The expression of mesoderm induction-early response 1 proteins in embryonic and adult mouse tissues

Martin, Leanne B. (Leanne Bridget) (2008) The expression of mesoderm induction-early response 1 proteins in embryonic and adult mouse tissues. Masters thesis, Memorial University of Newfoundland.

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Abstract

The mesoderm induction early response-1 gene (mi-er1) is a fibroblast growth factor-inducible early response gene. It is activated during mesoderm induction in Xenopus embryos and it encodes a nuclear protein that functions as a transcriptional regulator. The human orthologue of this gene has 12 distinct transcripts encoding six protein isoforms, which differ in their amino (N) and carboxy (C) terminal domains. The C-terminal variants, alpha and beta, differ in both the size and sequence of their C-terminal domain. -- Recently, the mouse orthologue of this gene was cloned and characterized and this study led us to determine the expression pattern of the MI-ER1 protein in mouse embryonic and adult tissues by immunohistochemistry. MI-ER1 was expressed in all mouse tissues analyzed, with an overall decrease in expression in the adult compared to embryonic tissues. MI-ER1 beta was the only isoform expressed in the embryo, while both MI-ER1 alpha and beta were expressed in adult tissues. In the adult, the alpha isoform was particularly expressed at a high level in endocrine tissues, such as the adrenal gland, pancreas, ovary, and testis. There was distinct pattern of MI-ER1 expression in the adult mid-brain, with high expression in the CA3 cells of the hippocampus and the pyramidal cells of the thalamus. -- A complex pattern of MI-ER1 alpha and beta subcellular localization was found in the embryo and adult tissues of the mouse. In the embryo, the beta isoform was found in both the nucleus and the cytoplasm. In adult tissues, the beta isoform was found in the nucleus (and possibly in the cytoplasm in some instances), while the alpha isoform was found in the cytoplasm. The only exception to this was the adult testis, where MI-ER1 alpha was found in both the nucleus and cytoplasm. Also, the spleen was the only adult tissue analyzed where MI-ER1 alpha was not expressed and where we could definitely conclude that MI-ER1 beta was located in the cytoplasm. -- The results of the current study were a powerful tool in providing the temporal and spatial expression of MI-ER1 in embryonic and adult mouse tissues. This work will be very significant for future work in the production of transgenic mice to further investigate functions of MI-ER1.

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