Andersen's syndrome is a rare disorder that has been defined with a triad: 
periodic paralysis, cardiac arrhythmia, and development anomalies. Muscle 
weakness has been reported in two-thirds of the patients. KCNJ2 remains the only 
gene linked to Andersen's syndrome; this gene encodes for the alpha-subunit of 
the strong inward-rectifier K+ channel Kir2.1. Several studies have shown that 
Andersen's syndrome mutations lead to a loss of function of the K+ channel 
activity in vitro. However, ex vivo studies on isolated patient muscle tissue 
have not been reported. We have performed muscle biopsies of controls and 
patients presenting with clinically and genetically defined Andersen's syndrome 
disorder. Myoblasts were cultured and characterized morphologically and 
functionally using the whole cell patch-clamp technique. No morphological 
difference was observed between Andersen's syndrome and control myoblasts at 
each passage of the cell culture. Cellular proliferation and viability were 
quantified in parallel with direct cell counts and showed no difference between 
control and Andersen's syndrome patients. Moreover, our data show no significant 
difference in myoblast fusion index among Andersen's syndrome and control 
patients. Current recordings carried out on myotubes revealed the absence of an 
inwardly rectifying Ba2+-sensitive current in affected patient cells. One 
consequence of the Ik1 current loss in Andersen's syndrome myotubes is a shift 
of the resting membrane potential toward depolarizing potentials. Our data 
describe for the first time the functional consequences of Andersen's syndrome 
mutations ex vivo and provide clues to the K+ channel pathophysiology in 
skeletal muscle.