Discovery and Functional Annotation of SIX6 Variants in Primary Open-Angle Glaucoma

Glaucoma is a leading cause of blindness worldwide. Primary open-angle glaucoma (POAG) is the most common subtype and is a complex trait with multigenic inheritance. Genome-wide association studies have previously identified a significant association between POAG and the SIX6 locus (rs10483727, odds ratio (OR) = 1.32, p = 3.87×10−11). SIX6 plays a role in ocular development and has been associated with the morphology of the optic nerve. We sequenced the SIX6 coding and regulatory regions in 262 POAG cases and 256 controls and identified six nonsynonymous coding variants, including five rare and one common variant, Asn141His (rs33912345), which was associated significantly with POAG (OR = 1.27, p = 4.2×10−10) in the NEIGHBOR/GLAUGEN datasets. These variants were tested in an in vivo Danio rerio (zebrafish) complementation assay to evaluate ocular metrics such as eye size and optic nerve structure. Five variants, found primarily in POAG cases, were hypomorphic or null, while the sixth variant, found only in controls, was benign. One variant in the SIX6 enhancer increased expression of SIX6 and disrupted its regulation. Finally, to our knowledge for the first time, we have identified a clinical feature in POAG patients that appears to be dependent upon SIX6 genotype: patients who are homozygous for the SIX6 risk allele (His141) have a statistically thinner retinal nerve fiber layer than patients homozygous for the SIX6 non-risk allele (Asn141). Our results, in combination with previous SIX6 work, lead us to hypothesize that SIX6 risk variants disrupt the development of the neural retina, leading to a reduced number of retinal ganglion cells, thereby increasing the risk of glaucoma-associated vision loss

Syphilis-Related Eye Disease Presenting as Bilateral Papilledema, Retinal Nerve Fiber Layer Hemorrhage, and Anterior Uveitis in a Penicillin-Allergic Patient

Purpose. Treponema pallidum is known as the “great masquerader” for its many presentations and ocular findings in patients who are infected and develop secondary and tertiary stage of syphilis. Syphilitic ocular manifestations include uveitis, chorioretinitis, retinitis, vasculitis, vitritis, and panuveitis all with or without decreased visual acuity. Human immunodeficiency virus (HIV) is known to expedite the progression of syphilis when patients are coinfected, thus compounding the potential ophthalmic presentations. This report summarizes the presentation, management, and clinical course of a patient with known HIV and penicillin allergy that presented with bilateral optic nerve edema, retinal hemorrhages, and iritis without vision loss

Large capsulorhexis related uveitis-glaucoma-hyphema syndrome managed by intraocular lens implant exchange and gonioscopy assisted transluminal trabeculotomy

Purpose: To report a case of uveitis-glaucoma-hyphema syndrome (UGHS) secondary to a large capsulorhexis with an intracaspular intraocular lens (IOL) managed with IOL exchange and gonioscopy assisted transluminal trabeculotomy (GATT). Case Report: A 73-year-old male patient presented with UGHS of the right eye in the setting of an intracapsular single-piece acrylic IOL with circumferential optic and partial haptics exposure due to a large capsulorhexis. In lieu of the patient's uncomplicated surgical history, subtle symptoms, and clinical findings, the diagnosis and referral was delayed until intraocular pressure reached a peak of 50 mmHg with recurrent anterior chamber cells. The patient underwent combined IOL exchange with placement of a 3-piece sulcus IOL and GATT, which finally resolved the UGHS. Conclusion: With respect to the increasing prevalence of intracapsular single-piece IOL implantation, it is important to recognize UGHS and thus fashion proper sized capsulorhexis to prevent this vision threatening complication. GATT may be considered to be one of the glaucoma surgeries combined with the IOL surgical procedures in UGHS

Effects of rho kinase inhibitors on intraocular pressure and aqueous humor dynamics in nonhuman primates and rabbits

Purpose: This study examines the effects of 2 Rho kinase inhibitors on intraocular pressure (IOP) and aqueous humor dynamics. Methods: IOPs of New Zealand albino rabbits with ocular normotension and cynomolgus macaques (nonhuman primate, NHP) with chronic unilateral laser-induced glaucoma were measured at baseline and periodically after a 9 a.m. dose of H-1152, Y-27632, or vehicle. In a separate group of NHPs, aqueous flow, outflow facility, uveoscleral outflow, and IOP were determined after treatment with Y-27632 or vehicle control. Results: Decreases in IOP were found in rabbits (n = 5) at 6 h after one dose of 2% Y-27632 (29%, P = 0.0002) or 1% H-1152 (35%, P = 0.0001), and in hypertensive eyes of NHPs (n = 7-9) at 3 h after one dose of 2% Y-27632 (35%, P = 0.005) or 1% H-1152 (51%, P = 0.0003). With 2 doses of 1% Y-27632 or vehicle in NHP hypertensive eyes (n = 12), significant drug effects were IOP reduction of 28% (P = 0.05) at 2.5 h after the second dose and increases in aqueous flow (36%; P = 0.013), uveoscleral outflow (59%, P = 0.008), and outflow facility (40%; P = 0.01). In normotensive eyes of the same animals, aqueous flow increased by 21% (P = 0.03). No significant change was found in any of the other parameters. Conclusions: Y-27632 and H-1152 lower IOP in rabbits and hypertensive eyes of NHPs for at least 6 h after single doses. The Y-27632 effect on IOP in hypertensive NHP eyes is caused by increases in outflow facility and uveoscleral outflow. An increase in aqueous humor formation attenuates but does not prevent an IOP decrease

<i>In vivo</i> zebrafish morpholino complementation assay showing the effect of <i>SIX6</i> nonsynonymous variants.

<p>Zebrafish embryos were microinjected with a translation blocking morpholino designed to target <i>six6a</i>. Total eye size (µm²) was measured 3 days post fertilization. Compared to the uninjected controls, morphants showed a significant reduction in eye size. Zebrafish were co-injected with the morpholino and a human <i>SIX6</i> allele (Glu93Gln, Glu129Lys, Asn141His, Leu205Arg, Thr212Met, or Ser242IIe). Results of each allele were compared to the <i>SIX6</i> non-risk allele (Ref). P-values are provided below the mean of each treatment.</p

<i>SIX6</i> variants identified by sequencing POAG cases and controls.

<p>Coordinates are based on the Hg19 reference; MAF = minor allele frequency;</p><p>AA = amino acid; GERP = Genomic Evolutionary Rate Profiling.</p

OCT measurements from POAG cases homozygous for rs33912345.

<p>SD = standard deviation; OCT = optical coherence tomography.</p

Functional evaluation of <i>SIX6</i> variants on the volume of the optic nerve.

<p>Representative whole mount images of acetylated-tubulin expression in the heads of zebrafish embryos injected with a control or <i>six6a</i> morpholino, rescued by co-injection with human non-risk SIX6 transcript or a transcript containing the Leu205Arg hypomorphic variant (A). Acetylated-tubulin staining is restricted primarily to axon tracts and can be used to visualize the optic nerve. Relative to the control morphants, volumetric regions of interest (ROI) along the optic nerve in <i>six6a</i> morphants were reduced significantly. Co-injection of human variants revealed a hypomorphic (Leu205Arg, Asn141His) or benign (Glu93Gln) role of the variants on the optic nerve (B). Sample size for all injection paradigms ranged from 7–9 and p-values are plotted for each comparison (*** p<0.001; ** p<0.01). No significant changes in the volume of other axonal tracts in the head (marked by an asterisk) were detected. Standard error of the mean is shown and white scale bars = 20 um.</p