Comparative analysis of vertebral transcriptome in Japanese seabass (Lateolabrax japonicus) fed diets with varying phosphorus/calcium levels.

Aquaculture jeopardizes the aquatic environment by discharge of the most dietary phosphorus (P) into the water. Reducing the dietary P level is a common approach for decreasing the P discharge but it may result in increased risk of P deficiency leading to vertebral deformities. However, the molecular mechanism of vertebral deformities is poorly understood. We assessed vertebral transcriptome and compared the genes associated with bone metabolism in Japanese seabass (Lateolabrax japonicus) fed three diets containing different P and Ca levels including: diet I (0.4% P, 0.3% Ca), diet II (0.8% P, 0.3% Ca) and diet III (0.8% P, 3% Ca). The results showed that P deficiency reduces the ossification of vertebrae and induces visible vertebral deformities. Moreover, 256 gens were up-regulated and 125 genes were down-regulated in fish fed P deficient diets. Furthermore, administration of the diet with adequate P and Ca excess (diet III) resulted in the significant enhancement in expression of 19 genes and reduced expression of 93 genes. Comparing group II with group III, expression of 109 genes was up-regulated and expression of 1369 genes was down-regulated. Gene ontology enrichment analysis revealed significant alterations in biological functions by P deficiency. In summary, these findings indicated that both dietary P shortage and Ca excess lead to reduced differentiation and proliferation of osteoblast and induce a higher activity of osteoclastogenesis, which could subsequently impair vertebral mineralization and cause skeletal deformities.