|Naivar, J - UNIVERSITY OF MISSOURI|
|Dyer, C - UNIVERSITY OF MISSOURI|
|Keisler, D - UNIVERSITY OF MISSOURI|
Submitted to: Society for the Study of Reproduction Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: July 27, 1996
Publication Date: N/A
Technical Abstract: Recently leptin, the obesity (ob) gene product, was identified in mice, rats, and humans as a factor controlling body weight. In mice, the receptor for leptin was cloned and found to be expressed in the choroid plexus and hypothalamus. Leptin has been reported to affect, in rodents, expression of neuropeptide Y (NPY), a potent modulator of LH secretion. The objective of this study was to determine if leptin signaling mechanism (i.e., the protein and its receptor) for controlling body weight homeostasis exist in sheep as they do in rodents. Total cellular RNA was isolated from sheep hypothalamic, pituitary, and adipose tissue. Reverse transcription-PCR(RT-PCR) products were cloned and sequenced by the dideoxy method and used as probes in ribonuclease protection assays (RPA). RT-PCR amplification of adipose tissue RNA (with primers designed from the mouse, rat, and human leptin cDNA sequences) generated a 347 bp product that was over 90% homologous to the published sequences. Primers derived from the leptin receptor cDNA amplified a 484 bp fragment that was over 85% identical to the mouse coding sequence, which was then used as a radiolabeled riboprobe in RPAs to detect leptin receptor mRNA in ovine pituitary. RT-PCR also confirmed the presence of leptin receptor in the ovine pituitary (specificity confirmed by southern blotting). In contrast, leptin receptor mRNA was not detected in hypothalamic RNA extracts using RPAs. However, RT-PCR amplification of the leptin receptor from hypothalamic tissues suggests low levels of its expression in those tissues. Identification of leptin receptor mRNA in adipose tissues, via RPA, suggests an opportunity exists for leptin to autoregulate its receptor.