Bon, Bregje W.M. van

Background Pathogenic variants in the zinc finger protein coding genes are rare causes of intellectual disability and congenital malformations. Mutations in the ZNF148 gene causing GDACCF syndrome (global developmental delay, absent or hypoplastic corpus callosum, dysmorphic facies; MIM #617260) have been reported in five individuals so far. Methods As a result of an international collaboration using GeneMatcher Phenome Central Repository and personal communications, here we describe the clinical and molecular genetic characteristics of 22 previously unreported individuals. Results The core clinical phenotype is characterised by developmental delay particularly in the domain of speech development, postnatal growth retardation, microcephaly and facial dysmorphism. Corpus callosum abnormalities appear less frequently than suggested by previous observations. The identified mutations concerned nonsense or frameshift variants that were mainly located in the last exon of the ZNF148 gene. Heterozygous deletion including the entire ZNF148 gene was found in only one case. Most mutations occurred de novo, but were inherited from an affected parent in two families. Conclusion The GDACCF syndrome is clinically diverse, and a genotype-first approach, that is, exome sequencing is recommended for establishing a genetic diagnosis rather than a phenotype-first approach. However, the syndrome may be suspected based on some recurrent, recognisable features. Corpus callosum anomalies were not as constant as previously suggested, we therefore recommend to replace the term ‘GDACCF syndrome’ with ‘ZNF148-related neurodevelopmental disorder’.

Mitogen-Activated Protein 3 Kinase 7 (MAP3K7, MIM 602614) encodes the ubiquitously expressed transforming growth factor β (TGF-β)–activated kinase 1 (TAK1), which plays a crucial role in many cellular processes. Variants in the MAP3K7 gene have been linked to 2 distinct disorders: frontometaphyseal dysplasia type 2 (FMD2, MIM #617137) and cardiospondylocarpofacial syndrome (CSCF, MIM #157800). The fact that different variants can induce 2 distinct phenotypes suggests a phenotype/genotype correlation, but no side-by-side comparison has been done thus far to confirm this. Here we significantly expand the cohort and the description of clinical phenotypes for individuals with CSCF and FMD2 who carry variants in MAP3K7. We show that in contrast to FMD2-causing variants, CSCF-causing variants in MAP3K7 have a loss-of-function effect. Additionally, patients with pathogenic variants in MAP3K7 are at risk for cardiac disease, have symptoms associated with connective tissue disease and we show overlap in clinical phenotypes of CSCF with Noonan syndrome. Together, we provide evidence for a molecular fingerprint of FMD2- versus CSCF-causing MAP3K7 variants and conclude that variants in MAP3K7 should be considered in the differential diagnosis of patients with syndromic congenital cardiac defects and/or cardiomyopathy, syndromic connective tissue disorders and in the differential diagnosis of Noonan syndrome.