A multi-cohort genome-wide association study in African ancestry individuals reveals risk loci for primary open-angle glaucoma.

Primary open-angle glaucoma (POAG), the leading cause of irreversible blindness worldwide, disproportionately affects individuals of African ancestry. We conducted a genome-wide association study (GWAS) for POAG in 11,275 individuals of African ancestry (6,003 cases; 5,272 controls). We detected 46 risk loci associated with POAG at genome-wide significance. Replication and post-GWAS analyses, including functionally informed fine-mapping, multiple trait co-localization, and in silico validation, implicated two previously undescribed variants (rs1666698 mapping to DBF4P2; rs34957764 mapping to ROCK1P1) and one previously associated variant (rs11824032 mapping to ARHGEF12) as likely causal. For individuals of African ancestry, a polygenic risk score (PRS) for POAG from our mega-analysis (African ancestry individuals) outperformed a PRS from summary statistics of a much larger GWAS derived from European ancestry individuals. This study quantifies the genetic architecture similarities and differences between African and non-African ancestry populations for this blinding disease.

Therapeutic targeting of the complement system in ocular disease.

The complement system is involved in the pathogenesis of several ocular diseases, providing a rationale for the investigation of complement-targeting therapeutics for these conditions. Dry age-related macular degeneration, as characterised by geographic atrophy (GA), is currently the most active area of research for complement-targeting therapeutics, with a complement C3 inhibitor approved in the United States earlier this year marking the first approved therapy for GA. This review discusses the role of complement in ocular disease, provides an overview of the complement-targeting agents currently under development for ocular conditions, and reflects on the lessons that can be learned from the preclinical investigations and clinical trials conducted in this field to date.

IL-22 receptor signaling in Paneth cells is critical for their maturation, microbiota colonization, Th17-related immune responses, and anti-Salmonella immunity.

Interleukin-22 (IL-22) signaling in the intestines is critical for promoting tissue-protective functions. However, since a diverse array of cell types (absorptive and secretory epithelium as well as stem cells) express IL-22Ra1, a receptor for IL-22, it has been difficult to determine what cell type(s) specifically respond to IL-22 to mediate intestinal mucosal host defense. Here, we report that IL-22 signaling in the small intestine is positively correlated with Paneth cell differentiation programs. Our Il22Ra1fl/fl;Lgr5-EGFP-creERT2-specific knockout mice and, independently, our lineage-tracing findings rule out the involvement of Lgr5+ intestinal stem cell (ISC)-dependent IL-22Ra1 signaling in regulating the lineage commitment of epithelial cells, including Paneth cells. Using novel Paneth cell-specific IL-22Ra1 knockout mice (Il22Ra1fl/fl;Defa6-cre), we show that IL-22 signaling in Paneth cells is required for small intestinal host defense. We show that Paneth cell maturation, antimicrobial effector function, expression of specific WNTs, and organoid morphogenesis are dependent on cell-intrinsic IL-22Ra1 signaling. Furthermore, IL-22 signaling in Paneth cells regulates the intestinal commensal bacteria and microbiota-dependent IL-17A immune responses. Finally, we show ISC and, independently, Paneth cell-specific IL-22Ra1 signaling are critical for providing immunity against Salmonella enterica serovar Typhimurium. Collectively, our findings illustrate a previously unknown role of IL-22 in Paneth cell-mediated small intestinal host defense.

Molecular Genetics and Functional Analysis Implicate CDKN2BAS1-CDKN2B Involvement in POAG Pathogenesis.

The genes in the 9p21 locus (CDKN2B-AS1 & CDKN2B) are widely associated with Primary open-angle glaucoma (POAG). However, the functional importance of this locus in POAG pathogenesis is still unexplored. This study investigated the role of CDKN2BAS1-CDKN2B axis in POAG. We observed significant association of CDKN2B-AS1 SNP rs4977756 with POAG and its endophenotypic traits (vertical cup-disc ratio (p = 0.033) and central corneal thickness (p = 0.008)) by screening African American POAG cases (n = 1567) and controls (n = 1600). A luciferase reporter assay in Human embryonic kidney 293T (HEK293T) cells revealed that the region surrounding rs4977756 likely serves as a transcriptional repressor. siRNA-mediated knockdown of CDKN2B-AS1 in HEK293T cells and trabecular meshwork (TM) cells resulted in significantly increased expression of CDKN2B, which was also observed in human POAG ocular tissues. Pathway focused qRT-PCR gene expression analysis showed increased cellular senescence, TGFß signaling and ECM deposition in TM cells after CDKN2B-AS1 suppression. In conclusion, we report that CDKN2B-AS1 may act as a regulator, and it could function by modulating the expression of CDKN2B. In addition, increase in CDKN2B levels due to CDKN2B-AS1 suppression may result in the senescence of trabecular meshwork cells leading to POAG pathogenesis.

Dual SMAD inhibition and Wnt inhibition enable efficient and reproducible differentiations of induced pluripotent stem cells into retinal ganglion cells.

Glaucoma is a group of progressive optic neuropathies that share common biological and clinical characteristics including irreversible changes to the optic nerve and visual field loss caused by the death of retinal ganglion cells (RGCs). The loss of RGCs manifests as characteristic cupping or optic nerve degeneration, resulting in visual field loss in patients with Glaucoma. Published studies on in vitro RGC differentiation from stem cells utilized classical RGC signaling pathways mimicking retinal development in vivo. Although many strategies allowed for the generation of RGCs, increased variability between experiments and lower yield hampered the cross comparison between individual lines and between experiments. To address this critical need, we developed a reproducible chemically defined in vitro methodology for generating retinal progenitor cell (RPC) populations from iPSCs, that are efficiently directed towards RGC lineage. Using this method, we reproducibly differentiated iPSCs into RGCs with greater than 80% purity, without any genetic modifications. We used small molecules and peptide modulators to inhibit BMP, TGF-ß (SMAD), and canonical Wnt pathways that reduced variability between iPSC lines and yielded functional and mature iPSC-RGCs. Using CD90.2 antibody and Magnetic Activated Cell Sorter (MACS) technique, we successfully purified Thy-1 positive RGCs with nearly 95% purity.

Differential interference contrast microscopy with adjustable plastic Sanderson prisms.

Differential interference contrast (DIC) microscopy is a technique to image spatially dependent gradients in optical path lengths. Contrast is produced through the splitting of polarized light with quartz Wollaston prisms. Here we demonstrate that light splitting for DIC microscopy can also be achieved with Sanderson prisms consisting of polycarbonate bars under a bending load. Comparable image contrast while imaging cultured cells was achieved with this alternative technique. These results demonstrate an inexpensive and easily adjustable alternative to traditional quartz Wollaston prisms.

SNP located in an AluJb repeat downstream of TMCO1, rs4657473, is protective for POAG in African Americans.

AIMS: To determine the association of single nucleotide polymorphisms (SNPs) downstream from the TMCO1 gene with primary open-angle glaucoma (POAG) in African Americans (AA). METHODS: AA subjects were recruited for the Primary Open-Angle African American Glaucoma Genetics (POAAGG) study from the Scheie Eye Institute and its satellite sites in Philadelphia. A region containing an AluJb repeat and seven SNPs, including rs4656461 near the TMCO1 gene, were PCR-Sanger sequenced from POAAGG cases (n=1537) and controls (n=1570). Association between POAG and SNPs near TMCO1 was investigated by logistic regression analysis. Phenotypic trait associations with these SNPs were assessed by analysis of variance. Electrophoretic mobility shift assay (EMSA) was performed to assess the affinity of human T-box 5 (TBX5) protein for a predicted binding motif in the TMCO1 region. Dual Luciferase assays were performed by transfecting recombinant plasmids containing the region surrounding the above SNPs in HEK293T and trabecular meshwork cells. RESULTS: The SNP rs4657473 (C>T) was associated with POAG; the TT genotype was protective (OR 0.20, 95% CI 0.09 to 0.42; p<0.001). No significant associations were found between the TMCO1 variants and phenotypic traits. EMSA confirmed the affinity of TBX5 for a predicted binding motif containing TMCO1 SNP rs4657475. Luciferase assays demonstrated a regulatory function for the genomic region around SNP rs4656561, located within AluJb repeat. CONCLUSION: Our results demonstrate that a SNP downstream of TMCO1, rs4657473, is associated with POAG in an AA population. Our studies suggest a regulatory role for the previously POAG-associated locus near the TMCO1 gene that may affect gene expression.

Whole-genome methylation profiling of the retinal pigment epithelium of individuals with age-related macular degeneration reveals differential methylation of the SKI, GTF2H4, and TNXB genes.

BACKGROUND: Age-related macular degeneration (AMD) is a degenerative disorder of the central retina and the foremost cause of blindness. The retinal pigment epithelium (RPE) is a primary site of disease pathogenesis. The genetic basis of AMD is relatively well understood; however, this knowledge is yet to yield a treatment for the most prevalent non-neovascular disease forms. Therefore, tissue-specific epigenetic mechanisms of gene regulation are of considerable interest in AMD. We aimed to identify differentially methylated genes associated with AMD in the RPE and differentiate local DNA methylation aberrations from global DNA methylation changes, as local DNA methylation changes may be more amenable to therapeutic manipulation. METHODS: Epigenome-wide association study and targeted gene expression profiling were carried out in RPE cells from eyes of human donors. We performed genome-wide DNA methylation profiling (Illumina 450k BeadChip array) on RPE cells from 44 human donor eyes (25 AMD and 19 normal controls). We validated the findings using bisulfite pyrosequencing in 55 RPE samples (30 AMD and 25 normal controls) including technical (n = 38) and independent replicate samples (n = 17). Long interspersed nucleotide element 1 (LINE-1) analysis was then applied to assess global DNA methylation changes in the RPE. RT-qPCR on independent donor RPE samples was performed to assess gene expression changes. RESULTS: Genome-wide DNA methylation profiling identified differential methylation of multiple loci including the SKI proto-oncogene (SKI) (p = 1.18 × 10-9), general transcription factor IIH subunit H4 (GTF2H4) (p = 7.03 × 10-7), and Tenascin X (TNXB) (p = 6.30 × 10-6) genes in AMD. Bisulfite pyrosequencing validated the differentially methylated locus cg18934822 in SKI, and cg22508626 within GTF2H4, and excluded global DNA methylation changes in the RPE in AMD. We further demonstrated the differential expression of SKI, GTF2H4, and TNXB in the RPE of independent AMD donors. CONCLUSIONS: We report the largest genome-wide methylation analysis of RPE in AMD along with associated gene expression changes to date, for the first-time reaching genome-wide significance, and identified novel targets for functional and future therapeutic intervention studies. The novel differentially methylated genes SKI and GTF2H4 have not been previously associated with AMD, and regulate disease pathways implicated in AMD, including TGF beta signaling (SKI) and transcription-dependent DNA repair mechanisms (GTF2H4).

Mutation spectrum of NDP, FZD4 and TSPAN12 genes in Indian patients with retinopathy of prematurity.

AIM: Retinopathy of prematurity (ROP) is a vasoproliferative eye disease in preterm infants. Based on its phenotypic similarities with familial exudative vitreo retinopathy (FEVR), the present study was conducted to screen the Norrin signalling pathway genes (already been implicated in FEVR) for understanding their involvement among Indian patients with ROP. METHODS: The study cohort consisted of patients with ROP (n=246) and controls (n=300) that included full term (n=110) and preterm babies devoid of ROP (n=190). Screening of the NDP, FZD4, TSPAN12 genes were accomplished by resequencing the entire coding and untranslated regions (UTR). The genotype data of the patients with ROP were analysed in the background of their clinical manifestations and further analysed in conjunction with other available data on these genes worldwide. RESULTS: Two novel variants in intron 1 (IVS1 +16A>G) and 3'UTR (c.5 22T>C) along with a previously reported change in the 5'UTR (c.395_409del14bp) were observed in the NDP gene in three patients with ROP. Screening of the FZD4 revealed four heterozygous variants, p.(Pro33Ser), p.(Pro168Ser), p.(Ile192Ile) and p.(Ile360Val), a compound heterozygous (p.(Pro33Ser)/p.(Pro168Ser)) and a 3'UTR (c*G>T) variants in the study cohort. Variants p.(Pro33Ser) and p.(Pro168Ser) were found to be significantly associated with ROP. A heterozygous variant p.(Leu119Arg) in TSPAN12 gene was observed in a patient with threshold ROP. However, a formal genotype-phenotype correlation could not be established due to the low frequencies of the variant alleles in these genes. CONCLUSIONS: This is a first study that revealed association of few variants in Norrin signalling genes among Indian patients with ROP that warrants further detailed investigation worldwide.

Angiopoietin receptor TEK interacts with CYP1B1 in primary congenital glaucoma.

Primary congenital glaucoma (PCG) is a severe autosomal recessive ocular disorder associated with considerable clinical and genetic heterogeneity. Recently, rare heterozygous alleles in the angiopoietin receptor-encoding gene TEK were implicated in PCG. We undertook this study to ascertain the second mutant allele in a large cohort (n = 337) of autosomal recessive PCG cases that carried heterozygous TEK mutations. Our investigations revealed 12 rare heterozygous missense mutations in TEK by targeted sequencing. Interestingly, four of these TEK mutations (p.E103D, p.I148T, p.Q214P, and p.G743A) co-occurred with three heterozygous mutations in another major PCG gene CYP1B1 (p.A115P, p.E229K, and p.R368H) in five families. The parents of these probands harbored either of the heterozygous TEK or CYP1B1 alleles and were asymptomatic, indicating a potential digenic mode of inheritance. Furthermore, we ascertained the interactions of TEK and CYP1B1 by co-transfection and pull-down assays in HEK293 cells. Ligand responsiveness of the wild-type and mutant TEK proteins was assessed in HUVECs using immunofluorescence analysis. We observed that recombinant TEK and CYP1B1 proteins interact with each other, while the disease-associated allelic combinations of TEK (p.E103D)::CYP1B1 (p.A115P), TEK (p.Q214P)::CYP1B1 (p.E229K), and TEK (p.I148T)::CYP1B1 (p.R368H) exhibit perturbed interaction. The mutations also diminished the ability of TEK to respond to ligand stimulation, indicating perturbed TEK signaling. Overall, our data suggest that interaction of TEK and CYP1B1 contributes to PCG pathogenesis and argue that TEK-CYP1B1 may perform overlapping as well as distinct functions in manifesting the disease etiology.

Abnormal Complement Activation and Inflammation in the Pathogenesis of Retinopathy of Prematurity.

Retinopathy of prematurity (ROP) is a neurovascular complication in preterm babies, leading to severe visual impairment, but the underlying mechanisms are yet unclear. The present study aimed at unraveling the molecular mechanisms underlying the pathogenesis of ROP. A comprehensive screening of candidate genes in preterms with ROP (n = 189) and no-ROP (n = 167) was undertaken to identify variants conferring disease susceptibility. Allele and genotype frequencies, linkage disequilibrium and haplotypes were analyzed to identify the ROP-associated variants. Variants in CFH (p = 2.94 × 10-7), CFB (p = 1.71 × 10-5), FBLN5 (p = 9.2 × 10-4), CETP (p = 2.99 × 10-5), and CXCR4 (p = 1.32 × 10-8) genes exhibited significant associations with ROP. Further, a quantitative assessment of 27 candidate proteins and cytokines in the vitreous and tear samples of babies with severe ROP (n = 30) and congenital cataract (n = 30) was undertaken by multiplex bead arrays and further validated by western blotting and zymography. Significant elevation and activation of MMP9 (p = 0.038), CFH (p = 2.24 × 10-5), C3 (p = 0.05), C4 (p = 0.001), IL-1ra (p = 0.0019), vascular endothelial growth factor (VEGF) (p = 0.0027), and G-CSF (p = 0.0099) proteins were observed in the vitreous of ROP babies suggesting an increased inflammation under hypoxic condition. Along with inflammatory markers, activated macrophage/microglia were also detected in the vitreous of ROP babies that secreted complement component C3, VEGF, IL-1ra, and MMP-9 under hypoxic stress in a cell culture model. Increased expression of the inflammatory markers like the IL-1ra (p = 0.014), MMP2 (p = 0.0085), and MMP-9 (p = 0.03) in the tears of babies at different stages of ROP further demonstrated their potential role in disease progression. Based on these findings, we conclude that increased complement activation in the retina/vitreous in turn activated microglia leading to increased inflammation. A quantitative assessment of inflammatory markers in tears could help in early prediction of ROP progression and facilitate effective management of the disease, thereby preventing visual impairment.