Genet. Sel. Evol. 34 (2002) 465-479
DOI: 10.1051/gse:2002018

Test for positional candidate genes for body composition on pig chromosome 6

Cristina Óvilo^a, Angels Oliver^b, José Luis Noguera^c, Alex Clop^d, Carmen Barragán^a, Luis Varona^c, Carmen Rodríguez^a, Miguel Toro^a, Armand Sánchez^d, Miguel Pérez-Enciso^c and Luis Silió<sup>a

a</sup>  Departamento de Mejora Genética Animal, SGIT-INIA, 28040 Madrid, Spain
^b  Centre de Tecnologia de la Carn, IRTA, 17121 Monells, Girona, Spain
^c  Area de Producció Animal, Centre UdL-IRTA, 25198 Lleida, Spain
^d  Departament de Ciència Animal i dels Aliments, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Spain

(Received 9 August 2001; accepted 14 February 2002)

Abstract
One QTL affecting backfat thickness (BF), intramuscular fat content (IMF) and eye muscle area (MA) was previously localized on porcine chromosome 6 in an F ₂ cross between Iberian and Landrace pigs. This work was done to study the effect of two positional candidate genes on these traits: H-FABP and LEPR genes. The QTL mapping analysis was repeated with a regression method using genotypes for seven microsatellites and two PCR-RFLPs in the H-FABP and LEPR genes. H-FABP and LEPR genes were located at 85.4 and 107 cM respectively, by linkage analysis. The effects of the candidate gene polymorphisms were analyzed in two ways. When an animal model was fitted, both genes showed significant effects on fatness traits, the H-FABP polymorphism showed significant effects on IMF and MA, and the LEPR polymorphism on BF and IMF. But when the candidate gene effect was included in a QTL regression analysis these associations were not observed, suggesting that they must not be the causal mutations responsible for the effects found. Differences in the results of both analyses showed the inadequacy of the animal model approach for the evaluation of positional candidate genes in populations with linkage disequilibrium, when the probabilities of the parental origin of the QTL alleles are not included in the model.

Key words: candidate gene / H-FABP / LEPR / QTL / pigs

Correspondence and reprints: Cristina Óvilo
    e-mail: ovilo@inia.es

© INRA, EDP Sciences 2002