Development of gene transfer technology for black tiger shrimp, Penaeus monodon

Combining Old and New Tricks: The Study of Genes, Neurons, and Behavior in Crayfish

For over a century the nervous system of decapod crustaceans has been a workhorse for the neurobiology community. Many fundamental discoveries including the identification of electrical and inhibitory synapses, lateral and pre-synaptic inhibition, and the Na⁺/K⁺-pump were made using lobsters, crabs, or crayfish. Key among many advantages of crustaceans for neurobiological research is the unique access to large, accessible, and identifiable neurons, and the many distinct and complex behaviors that can be observed in lab settings. Despite these advantages, recent decades have seen work on crustaceans hindered by the lack of molecular and genetic tools required for unveiling the cellular processes contributing to neurophysiology and behavior. In this perspective paper, we argue that the recently sequenced marbled crayfish, Procambarus virginalis, is suited to become a genetic model system for crustacean neuroscience. P. virginalis are parthenogenetic and produce genetically identical offspring, suggesting that germline transformation creates transgenic animal strains that are easy to maintain across generations. Like other decapod crustaceans, marbled crayfish possess large neurons in well-studied circuits such as the giant tail flip neurons and central pattern generating neurons in the stomatogastric ganglion. We provide initial data demonstrating that marbled crayfish neurons are accessible through standard physiological and molecular techniques, including single-cell electrophysiology, gene expression measurements, and RNA-interference. We discuss progress in CRISPR-mediated manipulations of the germline to knock-out target genes using the ‘Receptor-mediated ovary transduction of cargo’ (ReMOT) method. Finally, we consider the impact these approaches will have for neurophysiology research in decapod crustaceans and more broadly across invertebrates.

Transfection of crayfish hematopoietic tissue cells

Transfection is a powerful tool useful for studying gene function. Establishing transfection methods that enable highly efficient DNA uptake has become increasingly important. The crayfish hematopoietic tissue (Hpt) cell cultures have been proven to be suitable for studies on immunity and cell differentiation in crustaceans including shrimps, but no efficient gene transfer and expression method is available for these cells. Here we report a novel and highly efficient DNA transfection system based on electroporation. This method depends on a recombinant plasmid with the promoter from white spot syndrome virus immediate-early gene wsv249. This plasmid could be introduced into primary cells and efficiently express foreign genes by electroporation. By optimizing different electroporation parameters, more than 30% transfection efficiency could be achieved with the relative viability of cells around 50%. This is the first report of gene introduction to crayfish Hpt cells and will be useful for the expanding our research on crustacean immunity.

Function and regulation domains of a newly isolated putative β-actin promoter from pacific white shrimp

Current development of transgenic shrimp research has been hampered due to the lack of the suitable promoters and efficient transfection methods for crustaceans. A 1642 bp sequence, containing 5'-upstream sequence, exon 1, intron 1 and partial exon 2, which is responsible for transcriptional initiation of the newly reported shrimp β-actin (actinT1), has been isolated from the Pacific white shrimp (Litopenaeus vannamei) and named as SbaP. To determine its function and potential application in marine biotechnology, the sequence and functional domains were examined by constitutive expression of the luciferase reporter gene. We have identified 5' regions that play a central role in the expression of the β-actin gene. The proximal promoter (-1642/-1325) contains two highly conserved transcriptional sites, CCAAT box and CArG motif. Two negative (-1140/-924, -222/-21) and one positive (-810/-425) regulatory elements have been identified in intron1. Transient transfection assay with a construct containing proximal promoter and enhancer (SbaPΔ-222/+1Δ-1325/-924) regions of the shrimp β-actin coupled with luciferase and EGFP (enhanced green fluorescent protein) showed that the promoter was not only functional in sf21 cells, but promoter activity was more than 8-fold higher than a viral-origin promoter (ie1, white spot syndrome virus immediate early gene promoter). Furthermore, SbaPΔ-222/+1Δ-1325/-924 drove a successful expression of luciferase injection assay in vivo injection and also showed higher promoter activity than the ie1 promoter, suggesting that the expression vectors constructed with SbaPΔ-222/+1Δ-1325/-924 have important potential in gene transfer studies for shrimp and other crustacean species.

Gene transfection and expression in the primary culture of crayfish hemocytes

Lack of efficient gene delivery and expression methods is the major obstacle for crustacean research in the cellular level. Here, we reported the construction of an expression vector with a strong promoter from shrimp white spot syndrome virus. This vector could efficiently express foreign genes in the primary culture of crayfish hemocytes with the transfection efficiency between 5 and 10% by electroporation. Our findings provide a method for in vitro gene functional study in primary crayfish cells.

How to minimize formation and growth of tumours: potential benefits of decapod crustaceans for cancer research

Tumours have only rarely been observed in the decapod crustaceans, a large animal group of more than 10,000 species that includes the commercially important and well investigated shrimp, lobsters, crayfish and crabs. Analysis of the literature and information from cancer and diseases data bases revealed a total of 15 incidences, some of them being questionable. Even in the long-lived species, which can reach life spans of almost 100 years, neoplasias are virtually unknown. The data published so far suggest that the strikingly different frequencies of carcinogenesis between decapods and other well investigated animal groups like mammals, fish, insects and molluscs is based on differences of the metabolic pathways for carcinogens, the immune systems, and the regulation of stem cells. Therefore, representatives of the Decapoda may serve as useful models to study how organisms can successfully prevent or control spontaneously and environmentally induced cell proliferation. A particularly promising candidate for in-depth investigation of these topics is the marbled crayfish, a rather new clonal lineage that is presently being introduced as a laboratory model in development and epigenetics.