Claudin-2 expression increases with the frequency of local tight junction channel openings in MDCKI monolayers. (A) Tight junctions are distinct from plasma membrane ion channels and differ from gap junctions in their ability to define conductance between two extracellular compartments. (B) Trans-tight junction patch clamp placement. Yellow arrowheads show intercellular junction (Bar = 10 um). (C) Conductance events detected at -100 mV when claudin-2 was expressed (+Cldn-2). (D) In the absence of claudin-2 expression, the frequency of similar sized conductance events was dramatically reduced. From Weber et al., 2016. eLife.