TTN and hydrops fetalis: While TTNtvZ and TTNtvA alleles led to the synthesis of truncated TTN isoforms from both loci, the NMD of these truncated variants did not lead to the identification of dominant negative isoforms in the hearts of mutant rats, which highlighted the fact that TTNtv-induced truncated TTN follows position-independent NMD pathways in the emergence of the HF phenotype.