TISSUE DISTRIBUTION OF ESTROGEN-RECEPTOR-ALPHA (ER-ALPHA) AND ESTROGEN-RECEPTOR-BETA (ER-BETA) MESSENGER-RNA IN THE MIDGESTATIONAL HUMAN FETUS

We compared the expression profiles of the mRNAs of both estrogen rece ptors, ER-alpha and the recently cloned ER-beta, in the midgestational human fetus by semiquantitative RT-PCR. ER-alpha was most abundant in the uterus, and smaller quantities were detected in the ovary, testis , skin and gut. High amounts of ER-beta mRNA were present in fetal ova ries, testes, adrenals and spleen. In these tissues, the levels of ER- beta mRNA were higher than ER-alpha. In the uterus, however, ER-alpha mRNA was more abundant, and ER-beta mRNA was expressed only moderately . ER-beta mRNA was present at moderate to low levels in the thymus, pi tuitary gland, skin, lung, kidney and brain cortex. In the course of o ur work, using the ER-beta primers on genomic DNA, an intron of 2468 b p in length, located between nt 222 and 223 in the A/B domain of ER-be ta cDNA, was detected, cloned and sequenced. The study shows that the expression profile of the two ERs is different, and ER-beta is express ed in a variety of tissues during human fetal development, suggesting different, organ-specific roles for the two receptors.