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Face shape is in our genes

Researchers have made great strides in identifying genes that contribute to facial traits. The many characteristics that make up a person's face, nose size and face width, are determined by specific genes and their variations.

Several tyes of evidence suggest that a person's facial shape is controlled by their genes, but scientists can't explain how, according to John Shaffer PhD, of the University of Pittsburgh in Pennsylvania. He and his colleagues published their study August 25 in PLOS Genetics.

To identify facial gene variations, scientists searched the whole genome looking for associations between 20 facial characteristics measured from 3D images of 3,118 healthy individuals (European ancestry). They also looked at almost one million single base pair variations called SNPs, located across the entire human genome.

Facial width, the distance between the eyes, the size of the nose and the distance between the lips and eyes, all have statistically significant associations between SNPs. Researchers also analyzed two earlier, similar genome-wide studies to confirm their findings.

Several genetic regions contributing to face shape contain genes known to play a role in facial abnormalities. The scientists hope to eventually be able to identify genetic risk factors leading to anomalies such as cleft lip and/or palate, through these studies.

"Our analysis identified several genetic associations with facial features not previously described in earlier genome-wide studies.

"What is exciting is that many of these involve chromosomal regions harboring genes with known craniofacial function.

"Such findings can provide insights into the role genes play in forming the face and improve our understanding of the causal factors leading to certain craniofacial birth defects."

Seth Weinberg PhD, Corresponding author.

It is important to keep in mind these findings most likely represent only a small fraction of the genes influencing the size and shape of the human face.

Numerous lines of evidence point to a genetic basis for facial morphology in humans, yet little is known about how specific genetic variants relate to the phenotypic expression of many common facial features. We conducted genome-wide association meta-analyses of 20 quantitative facial measurements derived from the 3D surface images of 3118 healthy individuals of European ancestry belonging to two US cohorts. Analyses were performed on just under one million genotyped SNPs (Illumina OmniExpress+Exome v1.2 array) imputed to the 1000 Genomes reference panel (Phase 3). We observed genome-wide significant associations (p < 5 x 10−8) for cranial base width at 14q21.1 and 20q12, intercanthal width at 1p13.3 and Xq13.2, nasal width at 20p11.22, nasal ala length at 14q11.2, and upper facial depth at 11q22.1. Several genes in the associated regions are known to play roles in craniofacial development or in syndromes affecting the face: MAFB, PAX9, MIPOL1, ALX3, HDAC8, and PAX1. We also tested genotype-phenotype associations reported in two previous genome-wide studies and found evidence of replication for nasal ala length and SNPs in CACNA2D3 and PRDM16. These results provide further evidence that common variants in regions harboring genes of known craniofacial function contribute to normal variation in human facial features. Improved understanding of the genes associated with facial morphology in healthy individuals can provide insights into the pathways and mechanisms controlling normal and abnormal facial morphogenesis.

Article in PLOS Genetics: http://dx.plos.org/10.1371/journal.pgen.1006149

Citation: Shaffer JR, Orlova E, Lee MK, Leslie EJ, Raffensperger ZD, Heike CL, et al. (2016) Genome-Wide Association Study Reveals Multiple Loci Influencing Normal Human Facial Morphology. PLoS Genet 12(8): e1006149. doi:10.1371/journal. pgen.1006149

Image Credit: John Shaffer and colleagues

Funding: The National Institute for Dental and Craniofacial Research provided funding through the following grants: U01-DE020078 (SMW, MLM); U01-DE020057 (JCM, MLM); R01-DE016148 (MLM, SMW); U01-DE020054 (RAS); U01-DE024425 (MLM); K99-DE02560 (EJL). Funding for genotyping was provided by the National Human Genome Research Institute: X01-HG007821 (MLM, SMW, EF). Funding for initial genomic data cleaning by the University of Washington (CAL and CCL) was provided by contract #HHSN268201200008I from the National Institute for Dental and Craniofacial Research awarded to the Center for Inherited Disease Research (CIDR). Additional funding for was provided by the National Institute of Justice: 2013-DN-BX-K005 (RAS). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing Interests: The authors have declared that no competing interests exist.
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Aug 29, 2016   Fetal Timeline   Maternal Timeline   News   News Archive   

BOTTOM: composite Manhattan plot showing genetic association results for all 20 facial traits.
HORIZONTAL RED LINE: represents threshold for genome statistical significance at p < 5 x 10-8.
Seven genetic associations weve observed  that surpassed this threshold.
For each signal, the associated facial trait is shown above with chromosomal
location of top SNP and potentially relevant genes in immediate vicinity.
Image Credit:
John Shaffer and colleagues.



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