Research article

Impact of breed and sex on porcine endocrine transcriptome: a bayesian biometrical analysis

Miguel Pérez-Enciso^1,2 , André LJ Ferraz^1,3 , Ana Ojeda¹ and Manel López-Béjar⁴

¹Departament de Ciència Animal i dels Aliments, Facultat de Veterinària, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain

²Institut Català de Recerca i Estudis Avançats (ICREA), C/Lluis Companys 23, 08010 Barcelona, Spain

³Faculdade de Ciências Agrárias e Veterinária, Universidade Estadual Paulista (UNESP), 14884-900 Jaboticabal – SP, Brazil

⁴Departament de Sanitat i d'Anatomia Animals, Facultat de Veterinária, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain

author email corresponding author email

BMC Genomics 2009, 10:89doi:10.1186/1471-2164-10-89

Published:	24 February 2009

Abstract

Background

Transcriptome variability is due to genetic and environmental causes, much like any other complex phenotype. Ascertaining the transcriptome differences between individuals is an important step to understand how selection and genetic drift may affect gene expression. To that end, extant divergent livestock breeds offer an ideal genetic material.

Results

We have analyzed with microarrays five tissues from the endocrine axis (hypothalamus, adenohypophysis, thyroid gland, gonads and fat tissue) of 16 pigs from both sexes pertaining to four extreme breeds (Duroc, Large White, Iberian and a cross with SinoEuropean hybrid line). Using a Bayesian linear model approach, we observed that the largest breed variability corresponded to the male gonads, and was larger than at the remaining tissues, including ovaries. Measurement of sex hormones in peripheral blood at slaughter did not detect any breed-related differences. Not unexpectedly, the gonads were the tissue with the largest number of sex biased genes. There was a strong correlation between sex and breed bias expression, although the most breed biased genes were not the most sex biased genes. A combined analysis of connectivity and differential expression suggested three biological processes as being primarily different between breeds: spermatogenesis, muscle differentiation and several metabolic processes.

Conclusion

These results suggest that differences across breeds in gene expression of the male gonads are larger than in other endocrine tissues in the pig. Nevertheless, the strong presence of breed biased genes in the male gonads cannot be explained solely by changes in spermatogenesis nor by differences in the reproductive tract development.