Testis-determining factor

Testis-determining factor (TDF), also known as sex-determining region Y (SRY) protein, is a DNA-binding protein encoded by the SRY gene that is responsible for the initiation of male sex determination in humans.

Function

TDF is a member of the SOX (SRY-related HMG-box) family of transcription factors involved in the regulation of embryonic development and in the determination of cell fate. The protein encoded by this gene is a critical component of the sex-determining process in many mammalian species. It binds to DNA and regulates the expression of genes that cause a developing embryo to become male.

Structure

The SRY gene, which encodes the TDF protein, is located on the short (p) arm of the Y chromosome at position 11.3. The protein consists of a single HMG-box, which is responsible for DNA binding, and a less conserved region that is involved in transcriptional activation.

Role in Sex Determination

In the early stages of embryonic development, the gonads of males and females are identical. The presence of TDF, however, triggers the development of testes. This is achieved by the activation of the SOX9 gene, which leads to the differentiation of Sertoli cells. These cells then direct the gonads to develop into testes.

Clinical Significance

Mutations in the SRY gene can lead to a range of disorders of sex development (DSDs). These can include Complete Androgen Insensitivity Syndrome (CAIS) and Swyer Syndrome, both of which can result in individuals with XY chromosomes developing as females.

See Also

• Sex-determination system
• Y chromosome
• Sexual differentiation