Transcritome analysis from Cephalopod molluscs

The cephalopod mollusc, Nautilus is an enigmatic organism possible representing one of the most basal lineages in the group (sometimes it is considered as a living fossil). Thus, Nautilus is one of key emerging models to study the independent origin of complex brain organization and behavior. However, nothing is known about the molecular organization of its nervous system and virtually no genes were cloned. Here, using pyrosequencing approach we performed analysis of transcripts expressed in the central nervous system of Nautilus. Specifically, we developed a reduced representation sequencing method that can detect low abundant transcripts. Our method greatly reduces the amount of sequencing with more accurate quantification. Basically, sequential addition of adaptors paired with controlled digestion of cDNA generates a one transcript on read type of analysis. Combined 5’ with 3’ targeted libraries produces greater coverage of individual transcripts and high quality assembly. Our initial analysis allowed us to identify more than 50,000 of neuronal transcripts including virtually all major components of signal transduction pathways and a diversity of neuropeptides. The developed molecular resources and the ability to map gene expression should allow detailed study of the genomics of this brain with the resolution at the level of individual neurons and circuits, and provide critical information for future analysis of nervous system evolution.