Estrogen receptor alpha expression in the thymus of chick embryos during late stages of embryogenesis
Yonezawa, Y.(Okayama Univ. (Japan)) | Shin, Y.H. | Abe, A. | Kondo, Y.
In the present study, we examined the presence of estrogen receptor alpha (ERalpha) in the thymus of chick embryos using two methods, reverse transcription polymerase chain reaction(RT-PCR) with a primer set designed based on the sequence of chicken ERalpha-cDNA, and immunohistochemistry using anti-ER antibody which cross-reacts with chicken ERalpha. Expression of ERalpha mRNA was detected in the thymus of chick embryos at all stages of embryogenesis (14th to 19th day of embryogenesis) examined, as well as hen's oviducts which were used as a positive control. Scattered ERalpha-positive sites were observed in the medulla of the thymus, but no sites were detected in the cortex, indicating a medulla-limiting presence of ER-positive sites in the chicken thymus. At high magnification under microscopic observation, ER-positive cells were found specifically in Hassall's corpuscles or the cells in the vicinity of the Hassall's corpuscles in the medulla of the thymus. In mammalian species, Hassall's corpuscle is related to T-cell genesis in the thymus, although the physiological significance of the component in the chicken thymus has not been reported. The results of the present study raise the possibility that estrogen plays a role in T-cell differentiation in the thymus of chick embryos by acting on Hassall's corpuscle.
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