T. Ohkubo et al., PROLACTIN RECEPTOR GENE-EXPRESSION IN THE BRAIN AND PERIPHERAL-TISSUES IN BROODY AND NONBROODY BREEDS OF DOMESTIC HEN, General and comparative endocrinology, 109(1), 1998, pp. 60-68
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.