Myostatin (Mstn) is a conserved negative regulator of skeletal muscle mass in mammals. However, whether precise disruption of Mstn in livestock can be achieved and safely used to improve meat productivity has not been proven. We applied CRISPR/Cas9 system to generate Mstn knock-out (KO) rabbits and goats and then analyzed the changes in their phenotypes to answer this question. We efficiently generated 24 Mstn KO rabbits out of 32 newborn infants after embryo injection with two sgRNAs targeting rabbit Mstn, and found that the Mstn KO rabbits exhibited increased birthweight and a significantly increase in the weight ratios of the quadriceps and biceps muscles to the whole body. Mstn KO also caused high probability of enlarged tongue phenomenon and severe health problems such as stillbirth and early stage death. Using the same method, one out of four goats was generated with edition at Mstn locus. The early stage growth rate of this goat outperformed the control goats. In conclusion, we efficiently generated Mstn KO rabbits and goats using CRISPR/Cas9 technology. However, Mstn KO causes severe health problems and may also have the same effects on other species. This safety issue must be studied further before applied to animal reproduction processes.

In mammals, their proper development during the early cleavage stages strongly relies on the gene products newly transcribed by zygotic genome activation (ZGA). Long noncoding RNAs (lncRNAs) have been characterized as key regulators of the ZGA process in mice and human. However, the ZGA stage has not yet been identified and epigenetic regulations of the ZGA process remain largely unknown in goats. Here, we show that ZGA occurred at the 8-cell stage in goats. During ZGA, tri-methylation of H3K9 was dynamically changed but maintained strong staining in development arrested embryos. Using single-cell RNA sequencing, we identified 800 mRNAs and 250 lncRNAs as candidates of key molecules in goat preimplantation embryos. These mRNAs and lncRNAs were differentially expressed from 4- to 8-cell stage embryos and were strongly enriched in terms of retinoic acid receptor signaling pathway as well as signaling pathway regulating pluripotency of stem cells. In particular, we found that microinjection of siRNA against lnc_137 caused development arrest. Our results are consistent with the notion that lncRNAs play vital roles during ZGA, and the data presented here provide an excellent source for further ZGA lncRNA studies.

In summer, the high temperature affects animal growth and reproductive performance. Curcumin is a flavonoid with anti-oxidant and anti-inflammatory effects. To evaluate the effects of dietary curcumin supplement on the blood biochemical parameters and testicular gene expressions in Hu sheep in summer, a total of 144 male Hu sheep aged four months were randomly divided into three groups (Con, Cur1, and Cur2, n = 48). Sheep in Con, Cur1, and Cur2 groups were fed a basal diet supplement with 0, 450, and 900 mg (per sheep) curcumin daily, respectively. Sheep were fed for 35 days, including a pre-feed for seven days. The results showed that the supplement with 450 mg and 900 mg curcumin increased serum free fatty acid (NEFA) and glutathione peroxidase (GPX), as well as IgA and IgM. The supplement with 450 mg curcumin increased the IgG level, while the supplement with 900 mg curcumin had a lower IgG level than the supplement with 450 mg curcumin (p < 0.05). Dietary curcumin supplement increased testicular organ index, serum testosterone level, and testicular star mRNA expression (p < 0.05). Furthermore, dietary curcumin supplement linearly inhibited testicular apoptosis with increased testicular bcl-2 mRNA expression and decreased caspase-3 mRNA expression (p < 0.05). In conclusion, dietary curcumin supplement can promote lipid metabolism, antioxidant capacity, and immune response, as well as testicular development, in Hu sheep, which provides evidence of application of curcumin in sheep production.

Maternal mRNA clearance is critical for the early embryo development, which is under the tight control of RNA N6-methyladenosine (m⁶A). However, little information is known regarding the maternal mRNA clearance and mechanisms behind it in farm animals. In the present study, 3362 differentially expressed genes (DEGs) were found during the maternal-to-zygotic transition (MZT) and determined as maternal mRNAs in goat. Of which, 1961 was decreased at the 4-cell stage embryos, while 1401 was trigged down-regulation at the 8-cell stage embryos, which were termed as maternally encoded mRNA decay genes and zygotic genome activation (ZGA)-dependent maternal mRNAs, respectively. The expression of m⁶A reader YTHDF2 was increased during goat ZGA, and knockdown of YTHDF2 resulted in decreased blastocyst rate. In the 8-cell stage YTHDF2 knockdown embryos, the M-decay and Z-decay maternal mRNA clearance were impaired. Specifically, the expression of deadenylase (CNOT1 and CNOT11) and decapping enzymes (DCP1A and DCP2) was decreased. In conclusion, we ascertained maternal mRNAs and inferred that maternal mRNA clearance is also ZGA-dependent in goat. We reported that YTHDF2 is vital for goat early embryogenesis as it advances maternal mRNA clearance, which might through the recruitment of deadenylases and mRNA decapping enzymes. This work will be of great value for understanding the stochastic reprogramming events during MZT and achieving better development of goat embryos in vitro.

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