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First published online May 8, 2007
Journal of Experimental Biology 210, 1813-1824 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.02761

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Molecular characterization of an epithelial Ca²⁺ channel-like gene from crayfish Procambarus clarkii

Yongping Gao and Michele G. Wheatly^*

Department of Biological Sciences, Wright State University, Dayton, OH 45435, USA

^* Author for correspondence (e-mail: michele.wheatly{at}wright.edu)

Accepted 22 February 2007

This study describes the cloning, sequencing and functional characterization of an epithelial Ca²⁺ channel (ECaC)-like gene isolated from antennal gland (kidney) of the freshwater crayfish Procambarus clarkii. The full-length cDNA consisted of 2687 bp with an open reading frame of 2169 bp encoding a protein of 722 amino acids with a predicted molecular mass of 81.7 kDa. Crayfish ECaC had 76–78% identity at the mRNA level (80–82% amino acid identity) with published fish sequences and 56–62% identity at the mRNA level (52–60% amino acid identity) with mammalian ECaCs. Secondary structure of the crayfish ECaC closely resembled that of cloned ECaCs. Postmolt ECaC expression was exclusively restricted to epithelia associated with Ca²⁺ influx and was virtually undetectable in non-epithelial tissues (eggs, muscle). Compared with expression levels in hepatopancreas, expression in gill was 10-fold greater and expression was highest in antennal gland (15-fold greater than in hepatopancreas). Compared with baseline expression levels in intermolt stage, expression of ECaC in antennal gland increased 7.4- and 23.8-fold, respectively, in pre- and postmolt stages of the molting cycle. This increase was localized primarily in the labyrinth and nephridial canal, regions of the antennal gland associated with renal Ca²⁺ reabsorption. The ECaC in crayfish appears to be expressed in epithelia associated with unidirectional Ca²⁺ influx and relative expression is correlated with rate of Ca²⁺ influx.

Key words: crayfish, Procambarus clarkii, antennal gland, gill, hepatopancreas, epithelial Ca²⁺ channel, ECaC, mRNA expression and localization, molting cycle

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