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Fig. 4. In situ hybridization studies on Xenopus erythropoietin receptor. (A) Albino embryos were stained for expression of EpoR at various stages during development. Expression is first detected by in situ hybridization at stage 26–28 in the ventral blood island of the developing tail bud embryo. As development progresses the levels of EpoR in the ventral blood island increase dramatically (stages 30–36). After circulation has initiated (stage 32) individual blood cells can be detected in the vasculature of the embryo. (B) In situ hybridization for hematopoietic transcription factors GATA-1, GATA-2, SCL and LMO-2. Comparison of the expression of EpoR expression with that of the hematopoietic transcription factors indicates that the EpoR most resembles the expression pattern of the erythroid factor GATA-1. The expression of EpoR is detected by in situ hybridization after the onset of expression of GATA-1 in the anterior region of the ventral blood island (compare Fig. 4A, stage 28 with Fig. 4B, stage 25). |
