Growth and Hematologic Characteristics of Cloned Dogs Derived from Adult Somatic Cell Nuclear Transfer

Dog cloning-no longer science fiction

Since the generation of world's first cloned dog, Snuppy, in 2005, somatic cell nuclear transfer (SCNT) in dogs has been widely applied for producing several kinds of dogs with specific objectives. Previous studies have demonstrated that cloned dogs show normal characteristics in growth, blood parameters and behavioural aspect. Also, canine SCNT technique has been applied to propagate working dogs with excellent abilities in fields such as assistance of disabled people, drugs detection and rescue activity. Because dogs have similar habituation properties and share many characteristics including anatomic and physiological aspects with humans, they are also primary candidates for human disease models. Recently, transgenic dogs that express red fluorescent protein gene constitutively and green fluorescent protein gene conditionally have been generated. In addition, transgenic dogs with an overexpression of peroxisome proliferator-activated receptor-alpha in specific muscles were generated to enhance physical performance. In 2017, Snuppy was recloned with markedly increased pregnancy and delivery rates compared to the statistics from when Snuppy was first cloned. Such striking improvements in the cloning of dogs using SCNT procedures suggest that dog cloning could be applied in many fields of biomedical science for human diseases research, and the application of cloning is no longer science fiction.

Health and temperaments of cloned working dogs

Dogs serve human society in various ways by working at tasks that are based on their superior olfactory sensitivity. However, it has been reported that only about half of all trained dogs may qualify as working dogs through conventional breeding management because proper temperament and health are needed in addition to their innate scent detection ability. To overcome this low efficiency of breeding qualified working dogs, and to reduce the enormous costs of maintaining unqualified dogs, somatic cell nuclear transfer has been applied in the propagation of working dogs. Herein, we review the history of cloning working dogs and evaluate the health development, temperaments, and behavioral similarities among the cloned dogs. We also discuss concerns about dog cloning including those related to birth defects, lifespan, and cloning efficiency.

Cloning of the short-tailed Gyeongju Donggyeong dog via SCNT: conserving phenotypic inheritance

Somatic cell nuclear transfer is a useful tool to maintain genetic information of animals. The Gyeongju Donggyeong dog is a breed registered as natural monument in Korea. The unique feature of the Donggyeong dog is its tail, as the Donggyeong dog can be classified as either short tailed or tailless. The aim of this study was to preserve the Donggyeong dog’s unique feature by cloning. Fibroblasts were obtained from a short-tailed Donggyeong dog. In vivo matured oocytes were enucleated, microinjected with a donor cell and fused electrically. Reconstructed embryos were transferred to six recipient dogs. One surrogate became pregnant, and one short-tailed Donggyeong dog was delivered. This study demonstrated that the phenotype of the Donggyeong dog could be conserved by somatic cell nuclear transfer.

Early embryonic development, assisted reproductive technologies, and pluripotent stem cell biology in domestic mammals

Over many decades assisted reproductive technologies, including artificial insemination, embryo transfer, in vitro production (IVP) of embryos, cloning by somatic cell nuclear transfer (SCNT), and stem cell culture, have been developed with the aim of refining breeding strategies for improved production and health in animal husbandry. More recently, biomedical applications of these technologies, in particular, SCNT and stem cell culture, have been pursued in domestic mammals in order to create models for human disease and therapy. The following review focuses on presenting important aspects of pre-implantation development in cattle, pigs, horses, and dogs. Biological aspects and impact of assisted reproductive technologies including IVP, SCNT, and culture of pluripotent stem cells are also addressed.

Changes in the somatotrophic axis in genetically identical dogs

Because cloned dogs are genetically identical, variations among these animals can be a useful tool to elucidate mechanisms underlying phenotypic differences. To estimate the influence of genetic factors on phenotypic variation, changes in concentration patterns of growth hormone (GH), insulin like growth factor-1 (IGF-1), and IGF binding protein 3 (IGFBP-3) were compared among cloned and age-matched control dogs. In addition, the concentrations of GH and IGF-1 following administration of growth hormone releasing hormone (GHRH) and somatostatin (SRIF) were measured in both groups. In comparing hormone profiles, the control dogs had larger standard deviations from the means for GH, IGF-1, and IGFBP-3 than the clones. Also, the mean concentration of IGFBP-3 in clones was significantly lower than in the controls between 7 to 12 months of age, whereas the IGFBP-3 changes in clones and controls followed the same pattern. GHRH induced increased serum growth hormone concentration both in clones and controls. However, the concentration of IGF-1 was lower in clones than in controls, and larger standard variations were noted in the control group. In conclusion, the measured traits were more homogeneous in cloned animals than in controls, so cloned animals could be valuable for assessing effects of genotype and environment interactions.