Spatiotemporal regulation of hnRNP M and 2H9 gene expression during mouse embryonic development

Using the HeLa cell model along with an in vitro splicing system, we have p reviously shown that hnRNP M and 2H9 are involved in the pre-mRNA splicing process and most interestingly also in heat shock-induced transient splicin g arrest by transiently leaving the hnRNP complexes. Due to this unique reg ulatory function in a mechanism that turns splicing on and off, these two h nRNPs appear as important proteins for controlling gene expression. Here we investigated by in situ hybridization and immunohistochemical staining tec hniques the expression level of specific mRNA and protein during mouse embr yonic development. HnRNP M and 2H9 are found to be expressed at all examine d stages (6.5-18.5 days post-coitum), in a differential manner, and at vari ous levels depending on tissues, cell types and also embryonic stages; fair ly high levels of both hnRNPs are always observed in the central nervous sy stem. Furthermore, levels of colocalizing protein and transcript are not al ways present in the same proportion, thus suggesting a post-transcriptional regulation of hnRNP M and 2H9 gene expression. The complex spatiotemporal variations we observed might well anticipate a role for these two hnRNPs al so in modulating splicing, thereby influencing gene expression and further many physiological processes. (C) 2000 Elsevier Science B.V. All rights res erved.