John, Simon W. M.

Abstract The trabecular meshwork (TM) and ciliary body (CB) regulate aqueous humor dynamics and intraocular pressure (IOP), and TM/Schlemm’s canal (SC) dysfunction underlies glaucoma. Here, we present a spatially resolved multi-omics atlas of human TM and CB, integrating snRNA-seq, scRNA-seq, and snATAC-seq from over one million cells and nuclei across 112 donors with Xenium spatial transcriptomics. We identified 9 major cell classes and 21 cell types, revealing heterogeneity, including undercharacterized fibroblast and epithelial subpopulations. Spatial mapping supported TM fibroblast zonation and CB epithelial organization. Regulatory analyses identified cell type–specific programs, including OTX/PAX networks in CB epithelium and SMAD3/TGF-β signaling in fibroblasts. Integration with glaucoma loci showed enrichment of non-coding variants in regulatory elements associated with POAG and PACG. Age- and ancestry-associated remodeling revealed divergent fibroblast aging with increased PIEZO1 , suggesting impaired outflow and elevated IOP. Together, this high-resolution atlas links cellular, regulatory, and genetic variation to anterior segment function and glaucoma susceptibility.

Abstract Glaucoma is characterized by programmed cell death of retinal ganglion cells (RGCs) after axonal injury. Several studies have shown the cell-intrinsic drivers of RGC degeneration act in a compartment-specific manor. Recently, the transcription factors JUN and DDIT3 were identified as critical hubs regulating RGC somal loss after mechanical axonal injury. It is possible somal DDIT3 and JUN activity initiates axonal degeneration mechanisms in glaucoma. Alternatively, DDIT3 and JUN may act downstream of inciting degenerative mechanisms and only drive RGC somal loss. The MAP2Ks MKK4 and MKK7 control all JNK and JUN activity and can indirectly activate DDIT3. Furthermore, MKK4 and MKK7 have been shown to drive RGC axonal degeneration after mechanical axonal injury. The present work investigated whether JUN and DDIT3, or their upstream activators MKK4 and MKK7, control degeneration of RGC axons and somas after glaucoma-relevant injury. Ddit3 and Jun deletion did not prevent axonal degeneration in ocular hypertensive DBA/2J mice but prevented nearly all RGC somal loss. Despite robust somal survival, Ddit3 and Jun deletion did not preserve RGC somal viability (as assessed by PERG decline and soma shrinkage) in DBA/2J mice or after glaucoma-relevant mechanical axonal injury. In contrast, Mkk4 and Mkk7 deletion significantly lessened degeneration of RGC somas and axons, and preserved somal function and size after axonal injury. In summary, activation of MKK4 and MKK7 appears to be the inciting mechanism governing death of the entire RGC after glaucoma-relevant injury; driving death of the RGC soma (likely through activation of DDIT3 and JUN), decline in somal viability, and axonal degeneration via DDIT3 and JUN-independent mechanisms.