Increased pregnancy losses following serial somatic cell nuclear transfer in goats

Effects of Recloning on the Telomere Lengths of Mouse Terc+/- Nuclear Transfer-Derived Embryonic Stem Cells

Haploinsufficiency of genes that participate in the telomere elongation and maintenance processes, such as Terc and Tert, often lead to premature aging related diseases such as dyskeratosis congenita and aplastic anemia. Previously we reported that when mouse Terc+/- tail tip fibroblasts (TTFs) were used as the donor cells for somatic cell nuclear transfer (SCNT, also known as "cloning"), the derivative embryonic stem cells (ntESCs) had elongated telomeres. In the present work, we are interested to know if an additional round of SCNT, or recloning, could bring further elongation of the telomeres. Terc+/- TTFs were used to derive the first generation (G1) ntESCs, followed by a second round SCNT using G1-Terc+/- ntESCs as donor cells to derive G2-Tert+/- ntESCs. Multiple lines of G1- and G2-Terc+/- ntESCs were efficiently established, and all expressed major pluripotent markers and supported efficient chondrocyte differentiation in vitro. Comparing to the donor TTFs, telomere lengths of G1-ntESCs were elongated to the level comparable to that in wildtype ntESCs. Interestingly, recloning did not further elongate telomere lengths of the Terc+/- ntESCs. Together, our work demonstrates that while a single round of SCNT is a viable means to reprogram Terc haploinsufficient cells to the ESC state, and to elongate these cells' telomere lengths, a second round of SCNT does not necessarily further elongate the telomeres.

Sheep models of F508del and G542X cystic fibrosis mutations show cellular responses to human therapeutics

Cystic Fibrosis (CF) is a genetic disease caused by mutations in the CF transmembrane conductance regulator (CFTR) gene. The F508del and G542X are the most common mutations found in US patients, accounting for 86.4% and 4.6% of all mutations, respectively. The F508del causes deletion of the phenylalanine residue at position 508 and is associated with impaired CFTR protein folding. The G542X is a nonsense mutation that introduces a stop codon into the mRNA, thus preventing normal CFTR protein synthesis. Here, we describe the generation of CFTRF508del / F508del and CFTRG542X / G542X lambs using CRISPR/Cas9 and somatic cell nuclear transfer (SCNT). First, we introduced either F508del or G542X mutations into sheep fetal fibroblasts that were subsequently used as nuclear donors for SCNT. The newborn CF lambs develop pathology similar to CFTR -/- sheep and CF patients. Moreover, tracheal epithelial cells from the CFTRF508del / F508del lambs responded to a human CFTR (hCFTR) potentiator and correctors, and those from CFTRG542X / G542X lambs showed modest restoration of CFTR function following inhibition of nonsense-mediated decay (NMD) and aminoglycoside antibiotic treatments. Thus, the phenotype and electrophysiology of these novel models represent an important advance for testing new CF therapeutics and gene therapy to improve the health of patients with this life-limiting disorder.

Generating Cloned Goats by Somatic Cell Nuclear Transfer-Molecular Determinants and Application to Transgenics and Biomedicine

The domestic goat (Capra aegagrus hircus), a mammalian species with high genetic merit for production of milk and meat, can be a tremendously valuable tool for transgenic research. This research is focused on the production and multiplication of genetically engineered or genome-edited cloned specimens by applying somatic cell nuclear transfer (SCNT), which is a dynamically developing assisted reproductive technology (ART). The efficiency of generating the SCNT-derived embryos, conceptuses, and progeny in goats was found to be determined by a variety of factors controlling the biological, molecular, and epigenetic events. On the one hand, the pivotal objective of our paper was to demonstrate the progress and the state-of-the-art achievements related to the innovative and highly efficient solutions used for the creation of transgenic cloned does and bucks. On the other hand, this review seeks to highlight not only current goals and obstacles but also future challenges to be faced by the approaches applied to propagate genetically modified SCNT-derived goats for the purposes of pharmacology, biomedicine, nutritional biotechnology, the agri-food industry, and modern livestock breeding.

Spontaneous Atrial Fibrillation in Transgenic Goats With TGF (Transforming Growth Factor)-β1 Induced Atrial Myopathy With Endurance Exercise

BACKGROUND

There is increasing evidence that endurance exercise is associated with increased risk of atrial fibrillation (AF). However, it is unknown if the relationship between endurance exercise and AF is dependent on an atrial myopathy.

METHODS

Six cardiac-specific TGF (transforming growth factor)-β1 transgenic and 6 wild-type (WT) goats were utilized for these studies. Pacemakers were implanted in all animals for continuous arrhythmia monitoring and AF inducibility. AF inducibility was evaluated using 5 separate 10 s bursts of atrial pacing (160-200 ms). Three months of progressive endurance exercise (up to 90 minutes at 4.5 mph) was performed. Quantitative assessment of circulating microRNAs and inflammatory biomarkers was performed.

RESULTS

Sustained AF (≥30 s) was induced with 10 s of atrial pacing in 4 out of 6 transgenic goats compared with 0 out of 6 WT controls at baseline (P<0.05). No spontaneous AF was observed at baseline. Interestingly, between 2 and 3 months of exercise 3 out of 6 transgenic animals developed self-terminating spontaneous AF compared with 0 out of 6 WT animals (P<0.05). There was an increase in AF inducibility in both transgenic and WT animals during the first 2 months of exercise with partial normalization at 3 months (transgenic 67%; 100%; 83% versus WT 0%; 67%; 17%). These changes in AF susceptibility were associated with a decrease in circulating microRNA-21 and microRNA-29 during the first 2 months of exercise with partial normalization at 3 months in both transgenic and WT animals. Finally, MMP9 (matrix metallopeptidase 9) was increased during the second and third months of exercise training.

CONCLUSIONS

This study demonstrates a novel transgenic goat model of cardiac fibrosis (TGF-β1 overexpression) to demonstrate that endurance exercise in the setting of an underlying atrial myopathy increases the incidence of spontaneous AF. Furthermore, endurance exercise seems to increase inducible AF secondary to altered expression of key profibrotic biomarkers that is independent of the presence of an atrial myopathy.

Regulation and safety considerations of somatic cell nuclear transfer-cloned farm animals and their offspring used for food production

This document discusses recent developments in cloning of husbandry animals through somatic cell nuclear transfer, particularly with a view on improvements in their efficacy. Commercial developments in North and South America, Australia-New Zealand, and China are noted. The regulations and safety aspects surrounding the use of clones and their offspring for the purpose of food production are discussed. It is generally considered that foods from offspring of clones are no different than similar foods from conventional animals, yet besides safety, also ethical and animal welfare considerations come into play at the policy level. The related topic of detection and traceability of clones is discussed, which covers both molecular and documentary methods.

A sheep model of cystic fibrosis generated by CRISPR/Cas9 disruption of the CFTR gene

Cystic fibrosis (CF) is a genetic disease caused by mutations in the CF transmembrane conductance regulator (CFTR) gene. The major cause of limited life span in CF patients is progressive lung disease. CF models have been generated in 4 species (mice, rats, ferrets, and pigs) to enhance our understanding of the CF pathogenesis. Sheep may be a particularly relevant animal to model CF in humans due to the similarities in lung anatomy and development in the two species. Here, we describe the generation of a sheep model for CF using CRISPR/Cas9 genome editing and somatic cell nuclear transfer (SCNT) techniques. We generated cells with CFTR gene disruption and used them for production of CFTR-/- and CFTR+/- lambs. The newborn CFTR-/- sheep developed severe disease consistent with CF pathology in humans. Of particular relevance were pancreatic fibrosis, intestinal obstruction, and absence of the vas deferens. Also, substantial liver and gallbladder disease may reflect CF liver disease that is evident in humans. The phenotype of CFTR-/- sheep suggests this large animal model will be a useful resource to advance the development of new CF therapeutics. Moreover, the generation of specific human CF disease-associated mutations in sheep may advance personalized medicine for this common genetic disorder.