HTRA1 Overexpression Induces the Exudative Form of Age-related Macular Degeneration

Age-related macular degeneration (AMD) is a leading cause of vision loss and blindness in the elderly. The dry form is more common and accounts for about 85-90% of AMD patients in US, while Japanese AMD patients predominantly progress to wet-form or polypoidal choroidal vasculopathy (PCV). Recent studies have shown HTRA1, a serine protease gene, as major risk factor for wet form AMD (De Wan et al., Science 2006). Furthermore, we reported that the Japanese typical wet form AMD patients showed significant association with ARMS2/HTRA1 (Goto, Akahori et al., JOBDI 2009). The purpose of this study is to elucidate the function of ARMS2/HTRA1 gene promoter in wet-form AMD patients. The promoter sequence experiment showed that a great number of AMD patients had specific indel mutation in 3.8 kb upstream of HTRA1 gene. 2-3-fold increase of promoter activity was observed in indel HTRA1 promoter compared to control sequence (Iejima et al., JBC 2015). Furthermore, we created transgenic mice ubiquitously overexpressing mouse HtrA1 using the chicken act in promoter, continuous induction of HtrA1 in vivo was shown to lead to CNV, similar to wet AMD patients (Nakayama, Iejima et al., IOVS 2014). These results suggest that human HTRA1 expression is enhanced by AMD specific indel mutation in the promoter region of HTRA1 gene, and this enhanced HTRA1 may be concerned with induce retinal neovasucularization.