The sea cucumber Apostichopus japonicus is an important economic species in China. Its dorsal body wall color is commonly tawny, whereas its ventral surface is fawn. Albino sea cucumbers are rarely observed. In order to profile gene expression and screen albinism-related genes, we compared the transcriptome of albino samples with a control by 454 cDNA sequencing. We found that 6 539 identified genes on the basis of sequence similarity to known genes were expressed in the albino A. japonicus. The gene ontology analysis indicated that the transcription of genes associated with the terms of biological regulation and pigmentation was non-abundant in the albino library compared to the control. Based on an analysis using the Kyoto Encyclopedia of Genes and Genomics(KEGG) database, we identified 14 important genes that were involved in major intercellular signaling pathways related to melanin synthesis, such as tyrosine metabolism, the mitogen-activated protein kinase(MAPK) pathway, and melanogenesis. The expressions of fibroblast growth factor receptor 4(FGFR4), protein kinase C(PKC), protein kinase A(PKA), and Ras genes were significantly down-regulated in the albino transcriptome compared with the control, while the expressions of homogentisate 1, 2-dioxygenase gene(HGO), cAMP-responsive element binding protein(CREB), transcription factor AP-1(c-jun), and calmodulin(CaM) were significantly up-regulated(Fisher's exact test, p < 0.05). These differentially expressed genes could be candidate genes for revealing the mechanism of albinism and investigating regulation of melanin synthesis in A. japonicus.
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