A time course microarray analysis of post mortem skeletal muscle transcriptional profile in pigs.

Transcriptional profile of post mortem skeletal muscle tissue and the changes in time course are unexplored topics in molecular biology applied to meat quality studies. This issue is of particular interest considering the fact that the availability of post mortem muscles at commercial abattoirs is usually associated with substantial delays. On the other hand, the possibility of using post mortem samples for gene expression analysis opens new perspectives for the transcriptome analysis with potential applications for product authentication, quality assessment and forensics. The recovery of high quality RNA has been considered a prerequisite for gene expression investigation. However, it is commonly asserted that RNA is subjected to irreversible damages starting from the death of the animals. Therefore, it is usually considered that RNA cannot be efficiently used for expression analysis of tissues at different post mortem stages, even if several experiments with human and laboratory animal specimens have demonstrated that, depending on the tissue and pre mortem and post mortem conditions, RNA can remain stable for a long period after death. In this study, for the first time, we investigated the porcine skeletal muscle transcriptional profile in a post mortem time course. RNA extracted from porcine Semimembranosus muscles sampled at 20 minutes, 2, 6 and 24 hours post mortem was assessed by agarose gel and microfluidic capillary electrophoresis. Similar RIN values were obtained for all samples indicating their suitability for downstream gene expression evaluations. Then, Affymetrix GeneChip porcine genome microarrays were hybridised with RNA extracted at all post mortem time points. The results indicated that most of the genes did not change their level, confirming that RNA degradation might not play a major role during the first 24 hours post mortem. However, two groups of genes showing different trends of expression during the post mortem stages were identified. These results open new perspectives for the analysis of hypoxic/anoxic skeletal muscle gene expression and the possibility to identify meat quality predictors.