Background
This web-based, locus-specific mutation database has been constructed to aid clinicians and scientists working in the field of CHARGE syndrome and the CHD7 gene. The database contains all published variants and unpublished variants can be submitted. The CHD7 mutation database can be searched for patients and their clinical phenotype or for mutations. It can be used as a central, quick reference database for anyone who encounters a variant in the CHD7gene. Mutations are numbered according to the current reference sequence (GenBank Accession no. NM017780.2). Mutation nomenclature is according to the HGVS recommendations. You are free to use the database for your studies. The software is based on the online patient registry for dystrophic epidermolysis bullosa (Van den Akker et al., 2011). -Please cite http://www.CHD7.org/ when using the database.

About CHARGE syndrome and the CHD7 gene
Heterozygous mutations and deletions of the CHD7 gene (OMIM 608892) result in CHARGE syndrome (OMIM 214800), a complex of multiple congenital malformations involving the central nervous system, eye, ear, nose and mediastinal organs (Vissers et al., 2004). CHARGE is an acronym (Pagon et al., 1981). Clinical features include coloboma, heart defect, choanal atresia, retarded growth and development, genital hypoplasia, ear anomalies, deafness and semicircular canal hypoplasia (Jongmans et al., 2006; Bergman et al., 2011). Based on these features, the clinical criteria for CHARGE syndrome have been defined by Blake et al. (1998) and Verloes (2005) (see table below). CHD7 analysis is a major contributor to the diagnosis today, although not all clinically diagnosed patients with CHARGE syndrome carry a mutation in this gene (Bergman et al., 2011;Jongmans et al., 2006; Lalani et al., 2006). On the contrary, even in patients who do not fulfill the clinical criteria, CHD7 mutations may be found (Bergman et al. 2011b).

Table. Clinical criteria for CHARGE syndrome

	Major criteria	Minor criteria	Inclusion rule
Blake	Ocular coloboma, microphthalmia Choanal atresia or stenosis* Characteristic external ear anomaly, middle/inner ear malformations, mixed deafness Cranial nerve dysfunction	Cardiovascular malformations Tracheo-esophageal defects Genital hypoplasia or delayed pubertal development Cleft lip and/or palate Developmental delay Growth retardation Characteristic face	Typical CHARGE: 4 major criteria OR 3 major + 3 minor
Verloes	Ocular coloboma Choanal atresia Hypoplastic semicircular canals	Heart or esophagus malformation Malformation of the middle or external ear Rhombencephalic dysfunction including sensorineural deafness Hypothalamo-hypophyseal dysfunction (gonadotropin or growth hormone deficiency) Mental retardation	Typical CHARGE: 3 major OR 2 major + 2 minor Partial CHARGE: 2 major + 1 minor Atypical CHARGE: 2 major OR 1 major + 3 minor

* Cleft palate can be substituted for choanal atresia, since these anomalies rarely occur together.

About the data
The CHD7 mutation database is maintained by the Department of Genetics, University Medical Center Groningen, the Netherlands. The database will be updated regularly with data from new publications and unpublished data. Updates will be announced in the News field on the homepage and in the News archives. The two institutes that are currently working together on this database are: ? Departments of Genetics, University Medical Center Groningen, Groningen, the Netherlands ? Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen, the Netherlands Please contact Dr. Nicole Corsten-Janssen if you need any assistance with the data or database (charge@umcg.nl)

Adding your unpublished data
The inclusion of unpublished data will improve the scope of the data and the use of the registry. It is highly recommended that new as well as previously reported variants are submitted to the database, because extra data will improve its value, e.g. for interpreting unclassified variants and phenotype-genotype correlations. For easy inclusion into the database we provide a template and supporting document on how to provide your unpublished data. Please send the filled out template to charge@umcg.nl if you would like to have it included in the database. All users who add unpublished data to our database will be mentioned in the News field on the homepage and in the News archive.

About curation of unpublished data
The curator is Dr. Nicole Corsten-Janssen, MD, Department of Genetics, University Medical Center Groningen, Groningen, the Netherlands. All submitted data will be checked and completed where necessary. If questions remain, we will contact the user who submitted the data.

About the software
The database software has been built using MOLGENIS (Swertz and Jansen, 2007; Swertz et al., 2010), a collaborative open source project on a mission to generate great software for life science research. MOLGENIS is being developed and maintained by the Genomics Coordination Center (GCC), a rapidly growing bioinformatics group of 25 researchers, programmers and system managers at the University of Groningen, University Medical Center Groningen, Dept of Genetics, lead by Prof.dr. Morris Swertz.

More information is available at http://www.molgenis.org, the project can be found on https://github.com/molgenis .

Please contact Morris Swertz, m.a.swertz@rug.nl if you need assistance.