochondrial DNA from Manchado and Large White animals shows identical sequences for the control region D-loop, and also for the Cyt b ATPase8, ATPase6 and NADH5 genes. The IGF2 g.3072G>A mutation, apparently occurred in an Asian chromosome, is also present in the Manchado population. Both results agree with the quoted founder contribution of two British breeds, because Asian germplasm was introgressed into these breeds from the XVIII century. Finally, four alleles of the MC1R gene are segregating in this small population. The MC1R*3 allele is characteristic of Black Iberian variety and Large White breed. The MC1R*6 and MC1R*7 alleles are characteristic of Red Iberian pigs, and the first one of the Berkshire pigs. The unexpected presence of the MC1R*4 allele, characteristic of Duroc, indicates the contribution of this breed to the current Manchado germplasm

Identification of population-informative markers from high-density genotyping data through combined feature selection and machine learning algorithms: Application to European autochthonous and cosmopolitan pig breeds

Large genotyping datasets, obtained from high-density single nucleotide polymorphism (SNP) arrays, developed for different livestock species, can be used to describe and differentiate breeds or populations. To identify the most discriminating genetic markers among thousands of genotyped SNPs, a few statistical approaches have been proposed. In this study, we applied the Boruta algorithm, a wrapper of the machine learning random forest algorithm, on a database of 23 European pig breeds (20 autochthonous and three cosmopolitan breeds) genotyped with a 70k SNP chip, to pre-select informative SNPs. To identify different sets of SNPs, these pre-selected markers were then ranked with random forest based on their mean decrease accuracy and mean decrease gene indexes. We evaluated the efficiency of these subsets for breed classification and the usefulness of this approach to detect candidate genes affecting breed-specific phenotypes and relevant production traits that might differ among breeds. The lowest overall classification error (2.3%) was reached with a subpanel including only 398 SNPs (ranked based on their mean decrease accuracy), with no classification error in seven breeds using up to 49 SNPs. Several SNPs of these selected subpanels were in genomic regions in which previous studies had identified signatures of selection or genes associated with morphological or production traits that distinguish the analysed breeds. Therefore, even if these approaches have not been originally designed to identify signatures of selection, the obtained results showed that they could potentially be useful for this purpose

Inference of hidden population substructure of the Iberian pig breed using multilocus microsatellite data

Abstract The census and structure of Iberian pig breed have experienced important changes along the last decades. Bayesian methods based on multilocus genotypes have been applied for ascertaining the actual breed structure and for identifying genetically distinctive populations. DNA samples from 170 Iberian pigs previously assigned to the strains or varieties Torbiscal, Guadyerbas, Retinto, Entrepelado and Lampiño and 64 Duroc pigs were genotyped for 36 microsatellites. A best partition of only five clusters was estimated in the clustering analysis at group level, when the previous assignation to populations was taken into account. But the individual-based assessment of population structure, ignoring the previous assignation of animals to populations, showed a more complex partition of ten clusters. Results of admixture analyses for partitioning individuals into the inferred clusters showed an important proportion of admixed individuals pre-assigned to the Retinto, Entrepelado and Lampiño varieties. The frequencies of private alleles of the MC1R gene also evidenced an important genetic flow between these varieties. The future definition of conservation units in the Iberian breed should consider these results. Additional key words: clustering, MC1R gene, mixture and admixture analysis, within-breed variation. Resumen Inferencia de la subestructura de la raza porcina Ibérica a partir de genotipos multigénicos de microsatélites El censo y la estructura de la raza porcina Ibérica han experimentado cambios importantes durante las últimas décadas. Se han utilizado métodos bayesianos basados en genotipos multigénicos para discernir la actual estructura de la raza e identificar en ella poblaciones genéticamente singulares. Con este objetivo, se genotiparon 36 microsatélites en muestras de ADN procedentes de 170 cerdos Ibéricos asignados previamente a las estirpes o variedades Torbiscal, Guadyerbas, Retinto, Entrepelado y Lampiño además de 64 cerdos Duroc. Cuando se tuvo en cuenta esta asignación previa en el análisis, se obtuvo una partición óptima de sólo cinco clases, una de las cuales agrupaba las variedades Retinto y Entrepelado. El análisis individual, ignorando la asignación previa de los animales a las razas o variedades, permitió inferir una partición más compleja de diez clases. Los resultados de los análisis con modelos de mestizaje mostraron una importante proporción de animales mestizos preasignados a las variedades Retinto, Entrepelado y Lampiño. Las frecuencias de los alelos específicos del gen MC1R confirmaron el importante flujo genético producido entre estas variedades. Una futura definición de unidades de conservación en la raza Ibérica debería considerar estos resultados. Palabras clave adicionales: análisis de mezcla y mestizaje de poblaciones, clusters, gen MC1R, variación intrarracial

Diet-Induced Swine Model with Obesity/Leptin Resistance for the Study of Metabolic Syndrome and Type 2 Diabetes

The objective of the present study was to determine the suitability of a swine breed with leptin resistance and predisposition to obesity (the Iberian pig) as model for studies on metabolic syndrome and type 2 diabetes. Thus, six Iberian sows had ad libitum access to food enriched with saturated fat (SFAD group; food consumption was estimated to be 4.5 kg/animal/day) whilst four females acted as controls and were fed with 2 kg/animal/day of a commercial maintenance diet. After three months of differential feeding, SFAD animals developed central obesity, dyslipidemia, insulin resistance and impaired glucose tolerance, and elevated blood pressure; the five parameters associated with the metabolic syndrome. Thus, the current study characterizes the Iberian pig as a robust, amenable, and reliable translational model for studies on nutrition-associated diseases

Muscle transcriptome analysis reveals molecular pathways related to oxidative phosphorylation, antioxidant defense, fatness and growth in Mangalitsa and Moravka pigs

This work was aimed at evaluating loin transcriptome and metabolic pathway differences between the two main Serbian local pig breeds with divergent characteristics regarding muscle growth and fatness, as well as exploring nutrigenomic effects of tannin supplementation in Mangalitsa (MA) pigs. The study comprised 24 Mangalitsa and 10 Moravka (MO) males, which were kept under identical management conditions. Mangalitsa animals were divided in two nutritional groups (n = 12) receiving a standard (control) or tannin–supplemented diet (1.5%; MAT). Moravka pigs were fed the standard mixture. All animals were slaughtered at a similar age; 120 kg of average live weight (LW) and loin tissue was used for RNA‐seq analysis. Results showed 306 differentially expressed genes (DEGs) according to breed, enriched in genes involved in growth, lipid metabolism, protein metabolism and muscle development, such as PDK4, FABP4, MYOD1 and STAT3, as well as a relevant number of genes involved in mitochondrial respiratory activity (MT‐NDs, NDUFAs among others). Oxidative phosphorylation was the most significantly affected pathway, activated in Mangalitsa muscle, revealing the basis of a different muscle metabolism. Also, many other relevant pathways were affected by breed and involved in oxidative stress response, fat accumulation and development of skeletal muscle. Results also allowed the identification of potential regulators and causal networks such as those controlled by FLCN, PPARGC1A or PRKAB1 with relevant regulatory roles on DEGs involved in mitochondrial and lipid metabolism, or IL3 and TRAF2 potentially controlling DEGs involved in muscle development. The Tannin effect on transcriptome was small, with only 23 DEGs, but included interesting ones involved in lipid deposition such as PPARGC1B. The results indicate a significant effect of the breed on muscle tissue gene expression, affecting relevant biological pathways and allowing the identification of strong regulatory candidate genes to underlie the gene expression and phenotypic differences between the compared groups

Qxpak.5: Old mixed model solutions for new genomics problems

Mixed models have a long and fruitful history in statistics. They are pertinent to genomics problems because they are highly versatile, accommodating a wide variety of situations within the same theoretical and algorithmic framework. Qxpak is a package for versatile statistical genomics, specifically designed for sophisticated quantitative trait loci and association analyses. Multiple loci, multiple trait, infinitesimal genetic effects, imprinting, epistasis or sex linked loci can be fitted. The new version (v. 5) allows us, among other new features, to include either relationship matrices obtained with molecular information or user defined matrices that can be read from an input file. This feature can be used for genome selection or - more importantly - to correct for population structure in association studies. In crosses, two parental lines, not necessarily inbred, can be accommodated. This software aims at simplifying statistical genetic analyses implementing a coherent and unified approach by mixed models. It provides a tool that can be used in a wide variety of situations with ample genetic and statistical modeling flexibility. The software, a complete manual and examples are available at http://www.icrea.cat/Web/OtherSectionViewer.aspx?key=485&titol=Software:Qxpak.

Quantitative trait locus analysis of hybrid pedigrees: variance-components model, inbreeding parameter, and power

<p>Abstract</p> <p>Background</p> <p>For the last years reliable mapping of quantitative trait loci (QTLs) has become feasible through linkage analysis based on the variance-components method. There are now many approaches to the QTL analysis of various types of crosses within one population (breed) as well as crosses between divergent populations (breeds). However, to analyse a complex pedigree with dominance and inbreeding, when the pedigree's founders have an inter-population (hybrid) origin, it is necessary to develop a high-powered method taking into account these features of the pedigree.</p> <p>Results</p> <p>We offer a universal approach to QTL analysis of complex pedigrees descended from crosses between outbred parental lines with different QTL allele frequencies. This approach improves the established variance-components method due to the consideration of the genetic effect conditioned by inter-population origin and inbreeding of individuals. To estimate model parameters, namely additive and dominant effects, and the allelic frequencies of the QTL analysed, and also to define the QTL positions on a chromosome with respect to genotyped markers, we used the maximum-likelihood method. To detect linkage between the QTL and the markers we propose statistics with a non-central χ²-distribution that provides the possibility to deduce analytical expressions for the power of the method and therefore, to estimate the pedigree's size required for 80% power. The method works for arbitrarily structured pedigrees with dominance and inbreeding.</p> <p>Conclusion</p> <p>Our method uses the phenotypic values and the marker information for each individual of the pedigree under observation as initial data and can be valuable for fine mapping purposes. The power of the method is increased if the QTL effects conditioned by inter-population origin and inbreeding are enhanced. Several improvements can be developed to take into account fixed factors affecting trait formation, such as age and sex.</p