NEW YORK — A number of genetic loci that influence the shape of the human brain also have an effect on face shape, a new analysis has found.
Through a genome-wide association study, an international team of researchers uncovered more than 470 genetic loci that affect the shape of the human brain. Previous studies had pointed toward genetic links between brain and face shape, and researchers led by KU Leuven's Peter Claes found that more than six dozen of the loci they uncovered affecting brain shape also affect face shape, as they reported on Monday in Nature Genetics. Many of these shared loci are involved in development.
"This makes the genetic link between face and brain shape a convincing one," co-senior author Claes said in a statement.
None of these genetic loci affecting brain and face shape, though, had any overlap with behavioral-cognitive traits, discrediting pseudoscientific notions that someone's behavior or predisposition to a neuropsychiatric condition can be gleaned through the shape of their head.
"We found a clear genetic link between someone's face and their brain shape, but this overlap is almost completely unrelated to that individual's behavioral-cognitive traits," first author Sahin Naqvi from the Stanford University School of Medicine added in a statement.
Naqvi, Claes, and their colleagues adapted a brain phenotyping approach they previously developed to analyze the shape of the mid-cortical surface of the brains. They applied this approach to MRI scan data from 19,644 healthy individuals from the UK Biobank to capture and determine the morphology of their brains.
After adjusting for factors like total brain volume, height, and weight, the researchers conducted 285 multivariate genome-wide association studies, different analyses reflecting various morphological features. Overall, they uncovered 472 genome loci with genome-wide significance for an effect on brain shape. Of these, 351 had not previously been tied to brain morphology.
They further replicated about 65 percent of these loci in using MRI data from the Adolescent Brain Cognitive Development Study, and noted that a functional mapping and annotation analyses indicated that many of these loci fall close to genes involved in brain-specific processes like neurogenesis, morphogenesis-related processes like anatomical structure morphogenesis, and neurodevelopmental disorders.
As a previous study tied 203 genetic variants to the shape of the human face, the researchers searched for any overlap between the two sets of genetic loci. They found 76 genomic loci were implicated in both shaping the brain as well as shaping the face.
Many of these shared genetic loci are linked to genes that encode transcription factors that regulated gene activity during development. For instance, transcription factors like DLX5/6, SOX9, and ZEB2, among others, have a role in both neural crest formation and brain development.
Other shared genetic loci are associated with paracrine signaling through the fibroblast growth factor, Hedgehog, and bone morphogenetic protein pathways, all of which mediate signaling from the developing brain to the developing face.
After scouring publicly available genome-wide summary statistics, the researchers found little overlap between the shared face-and-brain shape genetic loci and loci tied to behavioral-cognitive traits like intelligence and neuroticism or neuropsychiatric disorders like schizophrenia or bipolar disorder.
This finding, the researchers noted, further discredits pseudoscientific concepts like physiognomy and phrenology that purported to be able to determine personality or other traits from people's faces.
Going forward, Claes said in an email that they plan to incorporate additional data into their analyses to examine genetic factors involved in face and brain shape across populations as well as address the European bias in such studies. He added that he is also looking into applying this approach to study other anatomical structures that can be imaged, such as the heart.