With regards to the mechanism(s) that might be responsible for the bell-shape profile of the angiogenic responses observed (Figure 7B,D), we propose that this might be mediated through changes in the balance, i.e., relative concentrations of pro- and anti-angiogenic factors present in HPS, such as VEGF and TPS-1. Here, TPSAB1 is linked to Hermansky-Pudlak syndrome.