The role of ras gene in the development of haemic neoplasia in Mytilus trossulus

Disseminated neoplasia has been reported in mussels (Mytilus spp) from numerous locations worldwide. This condition is progressive and fatal and the aetiology is unknown. In vertebrates, oncogenes such as ras, and tumour suppressor genes such as p53, play important roles in carcinogenesis. We have cloned a Mytilus trossulus homologue of the vertebrate ras gene, which shows conserved sequence in regions of functional importance. Neoplastic hemolymph samples derived from M. trossulus have been investigated for the presence of ras gene mutations and changes in expression

Intersex related gene expression profiles in clams Scrobicularia plana : molecular markers and environmental application

Intersex, the appearance of female characteristics in male gonads, has been identified in several aquatic species. It is a widespread phenomenon in populations of the bivalve, Scrobicularia plana, from the southwest coast of the U.K. Genes previously identified as differentially expressed (ferritin, testicular haploid expressed gene, THEG, proliferating cell nuclear antigen, PCNA; receptor activated protein kinase C, RACK; cytochrome B, CYB; and cytochrome c oxidase 1, COX1) in intersex clams relative to normal male clams, were selected for characterisation and an environmental survey of the Channel region. Transcripts were significantly differentially expressed at sites with varying intersex incidence and contaminant burdens. Significant correlations between specific gene expressions, key contaminants and sampling locations have been identified, though no single gene was associated with intersex incidence. The results highlight the difficulty in understanding the intersex phenomenon in molluscs where there is still a lack of knowledge on the control of normal reproduction

Gonadal atresia, estrogen-responsive, and apoptosis-specific mRNA expression in marine mussels from the East China coast: a preliminary study

This preliminary survey analysed mussel atresia incidences, estrogen-responsive and apoptotic-specific molecular end points, and aqueous and gonadal levels of selected estrogens from the East China coast. Estrogen levels were low (e.g. < LOD-28.36ng/L, < LOD-3.88ng/g wet weight of tissue for BPA) relative to worldwide freshwater environments, but high oocyte follicle atresia incidences (up to 26.6%) occurred at selected sites. Expression of estrogen-responsive ER2 was significantly increased in males relative to females at sites with high atresia incidences in females. A second estrogen-responsive gene, V9, was significantly increased at two sites in April in females relative to males; the opposite was true for the remaining two sites. Apoptosis-specific genes (Bcl-2, fas) showed elevated expression in males relative to females at the site with the highest atresia incidence. These results provide coastal estrogen levels and the utility of several estrogen-specific molecular-level markers for marine mussels

Identification of Reproduction-Specific Genes Associated with Maturation and Estrogen Exposure in a Marine Bivalve Mytilus edulis

Background: While it is established that vertebrate-like steroids, particularly estrogens (estradiol, estrone) and androgens (testosterone), are present in various tissues of molluscs, it is still unclear what role these play in reproductive endocrinology in such organisms. This is despite the significant commercial shellfishery interest in several bivalve species and their decline. Methodology/Principal Findings: Using suppression subtraction hybridisation of mussel gonad samples at two stages (early and mature) of gametogenesis and (in parallel) following controlled laboratory estrogen exposure, we isolate several differentially regulated genes including testis-specific kinases, vitelline lysin and envelope sequences. Conclusions: The differentially expressed mRNAs isolated provide evidence that mussels may be impacted by exogenous estrogen exposure

Conservation of cancer genes in the invertebrate, Mytilus edulis

Mussels are susceptible to a wide range of environmental toxicants, including carcinogens, and thus are often employed as bioindicator species. To elucidate the molecular aetiology of such neoplastic damage, we have cloned Mytilus edulis homologues of the vertebrate ras proto-oncogene, and p53 tumour suppressor gene. The M. edulis ras cDNA encodes a predicted protein of 184 amino acids. The DNA sequence analysis with vertebrate ras sequences demonstrates that the M. edulis ras cDNA is highly conserved in regions of functional importance, including mutational hot spots. The partial p53 sequence also demonstrates that M. edulis p53 is highly conserved in two regions of functional importance and that these regions also include four of the five mutational hot spots for this gene. In contrast, the M. edulis p53 sequence shows little similarity to the other published invertebrate p53-like sequences. The cancer gene sequences characterised herein will allow development of specific biomarkers of genotoxic damage

Cadmium induction of metallothionein isoforms in juvenile and adult mussel (Mytilus edulis)

Isoforms of metallothionein in the digestive gland of control and experimentally Cd-exposed mussels Mytilus edulis (200 mg l-1 Cd2+ and 400 mg l-1 Cd2+; 20 days) were studied using the RT-PCR. In addition, glutathione S-transferase (GSTpi) primers were designed in order to evaluate the reduction in the antioxidant defence systems (glutathione) accompanying the ageing process in the same organisms. Following experimental exposure, an accumulation of Cd was observed in the digestive gland of exposed mussels, both adults and juveniles, up to 500 times higher than in control. An induction of the dimeric form MT20 II was detected in 400 mg l-1 exposed mussels, as well as a visible inhibition of the monomeric form MT10 IV. After 20 days exposure juveniles expressed increased GSTpi compared with adults. Results reveal individual variation of both metallothioneins and GSTpi expression among control and Cd2+ exposed mussels of different ages. The ecotoxicological significance of MT utilisation in biomonitoring of seawater for trace metals has been considered in light of these results

Correction: Identification of Reproduction-Specific Genes Associated with Maturation and Estrogen Exposure in a Marine Bivalve Mytilus edulis

Fig 1 of the published article is incomplete. Please view the complete Fig 1 and its legend here

Correction: Identification of Reproduction-Specific Genes Associated with Maturation and Estrogen Exposure in a Marine Bivalve Mytilus edulis.

Fig 1 of the published article is incomplete. Please view the complete Fig 1 and its legend here

Reference gene selection for qPCR in mussel, Mytilus edulis, during gametogenesis and exogenous estrogen exposure

Purpose: The aim of this study is to develop a normalization method for real-time PCR data by analyzing the most stably expressed control genes in mussel (Mytilus edulis) reproductive tissue. Methods: To facilitate this, six candidate genes, including several commonly used in the literature, were investigated in mussels at different stages of gametogenesis and following experimental exposure to a model estrogen (17b-estradiol). GeNorm and NormFinder softwares were employed to assess the stability of the reference genes. Results: Our results demonstrate that the most stable reference genes are not the same in mussels at different stages of gametogenesis and in experimentally E2-exposed mussels. Interestingly, HEL (helicase) and ACT (actin) mRNA expression levels were most affected by the stage of gametogenesis and yet, in molluscan studies, ACT is possibly the most frequently used reference gene. Conclusions: We demonstrate that the experimental results are highly dependent on the reference gene chosen and that statistically significant contrasting differences between sample groups are present or absent depending on the reference gene employed. © 2012 Springer-Verlag