Sex-specific expression of CYP2C2 in transgenic mice and phenobarbital regulation of CYP2B by in situ injection
Li, Hong
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Permalink
https://hdl.handle.net/2142/20339
Description
Title
Sex-specific expression of CYP2C2 in transgenic mice and phenobarbital regulation of CYP2B by in situ injection
Author(s)
Li, Hong
Issue Date
1996
Doctoral Committee Chair(s)
Kemper, Byron W.
Department of Study
Biology
Discipline
Biology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Molecular
Language
eng
Abstract
To study the transcriptional regulation of CYP2C2, transgenic mice were generated using a DNA fragment containing 3500bp of CYP2C2 5$\sp\prime$-flanking region fused to a luciferase reporter gene. In one of three transgenic lines, this transgene was expressed in the liver and at a lower level in the kidney, not in the lung, spleen, testis, intestine, or heart, similar to the tissue-specific pattern of this gene in rabbits. Unlike expression in rabbits, the transgene was expressed in a male-specific pattern in liver and kidney, and was undetectable in the female. Expression in the male mice was repressed after castration, while testosterone could partially reverse the repression. The expression in females was stimulated after testosterone treatment and periodic injection of rat growth hormone (GH). The expression of the transgene was detected in 5-6 week-old mice and reached a high level at 8 weeks. Unlike in rabbit, this transgene was also detected in the brain, and the brain expression was not sex-specific. These results suggest that this 3500bp of CYP2C2 5$\sp\prime$-flanking region contains the basal transcriptional regulation elements for tissue-specific and developmental expression. This transgene may include the cis-regulatory element for sexual dimorphic expression or a nearby enhancer in the mouse genome may be responsible (position effect).
To study the phenobarbital regulation of CYP2B genes, an in situ transient transfection system was developed by directly injecting DNA into rat liver. With this method, a region from $-$2318 to $-$2155 (designated PBRE) of rat CYP2B2 was shown to be important for phenobarbital induction. The results suggest that the PBRE element is an enhancer, which regulates the phenobarbital response. A PBRE-like sequence was identified in the mouse Cyp2b-9 gene by sequence comparison, and this mPBRE sequence was cloned and analyzed in the same system. However, this sequence did not mediate a phenobarbital response. The effect of gender on phenobarbital induction has also been studied by this method. Gene expression was induced to a much higher extent in male rats than in females in response to phenobarbital, which is similar to what has been observed in vivo. This provides further support that the in situ transient transfection method by direct hepatocyte injection is a useful system to study regulation of P450 genes.
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