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Molecular screening for somatic mutations in corticotropic adenomas of dogs with pituitary-dependent
P A van Wijk1, A Rijnberk, R J Croughs
1Department of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine, Utrecht University, The Netherlands.
Abstract:
Pituitary tumorigenesis is now generally regarded as a multistep process of genomic damage leading to uncoupling of interdependent systems that control cell proliferation and differentiation. The alterations include mutations in genes encoding for proteins involved in signal transduction pathways, such as G-proteins and the p21 protein encoded for by the ras genes. Apart from their excessive secretion of ACTH, corticotropic adenomas are characterized by decreased sensitivity to inhibition by glucocorticoids. Therefore, mutations in the glucocorticoid receptor leading to decreased sensitivity to glucocorticoids may contribute to corticotropic tumor formation. In this study, 16 corticotropic adenomas of dogs with pituitary-dependent hyperadrenocorticism were screened for mutations in the Gs alpha, H-, K-, N-ras genes and the coding region of the DNA-binding domain of the glucocorticoid receptor. The cDNA fragment of the Gs alpha gene encompassed codons 159-240. The K-, and N-ras fragments spanned codons 1-71. The H-ras gene was only screened for mutations in codons 12/13 by direct sequencing of the PCR product. The cDNA fragment of the DNA-binding domain of the glucocorticoid receptor encompassed codons 410-500. The Gs alpha, K-ras, N-ras genes and the DNA-binding domain of the glucocorticoid receptor were screened by single-strand conformation polymorphism analysis. No mutations were found in the Gs alpha gene, the ras genes and the DNA-binding domain of the glucocorticoid receptor. It is concluded that mutations in the Gs alpha gene (codons 159-240), the K- and N-ras genes (codons 1-71), the H-ras gene (codons 12/13) and mutations in the DNA-binding domain of the glucocorticoid receptor do not play a role in the tumorigenesis of canine corticotropic adenomas.
Insights
Mutations in Gs alpha, ras genes, and glucocorticoid receptors do not cause canine pituitary tumors. This study screened 16 canine corticotropic adenomas, finding no genetic alterations linked to tumor development.
Area of Science:
- Veterinary Medicine
- Molecular Biology
- Oncology
Background:
- Pituitary tumorigenesis involves genetic damage affecting cell proliferation and differentiation.
- Corticotropic adenomas overproduce ACTH and show reduced sensitivity to glucocorticoids.
- Mutations in the glucocorticoid receptor may contribute to corticotropic tumor formation.
Purpose of the Study:
- To investigate mutations in specific genes associated with canine pituitary tumors.
- To screen for mutations in Gs alpha, H-, K-, N-ras genes, and the glucocorticoid receptor DNA-binding domain in canine corticotropic adenomas.
Main Methods:
- Screening of 16 canine corticotropic adenomas for mutations.
- Analysis of Gs alpha (codons 159-240), ras genes (H-, K-, N-ras codons 1-71 or 12/13), and glucocorticoid receptor DNA-binding domain (codons 410-500).
- Utilized single-strand conformation polymorphism (SSCP) analysis and direct sequencing.
Main Results:
- No mutations were detected in the Gs alpha gene.
- No mutations were found in the H-, K-, and N-ras genes.
- No mutations were identified in the DNA-binding domain of the glucocorticoid receptor.
Conclusions:
- Mutations in Gs alpha, ras genes, or the glucocorticoid receptor DNA-binding domain are not implicated in canine corticotropic adenoma tumorigenesis.
- These genetic alterations do not play a role in the development of pituitary-dependent hyperadrenocorticism in dogs.