CHARACTERIZATION OF THE CHICKEN FOLLICLE-STIMULATING-HORMONE RECEPTOR(CFSH-R) COMPLEMENTARY DEOXYRIBONUCLEIC-ACID, AND EXPRESSION OF CFSH-R MESSENGER-RIBONUCLEIC-ACID IN THE OVARY

Studies were conducted to characterize the chicken (c) FSH receptor (R ) cDNA, and to evaluate expression of cFSH-R mRNA in the hen ovary at known stages during follicle development. A total of 2.5 kb of nucleic acid sequence including the complete cFSH-R coding region was isolate d by a combination of the reverse-transcription polymerase chain react ion and 5'- and 3'-rapid amplification of cDNA ends techniques. Overal l, the nucleic acid sequence homology of the cFSH-R cDNA coding region is 71.8% and 72.2% compared to the rat and bovine FSH-R, respectively , while the deduced amino acid sequence identity for the receptor prot ein (693 amino acids) is 71.9% and 72.4%, respectively. By comparison, the cFSH-R nucleic acid and amino acid sequences are 60.1% and 49.4% identical to the respective cLH-R sequences. Northern blot analysis de tected a single 4.3-kb cFSH-R mRNA transcript, which was selectively e xpressed in ovarian (granulosa, theca, and stromal) tissues, but not t he oviduct, adrenal, liver, muscle, or brain. As the follicle develope d from the prehierarchical (6- to 8-mm diameter) to the largest preovu latory (F1 follicle) stage, cFSH-R mRNA levels progressively declined within both the granulosa and theca layers (p < 0.05). Moreover, cFSH- R mRNA levels were lower in whole atretic than in morphologically norm al 3- to 5-mm follicles (p = 0.0015). The pattern of cFSH-R mRNA expre ssion within the granulosa layer during follicle development was notab ly different from that of the recently reported cLH-R, in that cLH-R m RNA levels increase to become readily detectable coincident with drama tically increased steroidogenic capacity during the last few days befo re ovulation of the follicle. On the other hand, highest levels of cFS H-R mRNA in 6- to 8-mm (prehierarchical) follicles were consistent wit h a role for the cFSH-R in maintaining the viability of prehierarchica l follicles and in initiating granulosa cell differentiation at the ti me when follicles are selected into the preovulatory hierarchy.