The androgen receptor gene: A major modifier of speed of neuronal transmission and intelligence?
Introduction
Intelligence may be measured in a number of ways but all measures show considerable intra-population variation and evidence that genes have a significant influence on this variation [1], [2], [3]. There is a high genotypic correlation between tests of cognitive ability, and this has led to the belief that all intelligence comes from one general factor (g) [4], [5]. However, despite this strong association, the loci that are responsible for a large proportion of the variance in g have not yet been identified [6]. Genes that, when mutated, cause mental impairment are found on the X-chromosome at higher incidence than expected, and a large X-chromosome effect for cognitive abilities has been suggested for humans [7]. Therefore the X-chromosome is a likely place to find genes that influence g in a substantial way. One X-linked gene that has been implicated in mental retardation is the androgen receptor gene (AR). A link between variation in the AR, speed of neuronal transmission and g is the theme of this paper.
Section snippets
The androgen receptor gene
The AR is highly polymorphic in its N-terminal transactivation domain. This domain encodes a polyglutamine tract (CAGn) in the AR protein with a parametric mean of 21 CAGn and normal variation between 11 and 30 repeats [8]. In addition to sites such as the reproductive system and bone, the AR is strongly expressed in the CNS [9]. Loss-of-function mutations of the AR do not result in mental impairment, but a very short CAG chain in the AR is associated with mental retardation [10]. At the higher
The androgen receptor gene in human populations
CAGn is polymorphic in humans but it also shows variation in mean CAGn between populations. Furthermore, the population differences in CAGn appear to map on to population differences in g.
A consideration of over 1000 X-chromosomes from Africa, North America and Asia has shown that men of African descent have mean CAGn of between 16.7 to 17.8 repeats, those of European descent a mean of 19.7 repeats, and of Asian descent a mean of 20.1 repeats [18]. In contrast to many genes these differences
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Testosterone and androgen receptor gene polymorphism are associated with confidence and competitiveness in men
2017, Hormones and BehaviorCitation Excerpt :A lower number of CAG repeats has been linked to human aggressive behavior (Rajender et al., 2008), to greater upper body strength, and higher self-report measures of dominance (Simmons and Roney, 2011). The polymorphism is also hypothesized to play a role in cognitive skills (Manning, 2007), which bears on the performance aspects of the cognitive tasks often used in laboratory competitions. However, no research has investigated the role of the androgen receptor CAG repeat polymorphism in competitiveness so far.
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2010, Journal of the Neurological SciencesCitation Excerpt :Repeat sizes of 11–30 are associated with increased androgen sensitivity or high sperm counts [54]. Very low repeat numbers are associated with mental retardation, and repeat numbers of 30–40 associated with cognitive decline [54]. BSMA is caused by a polymorphic CAG tandem-repeat expansion of 40–62 repeats in exon 1 of the AR gene [1,20,22,26,44,51].
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