Expression of galaxin and oncogene homologs in growth anomaly in the coral Montipora capitata

Abstract

Growth anomaly (GA) is a coral disease characterized by enlarged skeletal lesions. Although negative effects of GA on several of coral's biological functions have been determined, the etiology and molecular pathology of this disease is very poorly understood. We studied the expression of 5 genes suspected to play a role in pathological development of GA in the endemic Hawaiian coral Montipora capitata, which is particularly susceptible to this disease. Transcript abundances of the 5 target genes in healthy tissue, GA-affected tissue, and unaffected tissue (apparently healthy tissue adjacent to GA) relative to 3 internal control genes (actin, NADH, and rpS3) were compared using quantitative reverse transcriptase PCR. Galaxin, which codes for a protein suspected to be involved in calcification and thus hypothesized to be differentially expressed in GA, was up-regulated in unaffected tissue but remained at baseline levels in GA tissue. The gene expressions of murine double minute 2 (MDM2) and tumor necrosis factor (TNF) remained unchanged in GA tissue. The expression of tyrosine protein kinase (TPK) and βγ-crystallin (BGC) were both down-regulated. These expression patterns were all inconsistent with the expression patterns of homologous genes in neoplastic diseases featuring similar morphological symptoms in humans. These expression data therefore suggest that the calcification mechanism is likely not enhanced in coral GA and that coral GA is not a malignant neoplasia.

Advances in coral immunity ‘omics in response to disease outbreaks

“…Off the coast of Hawai'i, high prevalence of GA has been documented on colonies of Montipora capitata in areas of dense human populations; however the precise cause of the disease is still not understood (Takabayashi et al, 2010;Aeby et al, 2011). To further understand the molecular drivers of this disease, Spies and Takabayashi (2013) used quantitative real-time-polymerase chain reaction (qRT-PCR) methods to quantify the DGE of several previously identified immune and onco-genes including galaxin, murine double minute 2 (MDM2), tumor necrosis factor (TNF), tyrosine protein kinase (TPK), and bg-crystallin (BGC). TNF was unchanged in GA compared with healthy and non-GA areas, whereas galaxin, a coral calcification gene, was upregulated in non-GA areas (Spies and Takabayashi, 2013).…”

“…To further understand the molecular drivers of this disease, Spies and Takabayashi (2013) used quantitative real-time-polymerase chain reaction (qRT-PCR) methods to quantify the DGE of several previously identified immune and onco-genes including galaxin, murine double minute 2 (MDM2), tumor necrosis factor (TNF), tyrosine protein kinase (TPK), and bg-crystallin (BGC). TNF was unchanged in GA compared with healthy and non-GA areas, whereas galaxin, a coral calcification gene, was upregulated in non-GA areas (Spies and Takabayashi, 2013). Later, a transcriptomic analysis of M. capitata affected by GA was performed and several genes involved in collagen, osteogenesis, and skeletal matrix production were significantly upregulated in GA-affected tissues (Frazier et al, 2017).…”

De novo metatranscriptome assembly and coral gene expression profile of Montipora capitata with growth anomaly

“…Since the main sign of this disease is the anomalously enlarged skeletal growth, some studies have taken oncological research approaches to coral GA. Histological and molecular studies targeting specific oncogenes and proteins have presented inconclusive and conflicting evidence for GA being hyperplastic in both Porites compressa [ 13 ] and M. capitata [ 16 ] and neoplastic (uncontrolled growth of cells that is not under physiologic control) in M. capitata [ 27 ]. A more recent study broadened the focus beyond oncogenes to a meta-transcriptomic analysis of the coral P. carnosa to identify genes affected by GA, yielding new insights into the impact of GA on osteogenesis, oncogenesis, and the immune system [ 11 ].…”

The Matrix Protein Cysrichin, a Galaxin-like Protein from Hyriopsis cumingii, Induces Vaterite Formation In Vitro

“…The cysrichin protein showed 16.03% consensus with the galaxin protein, and the most significant characteristic was the presence of repeated motifs of dicysteine residues. Galaxin is the most abundant and important protein in the coral organic matrix and relates to coral skeleton formation [ 25 ]. Framework proteins are frequently Cys-rich [ 26 , 27 ], and the double Cys motif can form intramolecular crosslinks through disulfide bonds [ 27 ].…”