De novo and rare inherited mutations implicate the transcriptional coregulator TCF20/SPBP in autism spectrum disorder.

BACKGROUND: Autism spectrum disorders (ASDs) are common and have a strong genetic basis, yet the cause of ∼70-80% ASDs remains unknown. By clinical cytogenetic testing, we identified a family in which two brothers had ASD, mild intellectual disability and a chromosome 22 pericentric inversion, not detected in either parent, indicating de novo mutation with parental germinal mosaicism. We hypothesised that the rearrangement was causative of their ASD and localised the chromosome 22 breakpoints. METHODS: The rearrangement was characterised using fluorescence in situ hybridisation, Southern blotting, inverse PCR and dideoxy-sequencing. Open reading frames and intron/exon boundaries of the two physically disrupted genes identified, TCF20 and TNRC6B, were sequenced in 342 families (260 multiplex and 82 simplex) ascertained by the International Molecular Genetic Study of Autism Consortium (IMGSAC). RESULTS: IMGSAC family screening identified a de novo missense mutation of TCF20 in a single case and significant association of a different missense mutation of TCF20 with ASD in three further families. Through exome sequencing in another project, we independently identified a de novo frameshifting mutation of TCF20 in a woman with ASD and moderate intellectual disability. We did not identify a significant association of TNRC6B mutations with ASD. CONCLUSIONS: TCF20 encodes a transcriptional coregulator (also termed SPBP) that is structurally and functionally related to RAI1, the critical dosage-sensitive protein implicated in the behavioural phenotypes of the Smith-Magenis and Potocki-Lupski 17p11.2 deletion/duplication syndromes, in which ASD is frequently diagnosed. This study provides the first evidence that mutations in TCF20 are also associated with ASD.

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

Craniosynostosis, the premature fusion of the cranial sutures, is a heterogeneous disorder with a prevalence of ∼1 in 2,200 (refs. 1,2). A specific genetic etiology can be identified in ∼21% of cases, including mutations of TWIST1, which encodes a class II basic helix-loop-helix (bHLH) transcription factor, and causes Saethre-Chotzen syndrome, typically associated with coronal synostosis. Using exome sequencing, we identified 38 heterozygous TCF12 mutations in 347 samples from unrelated individuals with craniosynostosis. The mutations predominantly occurred in individuals with coronal synostosis and accounted for 32% and 10% of subjects with bilateral and unilateral pathology, respectively. TCF12 encodes one of three class I E proteins that heterodimerize with class II bHLH proteins such as TWIST1. We show that TCF12 and TWIST1 act synergistically in a transactivation assay and that mice doubly heterozygous for loss-of-function mutations in Tcf12 and Twist1 have severe coronal synostosis. Hence, the dosage of TCF12-TWIST1 heterodimers is critical for normal coronal suture development.

Reduced dosage of ERF causes complex craniosynostosis in humans and mice and links ERK1/2 signaling to regulation of osteogenesis.

The extracellular signal-related kinases 1 and 2 (ERK1/2) are key proteins mediating mitogen-activated protein kinase signaling downstream of RAS: phosphorylation of ERK1/2 leads to nuclear uptake and modulation of multiple targets. Here, we show that reduced dosage of ERF, which encodes an inhibitory ETS transcription factor directly bound by ERK1/2 (refs. 2,3,4,5,6,7), causes complex craniosynostosis (premature fusion of the cranial sutures) in humans and mice. Features of this newly recognized clinical disorder include multiple-suture synostosis, craniofacial dysmorphism, Chiari malformation and language delay. Mice with functional Erf levels reduced to ∼30% of normal exhibit postnatal multiple-suture synostosis; by contrast, embryonic calvarial development appears mildly delayed. Using chromatin immunoprecipitation in mouse embryonic fibroblasts and high-throughput sequencing, we find that ERF binds preferentially to elements away from promoters that contain RUNX or AP-1 motifs. This work identifies ERF as a novel regulator of osteogenic stimulation by RAS-ERK signaling, potentially by competing with activating ETS factors in multifactor transcriptional complexes.

Atypical Crouzon syndrome with a novel Cys62Arg mutation in FGFR2 presenting with sagittal synostosis.

The management of a 1-year-old boy with Crouzonoid features is presented with a description of molecular genetic investigations that revealed a previously unreported mutation of the fibroblast growth factor receptor 2 (FGFR2) gene encoding the amino acid substitution p.Cys62Arg within the immunoglobin-like (IgI) domain. The patient presented in atypical fashion with severe sagittal synostosis but only mild exorbitism and hypertelorism. Owing to the progressively increasing size of the cranial occipital bullet, a total calvarial modeling procedure was performed at 8 months of age to correct the craniofacial deformity. Standard genetic testing of the major mutational "hotspots" associated with craniosynostosis was initially negative. However, further testing for atypical sites of mutation revealed a heterozygous nucleotide substitution (c.184T>C) in exon 3 of FGFR2. This mutation has not been previously reported and is only the second to be identified in the IgI domain; it was not present in either parent, indicating that it had arisen de novo. The child remains well 6 months postoperatively but will be monitored more closely compared with the usual protocol for nonsyndromic sagittal synostosis owing to the potential for increased risk of secondary complications. Key learning points from this case include the need for careful phenotypic evaluation of children presenting with apparently isolated sagittal synostosis and genetic testing for atypical mutations if the usual hotspots are negative.

Man or machine? The clinimetric properties of laser Doppler imaging in burn depth assessment.

Burns of an indeterminate depth present a challenge to burns surgeons and nurses on a daily basis in terms of healing and subsequent management, be it by a surgical or a more conservative approach. Laser Doppler imaging has become an important diagnostic modality in assisting the clinical decision-making process, being used widely in burns units throughout the United Kingdom and the rest of the world. Clinimetrics focuses on the methodology of measuring various biological parameters, and this article aims to describe laser Doppler imaging in this context by appraising the current body of evidence that illustrate its various properties. The authors conclude that indeterminate burn depth assessment should be a clinical judgment assisted by information provided by this device.