TLX2 and hydrops fetalis: Indeed, the majority of studies have shown that NCX is increased in HF (Sipido et al., 2002; Schillinger et al., 2003), although we should approach these data with caution due to the fact that expression levels do not necessarily give an indication of activity, especially when considering an exchanger where ion concentrations, phosphorylation state [of partner proteins (e.g., phospholemman) as well as NCX itself] in addition to other factors will ultimately influence the current generated by the exchanger.