Regulatory elements in SEM1-DLX5-DLX6 (7q21.3) locus contribute to genetic control of coronal nonsyndromic craniosynostosis and bone density-related traits.

Purpose: The etiopathogenesis of coronal nonsyndromic craniosynostosis (cNCS), a congenital condition defined by premature fusion of 1 or both coronal sutures, remains largely unknown. Methods: We conducted the largest genome-wide association study of cNCS followed by replication, fine mapping, and functional validation of the most significant region using zebrafish animal model. Results: Genome-wide association study identified 6 independent genome-wide-significant risk alleles, 4 on chromosome 7q21.3 SEM1-DLX5-DLX6 locus, and their combination conferred over 7-fold increased risk of cNCS. The top variants were replicated in an independent cohort and showed pleiotropic effects on brain and facial morphology and bone mineral density. Fine mapping of 7q21.3 identified a craniofacial transcriptional enhancer (eDlx36) within the linkage region of the top variant (rs4727341; odds ratio [95% confidence interval], 0.48[0.39-0.59]; P = 1.2E-12) that was located in SEM1 intron and enriched in 4 rare risk variants. In zebrafish, the activity of the transfected human eDlx36 enhancer was observed in the frontonasal prominence and calvaria during skull development and was reduced when the 4 rare risk variants were introduced into the sequence. Conclusion: Our findings support a polygenic nature of cNCS risk and functional role of craniofacial enhancers in cNCS susceptibility with potential broader implications for bone health.

A genome-wide association study implicates the BMP7 locus as a risk factor for nonsyndromic metopic craniosynostosis.

Our previous genome-wide association study (GWAS) for sagittal nonsyndromic craniosynostosis (sNCS) provided important insights into the genetics of midline CS. In this study, we performed a GWAS for a second midline NCS, metopic NCS (mNCS), using 215 non-Hispanic white case-parent triads. We identified six variants with genome-wide significance (P ≤ 5 × 10-8): rs781716 (P = 4.71 × 10-9; odds ratio [OR] = 2.44) intronic to SPRY3; rs6127972 (P = 4.41 × 10-8; OR = 2.17) intronic to BMP7; rs62590971 (P = 6.22 × 10-9; OR = 0.34), located ~ 155 kb upstream from TGIF2LX; and rs2522623, rs2573826, and rs2754857, all intronic to PCDH11X (P = 1.76 × 10-8, OR = 0.45; P = 3.31 × 10-8, OR = 0.45; P = 1.09 × 10-8, OR = 0.44, respectively). We performed a replication study of these variants using an independent non-Hispanic white sample of 194 unrelated mNCS cases and 333 unaffected controls; only the association for rs6127972 (P = 0.004, OR = 1.45; meta-analysis P = 1.27 × 10-8, OR = 1.74) was replicated. Our meta-analysis examining single nucleotide polymorphisms common to both our mNCS and sNCS studies showed the strongest association for rs6127972 (P = 1.16 × 10-6). Our imputation analysis identified a linkage disequilibrium block encompassing rs6127972, which contained an enhancer overlapping a CTCF transcription factor binding site (chr20:55,798,821-55,798,917) that was significantly hypomethylated in mesenchymal stem cells derived from fused metopic compared to open sutures from the same probands. This study provides additional insights into genetic factors in midline CS.

The incidence of raised intracranial pressure in nonsyndromic sagittal craniosynostosis following primary surgery.

OBJECT Raised intracranial pressure (ICP) is recognized to occur in patients with nonsyndromic isolated sagittal craniosynostosis (SC) prior to surgery. However, the incidence of raised ICP following primary surgery is rarely reported and there appears to be a widely held assumption that corrective surgery for SC prevents the later development of intracranial hypertension. This study reports the incidence of postoperative raised ICP in a large cohort of patients with SC treated by 1 of 2 surgical procedures in a single craniofacial unit. METHODS A retrospective review was performed of all patients with SC who underwent either a modified strip craniectomy (MSC) or calvarial remodeling (CR) procedure under the care of the Oxford Craniofacial Unit between 1995 and 2010 and who were followed up for more than 2 years. The influence of patient age at surgery, year of surgery, sex, procedure type, and the presence of raised ICP preoperatively were analyzed. RESULTS Two hundred seventeen children had primary surgery for SC and were followed up for a mean of 86 months. The overall rate of raised ICP following surgery was 6.9%, occurring at a mean of 51 months after the primary surgical procedure. Raised ICP was significantly more common in those patients treated by MSC (13 of 89 patients, 14.6%) than CR (2 of 128 patients, 1.6%). Also, raised ICP was more common in patients under 1 year of age, the majority of whom were treated by MCS. No other factor was found to have a significant effect. CONCLUSIONS Postoperative raised ICP was found in more than 1 in 20 children treated for nonsyndromic SC in this series. It was significantly influenced by the primary surgical procedure and age at primary surgery. Careful long-term follow-up is essential if children who develop raised ICP following surgery are not to be overlooked.

Long-term morphological outcomes in nonsyndromic sagittal craniosynostosis: a comparison of 2 techniques.

Correction of scaphocephaly is one of the principle goals of surgery in sagittal craniosynostosis. Reported relapse in head shape after surgery and continued head growth into late adolescence underscores the need for long-term outcomes to be considered when comparing between different surgical approaches in this condition; yet there are relatively few reports of results to 5 years and beyond in the literature. Therefore, a retrospective review was performed of the anthropometric data of 224 patients with sagittal craniosynostosis who underwent primary surgery between 1994 and 2012. During this period, patients underwent either a modified strip craniectomy (MSC) or calvarial remodeling (CR) procedure. Sixty-two patients were treated by MSC and followed up for a mean of 44 months. One hundred sixty-two patients had CR, with follow-up for a mean of 45 months. Overall, 90 patients were seen up to 5 years, and 47 patients to 9 years or more after surgery. The cephalic index (CI) of MSC-treated patients improved from a mean of 67.0 to 72.7, with 31% achieving a CI greater than 75 at one year. Calvarial remodeling was significantly more effective at correcting the scaphocephalic deformity. Patients treated with CR improved from a mean CI of 66.7 to 76.1. Sixty-two percent of the patients achieved a CI greater than 75. In both groups, outcomes were stable throughout follow-up with no significant relapse up to 14 years after surgery.

The preoperative incidence of raised intracranial pressure in nonsyndromic sagittal craniosynostosis is underestimated in the literature.

OBJECT: The presence of raised intracranial pressure (ICP) in untreated nonsyndromic, isolated sagittal craniosynostosis (SC) is an important functional indication for surgery. METHODS: A retrospective review was performed of all 284 patients presenting with SC to the Oxford Craniofacial Unit between 1995 and 2010. RESULTS: Intraparenchymal ICP monitoring was performed in 39 children following a standard unit protocol. Monitoring of ICP was offered for all patients in whom nonoperative management was considered on the basis of minimal deformity or in cases in which parents were reluctant to agree to corrective surgery. These patients presented at an older age than the rest of the cohort (mean age 56 months), with marked scaphocephaly (16/39, 41%), mild scaphocephaly (11, 28%), or no scaphocephalic deformity (12, 31%). Raised ICP was found in 17 (44%) patients, with no significant difference in its incidence among the 3 different deformity types. Raised ICP was not predicted by the presence of symptoms of ICP or developmental delay or by ophthalmological or radiological findings. CONCLUSIONS: The incidence of raised ICP in SC reported here is greater than that previously published in the literature. The lack of a reliable noninvasive method to identify individuals with elevated ICP in SC mandates consideration of intraparenchymal ICP monitoring in all patients for whom nonoperative management is contemplated.

Prevalence and complications of single-gene and chromosomal disorders in craniosynostosis.

OBJECTIVES: We describe the first cohort-based analysis of the impact of genetic disorders in craniosynostosis. We aimed to refine the understanding of prognoses and pathogenesis and to provide rational criteria for clinical genetic testing. METHODS: We undertook targeted molecular genetic and cytogenetic testing for 326 children who required surgery because of craniosynostosis, were born in 1993-2002, presented to a single craniofacial unit, and were monitored until the end of 2007. RESULTS: Eighty-four children (and 64 relatives) had pathologic genetic alterations (86% single-gene mutations and 14% chromosomal abnormalities). The FGFR3 P250R mutation was the single largest contributor (24%) to the genetic group. Genetic diagnoses accounted for 21% of all craniosynostosis cases and were associated with increased rates of many complications. Children with an initial clinical diagnosis of nonsyndromic craniosynostosis were more likely to have a causative mutation if the synostoses were unicoronal or bicoronal (10 of 48 cases) than if they were sagittal or metopic (0 of 55 cases; P = .0003). Repeat craniofacial surgery was required for 58% of children with single-gene mutations but only 17% of those with chromosomal abnormalities (P = .01). CONCLUSIONS: Clinical genetic assessment is critical for the treatment of children with craniosynostosis. Genetic testing of nonsyndromic cases (at least for FGFR3 P250R and FGFR2 exons IIIa/c) should be targeted to patients with coronal or multisuture synostoses. Single-gene disorders that disrupt physiologic signaling in the cranial sutures often require reoperation, whereas chromosomal abnormalities follow a more-indolent course, which suggests a different, secondary origin of the associated craniosynostosis.

Etiological heterogeneity and clinical characteristics of metopic synostosis: Evidence from a tertiary craniofacial unit.

Metopic synostosis (MS) accounts for approximately 10-15% of all craniosynostosis and is etiologically heterogeneous. This study aimed to examine the causes of MS, as observed in a tertiary craniofacial unit. We reviewed the case notes of 110 children with a diagnosis of MS, attending the craniofacial unit in Oxford between 1991 and 2008. Our results showed 38 children (38/110 or 34.6%) who had at least one additional structural abnormality or had a known syndromic diagnosis were classed as having syndromic MS. Chromosomal abnormalities were noted in 8/38 (21.4%) children: mosaic marker chromosome 2, 9p deletion (2/8), 11q deletion, 12pter deletion and duplication of 15q25 with other additional chromosomal abnormalities (3/8). Other syndromic diagnoses included Silver-Russell syndrome and Greig cephalopolysyndactyly. Prenatal exposure to sodium valproate (VPA) was noted in 8/110 children (7.8%), with the dose of the VPA being >or=1,000 mg/day in all cases. Other prenatal exposures reported in this study were: maternal diabetes (6/110), enoxaparin for hypercoagulable state (1/110), and thyroxine (1/110). The majority of patients (72/110 or 65.4%) had nonsyndromic MS. Speech delay was present in 11 children with nonsyndromic MS (11/72 or 15.3%) and 10 children with syndromic MS (10/38 or 26.3%). We conclude that approximately two-thirds of all MS is nonsyndromic. Prenatal exposure to VPA is a common cause of MS. Maternal diabetes, not previously linked to MS, was noted in 5.5% of cases. Chromosomal abnormalities account for about 6% of MS. An increased risk of speech delay is seen with both the syndromic and nonsyndromic forms.

Clinical dividends from the molecular genetic diagnosis of craniosynostosis.

A dozen years have passed since the first genetic lesion was identified in a family with craniosynostosis, the premature fusion of the cranial sutures. Subsequently, mutations in the FGFR2, FGFR3, TWIST1, and EFNB1 genes have been shown to account for approximately 25% of craniosynostosis, whilst several additional genes make minor contributions. Using specific examples, we show how these discoveries have enabled refinement of information on diagnosis, recurrence risk, prognosis for mental development, and surgical planning. However, phenotypic variability can present a significant challenge to the clinical interpretation of molecular genetic tests. In particular, the difficulty of analyzing the complex interaction of genetic background and prenatal environment in determining clinical features, limits the value of identifying low penetrance mutations.

Clinical dividends from the molecular genetic diagnosis of craniosynostosis.

A dozen years have passed since the first genetic lesion was identified in a family with craniosynostosis, the premature fusion of the cranial sutures. Subsequently, mutations in the FGFR2, FGFR3, TWIST1, and EFNB1 genes have been shown to account for approximately 25% of craniosynostosis, whilst several additional genes make minor contributions. Using specific examples, we show how these discoveries have enabled refinement of information on diagnosis, recurrence risk, prognosis for mental development, and surgical planning. However, phenotypic variability can present a significant challenge to the clinical interpretation of molecular genetic tests. In particular, the difficulty of analyzing the complex interaction of genetic background and prenatal environment in determining clinical features, limits the value of identifying low penetrance mutations.