Myostatin gene (MSTN) can inhibit the proliferation of myoblast, which in turn promotes muscle growth and inhibits adipocyte differentiation in livestock. MSTN mutation may lead to muscle hypertrophy or double-muscled (DM) phenotype. MSTN mutation animal, such as sheep, dog, and rabbit have been generated through CRISPR/Cas9 technology. However, goats with promising MSTN mutation have not been generated. We designed two sgRNAs loci targetting exon3 of MSTN gene to destroy the MSTN cysteines knots. We got seven goats from seven recipients, in which six were MSTN knocked-out (KO) goats, with a mutation rate of 85.7%. Destroyed cysteine knots caused MSTN structure inactivation. The average body weight gain (BWG) per day of MSTN KO goats was significantly higher than that of wild-type (WT) goats. MSTN KO goats showed abnormal sugar, fat, and protein metabolism compared with wild-type controls (MSTN+/+). Inheritance of mutations was observed in offspring of MSTN KO goats by PCR analysis.

Rabbits (Oryctolagus cuniculus) have been the very frequently used as animal models in the study of human lipid metabolism and atherosclerosis, because they have similar lipoprotein metabolism to humans. Most of hyperlipidemia and atherosclerosis rabbit models are produced by feeding rabbits a high-cholesterol diet. Gene editing or knockout (KO) offered another means of producing rabbit models for study of the metabolism of lipids and lipoproteins. Even so, apolipoprotein (Apo)E KO rabbits must be fed a high-cholesterol diet to induce hyperlipidemia.In this study, we used the CRISPR/Cas9 system anchored exon 7 of low-density lipoprotein receptor (LDLR) in an attempt to generate KO rabbits. We designed two sgRNA sequences located in E7:g.7055–7074 and E7:g.7102–7124 of rabbit LDLR gene, respectively. Seven LDLR-KO founder rabbits were generated, and all of them contained biallelic modifications. Various mutational LDLR amino acid sequences of the 7 founder rabbits were subjected to tertiary structure modeling with SWISS-MODEL, and results showed that the structure of EGF-A domain of each protein differs from the wild-type. All the founder rabbits spontaneously developed hypercholesterolemia and atherosclerosis on a normal chow (NC) diet. Analysis of their plasma lipids and lipoproteins at the age of 12 weeks revealed that all these KO rabbits exhibited markedly increased levels of plasma TC (the highest of which was 1013.15 mg/dl, 20-fold higher than wild-type rabbits), LDL-C (the highest of which was 730.00 mg/dl, 35-fold higher than wild-type rabbits) and TG accompanied by reduced HDL-C levels. Pathological examinations of a founder rabbit showed prominent aortic atherosclerosis lesions and coronary artery atherosclerosis.In conclusion, we have reported the generation LDLR-KO rabbit model for the study of spontaneous hypercholesterolemia and atherosclerosis on a NC diet. The LDLR-KO rabbits should be a useful rabbit model of human familial hypercholesterolemia (FH) for the simulations of human primary hypercholesterolemia and such models would allow more exact research into cardio-cerebrovascular disease.

Human copper/zinc superoxide dismutase (CuZn-SOD) and extracellular superoxide dismutase (EC-SOD) are two superoxide dismutases that scavenge reactive oxygen species (ROS). Their biological role of eliminating oxidative stress caused by excessive ROS levels in living organisms has been utilized in medical treatment, preventing skin photoaging and food preservation. In this study, we employed two sequences that encode human CuZn-SOD and EC-SOD, along with goat beta-casein 5' and 3' regulatory elements, to construct mammary gland-specific expression vectors. Bitransgenic goats were generated using somatic cell nuclear transfer (SCNT), which employed co-transfection to generate bitransgenic goat fetal fibroblast cells as donorcells, and the expression of human CuZn-SOD and EC-SOD and their biological activities were assayed in the milk. PCR and Southern blot analysis confirmed that the cloned goat harbors both hCuZn-SOD and hEC-SOD transgenes. rhCuZn-SOD and rhEC-SOD were expressed in the mammary glands of bitransgenic goat, as determined by western blotting. The expression levels were 100.14 ± 5.09 mg/L for rhCuZn-SOD and 279.10 ± 5.38 mg/L for rhEC-SOD, as determined using ELISA. A total superoxide dismutase assay with WST-8 indicates that the biological activity of rhCuZn-SOD and rhEC-SOD in goat milk is 1451 ± 136 U/mL. The results indicate that two expression vectors can simultaneously transfect goat fetal fibroblast cells as donor cells to produce transgenic goats by SCNT, and the CuZn-SOD and EC-SOD proteins secreted in the mammary glands showed biological activity. The present study thus describes an initial step in the production of recombinant human SODs that may potentially be used for therapeutic purposes.

Expression efficacy of recombinant protein in current expression systems is generally low. Therefore, the expression levels of recombinant proteins in the breast milk of transgenic animals are typically low. In view of this, the present study aimed to construct homozygous transgenic rabbits with a high expression level of recombinant human plasminogen activator (rhPA) during the entire lactation period. Homozygous transgenic rabbits were obtained using an effective rhPA mammary‑specific expression vector PCL25/rhPA. The expression level and thrombolytic ability of rhPA in the milk of both homozygous and hemizygous rabbits were detected by enzyme‑linked immunosorbent and fibrin agarose plate assays. It was observed that the expression of rhPA was constant during the entire lactation period in homozygous rabbits, while the expression of rhPA declined slowly in hemizygote rhPA transgenic rabbits during the lactation period. In addition, the expression of rhPA in homozygous transgenic rabbit was ~950 µg/ml, which was markedly higher in comparison with that in hemizygote rabbits. Furthermore, increased gene copy number was observed to increase the expression level of rhPA at the same integration vector.

BackgroundThromboses is a rapidly growing medical problem worldwide. Low-cost, high-scale production of thrombotic drugs is needed to meet the demand. The production of biomolecules in transgenic animals might help address this issue. To our knowledge, the expression of recombinant human plasminogen activator (rhPA) in goat mammary glands has never been reported before.MethodsWe constructed a mammary gland–specific expression vector, BLC14/rhPA, which encodes only the essential K2 fibrin-binding and P domains of wild-type tPA (deletion mutant of tPA lacking the F, E, and K1 domains), along with the goat β-lactoglobulin gene signal peptide-coding sequence. The mammary gland–specific expression vector BLC14/rhPA was transfected into goat fetal fibroblast cells by electroporation. After selection for 3 weeks by G418, stably transfected cell colonies were obtained. PCR analysis results indicated that 24 of the resistant clones were transgenic cell lines; of these, 8 lines were selected as the donor cells. The positive cells were starved for 72 h with DMEM/F12 medium containing 0.5% FBS and were then used as do. Finally, 256 reconstructed oocytes were transferred into 26 recipients, and 7 of them became pregnant (pregnancy rate, 26.9%). Two kids were obtained (BP21 and BP22). PCR analysis confirmed that both were transgenic goats. To analyze the heredity of the rhPA expressed in BP21 F0 and F1 transgenic goats, the F0 transgenic goat BP21 was mated with a normal male goat to generate an F1 transgenic goat. Enucleated metaphase II (MII) oocytes and positive donor cells were used to reconstruct embryos, which were transplanted into the oviducts of the recipients.ResultsWestern blot results showed a specific 39 kDa band. The rhPA expression level in transgenic goat whey was about 78.32 μg/mL by ELISA. Results of ELISA and the in vitro thrombolysis test (FAPA) showed that specific activity of the rhPA in the milk of F0 and F1 transgenic goats was 13.3 times higher than that of the reteplase reference material.ConclusionThus, we demonstrated that BLC14/rhPA was reasonably effective for expression in the mammary glands of transgenic goats, and was stably inherited by the offspring. This study provides the basis for the large-scale production of biological pharmaceuticals in transgenic animals. The expression of biopharmaceuticals by transgenic animals can be used for pharmacological research and bioactive analysis, and transgenic goats were demonstrated to be promising animals for the large-scale production of thrombolytic biopharmaceuticals.