Tissue-specific expression of the rat secretin precursor gene.

Secretin is a 27-amino acid gastrointestinal hormone that stimulates the secretion of bicarbonate-rich pancreatic fluid. We previously demonstrated that the secretin precursor gene is expressed in the brain as well as in the small intestine. In this study, we demonstrated that the abundance of secretin precursor mRNA in the heart, lung, and kidney was comparable to that of the small intestine. The nucleotide sequences of the coding regions of the secretin precursor mRNAs in these tissues were identical to those of the small intestine, indicating that secretin precursor proteins produced in these tissues are identical to those in the small intestine. This is the first report that the secretin precursor gene is also expressed in the heart, lung, kidney, and testis as well as in the gastrointestinal tract and brain.     

Tissue-specific expression of theHLA-DRA gene in transgenic mice

Transgenic mice were produced containing a 33 kilobase (kb) DNA fragment encompassing the five exons and all the known regulatory regions of the class IIHLA-DRA gene. The transgene displayed regulated expression [constitutive and interferon- (IFN)- induced] of the human products in most mouse tissues. The tissue distribution of theDRA transgene products more closely resembled that of their mouse homologues, the endogenous H-2 Ea products, than the wider distribution ofDRA products in humans. This was evident in several tissues (endothelia of small vessels, especially those of glomerular capillaries, Kupffer cells, and epithelial cells lining the gastrointestinal tract), known to differentially express class II molecules in the two species. Thus, the wider human specific pattern of expression requires an exact cis/trans complementation which is incompletely reconstituted in transgenic mice, suggesting that human specific cis-acting elements may have arisen during evolution to direct the expression of class II genes to those anatomical regions which usually lack them in the mouse. The only example of aberrant expression of theDRA gene in the present series of transgenic mice was in the dendritic and/or epithelial cells of the thymic cortex, which displayed greately reducedDRA levels in spite of a normal expression of the endogenous Ea molecules.     

Tissue-specific expression of the human renin gene in transgenic mice

Transgenic mice carrying human renin gene were produced by microinjection of 15 kilobases (kb) DNA molecules with up to 3 kb of 5'-flanking sequence and 1.2 kb of 3'-flanking sequence. The transgenes have been shown to be stably transmitted to progeny. It was revealed by RNase protection assay that the human renin gene in a transgenic mouse is expressed preferentially in the kidney. The human renin RNA was also detected at a small level in a variety of tissues such as brain, heart, lung, pancreas, spleen, stomach, testis, and thymus. The direct radioimmunoassay using a monoclonal antibody specific for the active site of human renin demonstrated the synthesis of human active renin in the transgenic mouse kidney. These results suggest that the human renin gene in the transgenic mouse is regulated in a tissue-specific manner.     

Tissue-specific developmental expression of the kallikrein gene family in the rat

Using a series of gene-specific oligonucleotide probes, we have explored the developmental pattern of expression of six members of the rat kallikrein gene family (PS, S1, S2, S3, K1, and P1) in the submandibular gland (SMG) and kidney of both sexes, the prostate and testis of the male, and the anterior pituitary gland (AP) of the female rat. PS (true kallikrein) mRNA was detected in early neonatal life in the SMG and kidney of both sexes. K1, a second kallikrein gene family member expressed in the adult kidney, had a developmental pattern similar to PS in the kidney. In contrast, tonin (S2), S3, K1, and P1, all of which are expressed in the adult SMG, did not reach detectable SMG mRNA levels until puberty in either the male or female rat. Both S3 and P1, which are expressed in the adult prostate, and the novel P1-like mRNA previously detected in the adult rat testis, first appeared in early puberty. In the female AP, PS mRNA levels were not detected until early puberty and thus exhibited a developmental profile different from that of prolactin. The demonstration that S1, S2, S3, P1, and K1 are not expressed in the SMG or prostate until puberty is consistent with the expression of these genes in these tissues being androgen-regulated; the first appearance of PS mRNA in the female AP in early puberty similarly reflects the estrogen dependence of PS gene expression in this tissue. The presence of PS mRNA levels in the SMG and kidney prior to sexual maturation reflects the androgen independence of PS gene expression and suggests that PS (true kallikrein) may play a constitutive and/or developmental role in SMG or renal physiology.     

Tissue-specific Salmonella Typhimurium gene expression during persistence in pigs

Salmonellosis caused by Salmonella Typhimurium is one of the most important bacterial zoonotic diseases. The bacterium persists in pigs resulting in asymptomatic 'carrier pigs', generating a major source for Salmonella contamination of pork. Until now, very little is known concerning the mechanisms used by Salmonella Typhimurium during persistence in pigs. Using in vivo expression technology (IVET), a promoter-trap method based on ΔpurA attenuation of the parent strain, we identified 37 Salmonella Typhimurium genes that were expressed 3 weeks post oral inoculation in the tonsils, ileum and ileocaecal lymph nodes of pigs. Several genes were expressed in all three analyzed organs, while other genes were only expressed in one or two organs. Subsequently, the identified IVET transformants were pooled and reintroduced in pigs to detect tissue-specific gene expression patterns. We found that efp and rpoZ were specifically expressed in the ileocaecal lymph nodes during Salmonella peristence in pigs. Furthermore, we compared the persistence ability of substitution mutants for the IVET-identified genes sifB and STM4067 to that of the wild type in a mixed infection model. The ΔSTM4067::kanR was significantly attenuated in the ileum contents, caecum and caecum contents and faeces of pigs 3 weeks post inoculation, while deletion of the SPI-2 effector gene sifB did not affect Salmonella Typhimurium persistence. Although our list of identified genes is not exhaustive, we found that efp and rpoZ were specifically expressed in the ileocaecal lymph nodes of pigs and we identified STM4067 as a factor involved in Salmonella persistence in pigs. To our knowledge, our study is the first to identify Salmonella Typhimurium genes expressed during persistence in pigs.     

Tissue-specific methylation patterns and expression of the human apolipoprotein AI gene.

To better understand the tissue-specific expression of the human apolipoprotein (apo)AI gene, we performed a detailed analysis of the pattern of methylation of the gene in various human adult and embryonic tissues and in tissues of transgenic mice harboring the human apo-AI gene. In addition, the gene was analyzed also in liver and intestine-derived human cell lines (HepG2 and Caco2, respectively). Using methyl-sensitive restriction enzymes (HpaII, HhaI, and SmaI) and the appropriate radioactive probes, we were able to determine separately the status of methylation of the 5'-end, the body of the gene, and 3'-end flanking sequences. The apo-AI gene in tissues that express the gene was undermethylated at the 5'-end. However, the 5'-end of the gene in sperm and in all adult tissues that do not express the gene was heavily methylated. The body of the gene which contains a CpG island and the 3'-end flanking sequences were, in general, hypomethylated except for specific sites that showed partial methylation. In contrast, while the gene showed tissue-specific expression already in a 12-week-old embryo, the 5'-end was invariably hypomethylated in all tissues of the embryo. A human apo-AI transgene has recently been shown to be active exclusively in the liver, while the endogenous gene is expressed in both liver and intestine (6). We show here that the 5'-end of the apo-AI transgene was methylated in all tissues of the mouse (including intestine) except liver. The results presented here demonstrate a clear correlation between hypomethylation of the 5'-end and activity of the apo-AI gene. However, the observed methylation pattern of the gene in embryonic tissues suggests that tissue-specific expression precedes formation of the tissue-specific methylation pattern.     

Tissue-specific regulation of renin-binding protein gene expression in rats.

Rat gene for renin-binding protein (RnBP) was shown to be expressed in the kidney, adrenal gland, brain, lung, spleen, ovary, testis, and heart. On sodium depletion and captopril administration, the rat showed a marked increase in the adrenal RnBP mRNA level and a slight decrease in the kidney RnBP mRNA level. In two-kidney, one clip hypertensive rats, the RnBP mRNA levels of the clipped and contralateral kidneys were unchanged and also its adrenal mRNA level was maintained at the control level. The recombinant rat RnBP was synthesized in Escherichia coli cells and purified to apparent homogeneity. The RnBP existed as a homodimer and formed a heterodimer with rat renin to inhibit renin activity extensively. Intravenous injection of the RnBP into rats resulted in a rapid and strong inhibition of plasma renin activity, which persisted at least for 2 h. These results suggest that the expression of RnBP gene in the kidney and adrenal gland is regulated independently, and the function of RnBP is related to electrolyte homeostasis, probably through the interaction with renin.     

Tissue-specific expression of the acetylcholinesterase gene in Drosophila melanogaster embryos

Summary Acetylcholinesterase activity is present in both particulate and soluble forms in wild-type Drosophila melanogaster embryos. The particulate form of the enzyme is localized in the CNS, while the soluble forms are non-CNS-specific. Deletion mapping studies show that all AChE activity is abolished if the cytological region between 87E1-2 and 87E4 is missing. An additional region mapping to the proximal part of the 87E4 band is needed for CNS-specific AChE activityAbbreviations AChE acetylcholinesterase (acetylcholine acetyl hydrolase, EC 3.1.1.7) - ChE pseudocholinesterase (acetylcholine acylhydrolase, EC 3.1.1.8) - BAP 1,5-bis(allyldimethylammoniumphenyl)-pentan-3-one dibromide - i-OMPA tetraisopropylpyrophosphoramide - CNS central nervous system     

Tissue-specific expression of the rat alpha 2u globulin gene family.

The rat alpha 2u globulin gene family encodes approximately 20 low-molecular-weight (20,000) proteins with pIs ranging from 4.5 to 7.9. alpha 2u globulin protein isoforms were detected in the liver and in the submaxillary, lachrymal, preputial, and mammary glands of Sprague-Dawley rats. The hormonal and developmental regulation of alpha 2u globulin synthesis in each of these tissues was unique, and it appears that different alpha 2u gene sets were transcribed in the various tissues.     

Tissue-specific expression of the rolA gene mediates morphological changes in transgenic tobacco

The spatial and temporal activity of the entire and individual promoter domains of the rolA gene of Agrobacterium rhizogenes was investigated and correlated with the distinctive features of the phenotypes of transgenic tobacco plants. The GUS assay was performed in the presence of an oxidative catalyst during the development of transgenic plants expressing chimeric genes containing the -glucuronidase coding sequence under the control of the different promoter domains. In situ hybridization was also used on transgenic plants harbouring rolA under the control of the entire or deleted promoter. This paper demonstrates for the first time that the entire rolA promoter, composed of domains, A, B and C, is silent in seeds, then activated at the onset of germination in the cotyledons and in the elengation zone of the radicle and is finally expressed throughout the vegetative and floral phases. Domains B+C, which were sufficient to induce wrinkled leaves and short internodes, were active in all the stem tissues, but only in the companion cells of the phloem strands of the leaves. Domain C, which specified a dwarf phenotype with normal leaves, was weakly expressed in the stem vascular bundles and in the leaf internal phloem. These results indicate that the vascular bundles are the primary targets for the generation of the short internode phenotype. Furthermore, the local expression of rolA in the stem vascular bundles induced a size reduction of the surrounding parenchyma cells, suggesting the existence of some diffusible factor(s) associated with the expression of the rolA gene.