Single Cells Make Seashells on the Seashore: using scRNAseq to uncover the role of haemocytes in molluscan biomineralization

How do molluscs build their shells? Shellfish farmers want to grow disease-resistant animals with strong shells, climate change scientists are concerned about the fate of calcifiers in warmer more acidic oceans, and biotechnology industries mine shells for bioactive compounds and material properties. Despite hundreds of years of scientific curiosity, our understanding on the cellular basis of seashell production is incomplete. In 2004, it was hypothesised that immune cells, called haemocytes, make intracellular calcium crystals and deposit them onto the shell. More recently, methods such as transcriptomics and proteomics revealed haemocytes have a molecular signature that could indicate biomineralisation functions. But a complete molluscan immune cell development (haematopoiesis) description and functional tests to confirm roles in biomineralisation are still lacking. The broad question this project will address is: do immune cells, called haemocytes, participate in mollusc shell secretion? To disentangle the potential role of haemocytes in biomineralization, from their known functions in immunity, the project will use the cutting-edge technique single-cell RNA-sequencing, in two mollusc model systems: Crepidula fornicata and Crassostrea gigas. The project will interrogate scRNAseq datasets to uncover the cell lineage and developmental events that give rise to haemocytes before conducting experiments to empirically test their function.