TAG-BASED RNA-Seq AS A TOOL TO EXAMINE GENE EXPRESSION DIFFERENCES IN RED DRUM Sciaenops ocellatus EGGS THAT DO AND DO NOT DEMONSTRATE METABOLIC PROGRAMMING

Previous work in our lab has shown that when the diet of red drum (Sciaenops ocellatus) broodstock is manipulated to produce different levels of docosahexaenoic acid (DHA) in the egg, resulting larvae demonstrate altered abilities to acquire and/or retain DHA in body tissues despite being provided high levels in their diet. This pattern is similar to a condition seen in terrestrial vertebrates and referred to in humans as Metabolic Programming. Due to constraints in sourcing large amounts of highly purified DHA with which to amend the broodstock diets, DHA levels are manipulated by using combinations of fresh and frozen feeds along with formulated pellets. This means that though the target DHA levels are reached, there are differences in other nutrients including other fatty acids. Despite these differences, the metabolic programming effect has persisted across several years and multiple brood groups. In 2016 however, there a brood group produced eggs that did not demonstrate the DHA programming effect. The diet used to produce these differences was substantially different from a diet used at the same time on a different brood group which did show the expected programming.

In order to better understand the mechanisms behind this metabolic programming in red drum, we collected batches of eggs containing high and low DHA from both brood groups along with 21-day post hatch larvae raised from these eggs to examine differences in gene expression. This was done through whole transcriptome sequencing using RNA Sequencing (RNA-Seq). To keep costs down, we used a type of tag-based RNA-Seq (Tag-Seq) that allowed us to pool multiple samples per lane. Reading of the sequences was performed on an Illumina HiSeq 2500 v4 using a single cell RapidRead. Results of a comparison of the two sets of eggs and larvae (with and without programming) will be discussed.