We have investigated the basis for liverspecific and sex-linked expression of hepatitis B surface antigen (HBsAg) gene in transgenic mice by monitoring the level of liver HBsAg mRNA and serum HBsAg at different stages of development and in response to sex-hormone regulation. Transcription of the HBsAg gene starts at day 15 of development, together with that of the albumin gene, and reaches a comparable level at birth. HBsAg mRNA level and HBsAg production are parallel in males and females during prenatal development and until the first month of life, but HBsAg gene expression increases 5-10 times in males at puberty. After castration, the level of expression decreases dramatically in both males and females and is subsequently increased by injection of testosterone or estradiol. Glucocorticoids also regulated positively expression of the HBsAg gene. Our results suggest that sex hormones play a role in hepatitis B virus gene expression during natural infection and could explain the difference in incidence of chronic carriers between men and women.The hepadnaviruses are small DNA viruses that multiply preferentially in the liver and establish chronic infection in their respective hosts. Much is known about the structure of the viral DNA, RNA, and gene products, but the regulation of hepadnavirus gene expression is still poorly understood, as are the mechanisms of chronicity and pathogenicity (1). To obtain an animal model for the chronic carrier state of hepatitis B virus (HBV), we produced in previous experiments two transgenic mouse strains containing the HBV DNA (except for the core gene) integrated into their genome (2). Both had high amounts of hepatitis B surface antigen (HBsAg) particles in the serum, and the liver was the main place of HBsAg mRNA synthesis. We also showed that in adults HBsAg levels in males were 5-10 times higher than in females. These observations led us to hypothesize that HBV gene expression is regulated by both liver-specific factors and sex steroids. The validity of our hypothesis was assessed by the fact that several genes maintained their normal regulation when injected into transgenic mice (3). Tissue specificity and hormonal control are conserved in transgenic mice containing, for example, genes fused to mouse mammary tumor virus regulatory sequences (4) or the avian transferrin gene (5). In experiments with the chloramphenicol acetyltransferase assay, HBV sequences were responsible for tissue specificity and glucocorticoid control (6, 7). However, the physiological regulation of gene expression can better be explored in a living animal. Therefore, we studied the time of appearance of HBsAg synthesis during development of transgenic mice and the differences between males and females. We also analyzed the effect of steroid hormones by castrating mice and then injecting different hormones. In this report we show that HBsAg gene expression is detected at day 15 of prenatal development, reaching a maximum at birth in both males and females. After birth, HBsAg gene expression d...
The neuropeptide alpha CGRP (calcitonin gene-related peptide) is involved in the complex process of pain signaling, but the precise contribution of alpha CGRP remains unclear. Here we show that mice lacking alpha CGRP display an attenuated response to chemical pain and inflammation. Furthermore, alpha CGRP(-/-) mice do not show changes in heroin self-administration or morphine tolerance, but display a marked decrease in morphine withdrawal signs, suggesting an important contribution of alpha CGRP to opiate withdrawal.
Transgenic mice carrying the H‐2K/human growth hormone (hGH) fusion gene were produced by microinjecting into the pronucleus of fertilized eggs DNA molecules containing 2 kb of the 5′ flanking sequences (including promoter) of the class I H‐2Kb gene joined to the coding sequences of the hGH gene. Thirteen transgenic mice were obtained which all contained detectable levels of hGH hormone in their blood. Nine grew larger than their control litter‐mates. Endogenous H‐2Kb and exogenous hGH mRNA levels were analysed by S1 nuclease digestion experiments. hGH transcripts were found in all the tissues examined and the pattern of expression paralleled that of endogenous H‐2K gene expression, being high in liver and lymphoid organs and low in muscle and brain. Thus 2 kb of the 5′ promoter/regulatory region of the H‐2K gene are sufficient to ensure regulated expression of hGH in transgenic mice. This promoter may therefore be of use to target the expression of different exogenous genes in most tissues of transgenic mice and to study the biological role of the corresponding proteins in different cellular environments.
In this study we compared the alpha-calcitonin gene-related peptide (alphaCGRP) and betaCGRP expression patterns in wild-type and knockout mice by using quantitative reverse transcriptase polymerase chain reaction and immunohistochemistry. In dorsal root ganglia and spinal cord of wild-type animals, alphaCGRP mRNA was about two times more abundant than betaCGRP mRNA. The betaCGRP mRNA was the only isoform expressed in the intestine. In alphaCGRP knockout mice, we found no change in betaCGRP mRNA levels in dorsal root ganglia and spinal cord compared with wild-type controls, but a twofold decrease in the intestine. CGRP immunoreactivity (IR) was detected in many small and some large neurons in the dorsal root ganglia, was found in sensory fibers and motor neurons in the spinal cord, and labeled neuromuscular junctions in wild-type mice. In the dorsal root ganglia of alphaCGRP knockout mice, punctate betaCGRP-IR again was predominantly found in small neurons. In the spinal cord, betaCGRP-IR fibers were localized to the outermost layer of the dorsal horn. IR was found in the cell bodies of motor neurons, but it was undetectable in neuromuscular junctions. In the intestine, CGRP-IR was localized to neurons of the myenteric plexus and to fibers in the mucosal folds, with similar staining intensity in both wild-type and knockout mice. Finally, CGRP-IR was undetectable in preganglionic fibers and postganglionic sympathetic neurons in mice from both genotypes. Our results indicate that alphaCGRP and betaCGRP are variably coexpressed in different functional aspects of the mouse nervous system. This pattern suggests distinct roles for betaCGRP in pain, neuromuscular, and gastrointestinal systems.
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