PLN and cardiac arrhythmia: More recently, a homozygous R4344Q knock-in mouse created by the Kontrogianni–Konstantopulous group developed cardiac arrhythmias under sedentary conditions and a DCM-like phenotype upon pressure overload, which the authors attributed to an increase in the affinity, as judged by co-immunoprecipitation, for a newly identified interaction between obscurin and phospholamban, a small inhibitory peptide of the SERCA pump in the SR membrane (14).