Six members of SLC30A/ZnTs family related with the control of zinc homeostasis: Characterization, mRNA expression and their responses to dietary ZnO nanoparticles in yellow catfish

Among various Zn transport proteins, SLC30A/ZnTs help Zn efflux from the cells and Zn compartmentation into the organelles, and so play important roles in the control of Zn homeostasis. The present study was conducted to clone and characterize six members (ZnT2, ZnT4, ZnT6, ZnT8, ZnT9 and ZnT10) of ZnT family and determine their expression patterns from yellow catfish Pelteobagrus fulvidraco. The influences of zinc oxide nanoparticles (ZnO NPs) in the diets on their mRNA expression were determined in several tissues, such as spleen, kidney, muscle and gill of yellow catfish. Six members (ZnT2, ZnT4, ZnT6, ZnT8, ZnT9 and ZnT10) of ZnT family of yellow catfish share similar domains to other fish and mammals. Their mRNAs were expressed in nine tissues (heart, liver, brain, spleen, kidney, muscle, mesenteric fat, intestine and gill), but at different levels. Dietary ZnO NPs addition increased Zn content in the spleen, kidney and gills, but not in the muscle. N,N,N′,N′-tetrakis(2-pyridylmethyl)-ethylenediamine (TPEN, Zn chelator) addition did not significantly influence Zn contents of four tested tissues of yellow catfish after high ZnO NPs feeding. The influences of dietary ZnO NPs addition on their mRNA levels in spleen, kidney, muscle and gill of yellow catfish were tissue-dependent. Our study, for the first time, identified and characterized six ZnT family members, found their ubiquitious expression among the tissues and elucidated their responses in yellow catfish fed ZnO NPs-added diet, indicating that these ZnT proteins act in tissue-specific manners in the control of Zn homeostasis.