Trends in Genetics
OpinionA high density of X-linked genes for general cognitive ability: a run-away process shaping human evolution?
Section snippets
Human X-chromosomal mental disability genes are evolutionarily conserved
In Table 3, we list non-syndromal MRX genes that, when mutated, lead to mental impairment as the only symptom. We propose that these genes have had a major impact on the rapid development of cognitive abilities during human evolution. As human beings, we are convinced that human evolution must be something special. Therefore, we are very interested to understand these ostensibly human-specific genes. However, as indicated in Table 3, organisms that are very distantly related to humans have
Female mate-choice has shaped the human mind
The observation of an excess of genes responsible for cognitive abilities on the X chromosome is reminiscent of an earlier observation that described an excess of sex- and reproduction-related genes on the human X chromosome 12. This phenomenon has been described as ‘the large X-chromosome effect’ 13, 14. We propose a large X-chromosome effect for general cognitive abilities in humans. It is reasonable to define the evolution of enhanced cognitive abilities as a specifically human trait. A
The brain and testis association
Many mental disability syndromes are associated with decreased fertility. In ten of the X-chromosomal syndromes listed in Table 1, reduced fertility or infertility is an additional symptom. We again performed X-chromosome- and autosome-specific queries of the OMIM database for entries containing both ‘mental retardation’ and symptoms influencing testis function (‘hypogonadism’ or ‘cryptorchidism'or ‘macroorchidism’). Interestingly, we found that entries matching these search criteria are about
The X chromosome in the evolution of vertebrate diversification and human cognitive abilities
Finally, there is a really surprising observation. The X chromosome has been in use as a sex chromosome for nearly 300 million years 11, and its gene content has been conserved 9, 10. However, evolution and speciation genetics revealed that the X chromosome was engaged in a dominant manner in the development of all characteristics that have been sexually selected for in the past 300 million years 19. Therefore, the most-conserved gene array was engaged in a dominant manner in the morphological
Acknowledgements
The ideas in this opinion paper were developed preparing lectures given at the retirements of Klaus Bender, Walther Traut, and Ulrich Wolf. Drs G. Assum and D. Kaufmann are thanked for fruitful discussions.
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2022, European Journal of Medical GeneticsCitation Excerpt :The Y chromosome is approximately one third the size of the X (57 Mb), and harbours just 64 protein-coding genes, 107 non-coding genes and 395 pseudogenes (Ensembl, 2021b). The X chromosome is enriched for genes mediating development of the nervous system (Mallard et al., 2021; Zechner et al., 2001), and both sex chromosomes are enriched for genes underlying reproductive function (Heard and Turner, 2011). Given the likely role of abnormal cardiac autonomic function, and gonadal hormones, in AF pathophysiology, the X and Y chromosomes appear good a priori candidates for harbouring risk variants.
X-chromosome regulation and sex differences in brain anatomy
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2020, The Plasticity of Sex: The Molecular Biology and Clinical Features of Genomic Sex, Gender Identity and Sexual Behavior
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