Myostatin site-directed mutation and simultaneous PPARγ site-directed knockin in bovine genome

Most studies on the acquisition of advantageous traits in transgenic animals only focus on monogenic traits. In practical applications, transgenic animals need to possess multiple advantages. Therefore, multiple genes need to be edited simultaneously. CRISPR/Cas9 technology has been widely used in many research fields. However, few studies on endogenous gene mutation and simultaneous exogenous gene insertion performed via CRISPR/Cas9 technology are available. In this study, the CRISPR/Cas9 technology was used to achieve myostatin (MSTN) point mutation and simultaneous peroxisome proliferator-activated receptor-γ (PPARγ) site-directed knockin in the bovine genome. The feasibility of this gene editing strategy was verified on a myoblast model. The same gene editing strategy was used to construct a mutant myoblast model with MSTN mutation and simultaneous PPARγ knockin. Quantitative reverse-transcription polymerase chain reaction, immunofluorescence staining, and western blot analyses were used to detect the expression levels of MSTN and PPARγ in the mutant myoblast. Results showed that this strategy can inhibit the expression of MSTN and promote the expression of PPARγ. The cell counting kit-8 cell proliferation analysis, 5-ethynyl-2'-deoxyuridine cell proliferation analysis, myotube fusion index statistics, oil red O staining, and triglyceride content detection revealed that the proliferation, myogenic differentiation, and adipogenic transdifferentiation abilities of the mutant myoblasts were higher than those of the wild myoblasts. Finally, transgenic bovine embryos were obtained via somatic cell nuclear transfer. This study provides a breeding material and technical strategy to breed high-quality bovine and a gene editing method to realize the mutation of endogenous genes and simultaneous insertion of exogenous genes in genomes.

Effect of season on the in-vitro maturation and developmental competence of buffalo oocytes after somatic cell nuclear transfer

Somatic cell nuclear transfer (SCNT) is a valuable technology tool with various uses in transgenic animals, regenerative medicine, and stem cell research. However, the efficiency of SCNT embryos appears to have poor developmental competency. Environmental issues may adversely affect SCNT embryos in buffalo. Thereafter, the present study aimed to explore the effect of season on the maturation of buffalo oocytes and subsequent developmental capability after parthenogenetic activation and SCNT in buffalo. Buffalo oocytes (n = 6353) were collected from local slaughterhouse at various seasons; spring (March-April), summer (May-August), autumn (September-November), and winter (December-January). A significant increase (p < 0.05) was recorded in the maturation rate (57.07%) at autumn compared with spring, summer, and winter (50.46, 50.93, and 50.66%, respectively). No significant differences were recorded in the fusion and the cleavage rates among all seasons. Blastocyst development rate was higher (p < 0.05) in autumn and winter (16.52 ± 8.45% and 15.98 ± 7.17%, respectively) than in spring and summer (9.47 ± 6.71% and 10.84 ± 6.58%, respectively) seasons. It could be concluded that the season had a significant effect on oocyte development competence which can be used for SCNT in buffalo.

Effects of PXD101 and Embryo Aggregation on the In Vitro Development of Mouse Parthenogenetic Embryos

To improve the isolation efficiency of parthenogenetic embryonic stem cells (pESCs) in mice, it is necessary to optimize the method to increase in vitro developmental competence of mice parthenogenetic blastocysts. Therefore, this study aims to investigate an optimal method for the production of mouse parthenogenetic blastocysts and isolation of pESC colonies by comparing the effects of two methods: (1) the treatment of histone deacetylase inhibitor PXD101 before, during, or after parthenogenetic activation; (2) parthenogenetic embryo aggregation; and (3) their combination treatment. The results suggest that application of PXD101 treatment and embryo aggregation could both improve the development of mouse parthenogenetic blastocysts (50 nM PXD101 treated 4 hours during activation and further 4 hours after activation: 40.0% vs. 20.0%; p < 0.05; two-cell embryo aggregation: 38.3% vs. 20.0%; p < 0.05) and also enhance the isolation rate of pESC colonies (PXD101: 33.3% vs. 11.8%; p < 0.05; two-cell embryo aggregation: 36.4% vs. 11.8%; p < 0.05). The combination of their treatments had the higher rate of parthenogenetic blastocyst development (41.7%) and significantly higher rate of pESC colony isolation from parthenogenetic blastocysts (45.0%); therefore, we concluded that the combination of these two methods (50 nM PXD101 treated for 8 hours and then aggregated at two-cell stage with 0.25% pronase for 10 minutes in our self-made concave) is considered the optimal way for the in vitro development of parthenogenetic blastocysts and subsequent pESC colony isolation in mice, opening new opportunities for application of this combination method to improve the parthenogenetic embryo development in other species.