Abstract 13613: Identification of a Novel Somatic Mutation in Sarcolipin Gene in Human Fetal Atrial Standstill
Sarcolipin (SLN), a key regulator of sarcoplasmic reticulum Ca2+ ATPase (SERCA) plays an important role in atrial Ca2+ homeostasis and therefore suggested as a possible candidate for genetic cause of atrial arrhythmias. The aim of this study was to find if the SLN gene has a causative role in human atrial standstill, a rare lethal disorder of atrial musculature. Genomic DNA from formalin fixed atrial tissue and fibroblast from deceased newborn with atrial standstill were used as templates in PCR reaction to amplify the coding exon of SLN and screened for mutation. DNA sequencing identified ATG → ATA transition mutation at the translation initiation site in 20% of clones from atrial DNA. There were no coding region mutations identified in clones obtained from fibroblast tissues. To validate our findings, we designed mutant specific PCR screening method and amplified the genomic DNA from control atria and atria and fibroblast tissues of fetal atrial standstill. PCR amplification occurs only with atrial DNA from atrial standstill and not from fibroblasts. These data indicate that the SLN ATA mutation is somatic and restricted to atria. Sequence analyses of SLN transcript indicate that in the absence of translation initiation codon, the translation can start from the downstream ATG at position 23. To verify this, we made a fusion constructs of WT and ATA mutant SLN with GFP and expressed in atrial specific HL-1 cells. Both wildtype SLN-GFP and truncated SLN (tSLN)-GFP expression observed with direct fluorescence microscopy and western blot analysis indicating that ATA mutation results in synthesis of truncated tSLN containing 10 amino acid C-terminal peptide. To analyze the regulation of SERCA function, we measured intracellular Ca2+ transients from Rhodmine 2-AM-loaded HL-l cells transfected with SLN-GFP or tSLN-GFP vectors We thus identified a novel somatic mutation in SLN gene in the atria of a patient with atrial standstill. Given that SLN plays a key role in atrial Ca2+ homeostasis, the tSLN could cause abnormal Ca2+ cycling and contribute for cardiac remodeling and atrial arrhythmias.
- © 2011 by American Heart Association, Inc.