HTRA1 and age-related macular degeneration: Multiple substrates of HTRA1 have been identified, including multiple extracellular matrix (ECM) proteins and TGF-gamma family members.[19, 22] Previous studies have identified a disease haplotype–an SNP within the HTRA1 promoter on chromosome 10q26 –that influences risk for AMD.[20, 21, 23] While the association of HTRA1 variants with AMD has been well-established, the role of HTRA1 in AMD pathogenesis is poorly understood.