Craniosynostosis is the pathologic fusion of the sutures of the calvaria. It is associated with significant morbidity, occasional mortality, and carries a considerable financial burden. Using a combination of candidate gene resequencing and comparative genome hybridization TWIST1 loss-of-function mutations and IGF1R and RUNX2 gain-of-function mutations have been identified. Expression array analysis coupled with network modeling has identified activation of an IGF1-RUNX2 pathway as a potential cause of craniosynostosis in a large subgroup of cases. The identification of a biologically based subgroup is a critical advance toward understanding the cause of synostosis as it affords an ability to focus research efforts on a phenotypically similar cohort of cases. This competitive renewal proposes the use of genomics, network modeling, animal models and novel cell biologic approaches to reveal genetic and developmental pathways which, when disrupted, result in premature calvarial fusion. New (Igf1rGOF) and existing (Igf1GOF, Gsk3bLOF, Twist1LOF) mouse resources will be used to model the polygenic inheritance of this disorder. Through interdisciplinary research efforts, three independent yet highly integrated aims will test the hypothesis that a subset of children with isolated single suture craniosynostosis has identifiable genetic variation that results in enhanced calvarial osteoblast differentiation throug activation of an IGF1-RUNX2 pathway.
Specific Aim 1 will identify changes in the cellular phenotype of osteoblasts demonstrating activation of the IGF1-RUNX2 pathway. We will utilize measures of osteoblast growth and differentiation as well as measures of cellular biomechanics to refine the biologic phenotype of our original cohort.
Specific Aim 2 will develop and characterize an inducible Igf1rR407H mouse model of the human IGF1RR406H gain-of-function mutation.11 We will breed and phenotype Igf1rR407H compound heterozygous mice using existing mutant mouse resources (Igf1GOF, Gsk3bLOF, Twist1LOF) to develop models for the polygenic inheritance of SSC in humans.
Specific Aim 3 will determine the contribution of genomic variation in the development of craniosynostosis among cases in the IGF1/RUNX2 subgroup. We will use transcriptome sequence data from the original cohort (N=211) and whole genome sequence data from the IGF1/RUNX2 subgroup cases (N=48) to refine the pathway and identify correlates between alteration in gene expression, coding variants and regulatory region variation. We will recruit a new SSC cohort to validate the transcriptomic and genomic variation identified. Major gaps exist in the diagnosis and management of isolated craniosynostosis including the lack of molecular diagnostic testing, adequate family counseling, and biologic therapies to reduce patient morbidity. There is an incomplete understanding of the causes of craniosynostosis and we lack experimental models. The development of these resources will improve clinical care, design biologically based therapies, and pursue primary prevention.

Public Health Relevance

Craniosynostosis is a common human birth defect resulting from premature fusion of the sutures of the skull. The causes of the most common single suture forms are poorly understood. In this proposal we will use modern genomic analytic techniques, animal models and novel in vitro assays to identify the biologic basis of this condition in order t improve clinical care, design biologically based therapies, and pursue primary prevention.

National Institute of Health (NIH)
National Institute of Dental & Craniofacial Research (NIDCR)
Research Project (R01)
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Skeletal Biology Development and Disease Study Section (SBDD)
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Harris, Emily L
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Seattle Children's Hospital
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Clarke, Christine M; Fok, Vincent T; Gustafson, Jennifer A et al. (2018) Single suture craniosynostosis: Identification of rare variants in genes associated with syndromic forms. Am J Med Genet A 176:290-300
Al-Rekabi, Zeinab; Wheeler, Marsha M; Leonard, Andrea et al. (2016) Activation of the IGF1 pathway mediates changes in cellular contractility and motility in single-suture craniosynostosis. J Cell Sci 129:483-91
Homayounfar, Negar; Park, Sarah S; Afsharinejad, Zahra et al. (2015) Transcriptional analysis of human cranial compartments with different embryonic origins. Arch Oral Biol 60:1450-60
Speltz, Matthew L; Collett, Brent R; Wallace, Erin R et al. (2015) Intellectual and academic functioning of school-age children with single-suture craniosynostosis. Pediatrics 135:e615-23
Carmichael, S L; Ma, C; Rasmussen, S A et al. (2015) Craniosynostosis and risk factors related to thyroid dysfunction. Am J Med Genet A 167A:701-7
Park, Sarah S; Beyer, Richard P; Smyth, Matthew D et al. (2015) Osteoblast differentiation profiles define sex specific gene expression patterns in craniosynostosis. Bone 76:169-76
Kim, Sun-Don; Yagnik, Garima; Cunningham, Michael L et al. (2014) MAPK/ERK Signaling Pathway Analysis in Primary Osteoblasts From Patients With Nonsyndromic Sagittal Craniosynostosis. Cleft Palate Craniofac J 51:115-9
Stamper, Brendan D; Park, Sarah S; Beyer, Richard P et al. (2012) Unique sex-based approach identifies transcriptomic biomarkers associated with non-syndromic craniosynostosis. Gene Regul Syst Bio 6:81-92
Justice, Cristina M; Yagnik, Garima; Kim, Yoonhee et al. (2012) A genome-wide association study identifies susceptibility loci for nonsyndromic sagittal craniosynostosis near BMP2 and within BBS9. Nat Genet 44:1360-4
Yagnik, Garima; Ghuman, Apar; Kim, Sundon et al. (2012) ALX4 gain-of-function mutations in nonsyndromic craniosynostosis. Hum Mutat 33:1626-9

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