ARHGEF1 and allergic asthma: 2007). Two of these, GEF‐H1 and Net1, are up‐regulated by TGF‐β in epithelia, thus enhancing RhoA‐dependent F‐actin expression/cell migration and epithelial‐to‐mesenchymal transition, respectively (Tsapara et al. 2010; Papadimitriou et al. 2012). Another RhoGEF, ARHGEF1 (p115‐RhoGEF, Lsc), not previously linked with TGF‐β, has been implicated in the T‐cell dysfunction associated with allergic asthma, and in the contractile effects of angiotensin II on hypertensive vascular smooth muscle (Brown et al. 2007; Guilluy et al. 2010).