Abstract
BackgroundTranscriptome 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.ResultsWe 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.ConclusionThese 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.
Highlights
Transcriptome variability is due to genetic and environmental causes, much like any other complex phenotype
These results suggest that differences across breeds in gene expression of the male gonads are larger than in other endocrine tissues in the pig
Differences in the amount of fat tissue are more likely to be caused by genetic signals that originate in the hypothalamus or in endocrine tissues rather than in the fat tissue itself
Summary
Transcriptome variability is due to genetic and environmental causes, much like any other complex phenotype. It is well known that variability at the transcriptome is in part due to genetic causes, much like any other complex phenotype, e.g., [1]. The large phenotypic differences that we observe between extant breeds of domestic species or between different ecotypes in wild species must be correlated to differences at the transcriptome level. The extent of these differences and their nature is, how-. An example is growth and leanness in livestock These two traits are the most important selection objectives in the majority of breeding programmes. They are very complex phenotypes that depend on a large number of tissues. Differences in the amount of fat tissue are more likely to be caused by genetic signals that originate in the hypothalamus or in endocrine tissues rather than in the fat tissue itself
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