Nager syndrome (MIM #154400) is the best-known preaxial acrofacial dysostosis, mainly characterized by craniofacial and preaxial limb anomalies. The craniofacial abnormalities mainly consist of downslanting palpebral fissures, malar hypoplasia, micrognathia, external ear anomalies, and cleft palate. The preaxial limb defects are characterized by radial and thumb hypoplasia or aplasia, duplication of thumbs and proximal radioulnar synostosis. Haploinsufficiency of SF3B4 (MIM *605593), which encodes SAP49, a component of the pre-mRNA spliceosomal complex, has recently been identified as the underlying cause of Nager syndrome. In our study, we performed exome sequencing in two and Sanger sequencing of SF3B4 in further ten previously unreported patients with the clinical diagnosis of Nager syndrome, including one familial case. We identified heterozygous SF3B4 mutations in seven out of twelve patients. Four of the seven mutations were shown to be de novo; in three individuals, DNA of both parents was not available. No familial mutations were discovered. Three mutations were nonsense, three were frameshift mutations and one T > C transition destroyed the translation start signal. In three of four SF3B4 negative families, EFTUD2 was analyzed, but no pathogenic variants were identified. Our results indicate that the SF3B4 gene is mutated in about half of the patients with the clinical diagnosis of Nager syndrome and further support genetic heterogeneity for this condition.
Luquetti DV, Hing AV, Rieder MJ et al (2013) “Mandibulofacial dysostosis with microcephaly” caused by EFTUD2 mutations: expanding the phenotype. Am J Med Genet A 161:108–113. doi:10.1002/ajmg.a.35696CrossRefGoogle Scholar
Petit P, Moerman P, Fryns JP (1993) Nager acrofacial dysostosis and preaxial polydactyly: a further example with lethal outcome. Genet Couns 4:135–137PubMedGoogle Scholar
The Treacher Collins Syndrome Collaborative Group (1996) Positional cloning of a gene involved in the pathogenesis of Treacher Collins syndrome. Nat Genet 12:130–136. doi:10.1038/ng0296-130CrossRefGoogle Scholar
Wieczorek D, Gener B, González MJM et al (2009) Microcephaly, microtia, preauricular tags, choanal atresia and developmental delay in three unrelated patients: a mandibulofacial dysostosis distinct from Treacher Collins syndrome. Am J Med Genet A 149A:837–843. doi:10.1002/ajmg.a.32747PubMedCrossRefGoogle Scholar