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Differences of ocular oscillations and neuro-retinal structures in patients with nystagmus caused by GPR143 and FRMD7
Lijuan Huang1, Biru Xu1, Ningdong Li1,2
1Department of Ophthalmology, The Second Affiliated Hospital of Fujian Medical University, Quanzhou, China.
Insights
Congenital nystagmus (CN) caused by GPR143 and FRMD7 gene mutations show similar ocular oscillations but differ in retinal and visual pathway changes. Clinical and electrophysiological tests aid in differentiating these genetic causes of nystagmus.
Area of Science:
- Ophthalmology
- Genetics
- Neuroscience
Background:
- Congenital nystagmus (CN) is an involuntary eye movement disorder often presenting in infancy.
- Mutations in G protein-coupled receptor 143 (GPR143) and FERM domain containing 7 (FRMD7) are known genetic causes of CN.
- Understanding genotype-phenotype correlations is crucial for diagnosis and management.
Purpose of the Study:
- To compare ocular oscillations in patients with GPR143 versus FRMD7 gene mutations causing CN.
- To investigate differences in retinal structure, function, and visual pathway integrity between these patient groups.
- To identify novel variants expanding the known mutation spectrum for GPR143 and FRMD7.
Main Methods:
- Retrospective review of medical records for CN patients with confirmed GPR143 or FRMD7 mutations (Jan 2018-May 2023).
- Ocular oscillation parameters recorded using Eyelink 1000 Plus.
- Retinal structure/function assessed via optical coherence tomography and multi-focal electroretinography (mERG).
- Visual pathway evaluation using visual evoked potentials (VEP); genetic analysis via next-generation sequencing.
Main Results:
- Foveal hypoplasia observed exclusively in the GPR143 mutation group.
- mERG revealed flat response topography in GPR143 patients compared to FRMD7 patients.
- VEP indicated bilateral amplitude inconsistency solely in the GPR143 mutation group.
- Ocular oscillation amplitude and frequency did not significantly differ between the two genetic groups.
Conclusions:
- Despite distinct etiologies, GPR143 and FRMD7 mutations can lead to similar ocular oscillation patterns in CN.
- Clinical examination and electrophysiological testing are vital for differential diagnosis.
- The study expands the known spectrum of GPR143 and FRMD7 variants associated with congenital nystagmus.
Purpose:
Mutations of G protein-coupled receptor 143 (GPR143) and FERM domain containing 7 (FRMD7) may result in congenital nystagmus (CN) in the first 6 months of life. We aimed to compare the differences in ocular oscillations between patients with these two gene mutations as well as the functional and structural changes in their retinas and visual pathways.
Methods:
Medical records were retrospectively reviewed to identify patients of congenital nystagmus with confirmed mutations in either GPR143 or FMRD7 genes from January 2018 to May 2023. The parameters of the ocular oscillations were recorded using Eyelink 1000 Plus. The retinal structure and function were evaluated using optical coherence tomography and multi-focal electroretinography (mERG). The visual pathway and optical nerve projection were evaluated using visual evoked potentials. The next-generation sequencing technique was used to identify the pathogenic variations in the disease-causing genes for CN.
Results:
Twenty nystagmus patients of GPR143 and 21 patients of FMRD7 who had been confirmed by molecular testing between January 2018 and May 2023 were included. Foveal hypoplasia was detected only in patients with the GPR143 pathogenic variant. mERG examination showed a flat response topography in the GPR143 group compared to the FRMD7 group. VEP showed that bilateral amplitude inconsistency was detected only in the patients with GPR143 gene mutation. The amplitude and frequency of the ocular oscillations were not found to differ between patients with two different genetic mutations.
Conclusions:
Although the etiology and molecular mechanisms are completely different between CN patients, they may have similar ocular oscillations. A careful clinical examination and electrophysiological test will be helpful in making a differential diagnosis. Our novel identified variants will further expand the spectrum of the GPR143 and FRMD7 variants.
