Melanotransferrin: New Homolog Genes and Their Differential Expression during Intestinal Regeneration in the Sea Cucumber Holothuria glaberrima

ABSTRACT Melanotransferrin (MTf) is a protein associated with oncogenetic, developmental, and immune processes which function remains unclear. The MTf gene has been reported in numerous vertebrate and invertebrate species, including echinoderms. We now report the finding of four different MTfs in the transcriptome of the sea cucumber Holothuria glaberrima. Sequence studies and phylogenetic analyses were done to ascertain the similarities among the putative proteins and their relationship with other transferrin family members. The genes were shown to be differentially expressed in various holothurian organs and to respond differently when the animals were challenged with the immune system activator lipopolysaccharide (LPS). Moreover, the four genes were found to be highly overexpressed during the early stages of intestinal regeneration. The finding of four different genes in the holothurian is particularly surprising, because only one MTf gene has been reported in all other animal species sequenced to date. This finding, combined with the increase expression during intestinal regeneration, suggests a new possible function of MTf in organ regenerative processes. GRAPHICAL ABSTRACT Four melanotranferrin genes are present in the sea cucumber Holothuria glaberrima. The higher levels of expression of these genes occur during intestinal regeneration, suggesting that the gene functions are associated with regenerative processes. Figure represents the sequence model of Hg MTf1, showing target region 26‐756. The model was created at ModBase: Database of Comparative Structure Models. Pieper U, Webb BM, Dong GQ, Schneidman‐Duhovny D, Fan H, Kim SJ, Khuri N, Spill YG, Weinkam P, Hammel M, Tainer JA, Nilges M, Sali A. 2014. MODBASE, a database of annotated comparative protein structure models and associated resources. Nucleic Acids Research 42:D336‐46.