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Am J Med Genet A. 2017 Nov;173(11):2886-2892. doi: 10.1002/ajmg.a.38471. Epub 2017 Sep 8.

Testing the face shape hypothesis in twins discordant for nonsyndromic orofacial clefting.

Author information

1
Center for Craniofacial and Dental Genetics, Department of Oral Biology, University of Pittsburgh, Pittsburgh, Pennsylvania.
2
Department of Electrical Engineering, ESAT/PSI, KU Leuven, Leuven, Belgium.
3
Medical Imaging Research Center, MIRC, UZ Leuven, Leuven, Belgium.
4
Multidisciplinary Cleft Lip and Palate Team Leuven, University Hospitals Leuven, Leuven, Belgium.
5
Department of Otorhinolaryngology, University Hospitals Leuven, Leuven, Belgium.
6
Department of Human Genetics, University Hospitals Leuven, Leuven, Belgium.
7
Department of Epidemiology, University of Southern Denmark, Odense, Denmark.
8
Department of Clinical Genetics and Department of Clinical Biochemistry and Pharmacology, Odense University Hospital, Odense, Denmark.
9
Murdoch Childrens Research Institute, Victoria, Australia.

Abstract

Nonsyndromic orofacial clefts (OFCs) are complex traits characterized by multifactorial inheritance and wide phenotypic variability. Numerous studies have shown subtle differences in the faces of unaffected relatives from cleft families compared to controls, the implication being that such outward differences are an incomplete expression reflecting an underlying genetic predisposition. Twins discordant for OFCs provide a unique opportunity to further test this idea, as the unaffected co-twin shares on average 50% (for dizygotic twins) and 100% (for monozygotic twins) of the genetic risk factors as the affected twin. We used 3D surface imaging and spatially-dense morphometry to compare facial shape in a sample of 44 unaffected co-twins and age- and sex-matched unaffected controls (n = 241). Unaffected co-twins showed statistically significant differences in the midface, lateral upper face, and forehead regions, compared to controls. Furthermore, co-twins were characterized by a distinct pattern of midfacial retrusion, broader upper faces, and greater protrusion of the mandible and brow ridges. This same general facial pattern was shown in both unaffected monozygotic and dizygotic co-twin subsets. These results provide additional support that altered facial shape is a phenotypic marker for OFC susceptibility.

KEYWORDS:

3D imaging; facial morphology; orofacial clefting; spatially-dense morphometrics; twins

PMID:
28884971
PMCID:
PMC5725745
DOI:
10.1002/ajmg.a.38471
[Indexed for MEDLINE]
Free PMC Article

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