Supporting data for "Molecular modularity and asymmetry of the molluscan mantle revealed by a gene expression atlas"

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 on species that deposit nacre, which is at odds with the majority of conchiferan species that fabricate shells using a crossed lamellar microstructure, <em>sensu lato</em>. By combining proteomic and transcriptomic sequencing with <em>in situ </em>hybridisation we have identified a suite of gene products associated with the production of the crossed-lamellar shell in <em>Lymnaea stagnalis</em>. With this spatial expression data we are able to generate novel hypotheses of how the adult mantle tissue coordinates the deposition of the calcified shell. These hypotheses include functional roles for unusual and otherwise difficult to study proteins such as those containing repetitive low complexity domains (RLCDs). The spatial expression readouts of the shell-forming genes we studied also reveal cryptic patterns of asymmetry and modularity in the shell-forming cells of larvae and adult mantle tissue. This molecular modularity of the shell-forming mantle tissue hints at an intimate association between structure, function and evolvability and may provide an elegant explanation for the evolutionary success of the second largest phylum among the Metazoa.