Eif4a3 is required for accurate splicing of the Xenopus laevis ryanodine receptor pre-mRNA

The Exon Junction Complex (EJC) plays a critical role in multiple posttranscriptional events, including RNA subcellular l calization, nonsense-mediated decay (NMD), and translation. We previously reported that knockdown of the EJC core component Eukaryotic initiation factor 4a3 (Eif4a3) results in full-body paralysis of embryos of the frog, Xenopus laevis. Here, we explore the cellular and molecular mechanisms underlying this phenotype. We find that cultured muscle cells derived from Eif4a3 morphants do not contract, and fail to undergo calcium-dependent calcium release in response to electrical stimulation or treatment with caffeine. We show that ryr transcripts are incorrectly spliced in Eif4a3 morphants, and demonstrate that inhibition of Xenopus Ryanodine receptor (Ryr) function similarly results in embryonic paralysis. These results suggest that the EJC mediates muscle cell function via regulation of pre-mRNA splicing during early vertebrate embryogenesis.