TY - JOUR T1 - New locus underlying auriculocondylar syndrome (ARCND): 430 kb duplication involving <em>TWIST1</em> regulatory elements JF - Journal of Medical Genetics JO - J Med Genet DO - 10.1136/jmedgenet-2021-107825 SP - jmedgenet-2021-107825 AU - Vanessa Luiza Romanelli Tavares AU - Sofia Ligia Guimarães-Ramos AU - Yan Zhou AU - Cibele Masotti AU - Suzana Ezquina AU - Danielle de Paula Moreira AU - Henk Buermans AU - Renato S Freitas AU - Johan T Den Dunnen AU - Stephen R F Twigg AU - Maria Rita Passos-Bueno Y1 - 2021/11/07 UR - http://jmg.bmj.com/content/early/2021/11/07/jmedgenet-2021-107825.abstract N2 - Background Auriculocondylar syndrome (ARCND) is a rare genetic disease that affects structures derived from the first and second pharyngeal arches, mainly resulting in micrognathia and auricular malformations. To date, pathogenic variants have been identified in three genes involved in the EDN1-DLX5/6 pathway (PLCB4, GNAI3 and EDN1) and some cases remain unsolved. Here we studied a large unsolved four-generation family.Methods We performed linkage analysis, resequencing and Capture-C to investigate the causative variant of this family. To test the pathogenicity of the CNV found, we modelled the disease in patient craniofacial progenitor cells, including induced pluripotent cell (iPSC)-derived neural crest and mesenchymal cells.Results This study highlights a fourth locus causative of ARCND, represented by a tandem duplication of 430 kb in a candidate region on chromosome 7 defined by linkage analysis. This duplication segregates with the disease in the family (LOD score=2.88) and includes HDAC9, which is located over 200 kb telomeric to the top candidate gene TWIST1. Notably, Capture-C analysis revealed multiple cis interactions between the TWIST1 promoter and possible regulatory elements within the duplicated region. Modelling of the disease revealed an increased expression of HDAC9 and its neighbouring gene, TWIST1, in neural crest cells. We also identified decreased migration of iPSC-derived neural crest cells together with dysregulation of osteogenic differentiation in iPSC-affected mesenchymal stem cells.Conclusion Our findings support the hypothesis that the 430 kb duplication is causative of the ARCND phenotype in this family and that deregulation of TWIST1 expression during craniofacial development can contribute to the phenotype.All data relevant to the study are included in the article or uploaded as supplementary information. ER -