Papers of the Week

Human-induced pluripotent stem cells (iPS cells) are efficiently differentiated into sensory neurons. These cells express the voltage-gated sodium channel Na1.7, which is a validated pain target. Na1.7 deficiency leads to pain insensitivity, whereas Na1.7 gain-of-function mutants are associated with chronic pain. During differentiation, the sensory neurons start spontaneous action potential firing around day 22, with increasing firing rate until day 40. Here, we used CRISPR/Cas9 genome editing to generate a HA-tag Na1.7 to follow its expression during differentiation. We used two protocols to generate sensory neurons: the classical small molecule approach and a directed differentiation methodology and assessed surface Na1.7 expression by Airyscan high-resolution microscopy. Our results show that maturation of at least 49 days is necessary to observe robust Na1.7 surface expression in both protocols. Electric activity of the sensory neurons precedes Na1.7 surface expression. A clinically effective Na1.7 blocker is still missing, and we expect this iPS cell model system to be useful for drug discovery and disease modeling.