Biomineralization is the process by which living organisms produce minerals. Although it occurs in every kingdom of life, one of the most familiar and beautiful examples is the snail shell. The diversification of the snail shell is thought to be related to the abundance and success of this group of animals (the second largest phylum in terms of species number, after arthropods). With ocean temperatures increasing worldwide, there is also an urgent need to understand how shells form and grow to protect aquaculture species like oysters, clams, and mussels. Shells begin forming during development, when shell gland cells express a suite of transcription factor proteins that in turn regulate shell matrix proteins; matrix proteins form a scaffold that controls calcium carbonate crystalization. This project examines shell matrix formation using a well-studied marine snail, Crepidula. Taking advantage of tools to modify the genome of this species, this project examines which specific transcription factors control matrix protein production, and how they influence shell structure and growth. These studies will be the first of their kind among molluscs. Another innovative aspect of this project is that matrix proteins will be studied in the living animal. The research will be brought into the classroom as part of an inquiry-based laboratory course where undergraduates, graduate students, and high school students can study mollusc shell development and test their own hypotheses.
Although much is known about the biomaterial properties, micro-structure, and evolution of molluscan shells, major questions remain about how they are made during the process of development. The overarching goal of this project is to make the first comprehensive study of the expression and function of extracellular matrix proteins embedded in the shell of the marine snail Crepidula atrasolea. Aim 1 will uncover the spatiotemporal expression patterns of shell gland-expressed regulatory genes and mantle tissue-expressed matrix genes, using scRNAseq, in situ hybridization, and proteomics. Aim 2 will use lineage tracing to show how the shell gland cells mature into the adult mantle tissue, and use CRISPR/Cas9 genome editing to make matrix protein-GFP fusions to study shell formation in vivo. Aim 3 will identify the upstream regulators of matrix proteins, and knock them down to test their function. This work will lead to the first bona fide gene regulatory network (GRN) for biomineralization in a mollusc. Aim 4 integrates this research into a new cell and developmental biology CURE lab class for undergraduates, graduate students, and high school students.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
