In this webinar, Oscar Perez-Leal, PhD, and Jon Weidanz, PhD, share insights into ExpressCells’ FAST-HDR gene editing system and highlight how it compares to traditional methods.


  • Current challenges in creating custom cell lines.
  • The technology behind ExpressCells’ FAST-HDR gene-editing system.
  • Examine several case studies using gene-edited cell lines.

Webinar Summary

Dr. Perez-Leal begins this webinar by discussing the drug discovery process and the importance of cell lines in developing novel therapeutic agents. Cell lines are crucial for in vitro research as they provide a reliable and inexpensive way of modeling pharmaceutical effects. As organoids become more commercially available to researchers, the use of cells in drug development becomes further relevant since organoids typically simulate human conditions better than animal models. However, strong imaging modalities are required to view these cellular responses.

Typically, stained cells are viewed by high content imaging (HCI). While HCI is extremely powerful at analyzing a high throughput of cells, it requires cell fixing and antibodies, and is not optimal for studying live cells. Technological advances such as CRISPR have improved upon this process as live cells can be visualized with fluorescent tags. However, CRISPR is not without its flaws, as creating a donor plasmid to transfect cells typically takes three weeks, while another four-to-eight weeks are required to isolate a line of pure, tagged cells. The FAST-HDR gene editing system by ExpressCells offers a solution to this problem, as it can tag up to three different proteins far more quickly than traditional methods. 

“Our approach was to develop a plasmid system for homologous donor recombination that was easy to assemble in a single reaction… and we included antibiotic selection genes that can  only be expressed if the genetic insertion occurs at the cytogenomic region.”

While ExpressCells can tag any cell line, they have also developed their own custom lines that can be used for a wide variety of applications. Dr. Perez-Leal highlights two of their cell lines in this webinar: one that identifies the inhibition of autophagy, and one that helps model microtubule dynamics as an anti-cancer target. He also discusses several other applications of the FAST-HDR system, such as visualizing live cells by HCI, tracking endogenous targets, studying the mechanism of action of novel compounds, and tagging proteins with non-fluorescent tags. While this technology has the potential to greatly speed up the drug development process, it does have a few limitations. For example, the selected cells must actively express target proteins and be a good host for DNA transfection. 

In the second portion of this webinar, Dr. Weidanz shares his research that led him to ExpressCell’s FAST-HDR technology, and how the team helped him overcome some of the challenges he faced. Dr. Weidanz has primarily focused on the major histocompatibility complex, which presents peptides to specific T cells or T cell receptor-like antibodies. These antibodies are often used for diagnostics and therapeutics, and have very fine binding specificity. Dr. Weidanz wanted to introduce a single amino acid mutation in the delivered peptide to demonstrate this binding specificity, but his team did not have the experience to do so. Therefore, he reached out to ExpressCells, who offered him a rapid timeline for delivering the knock-in mutation at a competitive price. The scientists at ExpressCells worked diligently to create his customized cell line, despite several difficulties in the developmental stage. 

“We selected ExpressCells really because of their fast homology-directed repair technology and expertise. … We felt very confident that we were in good hands.”

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  • How do you prevent the tag from interfering with protein function?
  • Was the problem with electroporation and lipofectin solved? 
  • What types of cell lines have you been able to modify with the FAST-HDR system?
  • How would you handle a very low expressing protein? 

To retrieve a PDF copy of the presentation, click on the link below the slide player. From this page, click on the “Download” link to retrieve the file.


Assistant Professor
Pharmaceutical Sciences Department
Temple University School of Pharmacy

Dr. Oscar Perez is an Assistant Professor in the Pharmaceutical Sciences Department of the School of Pharmacy at Temple University. Dr. Perez’s expertise lies in molecular biology, genome editing, and biosensor development for drug discovery. In particular, he is highly experienced in developing cellular models to identify promising compounds for novel targets. He received his medical degree from Universidad del Norte in Colombia in 2002 and did his postdoctoral training in Biochemistry and Molecular Biology at Temple University (2005 – 2009). He has received research funding from NIH and the pharmaceutical industry. Dr. Perez is an inventor on four issued patents, including the FAST-HDR plasmid system used by ExpressCells. Dr. Perez received a Masters in Innovation Management and Entrepreneurship from the Fox School of Business at Temple University in 2015 and has strong interests in commercializing his academic inventions. Dr. Perez is the co-founder of two startup biotech companies, Recensa Therapeutics, and ExpressCells.

Founding Director
North Texas Genome Center
University of Texas at Arlington

Jon Weidanz, MPH, Ph.D. is an Associate Vice President for Research and Professor in the College of Nursing and Health Innovation, and Director of Biotechnology and Systems Biology in the Multi-Interprofessional Center for Health Informatics at the University of Texas Arlington. Dr. Weidanz has broad experience and interest in biotechnology with particular knowledge and expertise in immunology, immuno-engineering, immunotherapy research and product development. His research has been funded by various agencies including the NIH, over many years to identify tumor-specific peptides presented by the human leukocyte antigen (HLA) system for use as potential targets for immunotherapy. As part of this focus, his laboratory developed methods to discover antibodies that recognize specific peptide/HLA complexes that his laboratory has dubbed as T-cell receptor mimicking (TCRm) antibodies. TCRm molecules share the binding selectivity traits of T-cell receptors while retaining the positive attributes of antibodies. TCRms are highly valued as research tools and his group has used them extensively to study antigen presentation in healthy and diseased cells including tumors. Furthermore, his laboratory has been active in research and development of other immunotherapeutic agents including soluble T-cell receptors, and multifunctional/multispecific protein-based molecules. His earlier interests led to the laboratory’s most recent exciting project, the discovery of a TCRm, EXX-1, to Qa-1b/Qdm peptide complex, the ligand for NKG2A/CD94 inhibitory receptor. The NKG2A axis is an immune checkpoint that suppresses the cytolytic function of Natural Killer cells and CD8+ T-cells in the tumor microenvironment. His laboratory has shown that EXX-1 TCRm can enhance anti-tumor immunity in mice. Translation of these recent basic research findings to immunotherapies for treating human cancers is being pursued by his former company, Abexxa Biologics that was acquired by Boehringer Ingelheim ( Additionally, Dr. Weidanz is a seasoned entrepreneur and innovator with more than 25 years of relevant corporate biotechnology accomplishments that include co-founding four biotech companies. Recently, he was elected to the National Academy of Inventors for his outstanding contributions as an innovator and for his efforts to commercialize university technologies.

Production Partner


Better knock-ins, better cell lines, better science. Oscar Perez-Leal, MD and Matt Handel established ExpressCells in 2018 with the mission to improve drug development and basic biological research by creating better cell lines. We do so using genetic engineering technology invented by Dr. Perez at the Temple University School of Pharmacy.

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