Concurrent and distinct transcription and translation of transforming growth factor-beta type I and type II receptors in rodent embryogenesis

The transforming growth factor-betas (TGF-betas) are multifunctional regulatory polypeptides that play a crucial role in many cell processes and function through a set of cell surface protein receptors that includes TGF-beta type I (RI) and type II (RII). The present study reports a comprehensive comparison of the patterns of expression of TGF-beta RI and RII proteins and mRNAs in the developing mouse embryo using immunohistochemical and in situ hybridization analyses. Although widespread expression of both TGF-beta receptors was detected throughout the embryonic development period so that many similarities occur in localization of the TGF-beta receptors, TGF-beta RI was expressed in a well-defined, non-uniform pattern that was different in many respects from that of TGF-beta RII. Whereas higher levels of TGF-beta RI compared to TGF-beta RII were detected in some tissues of the embryo at the beginning of organogenesis, the level of TGF-beta RII increased more dramatically than that of TGF-beta RI during late organogenesis; this was especially true in many neural structures where TGF-beta RI and RII were comparable by day 16. The lung, kidney and intestine, in which epithelial-mesenchymal interactions occur, showed a complex pattern of TGF-beta RI and Rll expression. Additionally, northern blot hybridization and reverse transcription-polymerase chain reaction (RT-PCR) amplification showed non-uniform expression of the transcripts for TGF-beta RI and RII in embryonic and adult mouse and rat tissues. These data show that regulation of TGF-beta1 RI and RII occurs concurrently, but distinctly, in a spatial and temporal manner in rodent embryogenesis which may allow control of signal transduction of TGF-beta during development

Depressed adrenomedullin in the embryonic transforming growth factor-beta1 null mouse becomes elevated postnatally

Transforming growth factor-beta (TGF-beta) and adrenomedullin are multifunctional regulatory proteins which are expressed in developing embryonic and adult tissues. Because of their colocalization, TGF-beta1 and adrenomedullin may be able to coordinately act to influence development and differentiation. In order to learn more about the biology of adrenomedullin in the absence of the effects of TGF-beta1 in vivo, we examined adrenomedullin in the TGF-beta1 null mouse. A generally lower amount of adrenomedullin was detected by immunohistochemical staining analysis in multiple tissues from embryonic TGF-beta1 null mice compared to wildtype animals, including the heart, lung, brain, liver, and kidney, among others. In contrast, immunohistochemical staining for adrenomedullin was more intense in tissues of the postnatal TGF-beta1 null mouse compared to the wildtype mouse. These observations were confirmed by quantitative real time RT-PCR for adrenomedullin in both embryos and postnatal animals, as well as in cultured mouse embryo fibroblasts from TGF-beta1 null and wildtype mice. In addition, when cultured mouse embryo fibroblasts were treated with a neutralizing monoclonal antibody against TGF-beta1, the levels of adrenomedullin expression were statistically reduced compared to untreated cells. Our data show that expression of adrenomedullin is reduced in tissues of the developing embryonic TGF-beta1 null mouse compared to the wildtype mouse, but increases during postnatal development in TGF-beta1 null mice. The elevated expression of adrenomedullin which occurs postnatally in the TGF-beta1 null mouse may be a cause or a consequence of the multifocal wasting syndrome which is characteristic of postnatal TGF-beta1 null mice

Upregulation of the cell-cycle regulator RGC-32 in Epstein-Barr virus-immortalized cells

Epstein-Barr virus (EBV) is implicated in the pathogenesis of multiple human tumours of lymphoid and epithelial origin. The virus infects and immortalizes B cells establishing a persistent latent infection characterized by varying patterns of EBV latent gene expression (latency 0, I, II and III). The CDK1 activator, Response Gene to Complement-32 (RGC-32, C13ORF15), is overexpressed in colon, breast and ovarian cancer tissues and we have detected selective high-level RGC-32 protein expression in EBV-immortalized latency III cells. Significantly, we show that overexpression of RGC-32 in B cells is sufficient to disrupt G2 cell-cycle arrest consistent with activation of CDK1, implicating RGC-32 in the EBV transformation process. Surprisingly, RGC-32 mRNA is expressed at high levels in latency I Burkitt's lymphoma (BL) cells and in some EBV-negative BL cell-lines, although RGC-32 protein expression is not detectable. We show that RGC-32 mRNA expression is elevated in latency I cells due to transcriptional activation by high levels of the differentially expressed RUNX1c transcription factor. We found that proteosomal degradation or blocked cytoplasmic export of the RGC-32 message were not responsible for the lack of RGC-32 protein expression in latency I cells. Significantly, analysis of the ribosomal association of the RGC-32 mRNA in latency I and latency III cells revealed that RGC-32 transcripts were associated with multiple ribosomes in both cell-types implicating post-initiation translational repression mechanisms in the block to RGC-32 protein production in latency I cells. In summary, our results are the first to demonstrate RGC-32 protein upregulation in cells transformed by a human tumour virus and to identify post-initiation translational mechanisms as an expression control point for this key cell-cycle regulator

Sequence Analysis of the Cloned mRNA Coding for Glyceraldehyde-3-Phosphate Dehydrogenase from Chicken Heart Muscle

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66279/1/j.1432-1033.1983.tb07239.x.pd