Zoological Studies

Cystic Fibrosis Transmembrane Conductance Regulator (CFTR): An Apical Marker Protein of Ionocytes for Identifying Hypo-osmoregulation in Gills of the Euryhaline Medaka Oryzias dancena

Chao-Kai Kang, Shu-Chuan Tsai, Shang-Tao Lin, Wan-Yu Lo, Tsung-Han Lee, and Pung-Pung Hwang (2012) This study used a monoclonal antibody against the human cystic fibrosis transmembrane conductance regulator (CFTR) to characterize its expression in gills of the brackish medaka Oryzias dancena.  Whole-mount double immunofluorescence staining of gills revealed that the CFTR protein was localized in apical membranes of Na⁺, K⁺-ATPase-immunoreactive ionocytes in gills of seawater (SW)-acclimated medaka.  Immunoreactive signals of the CFTR protein were detected by the antibody in gills of SW medaka rather than in those of freshwater (FW) fish.  Furthermore, the full-length complementary (c)DNA of Odcftr was cloned and identified from gill tissues to evaluate specific affinities of the CFTR antibody.  Using the RT-PCR to survey gene expressions in various tissues, Odcftr was prominently expressed in gills of the brackish medaka.  Higher messenger (m)RNA levels of Odcftr were found in gills of medaka acclimated to environments with increasing salinities.  The present study validated the salinity-dependent expression of the CFTR in branchial ionocytes of the brackish medaka and illustrated that the CFTR protein is a marker of the hypo-osmoregulatory role of the gill epithelium of this euryhaline teleost.