Novel PITX2 Homeodomain-Contained Mutations from ATRIAL Fibrillation Patients Deteriorate Calcium Homeostasis

Atrial fibrillation (AF) is the most common cardiac arrhythmia in human population, with an estimated incidence of 1–2% young adults but increasing to more than 10% 80+ years patients. Pituitary Homeobox 2, Paired Like Homeodomain 2 (PITX2c) loss-of-function mice revealed that this homeodomain (HD)-containing transcription factor plays a pivotal role atrial electrophysiology and calcium homeostasis point PITX2 as candidate gene for AF. To address issue, we recruited 31 AF patients genetic analyses both known risk alleles PITX2c open reading frame (ORF) re-sequencing. We found two-point mutations homedomain three other variants 5’untranslated region. A 65 old male patient without 4q25 recurrent displayed two distinct HD-mutations, NM_000325.5:c.309G>C (Gln103His) NM_000325.5:c.370G>A (Glu124Lys), which resulted change within highly conserved amino acid position. functional impact HD mutations, generated plasmid constructs mutated version each nucleotide variant (MD4 MD5, respectively) well dominant negative control construct was lacking (DN). Functional demonstrated MD4 MD5 decreased Nppa-luciferase transactivation by 50% 40%, respectively, similar DN (50%), while Shox2 promoter repression also impaired. Co-transactivation cardiac-enriched co-factors, such Gata4 Nkx2.5, similarly impaired, further supporting these correct function. Furthermore, when expressed HL1 cardiomyocyte cultures, mutants impaired endogenous expression regulatory proteins induced alterations sarcoplasmic reticulum (SR) accumulation. This favored alternating irregular transient amplitudes, causing deterioration beat-to-beat stability upon elevation stimulation frequency. Overall data demonstrate novel HD-mutations might be causative carrier.