ARTICLE Inactivation of IL11 Signaling Causes Craniosynostosis, Delayed Tooth Eruption, and Supernumerary Teeth Pekka Nieminen, 1, * Neil V. Morgan, 2 Aime ´e L. Fenwick, 3 Satu Parmanen, 1 Lotta Veistinen, 1 Marja L. Mikkola, 4 Peter J. van der Spek, 5 Andrew Giraud, 6 Louise Judd, 6 Sirpa Arte, 1,7 Louise A. Brueton, 2,8 Steven A. Wall, 9 Irene M.J. Mathijssen, 10 Eamonn R. Maher, 2,8 Andrew O.M. Wilkie, 3,9 Sven Kreiborg, 11,12 and Irma Thesleff 4 Craniosynostosis and supernumerary teeth most often occur as isolated developmental anomalies, but they are also separately mani- fested in several malformation syndromes. Here, we describe a human syndrome featuring craniosynostosis, maxillary hypoplasia, delayed tooth eruption, and supernumerary teeth. We performed homozygosity mapping in three unrelated consanguineous Pakistani families and localized the syndrome to a region in chromosome 9. Mutational analysis of candidate genes in the region revealed that all affected children harbored homozygous missense mutations (c.662C>G [p.Pro221Arg], c.734C>G [p.Ser245Cys], or c.886C>T [p.Arg296Trp]) in IL11RA (encoding interleukin 11 receptor, alpha) on chromosome 9p13.3. In addition, a homozygous nonsense mutation, c.475C>T (p.Gln159X), and a homozygous duplication, c.916_924dup (p.Thr306_Ser308dup), were observed in two north European families. In cell-transfection experiments, the p.Arg296Trp mutation rendered the receptor unable to mediate the IL11 signal, indicating that the mutation causes loss of IL11RA function. We also observed disturbed cranial growth and suture activity in the Il11ra null mutant mice, in which reduced size and remodeling of limb bones has been previously described. We conclude that IL11 signaling is essential for the normal development of craniofacial bones and teeth and that its function is to restrict suture fusion and tooth number. The results open up the possibility of modulation of IL11 signaling for the treatment of craniosynostosis. Introduction The development of craniofacial bones and teeth involves complex tissue interactions, cell migration, and coordi- nated growth. 1–3 The genetic networks and signaling path- ways underlying these developmental processes have been uncovered by the identification of gene mutations that cause human malformations and by mutational and exper- imental studies in model animals. 1,2,4 Genetic craniofacial malformations range from minor variations in tooth number to bone-formation defects such as craniosynosto- sis and severe malformation syndromes that affect multiple tissues and organs. Craniosynostosis, the prema- ture closure of cranial sutures, occurs in one of 2500 newborns, 2 and although it is sometimes associated with other congenital defects, most cases of craniosynostosis appear as isolated traits. Abnormalities in tooth number constitute the most common craniofacial anomalies; the prevalence of developmentally missing teeth is 6%–8% (excluding missing third molars), and that of supernu- merary teeth is 1.5%–3.5%. 4–6 Unlike most bones in the trunk and limbs, the facial and calvarial bones develop by direct intramembranous ossifi- cation of the mesenchymal condensations without a prior cartilaginous template. 1 The cells in the center of the condensations undergo osteoblast differentiation and start deposition of the mineralizing bone matrix. The bone grows as a result of continued proliferation and differenti- ation of the peripheral cells. As the individual bones approach each other, fibrous sutures form between the bones and function as joints, allowing further growth of the skull and face. Growth of intramembranous bones is also characterized by bone remodeling with localized apposition and resorption by osteoblasts and osteoclasts, respectively. The flat calvarial bones grow by bone apposi- tion at the exocranial side and at the osteogenic fronts at the sutures. Bone formation continues in the sutures until they become obliterated and the fusions between adjacent bones fix their relative positions. The calvarial and facial sutures remain patent after birth, and the timing of suture fusion is strictly regulated and varies between the indi- vidual sutures. 1 Institute of Dentistry, Biomedicum, P.O. Box 63, University of Helsinki, FIN-00014 Helsinki, Finland; 2 Centre for Rare Diseases and Personalised Medicine, School of Clinical Experimental Medicine, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK; 3 Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Headington, Oxford OX3 9DS, UK; 4 Institute of Biotechnology, P.O. Box 56, University of Helsinki, FIN-00014 Helsinki, Finland; 5 Erasmus MC Department of Bioinformatics (Ee1540), P.O. Box 2040, 3000CA Rotterdam, The Netherlands; 6 Murdoch Children’s Research Institute, Royal Children’s Hospital, Flemington Road, Parkville 3052, Australia; 7 Department of Oral and Maxillofacial Diseases, P.O. Box 263, Helsinki University Central Hospital, FIN-00029 Helsinki, Finland; 8 West Midlands Region Genetics Sevice, Clinical Genetics Unit, Birmingham Women’s Hospital, Edgbaston, Birmingham B15 2TG, UK; 9 Oxford Craniofacial Unit, Oxford Radcliffe Hospitals NHS Trust, John Radcliffe Hospital, Headington, Oxford OX3 9DU, UK; 10 Erasmus MC Department of Plastic Surgery (HS509) P.O. Box 2040, 3000CA, Rotterdam, The Netherlands; 11 Department of Pediatric Dentistry and Clinical Genetics, School of Dentistry, University of Copenhagen, 20 Noerre Alle ´, DK-2200 Copenhagen N, Denmark; 12 Department of Clinical Genetics, Copenhagen University Hospital, DK-2100 Copenhagen, Denmark *Correspondence: pekka.nieminen@helsinki.fi DOI 10.1016/j.ajhg.2011.05.024. Ó2011 by The American Society of Human Genetics. All rights reserved. The American Journal of Human Genetics 89, 67–81, July 15, 2011 67