Molecular modularity and asymmetry of the molluscan mantle revealed by a gene expression atlas.

15 pagesInternational audienceBackground: Conchiferan molluscs construct a biocalcified shell that likely supported much of their evolutionary success.However, beyond broad proteomic and transcriptomic surveys of molluscan shells and the shell-forming mantle tissue,little is known of the spatial and ontogenetic regulation of shell fabrication. In addition, most efforts have been focused onspecies that deposit nacre, which is at odds with the majority of conchiferan species that fabricate shells using acrossed-lamellar microstructure, sensu lato. Results: By combining proteomic and transcriptomic sequencing with in situhybridization we have identified a suite of gene products associated with the production of the crossed-lamellar shell inLymnaea stagnalis.With this spatial expression data we are able to generate novel hypotheses of how the adult mantle tissuecoordinates the deposition of the calcified shell. These hypotheses include functional roles for unusual and otherwisedifficult-to-study proteins such as those containing repetitive low-complexity domains. The spatial expression readouts ofshell-forming genes also reveal cryptic patterns of asymmetry and modularity in the shell-forming cells of larvae and adultmantle tissue. Conclusions: This molecular modularity of the shell-forming mantle tissue hints at intimate associationsbetween structure, function, and evolvability and may provide an elegant explanation for the evolutionary success of thesecond largest phylum among the Metazoa