CLN5 and lung carcinoma: In order to validate the findings from the two independent mouse cell models to a human system, we employed human HaCaT keratinocytes that are very well established for their signaling and physiological responses to all members of the TGFβ family including the BMPs [31], and human lung adenocarcinoma A549 cells, which also respond well to TGFβ family members and provide relevance to lung cancer (see below) [32].