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Title: FSH- AND LH-CELLS ORIGINATE AS SEPARATE CELL POPULATIONS AND AT DIFFERENT EMBRYONIC STAGES IN THE CHICKEN EMBRYO

Author
item PUELBA-OSORIO, N - TEXAS A&M UNIVERSITY
item Proudman, John
item COMPTON, A - TEXAS A&M UNIVERSITY
item CLEMENTS, K - TEXAS A&M UNIVERSITY
item DECUYPERE, E - UNIV OF LEUVEN, BELGIUM
item VANDESANDE, F - UNIV OF LEUVEN, BELGIUM
item BERGHMAN, L - TEXAS A&M UNIVERSITY

Submitted to: General and Comparative Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/26/2002
Publication Date: 9/4/2002
Citation: Puelba-Osorio, N., Proudman, J.A., Compton, A.E., Clements, K.E., Decuypere, E., Vandesande, F., Berghman, L.R. Fsh- and lh-cells originate as separate cell populations and at different embryonic stages in the chicken embryo. General and Comparative Endocrinology. 127:242-248. 2002

Interpretive Summary: Successful reproduction depends on the coordinated action of two pituitary hormones, luteinizing hormone (LH) and follicle stimulating hormone (FSH). In most species, these hormones are present in the same cells, called gonadotrophs. Only in chickens and cattle are LH and FSH contained in different gonadotrophs. We conducted this study to determine whether chicken pituitary cells develop in the embryo as bi-hormonal cells, as in other species, and then diverge into two separate cell types at some point during development, or whether their fate is determined during cell differentiation in the embryo. The differentiation of pituitary cells is believed to be determined by factors secreted by surrounding tissues that induce cells to become pituitary precursor cells, and then early pituitary- determining genes specify which type of pituitary cell each will become. We examined embryonic pituitaries for the presence of LH and FSH from very early in embryonic development (Day 7 of incubation) until the pituitary was fully differentiated (day 18). We found that gonadotrophs containing LH appeared first, on Day 9 of incubation, and FSH-containing gonadotrophs appeared on Day 13 of embryogenesis. At no time during development were both hormones observed in the same cell. This situation is unique in that it seems to imply the existence of separate cell lineages for FSH- and LH- producing cells, as opposed to the single gonadotrope lineage described in all other species studied so far. Cattle pituitary cells may develop similarly, but this has not been studied. This new knowledge of pituitary cell differentiation may help scientists better study the mechanisms which determine the functional fate of cells, as well as how the brain controls the independent secretion of LH and FSH.

Technical Abstract: The histological distribution of gonadotrophs containing either LH or FSH, but not both gonadotropins, has been demonstrated before in the juvenile and adult chicken throughout the caudal and cephalic anterior pituitary lobes. In the present investigation, the distribution of FSH- and/or LH- containing gonadotrophs was further investigated in the chicken embryo by use of the same homologous antibodies as used in our earlier study. Fluorescent dual-labeling immunohistochemistry revealed that during embryogenesis LH and FSH reside exclusively in separate gonadotrophs, as has been described before in the post hatch bird. LH-immunoreactive cells were observed for the first time at day 9 of embryogenesis. This is as much as 4 days earlier than the FSH-immunoreactive cells, which appeared at day 13 of embryogenesis. Our results confirm that FSH- and LH-containing gonadotrophs are distributed throughout both lobes of the anterior pituitary. No conspicuous differences were observed between the sexes in any of the aspects investigated. The described situation is unique in that it seems to imply the existence of separate cell lineages for FSH- and LH- producing cells, as opposed to the single gonadotrope lineage described in all other species studied so far, with the exception of bovine. Our data indeed raise the question as to which signaling and/or transcription factors may cause the unique dichotomy observed in the chicken gonadotrophs.