PROLACTIN RECEPTOR GENE-EXPRESSION IN THE BRAIN AND PERIPHERAL-TISSUES IN BROODY AND NONBROODY BREEDS OF DOMESTIC HEN

The objective of this study was to establish whether the gene encoding prolactin receptor (PRLR) is expressed in the hypothalamus and periph eral tissues of the domestic chicken and, if so, to determine whether there are breed differences in the structure or expression of the gene which might account for the observation that broodiness does not occu r in the White Leghorn hen but does occur in other breeds of domestic hens, including the bantam. A preliminary experiment demonstrated that the absence of broodiness in White Leghorns is not due to a lack of a prolactin response to the avian prolactin-releasing hormone vasoactiv e intestinal polypeptide. The largest amounts of PRLR mRNA in the brai n, which did not differ significantly between laying White Leghorns an d bantams, were found in the pituitary gland and basal and preoptic hy pothalamus. Small or nondetectable amounts were found in both breeds i n the forebrain, cerebellum, and optic lobes. Prolactin receptor mRNA was widely distributed in peripheral tissues in both breeds, in the fo llowing descending order of abundance: kidney, leg skin, brood patch, duodenum, intestine > thyroid gland > adrenal gland, liver, ovary much greater than adipose tissue > thymus, spleen > muscle > blood. Southe rn blotting analysis using four restriction enzymes and a chicken PRLR cDNA probe demonstrated identical digestion patterns for White Leghor n and bantam genomic DNA. Northern blotting analysis identified two si zes of chicken PRLR mRNA transcripts (7.5 and 3.3 kb) in hypothalami f rom laying White Leghorn and bantam hens. It is concluded that differe nces in the expression of broodiness in White Leghorn and bantam hens cannot be explained by differences in the amounts of PRLR mRNA in the hypothalamus or in the transcription or gross structure of the PRLR ge ne. (C) 1998 Academic Press.