Transgenic Animals in Biomedical Research and Drug Discovery

Transgenic Animals Meaning + Application Examples

In the rapidly evolving field of biomedical research, the use of transgenic animals has become a cornerstone for advancing scientific knowledge and developing new treatments. This article explores the concept of transgenic animals and their pivotal role in various research applications. By examining how these genetically modified organisms are engineered and utilized, we can appreciate their profound impact on our ability to model diseases, visualize cellular processes, and test potential therapies.

What are Transgenic Animals?

Transgenic animals are organisms in which exogenous DNA sequences  (transgenes) are intentionally inserted into their genome through genetic engineering techniques. These transgenes can be genes from other species or modified versions of their genes. 

In the case of zebrafish,  the most common approach to introduce these transgenes into the host is through plasmids. Plasmids are circular DNA vectors that can be modified to contain large, custom-made sequences of synthetic DNA. We design plasmids when we need to insert large stretches of synthetic DNA into a genome to create a model organism that, for instance, expresses a fluorescent protein or an exogenous gene. They serve as the starting point for any major transgenesis project. To promote the integration of these plasmids, we take advantage of a specialized enzyme named transposase that catalyzes the transfer of the desired sequence from the vector to the host.

By using transgenic animals, researchers can investigate the effects of specific genes on biological processes, have the possibility to elucidate their association with disease development and, in some cases, might test potential treatments.

Applications of Transgenic Models in Biomedical Research

In the field of  biomedical research, transgenic are commonly employed for several applications:

1. Genetic Disease Models: these models express human pathogenic genes (e.g. oncogenes or gene variants associated with rare disorders) to generate humanized zebrafish models.
2. Genetic Reporters: these transgenic animals are used to help scientists visualize selected cell types. For example, zebrafish transgenic lines expressing GFP in specific tissues are commonly used for image analysis, facilitating rapid tests and assays in the early stages of biomedical research. They can also be used to analyze or monitor biological processes of interest in a time-specific manner.
3. Optogenetic and Chemogenetic tools: these lines allow the active manipulation of cells or proteins by using external stimuli (e.g. one application of optogenetics in zebrafish is the temporal control of neuronal firing with light pulses). 
4. Gal4 or Cre-Recombinase Driver Lines: these modes are used to direct the expression of a gene of interest to a specific tissue. The GAl4-UAS system has two parts: a transcription activator protein (Gal4) and an enhancer to which this protein specifically binds to activate gene transcription (UAS). The Cre-LoxP recombination system consists of a single enzyme, Cre recombinase, that recombines a pair of short target sequences called the LoxP sequences. Placing LoxP sequences appropriately allows genes to be activated, repressed, excised or exchanged for other genes.

Transgenic Animal Models: A Gateway to Drug Discovery

Model organisms are indispensable in drug discovery research, serving as a link between theoretical compounds and real-world applications. The transition from molecular equations to in vivo animal models marks a pivotal stage in drug discovery, providing invaluable insights into disease mechanisms and treatment efficacy. Transgenic animal models open new avenues for fundamental investigation and for early-stage research in the drug discovery field. 

As we previously saw, these models are crucial in replicating genetic disorders or human diseases in a controlled laboratory setting, serving as the cornerstone of early drug discovery efforts. Moreover, transgenic animals can be employed as reporters for specific tissues or biological processes, making it possible for scientists to test compounds that effectively modulate a pathway of interest.

Transgenic Zebrafish: Illuminating Biomedical Research

Zebrafish presents an exceptional opportunity for drug discovery due to their genetic similarity to humans and their adaptability to the controlled environment of a laboratory. Zebrafish models, such as those expressing GFP, have the potential to streamline the study of specific human diseases, shedding light on how novel potential treatments may impact future human patients. 

In conclusion, transgenic animal models serve as indispensable tools in biomedical research, providing reliable data for effective early-stage drug discovery. By initiating early-stage studies with transgenic zebrafish, researchers can gather essential data on toxicity, safety, and efficacy at the outset of the drug development process. Alternative animal models like zebrafish simplify the intricate journey of drug development, offering researchers a valuable resource as they progress towards clinical trials.

REFERENCES:

[1] Merlino GT. Transgenic animals in biomedical research. FASEB J. 1991 Nov;5(14):2996-3001. doi: 10.1096/fasebj.5.14.1752364. 

[2] Houdebine, LM. (2007). Transgenic Animal Models in Biomedical Research. In: Sioud, M. (eds) Target Discovery and Validation Reviews and Protocols. Methods in Molecular Biology™, vol 360. Humana Press. https://doi.org/10.1385/1-59745-165-7:163

[3] Mukherjee, P., Roy, S., Ghosh, D. et al. Role of animal models in biomedical research: a review. Lab Anim Res 38, 18 (2022). https://doi.org/10.1186/s42826-022-00128-1

[4] Wei J, Zhang W, Li J, Jin Y, Qiu Z. Application of the transgenic pig model in biomedical research: A review. Front Cell Dev Biol. 2022 Oct 17;10:1031812. doi: 10.3389/fcell.2022.1031812.

By Miriam Martínez

Miriam is a Human Biologist expert in neuropharmacology. After a master’s degree in Pharmaceutical and Biotech Industry, she obtained her PhD in Biomedicine from Pompeu Fabra University (Barcelona). During her doctorate, she focused her research on the behavioral analysis of animal models for neurophenotypical characterization. Since then, she has been working in the healthcare marketing and publicity sector, where she has contributed to developing marketing campaigns for several pharmaceutical brands. In 2021, she joined ZeClinics with a branding and marketing strategy focus.