The transcription factor GATA1 is known to play an essential role in hematopoiesis, but its other roles have not been well characterized. The purpose of this study was to determine relationships between GATA1 and GATA2 and/or GATA3, and to identify their possible functions in ovine development. GATA1 mRNA was found in ovine conceptuses and endometrial epithelial regions of Day 15 (Day 0=day of estrus) cyclic and Days 15, 17, and 21 pregnant ovine uteri. GATA1 mRNA was strongly expressed in conceptuses on Day 21, when trophoblast attachment to the maternal endometrium progressed. Similarly, GATA1 protein expression was relatively high on Day 21. To localize GATA1 mRNA, ovine conceptuses and pregnant uteri were subjected to in situ hybridization on Days 15, 17, and 21, confirming that GATA1 mRNA was expressed in trophoblasts and uterine endometrial epithelial cells in these gestation days. The presence of GATA1 protein was further confirmed by immunohistochemistry. Because high GATA1 expression appeared to coincide with reduced GATA2/3 expression, a potential role of GATA1 was examined through transfection of a mouse Gata1 expression plasmid into bovine trophoblast F3 cells. This over-expression resulted in the down-regulation of endogenous GATA2 transcripts. These observations indicate that GATA1 exists in the ovine conceptus and uterus during the peri-attachment period, and suggest that GATA1 is integral to conceptus and endometrial development through the regulation of GATA2 and possibly other developmentally important genes.
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