The transgenic animal platform for biopharmaceutical production

Growth performance, reproductive traits and offspring survivability of genetically modified rams overexpressing toll-like receptor 4

Genetic modification provides a means to enhancing disease resistance in animals. Toll-like receptor 4 (TLR4), a member of the TLR family, is critical for the recognition of lipopolysaccharide (LPS)/endotoxin from Gram-negative bacteria by host immune cells, which initiates cell activation and subsequently triggers a proinflammatory response to the invading pathogens. In this study, the first generation of genetically modified (GM) sheep overexpressing TLR4 was produced by microinjection for better disease resistance. Compared with wild-type (WT) rams, the GM rams have similar growth performance, basic semen quality and spermatozoon ultrastructure. The offspring birth rates after cervical artificial insemination were also similar between GM (90.32%) and WT (92.38%) rams. Overall, the presence and expression of the TLR4 transgene in the genome did not appear to interfere with normal semen production, reproductive traits and the ability of transgene transmission to offspring. The expression levels of TLR4, tumor necrosis factor and interferon gamma genes in monocyte/macrophages from GM sheep were significantly higher than that from WT sheep at early stages after LPS stimulation. The GM offspring born from the founder transgenic ram inseminated ewes had similar survival rate with WT offspring (88.89% vs 84.86%) at weaning. The TLR4 transgene showed no deleterious effects on growth performance, reproductive traits and offspring survivability of GM rams. Therefore, the GM sheep overexpressing TLR4 provide a powerful experimental model for analyzing function of TLR4 in vivo during infection and inflammation.

Production of functional human nerve growth factor from the saliva of transgenic mice by using salivary glands as bioreactors

The salivary glands of animals have great potential to act as powerful bioreactors to produce human therapeutic proteins. Human nerve growth factor (hNGF) is an important pharmaceutical protein that is clinically effective in the treatment of many human neuronal and non-neuronal diseases. In this study, we generated 18 transgenic (TG) founder mice each carrying a salivary gland specific promoter-driven hNGF transgene. A TG mouse line secreting high levels of hNGF protein in its saliva (1.36 μg/mL) was selected. hNGF protein was successfully purified from the saliva of these TG mice and its identity was verified. The purified hNGF was highly functional as it displayed the ability to induce neuronal differentiation of PC12 cells. Furthermore, it strongly promoted proliferation of TF1 cells, above the levels observed with mouse NGF. Additionally, saliva collected from TG mice and containing unpurified hNGF was able to significantly enhance the growth of TF1 cells. This study not only provides a new and efficient approach for the synthesis of therapeutic hNGF but also supports the concept that salivary gland from TG animals is an efficient system for production of valuable foreign proteins.

Human lactoferrin efficiently targeted into caprine beta-lactoglobulin locus with transcription activator-like effector nucleases

Objective

To create genetically modified goat as a biopharming source of recombinant human lacotoferrin (hLF) with transcription activator-like effector nucleases.

Methods

TALENs and targeting vector were transferred into cultured fibroblasts to insert hLF cDNA in the goat beta-lactoglobulin (BLG) locus with homology-directed repair. The gene targeted efficiency was checked using sequencing and TE7I assay. The bi-allelic gene targeted colonies were isolated and confirmed with polymerase chain reaction, and used as donor cells for somatic cell nuclear transfer (SCNT).

Results

The targeted efficiency for BLG gene was approximately 10%. Among 12 Bi-allelic gene targeted colonies, five were used in first round SCNT and 4 recipients (23%) were confirmed pregnant at 30 d. In second round SCNT, 7 (53%), 4 (31%), and 3 (23%) recipients were confirmed to be pregnant by ultrasound on 30 d, 60 d, and 90 d.

Conclusion

This finding signifies the combined use of TALENs and SCNT can generate bi-allelic knock-in fibroblasts that can be cloned in a fetus. Therefore, it might lay the foundation for transgenic hLF goat generation and possible use of their mammary gland as a bioreactor for large-scale production of recombinant hLF.

CRISPR: express delivery to any DNA address

The sudden emergence and worldwide adoption of CRISPR gene-editing technology confronts humanity with unprecedented opportunities and choices. CRISPR's transformative impact on our future understanding of biology, along with its potential to unleash control over the most fundamental of biological processes, is predictable by already achieved applications. Although its origin, composition, and function were revealed only recently, close to 3000 CRISPR-based publications have appeared including insightful and diversely focused reviews referenced here. Adding further to scientific and public awareness, a recent symposium addressed the ethical implications of interfacing CRISPR technology and human biology. However, the magnitude of CRISPR's rapidly emerging power mandates its broadest assessment. Only with the participation of a diverse and informed community can the most effective and humanity-positive CRISPR applications be defined. This brief review is aimed at those with little previous exposure to the CRISPR revolution. The molecules that constitute CRISPR's core components and their functional organization are described along with how the mechanism has been harnessed to edit genome structure and modulate gene function. Additionally, a glimpse into CRISPR's potential to unleash genetic changes with far-reaching consequences is presented.

Expression of Active Fluorophore Proteins in the Milk of Transgenic Pigs Bypassing the Secretory Pathway

We describe the expression of recombinant fluorescent proteins in the milk of two lines of transgenic pigs generated by Sleeping Beauty transposon-mediated genetic engineering. The Sleeping Beauty transposon consisted of an ubiquitously active CAGGS promoter driving a fluorophore cDNA, encoding either Venus or mCherry. Importantly, the fluorophore cDNAs did not encode for a signal peptide for the secretory pathway, and in previous studies of the transgenic animals a cytoplasmic localization of the fluorophore proteins was found. Unexpectedly, milk samples from lactating sows contained high levels of bioactive Venus or mCherry fluorophores. A detailed analysis suggested that exfoliated cells of the mammary epithelium carried the recombinant proteins passively into the milk. This is the first description of reporter fluorophore expression in the milk of livestock, and the findings may contribute to the development of an alternative concept for the production of bioactive recombinant proteins in the udder.