A Novel de Novo Mutation Within EFNB1 Gene in a Young Girl with Craniofrontonasal Syndrome

Abstract

Craniofrontonasal syndrome is mainly characterized by frontonasal dysplasia, telorbitism, a broad nasal root, and frequently a bifid nose and coronal craniosynostosis. Craniofrontonasal syndrome is an X-linked disorder with an unusual pattern of inheritance because heterozygous females are more severely affected than hemizygous males. The craniofrontonasal syndrome–causing gene is EFNB1, localized in the border region of chromosome Xq12 and Xq13.1, encoding for protein ephrin-B1. Here we aim to investigate the underlying genetic defect of a young girl with craniofrontonasal syndrome. The patient underwent surgical correction of her craniofacial deformities. Genetic analysis was carried out by polymerase chain reaction. Products of exon 2 of the EFNB1 gene were sequenced as well as digested with BpmI enzyme. A novel de novo missense mutation 373G>A was identified within the EFNB1 gene, leading to the replacement of glutamic acid at amino acid position 125 with lysine. The replacement of Glu125 with Lys, which lies within the G-H loop, part of the dimerization ligand-receptor interface, is expected to disrupt the interaction between the Eph receptor and ephrin B1 ligand, thus leading to craniofrontonasal syndrome.