MAB21L1 and glaucoma: However, at the time of recruitment (at 40 years of age), the father of the severely affected female proband in family 2 did not have a history of early-onset glaucoma, despite being heterozygous for the R1034C variant, suggesting that, like other early-onset glaucoma (TEK, ANGPT1) (9, 10) or ocular developmental (MAB21L1) (21) genes, R1034C may cause a glaucoma phenotype with variable penetrance and/or expressivity.