A start codon mutation of the FRMD7 gene in two Korean families with idiopathic infantile nystagmus.
Idiopathic infantile nystagmus (IIN) is the involuntary oscillation of the eyes with onset in the first few months of life. The most common form of inheritance is X-linked, and mutations in FRMD7 gene are a major cause. To identify the FRMD7 gene mutations associated with X-linked IIN, we performed PCR-based DNA direct sequencing in 4 affected subjects from 2 Korean families. We also assessed structural abnormalities of retina and optic nerve head using optical coherence tomography (OCT). Genetic analysis revealed a A>G transversion at nucleotide c.1, the first base of the start codon. This mutation leads to the loss of the primary start codon ATG for methionine, which is replaced by a triplet GTG for valine. The alternative in-frame start codon is not present around a mutation. OCT revealed the morphological changes within the optic nerve head, including shallow cup depth and small cup-to-disc ratio. In summary, we identified a novel start codon mutation within the FRMD7 gene of 2 Korean families. Our data expands the mutation spectrum of FRMD7 causing IIN. We also demonstrated abnormal developments of afferent system in patients with FRMD7 mutations using OCT, which may help to understand the etiological factor in development of nystagmus.
Department of Neurology, Pusan National University School of Medicine, Research Institute for Convergence of Biomedical Science and Technology, Pusan National University Yangsan Hospital, Yangsan, Korea.
Jae-Hwan
JH
Choi
Department of Neurology, Pusan National University School of Medicine, Research Institute for Convergence of Biomedical Science and Technology, Pusan National University Yangsan Hospital, Yangsan, Korea.
Jin-Hong
JH
Shin
Department of Ophthalmology, Pusan National University School of Medicine, Research Institute for Convergence of Biomedical Science and Technology, Pusan National University Yangsan Hospital, Yangsan, Korea.
Je Hyun
JH
Seo
Department of Ophthalmology, Pusan National University School of Medicine, Research Institute for Convergence of Biomedical Science and Technology, Pusan National University Yangsan Hospital, Yangsan, Korea.
Jae-Ho
JH
Jung
Department of Neurology, Pusan National University Hospital, Pusan National University School of Medicine and Biomedical Research Institute, Busan, Korea.
Kwang-Dong
KD
Choi
D000328:Adult; D001483:Base Sequence; D002648:Child; D002675:Child, Preschool; D018387:Codon, Initiator / Q000235:genetics; D003598:Cytoskeletal Proteins / Q000235:genetics*; D005260:Female; D040181:Genetic Diseases, X-Linked / Q000000981:diagnostic imaging / Q000235:genetics* / Q000473:pathology; D006801:Humans; D008297:Male; D008565:Membrane Proteins / Q000235:genetics*; D009154:Mutation / Q000235:genetics*; D020417:Nystagmus, Congenital / Q000000981:diagnostic imaging / Q000235:genetics* / Q000473:pathology; D009900:Optic Nerve / Q000000981:diagnostic imaging / Q000473:pathology; D010375:Pedigree; D011859:Radiography; D056910:Republic of Korea; D041623:Tomography, Optical Coherence
D018387:Codon, Initiator; D003598:Cytoskeletal Proteins; C516168:FRMD7 protein, human; D008565:Membrane Proteins