To assess if ripasudil has a neuroprotective effect using mice with excitatory amino acid carrier 1 (EAAC1) deletion (EAAC1 knockout [KO] mice), a mouse model of normal tension glaucoma.
Many genome-wide association studies have identified common single nucleotide polymorphisms (SNPs) at the 9p21 glaucoma locus (CDKN2B/CDKN2B-AS1) to be significantly associated with primary open-angle glaucoma (POAG), with association being stronger in normal tension glaucoma (NTG) and advanced glaucoma.
Japanese patients with NTG (n = 213) and HTG (n = 212) and 191 control subjects were genotyped for 5 non-IOP-related genetic variants predisposing to POAG near the SRBD1, ELOVL5, CDKN2B/CDKN2B-AS1, SIX1/SIX6, and ATOH7 genes.
CDKN2B and CDKN2B-AS1 promoter methylation was measured quantitatively using the MassCleave assay, and assessed for association with the disease, and the genotype of the associated risk variants using IBM SPSS statistics 22.0 CpG sites at which methylation status was associated with NTG were validated using pyrosequencing.
The myocilin (MYOC) and optineurin (OPTN) genes were directly sequenced in 112 unrelated patients, including 17 with primary open‑angle glaucoma, 19 with juvenile open‑angle glaucoma, and 76 with normal tension glaucoma.
The optineurin (OPTN) E50K mutation was first identified in familial primary open-angle glaucoma (POAG), the onset of which is not associated with intraocular pressure (IOP) elevation, and is classified as normal-tension glaucoma (NTG).
Results suggested that genetic variation in five of the candidate genes (RDX, SNX16, OPA1, SOD2 and CYP1B1) is unlikely to confer major risk to develop normal tension glaucoma in the German population.
We then subdivided the case groups into two subtypes based on the value of intraocular pressure (IOP)--POAG with high IOP (high pressure glaucoma, HPG) and that with normal IOP (normal pressure glaucoma, NPG)--and performed the GWAS using the two data sets, as the prevalence of NPG in Japanese is much higher than in Caucasians.
The association of the allelic variation (Met98Lys) in the OPTN gene and the prevalence of POAG and NTG in unrelated Japanese patients suggest that they are involved in the pathogenesis of POAG and NTG.
In this study, subjects with glaucoma who had the OPTNE50K mutation were found to have NTG that appeared to be more severe than that in a control group of subjects with NTG without this mutation.
We have refined the previously reported association between OPA1 sequence changes and NTG by identifying a specific CC genotype at position +32 in IVS8 of the OPA1 gene that acts as a marker for NTG.
In this manuscript, we focus on the OPTN E50K mutation, the most common mutation for NTG, to describe the molecular mechanism of NTG by expressing a mutant Optn gene in cells and genetically modified mice.
Further, the TBK1 copy number variation segregated with normal-tension glaucoma in the family members of the probands, showing an autosomal dominant pattern of inheritance.