CHD7 is a member of the chromodomain helicase DNA‐binding (CHD) protein family that plays a role in transcription regulation by chromatin remodeling. Loss‐of‐function mutations in CHD7 are known to cause CHARGE syndrome, an autosomal‐dominant malformation syndrome in which several organ systems, for example, the central nervous system, eye, ear, nose, and mediastinal organs, are variably involved. In this article, we review all the currently described CHD7 variants, including 183 new pathogenic mutations found by our laboratories. In total, we compiled 528 different pathogenic CHD7 alterations from 508 previously published patients with CHARGE syndrome and 294 unpublished patients analyzed by our laboratories. The mutations are equally distributed along the coding region of CHD7 and most are nonsense or frameshift mutations. Most mutations are unique, but we identified 94 recurrent mutations, predominantly arginine to stop codon mutations. We built a locus‐specific database listing all the variants that is easily accessible at www.CHD7.org. In addition, we summarize the latest data on CHD7 expression studies, animal models, and functional studies, and we discuss the latest clinical insights into CHARGE syndrome. Hum Mutat 33:1149–1160, 2012.

Objective To delineate the epileptology, a key part of the SYNGAP1 phenotypic spectrum, in a large patient cohort. Methods Patients were recruited via investigators9 practices or social media. We included patients with (likely) pathogenic SYNGAP1 variants or chromosome 6p21.32 microdeletions incorporating SYNGAP1. We analyzed patients9 phenotypes using a standardized epilepsy questionnaire, medical records, EEG, MRI, and seizure videos. Results We included 57 patients (53% male, median age 8 years) with SYNGAP1 mutations (n = 53) or microdeletions (n = 4). Of the 57 patients, 56 had epilepsy: generalized in 55, with focal seizures in 7 and infantile spasms in 1. Median seizure onset age was 2 years. A novel type of drop attack was identified comprising eyelid myoclonia evolving to a myoclonic-atonic (n = 5) or atonic (n = 8) seizure. Seizure types included eyelid myoclonia with absences (65%), myoclonic seizures (34%), atypical (20%) and typical (18%) absences, and atonic seizures (14%), triggered by eating in 25%. Developmental delay preceded seizure onset in 54 of 56 (96%) patients for whom early developmental history was available. Developmental plateauing or regression occurred with seizures in 56 in the context of a developmental and epileptic encephalopathy (DEE). Fifty-five of 57 patients had intellectual disability, which was moderate to severe in 50. Other common features included behavioral problems (73%); high pain threshold (72%); eating problems, including oral aversion (68%); hypotonia (67%); sleeping problems (62%); autism spectrum disorder (54%); and ataxia or gait abnormalities (51%). Conclusions SYNGAP1 mutations cause a generalized DEE with a distinctive syndrome combining epilepsy with eyelid myoclonia with absences and myoclonic-atonic seizures, as well as a predilection to seizures triggered by eating.

Clinical and genetic heterogeneity in monogenetic disorders represents a major diagnostic challenge. Although the presence of particular clinical features may aid in identifying a specific cause in some cases, the majority of patients remain undiagnosed. Here, we investigated the utility of whole-exome sequencing as a diagnostic approach for establishing a molecular diagnosis in a highly heterogeneous group of patients with varied intellectual disability and microcephaly. Whole-exome sequencing was performed in 38 patients, including three sib-pairs, in addition to or in parallel with genetic analyses that were performed during the diagnostic work-up of the study participants. In ten out of these 35 families (29 %), we found mutations in genes already known to be related to a disorder in which microcephaly is a main feature. Two unrelated patients had mutations in the ASPM gene. In seven other patients we found mutations in RAB3GAP1, RNASEH2B, KIF11, ERCC8, CASK, DYRK1A and BRCA2. In one of the sib-pairs, mutations were found in the RTTN gene. Mutations were present in seven out of our ten families with an established etiological diagnosis with recessive inheritance. We demonstrate that whole-exome sequencing is a powerful tool for the diagnostic evaluation of patients with highly heterogeneous neurodevelopmental disorders such as intellectual disability with microcephaly. Our results confirm that autosomal recessive disorders are highly prevalent among patients with microcephaly.

Background—: Loss-of-function mutations in CHD7 cause Coloboma, Heart Disease, Atresia of Choanae, Retardation of Growth and/or Development, Genital Hypoplasia, and Ear Abnormalities With or Without Deafness (CHARGE) syndrome, a variable combination of multiple congenital malformations including heart defects. Heart defects are reported in 70% to 92% of patients with a CHD7 mutation, but most studies are small and do not provide a detailed classification of the defects. We present the first, detailed, descriptive study on the cardiac phenotype of 299 patients with a CHD7 mutation and discuss the role of CHD7 in cardiac development. Methods and Results—: We collected information on congenital heart defects in 299 patients with a pathogenic CHD7 mutation, of whom 220 (74%) had a congenital heart defect. Detailed information on the heart defects was available for 202 of these patients. We classified the heart defects based on embryonic cardiac development and compared the distribution to 1007 equally classified nonsyndromic heart defects of patients registered by EUROCAT, a European Registry of Congenital Anomalies. Heart defects are highly variable in patients with CHD7 mutations, but atrioventricular septal defects and conotruncal heart defects are over-represented. Sex did not have an effect on the presence of heart defects, but truncating CHD7 mutations resulted in a heart defect significantly more often than missense or splice-site mutations (χ ² , P <0.001). Conclusions—: CHD7 plays an important role in cardiac development, given that we found a wide range of heart defects in 74% of a large cohort of patients with a CHD7 mutation. Conotruncal defects and atrioventricular septal defects are over-represented in patients with CHD7 mutations compared with patients with nonsyndromic heart defects.

Genome-wide arrays are rapidly replacing conventional karyotyping in postnatal cytogenetic diagnostics and there is a growing request for arrays in the prenatal setting. Several studies have documented 1–3% additional abnormal findings in prenatal diagnosis with arrays compared to conventional karyotyping. A recent meta-analysis demonstrated that 5.2% extra diagnoses can be expected in fetuses with ultrasound abnormalities. However, no consensus exists as to whether the use of genome-wide arrays should be restricted to pregnancies with ultrasound abnormalities, performed in all women undergoing invasive prenatal testing or offered to all pregnant women. Moreover, the interpretation of array results in the prenatal situation is challenging due to the large numbers of copy number variants with no major phenotypic effect. This also raises the question of what, or what not to report, for example, how to deal with unsolicited findings. These issues were discussed at a working group meeting that preceded the European Society of Human Genetics 2011 Conference in Amsterdam. This article is the result of this meeting and explores the introduction of genome-wide arrays into routine prenatal diagnosis. We aim to give some general recommendations on how to develop practical guidelines that can be implemented in the local setting and that are consistent with the emerging international consensus. Hum Mutat 33:923–929, 2012.