Free Access
Reprod. Nutr. Dev.
Volume 43, Number 5, September-October 2003
Page(s) 459 - 469
Reprod. Nutr. Dev. 43 (2003) 459-469
DOI: 10.1051/rnd:2003032

Real-time RT-PCR and cDNA macroarray to study the impact of the genetic polymorphism at the $\alpha_{s1}$-casein locus on the expression of genes in the goat mammary gland during lactation

Christine Lerouxa, b, Fabienne Le Provosta, Elisabeth Petita, Laurence Bernardb, Yves Chilliardb and Patrice Martina

a  Laboratoire de Génétique biochimique et de Cytogénétique, Institut National de la Recherche Agronomique, Domaine de Vilvert, 78352 Jouy-en-Josas, France
b  Unité de Recherches sur les Herbivores, Équipe Tissu Adipeux et Lipides du Lait, Institut National de la Recherche Agronomique, Theix, 63122 Saint-Genès-Champanelle, France

Milk fat has a large effect on nutritional, technological and sensorial properties of milk products. The milk fat content and composition are modulated by genetics and nutritional factors and imply a large number of enzymes. The regulation of their gene expression in the mammary gland still needs to be clarified. An association between the extensive polymorphism at the $\alpha_{s1}$-casein ( $\alpha_{s1}$-Cas) locus and both the lipid content and the characteristics of this fraction in caprine milk has been demonstrated. In order to decipher the mechanism responsible for this impact, a quantification of the transcripts of four lipogenic key enzymes (acetyl-CoA carboxylase, fatty acid synthase, lipoprotein lipase and stearoyl-CoA desaturase)was performed using real-time RT-PCR, suggesting an absence of association between the $\alpha_{s1}$-Cas genotype and expression variability of the studied genes. This approach has been completed by a more global analysis using a first generation of ruminant macroarray gathering 400 gene probes. The comparison of the expression profiles of lactating goat $\alpha_{s1}$-Cas A/A (strong allele) and F/F (defective allele) mammary gland allowed to confirm the expected variability in the expression of known genes (such as those encoding the $\alpha_{s1}$-casein) in ruminant mammary tissues as well as to identify up- and down-regulated genes. A second generation of ruminant cDNA macroarray extended to a few thousands of genes is currently in progress and will be applied to study different factors such as the nutritional regulation of gene expression in themammary gland.

Key words: goat milk / casein / fatty acids / genetic polymorphism / macroarray / lipogenesis

Correspondence and reprints: Christine Leroux

© INRA, EDP Sciences 2003