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Effects of CRISPR/Cas9 knockout of the melanocortin-4 receptor (mc4r) gene in channel catfish, Ictalurus punctatus, were investigated. Three sgRNAs targeting the channel catfish mc4r gene in conjunction with Cas9 protein were microinjected in embryos and mutation rate, inheritance, and growth were studied. Efficient mutagenesis was achieved as demonstrated by PCR, Surveyor® assay, and DNA sequencing. An overall mutation rate of 33% and 33% homozygosity/bi-allelism was achieved in 2017. Approximately 71% of progeny inherited the mutation. Growth was generally higher in MC4R mutants than controls (CNTRL) at all life stages and in both pond and tank environments. There was a positive relationship between zygosity and growth, with F

Omega-3 polyunsaturated fatty acids (n-3 PUFAs), particularly eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3), play a very important role in human health. Channel catfish (Ictalurus punctatus) is one of the leading freshwater aquaculture species in the USA, but has low levels of EPA and DHA compared to some fish such as salmon. To improve EPA and DHA content, a modification of the n-3 PUFA biosynthetic pathway was achieved through the insertion of an elovl2 transgene isolated from masu salmon (Oncorhynchus masou) driven by a carp β-actin promoter using a two-hit by gRNA and two oligos with a targeting plasmid (2H2OP) CRISPR/Cas9 approach. Integration rate of the transgene was high (37.5%) and detected in twelve different tissues of P

The CRISPR/Cas9 platform holds promise for modifying fish traits of interest as a precise and versatile tool for genome manipulation. To reduce introgression of transgene and control reproduction, catfish species have been studied for upscaled disease resistance and intervening of reproduction to lower the potential environmental risks of introgression of escapees’ as transgenic animals. Taking advantage of the CRISPR/Cas9-mediated system, we succeeded in integrating the cathelicidin gene from an alligator (Alligator sinensis;As-Cath) into the target luteinizing hormone (LH) locus of channel catfish (Ictalurus punctatus) using two delivery systems assisted by double-stranded DNA (dsDNA) and single-stranded oligodeoxynucleotides (ssODNs), respectively. In this study, high knock-in (KI) efficiency (22.38%, 64/286) but low on-target was achieved using the ssODN strategy, whereas adopting a dsDNA as the donor template led to an efficient on-target KI (10.80%, 23/213). On-target KI ofAs-Cathwas instrumental in establishing theLHknockout (LH−_As-Cath+) catfish line, which displayed heightened disease resistance and reduced fecundity compared to the wild-type sibling fish. Furthermore, implanting with HCG and LHRHa can restore the fecundity, spawnability and hatchability of the new transgenic fish line. Overall, we replaced theLHgene with an alligator cathelicidin transgene and then administered hormone therapy to gain complete reproductive control of disease-resistant transgenic catfish in an environmentally sound manner. This strategy not only effectively improves the consumer-valued traits, but also guards against genetic contamination. This is a breakthrough in aquaculture genetics to confine fish reproduction and prevent the establishment of transgenic or domestic genotypes in the natural environment.

CRISPR/Cas9-mediated knock-in (KI) has a wide application in gene therapy, gene function study, and transgenic breeding programs. Unlike gene therapy, which requires accurate KI to correct gene mutation, transgenic breeding programs can accept robust KI as long as integration does not interrupt normal gene functions and result in any negative pleiotropic effects. High KI efficiency is required to reduce the breeding cost and shorten the breeding period, especially in transferring multiple foreign genes to a single individual. To elevate the KI efficacy and achieve multiple gene KIs simultaneously, we introduced a new strategy that enables transgene integration into numerous sites of the genome by targeting long repeated sequences (LRSs). Using this simple strategy, for the first time we successfully generated transgenic fish carrying the masu salmon (

Channel catfish, Ictalurus punctatus, have limited ability to synthesize Ω-3 fatty acids due to a lack of elongases and desaturases. The ccβA-msElovl2 transgene containing masu salmon, Oncorhynchus masou, elongase gene driven by the common carp, Cyprinus carpio, beta-actin promoter was inserted into the channel catfish melanocortin-4 receptor (mc4r) gene site using the two-hit two-oligo with plasmid (2H2OP) method. The best performing sgRNA resulted in a knockout mutation rate of 92% with 69% homozygosity/bi-allelism, a knock-in rate of 54% and a simultaneous knockout/knock-in rate of 49%. Fish simultaneously mutated with the ccβA-msElovl2 transgene knock-in and mc4r knockout (Elovl2) were 41.8% larger than controls at 6 months post-hatch. Mean eicosapentaenoic acid (EPA, C20:5n-3) levels in Elov2 mutants and MC4R mutants were 121.6% and 94.1% higher than in controls, respectively. Observed mean docosahexaenoic acid (DHA, C22:6n-3) and total EPA+DHA content was 32.8% and 45.1% higher, respectively, in Elovl2 fish than controls. To our knowledge this is the first example of multiplexed genetic engineering and gene editing of a commercially important aquaculture species for valuable performance traits. With a high mutation rate, improved growth, and higher omega-3 fatty acid content, the use of Elovl2 channel catfish appears beneficial for application on commercial farms.

An acute cyprinid herpesvirus 2 (CyHV-2) infection of crucian carp (Carassius auratus gibelio) is characterized with hemorrhagic inflammation and high mortality. Berberine is a biologically active plant alkaloid with an anti-inflammation function involving the regulation of transcription factor NF-κB and its downstream inflammation-related genes in mammalian organisms. Our previous study had indicated that BBH (berberine chloride hydrate) inhibited gene expression and replication of CyHV-2, and might serve as a potential small molecular drug for controlling CyHV-2 infection in crucian carp. Here, NF-κB signaling in CyHV-2-infected crucian carp treated with BBH was investigated both in vitro and in vivo. Real-time RT-PCR and ELISA assays revealed that CyHV-2 could activate the NF-κB signaling resulting in up-regulation of its downstream pro-inflammatory gene expression including IL-6, IL-8, IL-1β and TNF-ɑ. BBH could attenuate NF-κB signaling and downregulate the expression of its downstream inflammatory cytokines in a dose-dependent manner both in vivo and in vitro. BBH not only dose-dependently inhibits viral load in CyHV-2-susceptible crucian carp cell lines in infection and inhibition assays, but also ameliorates inflammatory injury in CyHV-2-targeted organ in histopathology examinations. Thus, negative regulation of NF-κB by BBH should contribute to BBH-mediated protection of crucian carp from CyHV-2 infection via attenuating viral gene expression and host inflammatory response simultaneously.

Channel catfish (Ictalurus punctatus) is the primary culture species in the US along with its hybrid made with male blue catfish, I. furcatus. In an effort to improve the nutritional value of channel catfish, the masou salmon Δ5-desaturase like gene (D5D) driven by the common carp beta-actin promoter (βactin) was inserted into channel catfish. The objectives of this study were to determine the effectiveness of βactin-D5D for improving n-3 fatty acid production in F1 transgenic channel catfish, as well as examine pleiotropic effects on growth, proximate analysis, disease resistance, and other performance traits. Transgenic F1 channel catfish showed a 33% increase in the relative proportion of n-3 fatty acids coupled with a 15% decrease in n-6 fatty acids and a 17% decrease in n-9 fatty acids when compared to non-transgenic full-siblings (P

Grass carp reovirus (GCRV) infection causes apoptosis in Ctenopharyngodon idella kidney cells (CIK). However, the cause of GCRV-induced apoptosis and its signaling pathways remain unknown. This study investigated the role of TNF-α-induced capase-8 pathways in mediating GCRV-induced apoptosis in the grass carp (Ctenopharyngodon idella). Recombinant TNF-α was expressed and purified from Escherichia. coli. The western blot assay indicated that TNF-α expression level in kidney and spleen was higher than that in liver. In apoptosis assay, recombinant TNF-α triggered significant apoptosis in CIK cells, which was characterized by increased mRNA levels of TNF-α, TRADD or caspase-8, and enhanced caspase-8 activity in CIK cells. To confirm the biological activity of TNF-α during GCRV infection, significant apoptosis in CIK cells was induced by GCRV correlating with enhanced caspase-8 activity, increased mRNA level of TNF-α, TRADD or caspase-8, increased protein level of TNF-α in CIK cells and cell supernatant, suggesting that TNF-α-induced capase-8 pathways might be involved in GCRV-triggered apoptosis. Furthermore, treatment with an anti-TNF-α polyclonal antibody significantly decreased the degree of apoptosis in infected CIK cells compared with cells treated with a control antibody, which confirmed that TNF-α was a key mediator involved in GCRV-induced apoptosis. Taken together, these results indicated that GCRV might trigger apoptosis via TNF-α induced capase-8 pathways in CIK cells.