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SF1 polymorphisms in the mouse and steroidogenic potential.
Bernard P Schimmer1, Martha Cordova, Jennivine Tsao
1Banting and Best Department of Medical Research, University of Toronto, Toronto, ON Canada M5G 1L6. bernard.schimmer@utoronto.ca
Endocrine Research
|January 18, 2003
Summary
ACTH resistance in mouse adrenal tumors stems from reduced steroidogenic factor-1 (SF1) activity. A specific SF1 polymorphism (S172) may indicate lower steroidogenic potential, possibly due to linked genes.
Area of Science:
- Endocrinology
- Molecular Biology
- Genetics
Background:
- Adrenocorticotropic hormone (ACTH) resistance in mouse adrenocortical tumor cells is linked to defects in steroidogenic factor-1 (SF1).
- SF1 regulates the expression of key genes in steroidogenesis, including the ACTH receptor (MC2R).
- Mutant cell lines exhibit reduced SF1 activity, impacting MC2R expression and leading to ACTH resistance.
Purpose of the Study:
- To investigate the molecular basis of ACTH resistance in mouse adrenocortical tumor cell mutants.
- To characterize the role of a specific SF1 polymorphism (A172 vs. S172) in steroidogenesis.
- To explore the potential association between SF1 alleles and steroidogenic capacity in different mouse strains.
Main Methods:
- Analysis of SF1 gene sequences in mutant and wild-type cell lines.
- Reporter gene assays to assess the transcriptional activity of different SF1 variants.
- Gene copy number analysis of SF1 and neighboring genes (GCNF, LHX2) in mutant clones.
- Correlation analysis of SF1 alleles with steroidogenic capacity in various mouse strains.
Main Results:
- Mutant cell lines possess an SF1 gene with an Alanine to Serine change at codon 172 (SF1(S172)).
- This SF1(S172) variant is a polymorphism present in the original hybrid mouse strain, not a spontaneous mutation.
- Reporter assays showed only modest differences in transcriptional activity between SF1(A172) and SF1(S172).
- The SF1(S172) allele was amplified in three of four mutants, along with GCNF and LHX2.
- Mouse strains with high steroidogenic capacity possess the SF1(A172) allele, while those with low capacity have the SF1(S172) allele.
Conclusions:
- ACTH resistance in these mutants is likely caused by a gene linked to the SF1(S172) allele, rather than the polymorphism itself.
- The SF1(S172) allele may serve as a marker for reduced steroidogenic potential in mice.
- Further research is needed to identify the specific linked gene responsible for the observed ACTH resistance.