Wednesday, October 10, 2007

Gene Expression Profiling of Cuticular Proteins across the Moult Cycle of the Crab Portunus pelagicus


Crustaceans represent an attractive model to study biomineralization and cuticle matrix formation as these events are precisely timed to occur at certain stages of the moult cycle. Moulting, the process by which crustaceans shed their exoskeleton, involves the partial breakdown of the old exoskeleton and the synthesis of a new cuticle. This cuticle is subdivided into layers some of which become calcified and some which remain uncalcified. The cuticle matrix consists of many different proteins which confer the physical properties, such as pliability, of the exoskeleton.


We have used a custom cDNA microarray chip, developed for the blue swimmer crab Portunus pelagicus, to generate expression profiles of genes involved in exoskeletal formation across the moult cycle. Twenty-one distinct moult cycle related differentially expressed transcripts representing crustacean cuticular proteins were isolated. Thirteen contain copies of the cuticle_1 domain, previously isolated from calcified regions of the crustacean exoskeleton. Four transcripts contain a chitin_bind_4 domain (RR consensus sequence), associated with both the calcified and un-calcified cuticle of crustaceans. Four transcripts contain an unannotated domain (PfamB_109992) previously isolated from C. pagurus. Additionally cryptocyanin, a hemolymph protein, involved in cuticle synthesis and structural integrity, also displays differential expression related to the moult cycle. Moult stage-specific expression analysis of these transcripts revealed that differential gene expression occurs both among transcripts containing the same domain and among transcripts containing different domains.


The large variety of genes associated with cuticle formation, and their differential expression across the crustacean moult cycle, point to the complexity of the processes associated with cuticle formation and hardening which involve many components and require strict regulatory mechanisms. This study provides a molecular entry path into the investigation of the gene networks associated with cuticle formation.

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