Pheromones, epigenetic imprinting and brain morphology

In 1996 our review article detailed epigenetic effects of pheromones in the context of genomic imprinting effects. Here’s the latest news.

Genomic Imprinting Effects of the X Chromosome on Brain Morphology
J. Neurosci. 2013;33 8567-8574J ean-Francois Lepage, David S. Hong, Paul K. Mazaika, Mira Raman, Kristen Sheau, et al.

X-Chromosome Imprinting Affects Brain Morphology

Epigenetic modification of specific genes in eggs or sperm (genomic imprinting) prevents expression of maternal or paternal alleles in offspring. Imprinting of X-chromosome genes has sex-specific effects, because only females are affected by imprinting on paternally inherited X chromosomes (X^p) and imprinting on maternally inherited X chromosomes (X^m) only affects half of female cells, because one X chromosome is inactivated in each cell. Whether imprinting of X-linked genes contributes to sexual dimorphism in brain anatomy and cognition is unclear. To address this question, Lepage et al. examined girls with Turner syndrome, in which either X^p or X^m and X inactivation are absent. Differences in cortical thickness, surface area, and volume were found in several regions. For example, cortical thickness in temporal areas was greater in X^p than in X^m girls, whereas gray matter volume in superior frontal regions was greater in X^m than in X^p girls. The results suggest that imprinting of X-chromosome genes can influence sexual dimorphism in the brain.

Article excerpt: The present findings have direct implications for our understanding of the epigenetic mechanisms involved in sexual dimorphism of the brain that are taking place early in development.

My comment: 16+ years post publication of our review, and some people are just now starting to catch on. Epigenetic imprinting is not limited to certain species, and epigenetic effects of nutrients and pheromones control species diversity. Clearly, not only can imprinting of X-chromosome genes in mammals influence sexual dimorphism in the brain, it will influence nutrient-dependent pheromone-controlled adaptive evolution of the brain and behavior as it influences genetically predisposed, epigenetically-effected human embodied cognition. How could it not?

Excerpted from our review: From Fertilization to Adult Sexual Behavior (1996)

“Yet another kind of epigenetic imprinting occurs in species as diverse as yeast, Drosophila, mice, and humans and is based upon small DNA-binding proteins called “chromo domain” proteins, e.g., polycomb. These proteins affect chromatin structure, often in telomeric regions, and thereby affect transcription and silencing of various genes (Saunders, Chue, Goebl, Craig, Clark, Powers, Eissenberg, Elgin, Rothfield, and Earnshaw, 1993; Singh, Miller, Pearce, Kothary, Burton, Paro, James, and Gaunt, 1991; Trofatter, Long, Murrell, Stotler, Gusella, and Buckler, 1995). Small intranuclear proteins also participate in generating alternative splicing techniques of pre-mRNA and, by this mechanism, contribute to sexual differentiation in at least two species, Drosophila melanogaster and Caenorhabditis elegans (Adler and Hajduk, 1994; de Bono, Zarkower, and Hodgkin, 1995; Ge, Zuo, and Manley, 1991; Green, 1991; Parkhurst and Meneely, 1994; Wilkins, 1995; Wolfner, 1988). That similar proteins perform functions in humans suggests the possibility that some human sex differences may arise from alternative splicings of otherwise identical genes.

A potential ramification of epigenetic imprinting and alternative splicing may be occurring in Xq28, a chromosomal region implicated in homosexual orientation (Brook, 1993; Hu, Pattatucci, Patterson, Li, Fulker, Cherny, Kruglyak, and Hamer, 1995; Turner, 1995). Xq28 contains one of the X chromosome’s two pseudoautosomal regions (PARs), adjoins the telomere, and has various means of gene expression control (D’Esposito, Ciccodicola, Gianfrancesco, Esposito, Flagiello, Mazzarella, Schiessinger, and D’Urso (1996). Xq28, therefore, is a chromosomal region that has many of the heterochromatic and telomeric characteristics that participate in sexual determination and behavior in other species.