Molecular cloning, characterization and expression analysis of melanotransferrin from the sea cucumber Apostichopus japonicus

Draft Genome of the Sea Cucumber Holothuria glaberrima, a Model for the Study of Regeneration

Regeneration is one of the most fascinating and yet least understood biological processes. Echinoderms, one of the closest related invertebrate groups to humans, can contribute to our understanding of the genetic basis of regenerative processes. Among echinoderms, sea cucumbers have the ability to grow back most of their body parts following injury, including the intestine and nervous tissue. The cellular and molecular events underlying these abilities in sea cucumbers have been most extensively studied in the species Holothuria glaberrima. However, research into the regenerative abilities of this species has been impeded due to the lack of adequate genomic resources. Here, we report the first draft genome assembly of H. glaberrima and demonstrate its value for future genetic studies. Using only short sequencing reads, we assembled the genome into 89,105 scaffolds totaling 1.1 gigabases with an N50 of 25 kilobases. Our BUSCO assessment of the genome resulted in 894 (91.4%) complete and partial genes from 978 genes queried. We incorporated transcriptomic data from several different life history stages to annotate 51,415 genes in our final assembly. To demonstrate the usefulness of the genome, we fully annotated the melanotransferrin (Mtf) gene family, which have a potential role in the regeneration of the sea cucumber intestine. Using these same data, we extracted the mitochondrial genome, which showed high conservation to that of other holothuroids. Thus, these data will be a critical resource for ongoing studies of regeneration and other studies in sea cucumbers.

Comparative expression analysis of immune-related factors in the sea cucumber Apostichopus japonicus

In order to preliminarily explore the joint involvement of different immune-related factors during the same immune process in Apostichopus japonicus, the transcriptional expression of Cu/Zn superoxide dismutase (Cu/Zn-SOD), catalase (CAT), c-type lysozyme (c-LYZ), i-type lysozyme (i-LYZ), cathepsin D, melanotransferrin (MTF), Toll, c-type lectin (c-LCT) and complement 3 (C3) during the development from fertilized eggs to juveniles and after challenging the juveniles with Vibrio splendidus, Pseudoalteromonas nigrifaciens, Shewanella baltica and Bacillus cereus, respectively, was measured using the method of quantitative real-time PCR (qRT-PCR), and then the correlations among different immune-related factors were analyzed. The results showed that the selected immune-related factors were expressed at all of the determined developmental stages and significantly up-regulated at doliolaria stage, suggesting the selected factors are indispensable immune components and the immune system might be broadly activated at doliolaria stage in A. japonicus. After challenged with four pathogenic bacteria, Cu/Zn-SOD, CAT, i-LYZ, cathepsin D, MTF, Toll, C3 were all significantly down-regulated at 4 h, indicating that some components of A. japonicus immune system might be inhibited at the beginning of pathogenic bacteria invasion. The immune-responsive analysis also showed that the significant regulation in Toll after challenged with four tested bacteria, that in MTF after challenged with S. baltica and that in C3 after challenged with P. nigrifaciens were all minus, suggesting Toll, MTF and C3 are probably the primary targets of pathogenic bacteria attack. Furthermore, the correlation analysis indicated that, all of the selected immune-related factors except cathepsin D might be in the same immune regulatory network during A. japonicus development, while all of the selected immune-related factors except c-LYZ might be in the same responsive regulatory network after challenged with four pathogenic bacteria. Altogether, A. japonicus immune system exhibited high complexity in regulation during organism development and after bacterial challenges.

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

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.

Cloning, Expression, and Characterization of Capra hircus Golgi α-Mannosidase II

Golgi α-mannosidase II (GMII), a key glycosyl hydrolase in the N-linked glycosylation pathway, has been demonstrated to be closely associated with the genesis and development of cancer. In this study, we cloned cDNA-encoding Capra hircus GMII (chGMII) and expressed it in Pichia pastoris expression system. The chGMII cDNA contains an open reading frame of 3432 bp encoding a polypeptide of 1144 amino acids. The deduced molecular mass and pI of chGMII was 130.5 kDa and 8.04, respectively. The gene expression profile analysis showed GMII was the highest expressed gene in the spleen. The recombinant chGMII showed maximum activity at pH 5.4 and 42 °C and was activated by Fe(2+), Zn(2+), Ca(2+), and Mn(2+) and strongly inhibited by Co(2+), Cu(2+), and EDTA. By homology modeling and molecular docking, we obtained the predicted 3D structure of chGMII and the probable binding modes of chGMII-GnMan5Gn, chGMII-SW. A small cavity containing Tyr355 and zinc ion fixed by residues Asp290, His176, Asp178, and His570 was identified as the active center of chGMII. These results not only provide a clue for clarifying the catalytic mechanism of chGMII but also lay a theoretical foundation for subsequent investigations in the field of anticancer therapy for mammals.

A review of the immune molecules in the sea cucumber

It is very important to identify and characterize the immune-related genes that respond to pathogens. Until recently, only some of the immune-related genes in sea cucumbers had been characterized. Their expression patterns after pathogen challenges have been analyzed via expressed sequence tag libraries, microarray studies and proteomic approaches. These genes include lectins, antimicrobial peptides, lysozyme, enzymes, clotting protein, pattern recognition proteins, Toll receptors, complement C3 and other humoral factors that might participate in the innate immune system of sea cucumbers. Although the participation of some of these immune molecules in the sea cucumber's innate immune defense against invading pathogens has been demonstrated, the functions of many of the molecules remain unclear. This review focuses on the discovery and functional characterization of the immune-related molecules from the sea cucumber for the first time and provides new insights into the immune mechanisms of the sea cucumber, which opens new possibilities for developing drugs for novel anti-bacterial and antiviral applications in fisheries.