The ecological adaptability of cloned sheep to free-grazing in the Tengger Desert of Inner Mongolia,China

Since the birth of the first cloned sheep,somatic cell nuclear transfer technology has been successfully used to clone a variety of mammals.Cloned livestock have no apparent health risks,and the quality and safety of the cloned animal products are similar to non-cloned animals.The social behavior and environmental adaptability of postnatal cloned animals,especially when used for grassland farm production purposes,is unknown.In the present study,the cloned Dorper sheep equipped with GPS location devices were free-grazed in a harsh natural environment similar to conditions commonly experienced by Mongolian sheep.The main findings of this research were as follows.(1)Under free-grazing conditions,the cloned sheep showed excellent climatic and ecological adaptability.In extreme temperature conditions ranging from–30 to 40°C,the cloned sheep maintained acceptable body condition and behaved as other sheep.(2)The cloned sheep quickly adapted from a herd feeding strategy to the harsh environment and quickly exhibited a grazing regimen as other free-grazing sheep.(3)The cloned sheep exhibited free-grazing patterns and social behavior as other sheep.(4)The cloned sheep in the harsh environment thrived and produced healthy lambs.Overall,the cloned Dorper sheep exhibited excellent ecological adaptation,which is an important consideration for breeding meat sheep by cloning.The Dorper sheep readily adapted to the free-grazing conditions on the Mongolian plateau grassland,which attests to their ability to withstand harsh environmental conditions.

Modification of alternative splicing in bovine somatic cell nuclear transfer embryos using engineered CRISPR-Cas13d

Animal cloning can be achieved by somatic cell nuclear transfer(SCNT),but the resulting live birth rate is relatively low.We previously improved the efficiency of bovine SCNT by exogenous melatonin treatment or by overexpression of lysine-specific demethylase 4D(KDM4D)and 4E(KDM4E).In this study,we revealed abundant alternative splicing(AS)transitions during fertilization and embryonic genome activation,and demonstrated abnormal AS in bovine SCNT embryos compared with in vitro fertilized embryos.We used the CRISPR-Cas13d RNA-targeting system to target cis-elements of ABI2 and ZNF106 pre-m RNA to modify AS,thus reducing the ratio of abnormal-isoform SCNT embryos by nearly 50%and achieving a high survival rate(11%–19%).These results indicate that this system may provide an efficient method for bovine cloning,while also paving the way for further improvements in the efficiency of SCNT.