FAIRCLOTH, LM*; SHAFER, TH; University of North Carolina Wilmington; University of North Carolina Wilmington: Expression of Various Genes for Cuticle Proteins in the Blue Crab, Callinectes sapidus

The blue crab is an ideal organism in which to study biomineralization. Throughout its life it goes through many molt cycles in which the exoskeleton is shed and a new cuticle is laid down and calcified. However, some regions of the cuticle (i.e. the joints) do not calcify and remain flexible to allow for movement. The hypodermis is the tissue responsible for secreting the proteins that make up the cuticle. An EST database has been made from mRNAs extracted from the hypodermis both before and after the molt. Using this database multiple transcripts have been identified by their similarity to cuticle proteins from other crustaceans and insects. The expression patterns of these proteins were determined using Northern blotting and real-time PCR. For example, one gene showed similarity to a protein from the calcified cuticle of Cancer pagarus, and Northern blotting revealed that it is expressed only after the molt in the hypodermis secreting cuticle that will calcify. Real-time PCR data show this same pattern and also reveal that the level of expression increases from 1 hour after the molt to 24 hours after the molt. Another gene was expressed only in arthrodial (noncalcifying) hypodermis both before and after the molt. With this information on several different genes, we can begin to infer the roles their corresponding proteins play in the formation and calcification of the blue crab cuticle.