Expression profile of caseins, estrogen and prolactin receptors in mammary glands of dairy ewes

In this study, we analyzed the developmental expression of estrogen receptors (ESR1 and ESR2), prolactin receptors (PRLR) and casein genes (CSN1S1, CSN1S2, CSN2 and CSN3) in the ewe mammary glands from prepubertal stage to involution. Using Real-time PCR we showed that the activation of casein genes transcription was up regulated during lactation and significantly down regulated before lambing and at involution in comparison to the expression measured in the prepubertal group. The highest expression of ESR1 and ESR2 genes occurred in prepubertal group compared to adult group. The PRLR expression of the short and long forms was up regulated before lambing and down regulated during lactation and involution. Thus, the mRNA expression data for ESRs and PRLR show clear regulatory changes suggesting involvement of these receptors in sheep mammary glands during development to involution. Casein genes transcription could be primed through PRLR signal, but other factors may be necessary for milk protein long-term expression during lactation.