SRY gene mutation analysis and functional effects in cases of XY gonadal dysgenesis

Author(s)

José Luiz Rosenberis Cunha Júnior

• Document type: Master's Dissertation
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia
• Defense date: 2010-02-25

Examining board members

Maricilda Palandi de Mello; Adriano Rodrigues Azzoni; Luciana Campos Paulino

• Advisor: Maricilda Palandi de Mello; Fernanda Caroline Soardi; Celso Eduardo Benedetti

Abstract

The SRY (Sex Determining Region in chromosome Y) gene expression is responsible for testicular determination during embrionary development. Mutations in SRY are found in many cases of anomalies of gonadal development. This project analyzed the functional effect of a mutation in SRY promoter region; the mutation is a 3-bp deletion in a consensus binding site for Sp1 transcription factor. The patient presented 46,XY pure gonadal dysgenesis, and a family history of relatives with different levels of genital ambiguity. Her father shares the same mutation in the SRY promoter region. In order to investigate the effects of the mutation upon the molecular mechanisms that regulate SRY gene expression, the interaction of the Sp1 transcription factor with normal and mutant binding sites was analyzed by EMSA (Electrophoretic Mobility Shift Assay). Each of Sp1A and Sp1B normal sites binds to a single Sp1 molecule, whereas the 3-bp deletion in Sp1A abolishs the binding to this site. Probably, the lack of Sp1 binding to the Sp1A site prevented the formation of a stable transcription complex, reducing the level of SRY expression and leading to the absence of testicles and complete sex reversal in the patient. Parallely, the effect of the mutation was analyzed by a reporter gene assay, indicating that the normal promoter is almost two times more efficient than the mutant promoter in the activation of luciferase gene expression using HeLa cells. However, further transfection experiments with other cell lineages must be performed to confirm this result. In addition, the effect of a new mutation (E89K, located in the SRY gene coding region) was analyzed by testing the ability of the SRY mutant protein to bind its DNA consensus sequence. EMSA assays revealed that the E89K mutation, which is associated with 46,XY pure gonadal dysgenesis, strongtly reduced the SRY protein binding activity in vitro. This result is a strong evidence that the reduced activity of SRY mutant protein was not sufficient to trigger the testicular determination in the patient, leading to the pure gonadal dysgenesis phenotype. Screening of mutations in the SRY gene coding and promoter regions was also performed in six diferent patients with 46,XY gonadal dysgenesis. However, other mutations have not been identified (AU)

• FAPESP's process: 07/00900-0 - Mutation analysis and effects on the SRY gene expression in XY gonadal dysgenesis
• Grantee: José Luiz Rosenberis Cunha Júnior
• Support Opportunities: Scholarships in Brazil - Master