Hamsters have long been overlooked as animal models in reproductive biology research, despite their superior reproductive performance and significant contributions to the field. However, recent advancements in gene-targeting techniques have opened up new possibilities for utilizing hamsters as valuable models. In this article, we will explore the past, present, and future of gene-targeted hamsters.
The Rise of Gene Knockout Mice
The laboratory mouse has been the go-to animal species for biomedical research, largely due to the availability of mouse embryonic stem cell (ESC) lines that can be used to produce gene knockout mice. These mice have been instrumental in advancing our understanding of various diseases and genetic disorders. However, hamsters have never been widely used in gene-targeting studies due to the lack of reliable ESC lines and the developmental challenges they pose.
Overcoming Developmental Challenges
One strategy for producing gene-targeted animals is somatic cell nuclear transfer (SCNT), which involves transferring gene-targeted somatic cells into recipient embryos. This method has been successful for farm animals like pigs, bovines, goats, and sheep. Unfortunately, SCNT is nearly impossible to perform in hamsters due to the high sensitivity of their oocytes to micromanipulation in vitro.
Exploring Alternative Techniques
Researchers have explored alternative techniques to overcome the challenges of gene targeting in hamsters. In 2009, zinc finger nucleases (ZFNs) were used to produce gene knockout rats, marking the first application of genome-editing technology in animals. ZFNs are engineered proteins that combine DNA-binding ability with nuclease activity to induce targeted mutations. However, applying ZFNs to hamsters proved difficult due to their in vitro sensitivity.
The CRISPR Revolution
In 2013, the CRISPR/Cas system revolutionized the production of animal models by making it simple, efficient, and cost-effective. CRISPR/Cas works by using single-guide RNAs (sgRNAs) and the Cas9 enzyme to induce targeted mutations in the genome. Although challenging, researchers were able to successfully generate gene knockout hamsters using CRISPR/Cas through microinjection of sgRNAs and Cas9. However, the sensitivity of hamster zygotes to in vitro environments posed a significant hurdle.
In Vivo Transfection Technique
To overcome the challenges of culturing hamster embryos, a new technique developed by Ohtsuka’s group at Tokai University was employed. This technique involves injecting sgRNA/Cas9 into the oviducts of hamsters and applying electric pulses, eliminating the need for traditional embryo handling procedures. This innovative approach has successfully produced gene knockout hamsters, including those with a knocked-out tyrosinase gene that displays an albino coat color.
The Future Looks Bright
With the advancements in gene-targeting techniques and the successful generation of gene knockout hamsters, the future of hamsters as animal models in reproductive biology research is promising. Researchers can now explore hamsters’ unique reproductive abilities and contributions to the field. By understanding the genetic mechanisms behind reproductive processes in hamsters, we can gain valuable insights that can be applied to human reproductive health.
In conclusion, hamsters are finally getting the attention they deserve in the field of reproductive biology research. The development of gene-targeting techniques, such as CRISPR/Cas and in vivo transfection, has opened up exciting new possibilities for studying reproductive processes in these small but remarkable creatures. As researchers continue to unlock the genetic secrets of hamsters, we can look forward to a future where these furry animals play a crucial role in advancing our understanding of reproductive biology.