Mutations of TCF12, encoding a basic-helix-loop-helix partner of TWIST1, are a frequent cause of coronal craniosynostosis

Abstract

BackgroundCraniosynostosis, the premature fusion of the cranial sutures, is the second most common craniofacial malformation. A genetic aetiology can be identified in about 21% of cases, including mutations of TWIST1 that cause Saethre-Chotzen syndrome and are associated with coronal synostosis. By contrast, the cause of non-syndromic craniosynostosis is largely unknown. MethodsWe undertook exome sequencing of seven individuals with bilateral coronal synostosis, identifying mutations of TCF12 in three samples. We sequenced TCF12 in a further 347 patients with craniosynostosis. We performed mutation testing in extended families and determined the effects of mutations on mRNA expression. We examined the genetic interaction between loss-of-function mutations of Tcf12 and Twist1 in mice. FindingsHeterozygous TCF12 mutations were present in 38 of the 347 unrelated patients with craniosynostosis. These included 22 (32%) of 69 with isolated bilateral coronal synostosis, and 14 (10%) of 141 with unilateral coronal synostosis, but none with premature fusion of only the metopic, sagittal, or lambdoid sutures (p<10−6). An additional two patients had either bilateral or right coronal synostosis in addition to sagittal synostosis. 14 cases arose de novo, but vertical transmission was demonstrated in 23 families. 16 mutation-positive individuals (47%) had craniosynostosis or suspicious clinical features, but 19 (53%) of 35 mutation-positive relatives were non-penetrant for craniosynostosis. TCF12 mutations were associated with diminished mRNA expression, indicating haploinsufficiency. With appropriate surgical correction the clinical outcome was usually good; six of 66 individuals had learning disability. Mice doubly heterozygous for Twist1 and Tcf12 mutations had severe bilateral coronal synostosis. InterpretationMutations of TCF12 are a frequent and specific cause of coronal craniosynostosis; mutation testing is indicated in the assessment of these patients. Genetic interaction of Tcf12 and Twist1 is crucial for coronal suture development. FundingNational Institute for Health Research Biomedical Research Centre, Oxford (BRC)/Oxford University Clinical Academic Graduate School (OUCAGS), and Oxfordshire Health Services Research Committee (OHSRC), Oxford Craniofacial Unit Charitable Fund; Thames Valley Comprehensive Local Research Network; The Dutch Center for Translational Molecular Medicine; Carolien Bijl Foundation; US National Institutes for Health; Wellcome Trust.