Evidence of a steroidogenic enzyme gene dose effect on adrenal gene expression in hereditary rabbit congenital adrenal hyperplasia

Kotaro Iwamoto, Ximing Yang, Fraser M. Rogerson, J. Ian Mason, James Artwohl, Kristine Bolin, Paul Klimah, Pieter Swart, Songya Pang*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

We previously reported the gene deletion encoding cytochrome P-450 cholesterol side-chain cleavage enzyme (P-450scc, resulting in complete elimination of the adrenal gene expression and causing congenital adrenal hyperplasia in the rabbit. Using the rabbit congenital adrenal hyperplasia model, we investigated the wild type (wt) P-450scc gene dose effect on gene expression in three P-450scc genotype animals [wt/wt, wt/mutant (mt), mt/mt] identified by Southern blot analysis. Northern blots using a rabbit P-450scc cDNA probe revealed 1 no detectable P-450scc mRNA in individual adrenals of animals with congenital adrenal hyperplasia (mt/mt) and approximately half or slightly less than half the levels of the mRNA in the pooled adrenals of five heterozygous (wt/mt) newborn animals compared with the mRNA levels in the pooled adrenals of five homozygous normal (wt/wt) newborn animals. Identical P-450scc mRNA levels were found individual adrenals of adult animals with regard to the P-450scc genotype, although at a higher expression level than in the newborn animals of the same genotype. Control Northern blots using human CPY21-B cDNA and cytoplasmic actin cDNA probes confirmed the accuracy and integrity of RNA. Western immu-noblotting using antiovine P-450scc antibody revealed decreased P-450scc protein in the adrenals of wt/mt animals at approximately half the level of the P-450scc protein in the adrenals of the wt/wt animals. Baseline and ACTH-stimulated serum corticosterone (B) levels in vivo were similar between the age-matched wt/mt and wt/wt animals, whereas ACTH-stimulated B levels in adult animals were higher than those in the newborn animals irrespective of P-450scc genotype. These data demonstrated for the first time the presence of a wt steroidogenic enzyme gene dose effect on gene expression in vivo at the levels of the mRNA and enzyme protein. With age, the gene dose-related gene expression was maintained, although at higher expression levels. The normal adrenal B-pro-ducing capacity in heterozygous, wt/mt animals despite the markedly decreased P-450scc gene expression suggests the presence of either a mechanism compensating the availability of mitochondrial cholesterol substrate to overcome the decreased P-450scc or rate-limiting effect of P-450scc in the conversion of excess cholesterol substrate available in the adrenal mitochondria. The greater B-producing capacity under ACTH stimulation in the adult animals compared with the newborn animal irrespective of P-450scc genotype therefore is likely from the greater adrenal receptor capacity for ACTH rather than from the greater P-450scc gene expression level.

Original languageEnglish (US)
Pages (from-to)660-666
Number of pages7
JournalPediatric research
Volume36
Issue number5
DOIs
StatePublished - Nov 1994

ASJC Scopus subject areas

  • Pediatrics, Perinatology, and Child Health

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