|ZFIN ID: ZDB-PUB-071009-17|
Expression and water calcium dependence of calcium transporter isoforms in zebrafish gill mitochondrion-rich cells
Liao, B.K., Deng, A.N., Chen, S.C., Chou, M.Y., and Hwang, P.P.
|Source:||BMC Genomics 8(1): 354 (Journal)|
|Registered Authors:||Chen, Shyh-Chi, Chou, Ming-Yi, Hwang, Pung Pung|
|PubMed:||17915033 Full text @ BMC Genomics|
Liao, B.K., Deng, A.N., Chen, S.C., Chou, M.Y., and Hwang, P.P. (2007) Expression and water calcium dependence of calcium transporter isoforms in zebrafish gill mitochondrion-rich cells. BMC Genomics. 8(1):354.
ABSTRACTBACKGROUND: Freshwater fish absorb Ca2+ predominantly from ambient water, and more than 97% of Ca2+ uptake is achieved by active transport through gill mitochondrion-rich (MR) cells. In the current model for Ca2+ uptake in gill MR cells, Ca2+ passively enters the cytosol via the epithelium Ca2+ channel (ECaC), and then is extruded into the plasma through the basolateral Na+/Ca2+ exchanger (NCX) and plasma membrane Ca2+-ATPase (PMCA). However, no convincing molecular or cellular evidence has been available to support the role of specific PMCA and/or NCX isoforms in this model. Zebrafish (Danio rerio) is a good model for analyzing isoforms of a gene because of the plentiful genomic databases and expression sequence tag (EST) data. RESULTS: Using a strategy of BLAST from the zebrafish genome database (Sanger Institute), 6 isoforms of PMCAs (PMCA1a, PMCA1b, PMCA2, PMCA3a, PMCA3b, and PMCA4) and 7 isoforms of NCXs (NCX1a, NCX1b, NCX2a, NCX2b, NCX3, NCX4a, and NCX4b) were identified. In the reverse-transcriptase polymerase chain reaction (RT-PCR) analysis, 5 PMCAs and 2 NCXs were ubiquitously expressed in various tissues including gills. Triple fluorescence in situ hybridization and immunocytochemistry showed the colocalization of zecac, zpmca2, and zncx1b mRNAs in a portion of gill MR cells (using Na+-K+-ATPase as the marker), implying a subset of ionocytes specifically responsible for the transepithelial Ca2+ uptake in zebrafish gills. The gene expressions in gills of high- or low-Ca2+-acclimated zebrafish by quantitative real-time PCR analysis showed that zecac was the only gene regulated in response to environmental Ca2+ levels, while zpmcas and zncxs remained steady. CONCLUSIONS: The present study provides molecular evidence for the specific isoforms of Ca2+ transporters, zECaC, zPMCA2, and zNCX1b, supporting the current Ca2+ uptake model, in which ECaC may play a role as the major regulatory target for this mechanism during environmental challenge.