Role of Chd7 in Zebrafish: A Model for CHARGE Syndrome Shunmoogum A. Patten1,2., Nicole L. Jacobs-McDaniels3., Charlotte Zaouter1, Pierre Drapeau4, R. Craig Albertson3,5, Florina Moldovan1,2* 1 Sainte-Justine Hospital Research Center, Montreal, Quebec, Canada, 2 Faculty of Dentistry, University of Montreal, Montreal, Quebec, Canada, 3 Department of Biology, Syracuse University, Syracuse, New York, USA, 4 Department of Pathology and Cell Biology, Faculty of Medicine, University of Montreal, Montreal, Quebec, Canada, 5 Department of Biology, University of Massachusetts, Amherst, Massachusetts, USA Abstract CHARGE syndrome is caused by mutations in the CHD7 gene. Several organ systems including the retina, cranial nerves, inner ear and heart are affected in CHARGE syndrome. However, the mechanistic link between mutations in CHD7 and many of the organ systems dysfunction remains elusive. Here, we show that Chd7 is required for the organization of the neural retina in zebrafish. We observe an abnormal expression or a complete absence of molecular markers for the retinal ganglion cells and photoreceptors, indicating that Chd7 regulates the differentiation of retinal cells and plays an essential role in retinal cell development. In addition, zebrafish with reduced Chd7 display an abnormal organization and clustering of cranial motor neurons. We also note a pronounced reduction in the facial branchiomotor neurons and the vagal motor neurons display aberrant positioning. Further, these fish exhibit a severe loss of the facial nerves. Knock-down of Chd7 results in a curvature of the long body axis and these fish develop irregular shaped vertebrae and have a reduction in bone mineralization. Chd7 knockdown also results in a loss of proper segment polarity illustrated by flawed efnb2a and ttna expression, which is associated with later vascular segmentation defects. These critical roles for Chd7 in retinal and vertebral development were previously unrecognized and our results provide new insights into the role of Chd7 during development and in CHARGE syndrome pathogenesis. Citation: Patten SA, Jacobs-McDaniels NL, Zaouter C, Drapeau P, Albertson RC, et al. (2012) Role of Chd7 in Zebrafish: A Model for CHARGE Syndrome. PLoS ONE 7(2): e31650. doi:10.1371/journal.pone.0031650 Editor: Christoph Winkler, National University of Singapore, Singapore Received August 10, 2011; Accepted January 10, 2012; Published February 20, 2012 Copyright: 2012 Patten et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: Dr. Moldovan was supported by Yves Cotrel Foundation and Dr. Patten was supported by CHU Sainte-Justine and Foundation of the Stars scholarship. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: florina.moldovan@umontreal.ca . These authors contributed equally to this work. Introduction Mutations in the CHD7 gene (NM_017780) in 8q12.1 were identified as causative for CHARGE (Coloboma, Heart defects, Atresia of the choanae, Retarded growth and development, Genital hypoplasia, Ear anomalies; OMIM # 214800)) syndrome [1,2,3,4,5]. Heterozygosity for nonsense, deletion or missense CHD7 mutations is estimated to occur in 60–80% of patients with CHARGE syndrome; these mutations are distributed throughout the coding sequence and do not appear to be correlated with specific aspects of the clinical phenotype [6,7,8]. The majority of CHD7 mutations identified thus far are de novo; however, evidence for germline mosaicism has been suggested for families with multiple affected siblings [9] . Children affected by CHARGE syndrome have a variable association of features including ocular deficits, heart malfunctioning, olfactory dysfunction, retarded growth, vestibular dysfunction, cranial nerve anomalies and intellectual disability [2,4,10]. All of these characteristics have variable degrees of penetrance, with some being present in virtually all CHARGE patients, whereas others are less frequently observed [11]. Although there is clear evidence that mutations in CHD7 gene are causative in CHARGE syndrome, the pathogenic mechanisms elicited by these mutations that lead to organs and systems dysfunction are not fully understood. Chd7 is one of nine members of the chromodomain helicase DNA- binding (Chd) domain family of ATP-dependent chromatin remodeling enzymes [12]. It consists of functional domains such as a chromatin organization modifier, SNF2-related helicase/ ATPase and BRK [12,13]. Recently, DNA-binding sites on chromatin have shown that chd7 binding is correlated to areas of mono- and dimethylated lysine 4 of histone H3 [14,15]. The Chd7 Drosophila ortholog, Kismet down-regulates transcriptional elonga- tion by RNA polymerase II through the recruitment of ASH1 and TRX and may be involved in the maintenance of stem cell pluripotency by regulating methylation of histone H3 lysine 27. Chd7 is also implicated in cell fate specification of mesenchymal stem cells [16] . During osteoblast and adipocyte differentiation, Chd7 forms a complex with NLK, SETDB1 and PPAR-c, then binds to histone H3 at PPAR-c target promoters and suppresses ligand-induced transactivation of PPAR-c target genes, which leads to a change in cell fate [16] . Recently, Chd7 has been shown act synergistically with PBAF to promote neural crest gene expression and cell migration [17]. Thus, Chd7 is thought to play a variety of essential roles during development in many species. PLoS ONE | www.plosone.org 1 February 2012 | Volume 7 | Issue 2 | e31650