What is the Origin of AR Gene CAG Repeats?

The term is derived from the genetic nomenclature for the Androgen Receptor (AR) gene and the sequence of the repeated codons (CAG), which codes for the amino acid glutamine. The discovery of these trinucleotide repeats and their clinical significance emerged from molecular genetics research in the late 20th century, specifically through studies investigating androgen insensitivity syndromes and spinal and bulbar muscular atrophy (Kennedy's disease).

What is the Mechanism of AR Gene CAG Repeats?

The CAG repeat sequence translates into a polyglutamine tract within the N-terminal transactivation domain of the androgen receptor protein. A longer polyglutamine tract (more CAG repeats) leads to a conformational change that diminishes the receptor's ability to effectively bind to DNA and initiate the transcription of androgen-responsive genes, thus reducing overall androgen signaling. Conversely, a shorter repeat length enhances the receptor's transactivation capacity, resulting in greater cellular responsiveness to hormones like testosterone and dihydrotestosterone.

AR Gene CAG Repeats ∞ Area

AR Gene CAG Repeats

Meaning

AR Gene CAG Repeats refer to a specific, highly polymorphic trinucleotide repeat sequence (Cytosine-Adenine-Guanine) located within the exon 1 of the Androgen Receptor (AR) gene on the X chromosome. The number of these tandem repeats is inversely correlated with the transcriptional activity of the androgen receptor, meaning a shorter repeat length generally results in a more sensitive and potent receptor response to circulating androgens. Clinically, the length of this sequence is a genetic marker that can influence an individual’s androgen sensitivity and subsequent risk for certain hormone-related conditions.