Primary open-angle glaucoma (POAG) is a leading cause of irreversible vision loss, yet much of the genetic risk remains unaccounted for, especially in African-Americans who have a higher risk for developing POAG. We conduct a multiethnic genome-wide association study (GWAS) of POAG in the GERA cohort, with replication in the UK Biobank (UKB), and vice versa, GWAS in UKB with replication in GERA. We identify 24 loci (P < 5.0 × 10−8), including 14 novel, of which 9 replicate (near FMNL2, PDE7B, TMTC2, IKZF2, CADM2, DGKG, ANKH, EXOC2, and LMX1B). Functional studies support intraocular pressure-related influences of FMNL2 and LMX1B, with certain Lmx1b mutations causing high IOP and glaucoma resembling POAG in mice. The newly identified loci increase the proportion of variance explained in each GERA race/ethnicity group, with the largest gain in African-Americans (0.5–3.1%). A meta-analysis combining GERA and UKB identifies 24 additional loci. Our study provides important insights into glaucoma pathogenesis.

A mismatch between optical power and ocular axial length results in refractive errors. Uncorrected refractive errors constitute the most common cause of vision loss and second leading cause of blindness worldwide. Although the retina is known to play a critical role in regulating ocular growth and refractive development, the precise factors and mechanisms involved are poorly defined. We have previously identified a role for the secreted serine protease PRSS56 in ocular size determination and PRSS56 variants have been implicated in the etiology of both hyperopia and myopia, highlighting its importance in refractive development. Here, we use a combination of genetic mouse models to demonstrate that Prss56 mutations leading to reduced ocular size and hyperopia act via a loss of function mechanism. Using a conditional gene targeting strategy, we show that PRSS56 derived from Müller glia contributes to ocular growth, implicating a new retinal cell type in ocular size determination. Importantly, we demonstrate that persistent activity of PRSS56 is required during distinct developmental stages spanning the pre- and post-eye opening periods to ensure optimal ocular growth. Thus, our mouse data provide evidence for the existence of a molecule contributing to both the prenatal and postnatal stages of human ocular growth. Finally, we demonstrate that genetic inactivation of Prss56 rescues axial elongation in a mouse model of myopia caused by a null mutation in Egr1. Overall, our findings identify PRSS56 as a potential therapeutic target for modulating ocular growth aimed at preventing or slowing down myopia, which is reaching epidemic proportions.

Glaucoma is a leading cause of blindness affecting up to million people worldwide. High intraocular pressure (IOP) is a major risk factor for glaucoma. Inefficient aqueous humor (AqH) outflow resulting from structural or functional alterations in ocular drainage tissues are well established to cause high IOP, but the genes and pathways involved are poorly understood. We previously demonstrated that mutations in the gene encoding the serine protease PRSS56 induces ocular angle-closure and high IOP in mice and identified reduced ocular axial length as a potential contributing factor. Here we show that Prss56-/mice also exhibits an abnormal iridocorneal angle configuration characterized by a posterior shift of ocular drainage structures relative to the ciliary body and iris. Notably, we show that retina-derived PRSS56 is required between postnatal days 13 and 18 for proper iridocorneal configuration and that abnormal positioning of the ocular drainage tissues is not dependent on ocular size reduction in Prss56-/mice. Furthermore, we demonstrate that the genetic context modulates the severity of IOP elevation in Prss56 mutant mice and describe a progressive degeneration of ocular drainage tissues that likely contributes to the exacerbation of the high IOP phenotype observed on the C3H/HeJ genetic background. Finally, we identified five rare PRSS56 variants associated with human primary congenital glaucoma, a condition characterized by abnormal development of the ocular drainage structures. Collectively, our findings point to a role for PRSS56 in the development and maintenance of ocular drainage tissues and IOP homeostasis, and provide new insights into glaucoma pathogenesis.

Precise regulation of ocular size is a critical determinant of normal visual acuity. Although it is generally accepted that ocular growth relies on a cascade of signaling events transmitted from the retina to the sclera, the factors and mechanism(s) involved are poorly understood. Recent studies have highlighted the importance of the retinal secreted serine protease PRSS56 and transmembrane glycoprotein MFRP, a factor predominantly expressed in the retinal pigment epithelium (RPE), in ocular size determination. Mutations in PRSS56 and MFRP constitute a major cause of nanophthalmos, a condition characterized by severe reduction in ocular axial length/extreme hyperopia. Interestingly, common variants of these genes have been implicated in myopia, a condition associated with ocular elongation. Consistent with these findings, mice with loss of function mutation in PRSS56 or MFRP exhibit a reduction in ocular axial length. However, the molecular network and cellular processes involved in PRSS56- and MFRP-mediated ocular axial growth remain elusive. Here, we show that Adamts19 expression is significantly upregulated in the retina of mice lacking either Prss56 or Mfrp. Importantly, using genetic mouse models, we demonstrate that while ADAMTS19 is not required for ocular growth during normal development, its inactivation exacerbates ocular axial length reduction in Prss56 and Mfrp mutant mice. These results suggest that the upregulation of retinal Adamts19 is part of an adaptive molecular response to counteract impaired ocular growth. Using a complementary genetic approach, we show that loss of PRSS56 or MFRP function prevents excessive ocular axial growth in a mouse model of early-onset myopia caused by a null mutation in Irbp, thus, demonstrating that PRSS56 and MFRP are also required for pathological ocular elongation. Collectively, our findings provide new insights into the molecular network involved in ocular axial growth and support a role for molecular crosstalk between the retina and RPE involved in refractive development.

Angle-closure glaucoma (ACG) is a severe form of glaucoma affecting up to 16 million people worldwide. In ACG, physical blockage of the ocular drainage tissue by the peripheral iris impedes the drainage of aqueous humor resulting in elevated intraocular pressure (IOP) and subsequent optic nerve damage. Despite the high prevalence of ACG, the precise mechanism(s) underlying pathogenesis are only partially understood. We have previously demonstrated that a mutation in the gene encoding the serine protease PRSS56 causes an ACG phenotype in mice. Notably, Prss56 mutant mice exhibit a reduced ocular axial length and a lens occupying a larger ocular volume compared to WT mice, recapitulating characteristic features of human AGC. Our findings utilizing mouse genetic models demonstrate that loss of PRSS56 function results in altered configuration of ocular angle structures characterized by a posterior shift in the positioning of the ocular drainage tissue relative to the ciliary body and iris during development, leading to a physical blockage of drainage structure (angle closure) and high IOP. Utilizing a previously employed genetic strategy of rescuing mutant Prss56 mediated reduction in ocular size by inactivation of EGR1 (Egr1;Prss56 double mutants) we determined the influence of ocular size on developmental positioning of the ocular angle tissues. Our findings suggest that abnormal positioning of the drainage structure as a result of loss of PRSS56 function is uncoupled from its effect on ocular axial length reduction. Furthermore, we demonstrate that the IOP elevation observed in Prss56 mutant mice is genetic context-dependent and identify a dominant modifier locus on Chromosome 2 of the C3H/HeJ genome conferring susceptibility to high IOP. Overall, our findings reveal a novel role for PRSS56 in the proper configuration of the iridocorneal angle and provide new insight into the developmental pathways implicated in glaucoma pathogenesis.