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A novel cytochrome P450 expressed primarily in brain
G Stapleton1, M Steel, M Richardson
1Centre for Genome Research, University of Edinburgh, United Kingdom.
The Journal of Biological Chemistry
|December 15, 1995
Summary
A novel gene, hippocampal transcript-1 (hct-1), is highly expressed in the brain and shares similarities with steroid-metabolizing enzymes. This suggests hct-1 may play a role in neurosteroid metabolism and cognitive function.
Area of Science:
- Neuroscience
- Biochemistry
- Genetics
Background:
- Hippocampal transcript-1 (hct-1) was identified through differential screening of a rat hippocampal cDNA library.
- hct-1 expression is enriched in the hippocampus but also found in liver and kidney, with minimal detection in reproductive and adrenal tissues.
- Hepatic expression of hct-1 in rats exhibits sexual dimorphism, being significantly lower in females.
Purpose of the Study:
- To characterize the novel gene hct-1 and investigate its expression patterns and potential function.
- To determine the evolutionary conservation and sequence homology of hct-1.
- To explore the potential role of hct-1 in brain steroid metabolism.
Main Methods:
- Differential screening of a rat hippocampal cDNA library.
- Quantitative expression analysis in various rat and mouse tissues.
- Sequence analysis of rat and mouse hct-1 cDNAs.
- Genomic Southern blot analysis in mouse, rat, and human.
Main Results:
- hct-1 expression is predominantly in the brain, particularly the hippocampus and corpus callosum in mice.
- Sequence analysis reveals hct-1 is a novel cytochrome P450 (CYP) enzyme, most similar to cholesterol 7 alpha-hydroxylase (CYP7).
- A single hct-1 gene is conserved across mouse, rat, and human genomes.
- Hepatic hct-1 expression is sexually dimorphic in rats, reduced in females.
Conclusions:
- hct-1 represents a previously unreported type of CYP enzyme, designated CYP7B.
- The primary expression site in the brain suggests a unique role for hct-1 compared to other CYPs.
- Given its similarity to steroid-metabolizing CYPs and brain expression, hct-1 likely participates in neurosteroid metabolism, potentially influencing cognitive functions.