Next-generation sequencing identifies a novel frameshift variant in FRMD7 in a Chinese family with idiopathic infantile nystagmus
JOURNAL OF CLINICAL LABORATORY ANALYSIS
Authors: Wang, Fengqi; Guan, Hongzai; Liu, Wenmiao; Zhao, Guiqiu; Liu, Shiguo
Abstract
Background Idiopathic infantile nystagmus (IIN) is a high genetically heterogeneous ophthalmic disease and is often associated with pathogenic mutations in FRMD7 and GPR143, respectively. Idiopathic infantile nystagmus manifests as involuntary periodic rhythmic oscillation of the eyes in the very early life, which decreases visual acuity and affects the quality of life. Objective and Methods The aim of our study was to reveal a possible pathogenic variant through the investigation of a Chinese Han family with IIN with an implementation of a next-generation sequencing method. Isolated DNA analysis was followed by Sanger sequencing validation. We also performed the detailed ophthalmological examination of family members. Results We identified a novel frameshift variant in FRMD7 (NM_194277.2: c.1419_1422dup, p.Tyr475fs), which leads to a frameshift mutation since tyrosine (Tyr) at 475 codon of FRMD7 protein (p.Tyr475fs) and co-segregates with IIN phenotype in this family. Conclusions We found a novel frameshift FRMD7 variant in a Chinese Han family, which may be causative variant for IIN and can further enrich the mutation spectrum and uncover the etiology of IIN.
Clinical and molecular findings of FRMD7 related congenital nystagmus as adifferential diagnosis of ocular albinism
OPHTHALMIC GENETICS
Authors: Michaud, Vincent; Defoort-Dhellemmes, Sabine; Drumare, Isabelle; Pennamen, Perrine; Plaisant, Claudio; Lasseaux, Eulalie; Arveiler, Benoit
Abstract
Background: Congenital nystagmus is one of the most common neuro-ophthalmological disorders. X chromosome-linked forms are associated with pathogenic variants of the GPR143 and FRMD7 genes.Materials and Methods: Patients' DNA was analyzed using a next-generation sequencing (NGS) panel of genes involved in albinism and related pathologies (TYR, OCA2, TYRP1, SLC45A2, SLC24A5, C10ORF11, GPR143, SLC38A8, HPS 1 to 10, LYST, MITF, FRMD7)Results: We report a 4 generation family with 5 affected members initially referred for molecular diagnosis of ocular albinism. A missense variant of FRMD7 was found in 3 affected cases and one female carrier. We show that the disease in the affected girl is due to skewed inactivation of the X chromosome.Conclusions: By compiling all the published cases we discuss the variable penetrance among females due to different types of mutation and to X-inactivation.