NEW YORK (GenomeWeb) – Genes showing strong signals of selection since humans split from Neanderthals and Denisovans are among those mediating human nose shape, a new study in Nature Communications suggests.
"Finding out the role each gene plays helps us to piece together the evolutionary path from Neanderthal to modern humans," first author Kaustubh Adhikari, a cell and developmental biology researcher at the University College London, said in a statement. "It brings us closer to understanding how genes influence the way we look, which is important for forensics applications."
Researchers from UCL and other centers around the world did a genome-wide association study focused on finding genetic factors associated with more than a dozen facial features. Based on data for some 6,000 individuals of Latin American ancestry, they uncovered four main loci with apparent ties to nose-related traits, including sites spanning cartilage- and bone growth-related genes.
"It has long been speculated that the shape of the nose reflects the environment in which humans evolved. For example, the comparatively narrower nose of Europeans has been proposed to represent an adaptation to a cold, dry climate," senior author Andrés Ruiz-Linares, a genetics, evolution, and environment researcher at the UCL Genetics Institute, said in a statement. "Identifying genes affecting nose shape provides us with new tools to examine this question, as well as the evolution of the face in other species."
The team relied on array-based genotyping data for 5,958 Latin American individuals from Brazil, Colombia, Chile, Mexico and Peru, who were recruited by members of the CANDELA consortium. Participants' faces were categorized for 14 lip, chin, nose, cheekbone, and other facial features with the help of facial photos.
From the directly genotyped and imputed SNPs in these samples, the researchers identified apparent associations for a handful of facial features, particularly nose-related traits.
For example, loci on chromosomes 7 and 20 in the vicinity of the GLI3 and PAX3 genes, respectively, were associated with nose wing — aka, nostril — breadth, while breadth of the nose bridge was linked to a site on chromosome 6 near the RUNX2 gene.
A fourth locus encompassing the DCHS2 gene on chromosome 4 was significantly associated with so-called columella inclination, a pointiness measure based on the angle between the base and tip of an individual's schnozz.
The researchers' quantitative locus analyses also implicated PAX3 in nasion position, which describes the deepest point on the nasal bridge, and led them to SNPs in the chromosome 2 gene EDAR that tracked with chin protrusion measurements in the Latin American cohort.
Similar genetic regions turned up when the researchers focused their analysis on 2,955 of the study participants who had three-dimensional facial reconstructions done.
And the authors of the study noted that at least three of the nose shape-related genes — GLI3, PAX3, and RUNX2 — were previously described as being among the most differentiated genes when comparing modern humans with archaic hominins such as Neanderthals and Denisovans.