title: Auriculo-condylar syndrome: mapping of a first locus and evidence for genetic heterogeneity.
abstract: Auriculo-condylar syndrome (ACS), an autosomal dominant disorder of first and second pharyngeal arches, is characterized by malformed ears ('question mark ears'), prominent cheeks, microstomia, abnormal temporomandibular joint, and mandibular condyle hypoplasia. Penetrance seems to be complete, but there is high inter- and intra-familial phenotypic variation, with no evidence of genetic heterogeneity. We herein describe a new multigeneration family with 11 affected individuals (F1), in whom we confirm intra-familial clinical variability. Facial asymmetry, a clinical feature not highlighted in other ACS reports, was highly prevalent among the patients reported here. The gene responsible for ACS is still unknown and its identification will certainly contribute to the understanding of human craniofacial development. No chromosomal rearrangements have been associated with ACS, thus mapping and positional cloning is the best approach to identify this disease gene. To map the ACS gene, we conducted linkage analysis in two large ACS families, F1 and F2 (F2; reported elsewhere). Through segregation analysis, we first excluded three known loci associated with disorders of first and second pharyngeal arches (Treacher Collins syndrome, oculo-auriculo-vertebral spectrum, and Townes-Brocks syndrome). Next, we performed a wide genome search and we observed evidence of linkage to 1p21.1-q23.3 in F2 (LOD max 3.01 at theta=0). Interestingly, this locus was not linked to the phenotype segregating in F1. Therefore, our results led to the mapping of a first locus of ACS (ACS1) and also showed evidence for genetic heterogeneity, suggesting that there are at least two loci responsible for this phenotype.
authors.affiliation: Instituto de Biociências, Universidade de São Paulo, São Paulo, São Paulo, Brazil.
authors.forename: Cibele
authors.initials: C
authors.lastname: Masotti
authors.forename: Karina G
authors.initials: KG
authors.lastname: Oliveira
authors.forename: Fabiana
authors.initials: F
authors.lastname: Poerner
authors.forename: Alessandra
authors.initials: A
authors.lastname: Splendore
authors.forename: Josiane
authors.initials: J
authors.lastname: Souza
authors.forename: Renato da Silva
authors.initials: Rda S
authors.lastname: Freitas
authors.forename: Roseli
authors.initials: R
authors.lastname: Zechi-Ceide
authors.forename: Maria Leine
authors.initials: ML
authors.lastname: Guion-Almeida
authors.forename: Maria Rita
authors.initials: MR
authors.lastname: Passos-Bueno
mesh_terms: D002874:Chromosome Mapping; D002878:Chromosomes, Human, Pair 1 / Q000235:genetics; D004431:Ear, External / Q000002:abnormalities*; D005146:Facial Asymmetry / Q000151:congenital / Q000235:genetics; D005260:Female; D018740:Genetic Heterogeneity; D008040:Genetic Linkage; D005819:Genetic Markers; D006801:Humans; D008126:Lod Score; D008297:Male; D008335:Mandibular Condyle / Q000002:abnormalities*; D010375:Pedigree; D013577:Syndrome
chemical_list: D005819:Genetic Markers