Changes in estrogen receptor alpha expression in the bursa of Fabricius during chick embryonic development

Abstract

Sex steroid hormones have been reported to be modulators that augment or suppress immune functions. Applying estrogen to chick embryos has been reported to influence antibody production after hatching, suggesting that estrogen acts on B cell differentiation and proliferation in the bursa of chick embryos. We previously reported the presence of estrogen receptor a (ERa) in the bursa during the late period of embryogenesis. In the present study we examined the time course of ERa expression in the bursa of chick embryos at the late period of embryogenesis by ERa-messenger RNA (mRNA) expression analysis by reverse-transcription-polymerase chain reaction (RT-PCR) using primers for chicken ERa, and immunohistochemistry using an anti-ER antibody. The quantity of ERa-mRNA expressed, estimated from the relative densities of the ERa RT-PCR products to those of b-actin, changed with time during the late period of embryogenesis (day 10 to day 21). ERa-mRNA expression was observed at all ages examined in the present experiment. The expression increased between day 10 and day 15 of embryogenesis and then the value was decreased between day 15 and day 21 of embryogenesis. The numbers of ER-positive cells in the bursa also changed with time during the late period of embryogenesis (day 14 to day 18). ER-positive cells showed the highest level on day 14 of embryogenesis, and then the value declined. ER-positive cells were observed in lymphoid follicular cells, stromal cells and epithelial cells, and the density of ER-positive cells was highest in epithelial cells among the three cell components of the bursa. The high level of ER expression in the bursa of Fabricius (BF) of chick embryos at the late period of embryogenesis suggests that this stage of embryogenesis is critical in B cell differentiation in the bursa in connection with estrogen effects on antibody production after hatching.

Localization of Estrogen Receptor in the Central Lymphoid Organs of Chickens during the Late Stage of Embryogenesis

“…7,8) In present study, we also found that ER mRNA was expressed in the chick thymus and BF by RT-PCR analysis. In this study, ER expression was established by two methods, immunohistochemistry and RT-PCR analysis, in the chick thymus and the BF.…”

“…Shin et al reported that the lymphoid follicle, the stromal area, and the surface epithelial areas expressed ER, but that the lymphocytes showed negative results for ER expression. 8) These discrepancies might be explained by differences in the methods used for tissue fixation. In previous studies, the formalin fixation method and paraffin-embedded sections were used; 7,8) in contrast, in the study, frozen sections were used.…”

“…8) These discrepancies might be explained by differences in the methods used for tissue fixation. In previous studies, the formalin fixation method and paraffin-embedded sections were used; 7,8) in contrast, in the study, frozen sections were used. A frozen section is preferable because the immunoreactivity of the antibody is maintained and there is less possibility of non-specific binding.…”

“…In ER, forward primer was 5 0 -CGTGGAAAGCAACAAGACA-3 0 (ER-F) and reverse primer was 5 0 -AAGCCTCCCCGTTCCTGG-3 0 (ER-R). 6,8) In -actin, forward primer was 5 0 -GATATGGAGAAGATCTGGCACC-3 0 and reverse primer was 5 0 -TGAAGGTCTCAAACATGATCTG-3 0 . 7) In the ER, new forward primer was 5 0 -GCTCAGCTCCTCCTTATCCTCTCT-CAC-3 0 (ER-FN) and new reverse primer was 5 0 -AATGAGAT-GAAGCTGGTGCGGTTGTC-3 0 (ER-RN).…”

“…6,7) Recently, in chick embryos and newly hatched chicks, ER was detected only in Hassall's corpuscles, which are localized in the thymic medulla. 7) In the BF, ER was detected in the lymphoid follicle, stromal, and epithelial areas, 8) but the details of the distribution of chick ER in the thymus and BF is not clear, and cellular identification of ER-positive cells in the thymus has not yet been reported.…”