Related Experiment Videos
A polymorphic form of steroidogenic factor 1 associated with ACTH receptor deficiency in mouse adrenal cell mutants
Bernard P Schimmer1, Martha Cordova, Jennivine Tsao
1Banting and Best Department of Medical Research, University of Toronto, Toronto, Ontario, Canada. bernard.schimmer@utoronto.ca
Abstract:
We have described a family of adrenocortical tumor cell mutants (including clones OS3, Y6, and 10r9) that are resistant to ACTH because they fail to express the gene encoding the ACTH receptor (MC2R). The MC2R deficiency results from a mutation that impairs the activity of the nuclear receptor steroidogenic factor 1 (SF1) at the MC2R promoter. In this report, we show that ACTH resistance in the mutant clones is associated with a Sf1 gene that has Ser at codon 172 instead of Ala. In two of the three mutant clones, this Sf1 allele is amplified together with flanking DNA from chromosome 2 that includes the genes encoding germ cell nuclear factor and the beta-type proteosome subunit Psmb7. SF1(A172) and SF1(S172) exhibit little or no difference in transcriptional activity in SF1-dependent reporter gene assays, suggesting that SF1(S172) per se is not directly responsible for the loss of MC2R expression. Instead, the Sf1(S172) allele appears to be a marker of ACTH resistance in this family of adrenocortical tumor cell mutants, possibly reflecting the activity of a neighboring gene.
Insights
Adrenocortical tumor cells resistant to ACTH lack the ACTH receptor (MC2R) due to impaired steroidogenic factor 1 (SF1) activity. A specific SF1 mutation (S172) is linked to this resistance, acting as a potential marker.
Area of Science:
- Endocrinology
- Molecular Biology
- Genetics
Background:
- Adrenocortical tumors can exhibit resistance to adrenocorticotropic hormone (ACTH).
- This resistance is often linked to a deficiency in the ACTH receptor (MC2R) gene expression.
- Steroidogenic factor 1 (SF1) plays a crucial role in regulating MC2R gene expression.
Purpose of the Study:
- To investigate the genetic basis of ACTH resistance in a family of adrenocortical tumor cell mutants.
- To determine the role of a specific mutation in the Steroidogenic factor 1 (SF1) gene in MC2R deficiency.
Main Methods:
- Analysis of adrenocortical tumor cell mutants (OS3, Y6, 10r9) resistant to ACTH.
- Sequencing of the Steroidogenic factor 1 (SF1) gene to identify mutations.
- Reporter gene assays to assess SF1 transcriptional activity.
- Chromosomal analysis to identify gene amplification.
Main Results:
- ACTH resistance in mutant clones is associated with an Sf1 gene mutation changing Ser at codon 172 instead of Ala (SF1(S172)).
- In two of three clones, the Sf1(S172) allele is amplified with neighboring genes on chromosome 2.
- SF1(S172) shows similar transcriptional activity to wild-type SF1(A172) in reporter assays.
Conclusions:
- The SF1(S172) allele is a marker for ACTH resistance in these adrenocortical tumor mutants.
- The resistance may be due to the influence of a neighboring gene co-amplified with SF1(S172), rather than a direct effect of the SF1 mutation itself.