CRG; HH5; IS3; KAL5
The CHD7 gene is associated with autosomal dominant CHARGE syndrome (MedGen UID: 75567) and Kallmann syndrome (MedGen UID: 102469).
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Invitae tests that include this gene:
The CHD7 gene encodes a chromodomain helicase DNA-binding protein, which regulates gene expression by chromatin remodeling and is essential for proper neural-crest formation during development.
The CHD7 gene is associated with autosomal dominant CHARGE syndrome, a highly variable disorder affecting many parts of the body with characteristic features, including ocular coloboma, heart defects, choanal atresia, retarded growth and development, genital abnormalities, and ear anomalies (PMID: 17299439, 21378379). The acronym CHARGE refers to a set of non-random congenital malformations: coloboma of the eye, heart malformation, atresia of the choanae, retarded growth and/or development, genital hypoplasia, and ear anomalies (PMID: 9545604).
More specifically, individuals with CHARGE syndrome tend to have bilateral ocular colobomas involving the chorioretina and optic nerve, which can result in visual field defects in the upper quadrant, refractive errors, severe myoptic astigmatism, anisometropia, microphthalmia, microcornea, and reduced visual acuity (PMID: 20186815). The heart defects associated with CHARGE include tetralogy of Fallot, patent ductus arteriosus, atrial septal defects, and solitary septal defects, all in varying combinations (PMID: 20186815). Choanal atresia is highly correlated with CHARGE and tends to be osseous and bilateral (PMID: 17299439). Other ear, nose, and throat anomalies include laryngeal cleft, subglottic stenosis, hyposmia, tracheomalacia, tracheoesophageal fistula, and cleft palate/lip (PMID: 20186815). Although choanal atresia is associated with CHARGE, it is not commonly found in conjunction with cleft palate (PMID: 16615981, 17299439). Growth defects include short stature and low birth weight (PMID: 16615981). Hypogonadotropic hypogonadism and delayed puberty can be seen in males, and hypoplasia of the uterus and labia can occur in females (PMID: 20186815). Hearing-related abnormalities associated with CHARGE include deafness, inner and external ear abnormalities, deficiency in at least one of the semicircular canals, and cochlear hypoplasia (PMID: 20186815, 16615981).
Pathogenic variants in CHD7 have been reported in individuals with Kallman syndrome, which is characterized by hypogonadotropic hypogonadism due to gonadotropin hormone deficiency and anosmia (impaired sense of smell; PMID: 16882753, 15001591). However, these individuals may also have additional features characteristic of CHARGE syndrome.
Due to the multiple life-threatening medical conditions present in individuals with CHARGE syndrome, infant mortality is high, and there is increased mortality and morbidity throughout childhood, adolescence, and adulthood (PMID: 20186815, 2317068, 29088501).
The CHD7 gene encodes a chromodomain helicase DNA-binding protein, which regulates gene expression by chromatin remodeling and is essential for proper neural crest formation during embryonic development (PMID: 20130577, 20591827). More specifically, the CHD7-encoded protein binds to enhancer elements and assists in the process of chromatin looping, which ultimately impacts transcriptional regulation by bringing the enhancer closer to the transcription start sites (PMID: 20186815). The characteristic features found in CHARGE syndrome are likely caused by the dysregulation of CHD7-targeted genes, which are responsible for the proliferation, differentiation, and migration of developing cell types and tissues, including eye, ear, heart, and the olfactory system (PMID: 20186815). Loss-of-function variants in CHD7 are known to be pathogenic (PMID: 16400610, 22461308).
CHD7 exhibits autosomal dominant inheritance. This means that an individual with a pathogenic variant has a 50% chance of passing the variant on to their offspring. Most individuals with CHARGE syndrome harbor a de novo pathogenic variant. However, in rare cases, a pathogenic variant may be inherited from a mildly affected parent (PMID: 17299439). Germline mosaicism has also been reported (PMID: 19475719).
Medical management for patients with CHARGE is improved by coordinated multidisciplinary care (PMID: 9545604, 2317068). Focus may be often placed on more severe, life-threatening health issues; however, it is important not to overlook minor features when treating patients with CHARGE (PMID: 29168326). The proposed management guidelines for CHARGE include the following.
Review date: March 2018
Invitae is a College of American Pathologists (CAP)-accredited and Clinical Laboratory Improvement Amendments (CLIA)-certified clinical diagnostic laboratory performing full-gene sequencing and deletion/duplication analysis using next-generation sequencing technology (NGS).
Our sequence analysis covers clinically important regions of each gene, including coding exons, +/- 10 base pairs of adjacent intronic sequence in the transcript listed below. In addition, analysis covers the select non-coding variants specifically defined in the table below. Any variants that fall outside these regions are not analyzed. Any specific limitations in the analysis of these genes are also listed in the table below.
Based on validation study results, this assay achieves >99% analytical sensitivity and specificity for single nucleotide variants, insertions and deletions <15bp in length, and exon-level deletions and duplications. Invitae's methods also detect insertions and deletions larger than 15bp but smaller than a full exon but sensitivity for these may be marginally reduced. Invitae’s deletion/duplication analysis determines copy number at a single exon resolution at virtually all targeted exons. However, in rare situations, single-exon copy number events may not be analyzed due to inherent sequence properties or isolated reduction in data quality. Certain types of variants, such as structural rearrangements (e.g. inversions, gene conversion events, translocations, etc.) or variants embedded in sequence with complex architecture (e.g. short tandem repeats or segmental duplications), may not be detected. Additionally, it may not be possible to fully resolve certain details about variants, such as mosaicism, phasing, or mapping ambiguity. Unless explicitly guaranteed, sequence changes in the promoter, non-coding exons, and other non-coding regions are not covered by this assay. Please consult the test definition on our website for details regarding regions or types of variants that are covered or excluded for this test. This report reflects the analysis of an extracted genomic DNA sample. In very rare cases, (circulating hematolymphoid neoplasm, bone marrow transplant, recent blood transfusion) the analyzed DNA may not represent the patient's constitutional genome.
|Gene||Transcript reference||Sequencing analysis||Deletion/Duplication analysis|