Biomedical subjects

J J Peschon

Publications and source records attributed to J J Peschon.

43 records · Page 3Linked to original sources

PubMed1989

Protamine 3'-untranslated sequences regulate temporal translational control and subcellular localization of growth hormone in spermatids of transgenic mice.

Although the mouse protamine 1 gene (mP1) is first transcribed in round spermatids, its mRNA is not translated until about 1 week later in elongating spermatids. To determine what mP1 sequences are important for its transcriptional and translational regulation, we have constructed fusions between mP1 and the human growth hormone (hGH) structural gene and analyzed their expression in transgenic mice. We show that mP1 sequences 5' to the start of transcription are sufficient to confer spermatid-specific expression on the hGH gene. We also show that 156 nucleotides of mP1 3'-untranslated sequence is sufficient to confer mP1-like translational regulation on the hGH mRNA. Interestingly, the subcellular localization of hGH was dependent on the time during spermiogenesis that it was made. Synthesis of hGH in early round spermatids resulted in localization in the acrosome, whereas synthesis in late elongating spermatids resulted in intracellular, but not acrosomal, localization.

Acrosome↗

PubMed1989

Expression of mouse protamine 1 genes in transgenic mice.

Mouse protamine genes are expressed exclusively in spermatids. Mouse protamine 1 (mP1) transcriptional regulatory elements can target the expression of either marked mP1 transgenes or mP1 chimeric genes to spermatids in transgenic mice. Sequences between -40 and -465 bp relative to the transcription start site are required for expression in spermatids, whereas sequences 3' of the point of translation initiation are dispensable. mP1 transcriptional regulatory sequences were used to direct the expression of a toxic gene product to spermatids. The phenotypic consequences of toxin expression in spermatids are described.

Animals↗

PubMed1988

Sequence homologies in the mouse protamine 1 and 2 genes.

To identify candidates for cis-acting sequences that regulate the stage and cell-specific expression of the two coordinately regulated protamine genes in the mouse, genomic clones were isolated and the nucleotide sequences of the 5' flanking regions and coding regions were compared. Unlike most histone genes and the multigene family of trout protamine genes which are intronless, each mouse protamine gene has a single, short intervening sequence. Although the coding regions do not share significant nucleotide homology, the 5' flanking regions contain several short homologous sequences that may be involved in gene regulation. An additional shared sequence is present in the 3' untranslated region surrounding the poly(A) addition signal in both genes.

Amino Acid Sequence↗

PubMed1988

Heart and bone tumors in transgenic mice.

Tissue-specific tumorigenesis can be induced in transgenic mice by the directed expression of simian virus 40 (SV40) large tumor (T) antigen. In an attempt to determine the susceptibility of haploid, round spermatids to neoplastic transformation by this oncogene, transgenic mice were generated that harbored a chimeric gene composed of the SV40 T-antigen genes fused to the 5' and 3' flanking sequences of the mouse protamine 1 gene. The transgene was expressed in round spermatids and, surprisingly, in the heart and temporal bone as well. Expression in the heart resulted in rhabdomyosarcomas that always appeared in the right atrium. Bilateral osteosarcomas developed within the petrous portion of the temporal bone. No testicular pathology was observed. T-antigen immunostaining was readily detected in tumor tissue but not in the testis. In addition, SV40 transcripts were processed differently in testis and tumor tissue. Transgenic mouse lines were established that routinely develop these tumors, and they should provide a valuable resource for studies involving cardiac and bone physiology and neoplasia. The atrial tumor cells can be maintained in vitro and some continue to display a cardiac muscle phenotype.

Animals↗

PubMed1987

Spermatid-specific expression of protamine 1 in transgenic mice.

Protamines are abundant basic proteins involved in the condensation of sperm chromatin. In the mouse, protamine genes are transcribed postmeiotically in round spermatids. We have cloned and sequenced the mouse protamine 1 gene. Ten lines of transgenic mice harboring marked protamine 1 sequences were generated by microinjection of fertilized eggs. Transcription of the transgene is restricted to round spermatids and in several cases exceeds that of the endogenous gene. The cis-acting sequences required for tissue-specific protamine expression reside on a 2.4-kilobase restriction fragment. Prospects for using transgenic mice to address fundamental questions of male germ-cell development are discussed.

Animals↗

PubMed1983

Kinetics of enzymes subject to very strong product inhibition: analysis using simplified integrated rate equations and average velocities.

Enzymes which catalyze energetically unfavorable reactions in the physiological direction are likely to be strongly inhibited by the reaction products. (Some energetically favorable reactions may also display strong "product inhibition" when assayed in the reverse direction.) In some cases, the inhibition caused by an accumulating product is so potent that true initial velocities cannot be directly determined using conventional assay methods. Continuous removal of the inhibitory product may be mitigated against by the nature of the assay or the unavailability of the appropriate coupling enzyme. It can be shown that if (a) only one inhibitory product is allowed to accumulate and (b) the substrate concentrations remain essentially constant over the assay period (i.e. Kproduct less than or equal to 10(-2)Ksubstrate, so that the decreasing reaction rate stems only from progressive product inhibition), then plots of reciprocal average (apparent) velocity (i.e. 1/v = t/[P]) versus [P] are linear and extrapolate to 1/v0, the reciprocal of the initial uninhibited velocity at the fixed substrate concentrations. Intercept replots give the usual initial velocity reciprocal plot patterns and permit Vmax and the substrate Km's to be determined. Slope replots are diagnostic of the type of inhibition exerted by the accumulating product and permit the inhibition constants to be determined. If all the appropriate coupling enzymes are available, some kinetic mechanisms can be diagnosed using data derived from the reaction progress curves in the presence of one accumulating product at a time.

Enzyme Inhibitors↗

PubMedDate not supplied

Expression of TNF and the necessity of TNF receptors in bleomycin-induced lung injury in mice.

Bleomycin (BLM) induction of lung fibrosis in mice is an established model to study the mechanism of pulmonary fibrosis. Cytokine secretion has been implicated as a fundamental component of the lung fibrotic process observed in response to BLM. Among the cytokines implicated in lung fibrosis, Tumor necrosis factor (TNF) alpha has been considered to play a fundamental role. In the present study, we characterized the cellular sources of TNF during BLM-induced lung injury and examined the importance of TNF receptors in this process. To characterize the expression of TNF, we utilized two strains of mice, one sensitive (C57BL/6) and one resistant (BALB/c) to BLM-induced lung injury. Mice received BLM (120 mg/kg total) or saline, as control, by multiple subcutaneous injections. BLM induced the development of inflammation in subpleural areas only in the lungs of BLM-sensitive mice. These subpleural areas were characterized by infiltration of CD68-positive macrophages and increased collagen deposition. BLM enhanced the expression of TNF mRNA in BLM-sensitive, but not in BLM-resistant, mice. In situ hybridization studies localized the expression of TNF in the areas of BLM-induced inflammation in 6% and 27% of macrophages at 14 and 21 days post BLM treatment. In addition to TNF, BLM exposure resulted in the upregulated expression of transforming growth factor (TGF)-beta 1, but not interleukin (IL)-1, mRNA in the lungs of both murine strains at 14 and 21 days. This upregulated expression of TGF-beta 1 mRNA was greater in the lungs of BLM-sensitive mice. In separate experiments, double TNF receptor knockout mice were exposed to BLM. These animals demonstrated an increased expression of TNF, but not TGF-beta 1, mRNA in response to BLM and did not exhibit histologic evidence of lung injury following BLM exposure. In summary, the upregulation of TNF mRNA in macrophages correlated with the appearance of inflammation following BLM exposure and was limited to the BLM-sensitive strain. Furthermore, in addition to the release of the TNF ligand, it appears that the presence of TNF receptors is necessary for the development of BLM-induced lung injury, and signaling through these receptors may contribute to the regulation of the TGF-beta 1 mRNA expression observed in response to bleomycin. These results provide further support for a role of macrophages and TNF in the induction of lung inflammation.

Animals↗