Cell atlas of the human ocular anterior segment: Tissue-specific and shared cell types

The anterior segment of the eye consists of the cornea, iris, ciliary body, crystalline lens and aqueous humor outflow pathways. Together, these tissues are essential for the proper functioning of the eye. Disorders of vision have been ascribed to defects in all of them; some, including glaucoma and cataract, are among the most prevalent causes of blindness in the world. To characterize the cell types that comprise these tissues, we generated an anterior segment cell atlas of the human eye using high throughput single-nucleus RNA sequencing (snRNAseq). We profiled 191,992 nuclei from non-diseased anterior segment tissues from 6 human donors, identifying >60 cell types. Many of these cell types were discrete, whereas others, especially in lens and cornea, formed continua corresponding to known developmental transitions that persist in adulthood. Having profiled each tissue separately, we performed an integrated analysis of the entire anterior segment revealing that some cell types are unique to single structure whereas others are shared across tissues. The integrated cell atlas was then used to investigate cell type-specific expression patterns of more than 900 human ocular disease genes identified either through Mendelian inheritance patterns or genome-wide association studies (GWAS). SIGNIFICANCE STATEMENTSeveral of the most prevalent blinding ocular conditions worldwide, including glaucoma, cataract and uncorrected refractive error, involve structures of the anterior segment of the human eye, which consists of the cornea, iris, ciliary body, crystalline lens and aqueous humor outflow pathways. In addition to providing transcriptomic profiles of the cell types within individual tissues, this work contributes to our understanding of the relatedness and diversity of these cell types across contiguous tissues by generating an integrated anterior segment cell atlas and documenting the expression of over 900 disease-associated genes in each cell type. By allowing simultaneous interrogation of cell-type specific expression of genes across multiple tissues, the atlas may yield broad insight into normal and disease-associated anterior segment functions.