Dr. Jennifer A. Doudna

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– Diya K Prasad

CRISPR is a word that fuels the imagination of science enthusiasts with its never-ending applications and simplistic design. Basic sciences, biotechnology and disease therapy are a few of the many realms where CRISPR thrives today. Among the visionaries behind the creation of this stellar molecular tool stands Dr. Jennifer Doudna.  

Dr. Jennifer A. Doudna is a professor of Biochemistry, Molecular Biology and Chemistry at the University of California, Berkeley. Born in Washington, D.C, Dr. Doudna moved to Hilo, Hawaii at the age of 7. Her father was a professor of American literature at the University of Hawaii and her mother was a lecturer of history in a local community college. Their lack of a scientific background did not prompt them to discourage Dr. Doudna’s passion for the sciences. Her love for science first blossomed in the soil of the rainforests surrounding her home, which she would often venture into. Biochemistry became an avid area of interest after she read James Watson’s ‘Double Helix’, gifted to her by her father. 

One summer, her parents introduced her to Dr. Don Hemmes, a family friend and scientist at the University of Hawaii. She got her first hands-on experience in research at his lab, where she was tasked to investigate how the fungi Phytophthora palmivora infected papyrus plants. Although the project only lasted a few weeks, it resulted in the unveiling of the crucial role calcium ions played in the development of the fungus. It also fueled her desire for a future in science.   

Her love for biochemistry led her to Pomona College, California, known for its established biochemistry program. There, she took her first step into the world of research, joining the lab of Dr. Sharon Panasenko. Dr. Panasenko proved not only to be an excellent scientist but was also a great mentor to young Dr. Doudna. Panasenko served as a reminder to Dr. Doudna that women too can thrive in the male-dominated world of academia. (Marino, 2004)

After receiving her Bachelors in Chemistry in 1985, she attended Harvard University for graduate school. There she worked under Dr. Jack W. Szostak, a 2009 Nobel laureate. His work aimed at understanding the alleged role played by RNA in the origin of life as per the RNA world theory. This theory hypothesizes that RNA evolved before DNA and expands on the roles played by RNA that go beyond that of genetic material. This serves as a theme for much of Dr. Doudna’s research ventures to date. Along with Szostak, Dr. Doudna engineered a self-replicating catalytic RNA that could copy an RNA template. (Rajagopal, Doudna & Szostak, 1989) This gave weight to the hypothesis that RNA has a catalytic role in addition to its role as an intermediate messenger and hence preceded DNA in existence. 

Following along the same stream of questioning, Dr. Doudna wanted to understand the biochemical and structural characteristics of RNA that aided in its catalytic role. She aimed to do just that in her post-doctoral studies, working with the Nobel laureate Dr. Thomas R Cech from the University of Colorado. He, along with Dr. Sidney Altman, received the Nobel prize in Chemistry in 1989 for discovering the catalytic properties of RNA.Dr.

Doudna worked as a research fellow in Cech’s laboratory, where she attempted to elucidate the three-dimensional structure of RNA.She continued her attempts at Yale in 1994. There, she was awarded the position of assistant professor in the Department of Molecular Biophysics and Biochemistry.  Her venture into painting the structural portrait of RNA led to the publishing of two landmark papers describing the structures of two large RNAs: the P4-P6 domain of Tetrahymena thermophila group 1 intron ribozyme, and the hepatitis delta virus ribozyme (Ferre-d’Amare, Zhou & Doudna, 1998; Cate et al., 1996). Subsequent studies by Dr. Doudna on the P4-P6 domain highlighted similarities between proteins and RNA. For example, a core consisting of five magnesium ions that were found to be clustered in a region of the P4-P6 domain was similar to how protein structures fold around a hydrophobic core. (Cate, Hanna & Doudna, 1997) 

Dr. Doudna resumed her study of RNA at the University of California, Berkeley in 2002. It was in 2005 that word of CRISPR reached her via a phone call from her colleague at Berkeley, Dr. Jillian Banfield. Banfield had noticed repetitive sequences in the genome of bacterial communities that lived in high acidic wastewater from a mine in Northern California and wanted to know whether it aided in bacterial immunity against viruses (Doudna & Sternberg, 2017). Dr. Doudna was fascinated by this and began her venture into understanding the wonders behind this phenomenon. 

In 2011, Dr. Doudna met Dr. Emmanuelle Charpentier, the brilliant microbiologist she shares her Nobel prize with. This was a fateful meeting that benefitted both parties exceptionally. Dr. Charpentier had noticed a protein, Cas9, associated with CRISPR that aided Streptococcus pyogenes in its battle against viruses. She had also found another component of the system, called tracrRNA, that aided in the cleaving of the viral DNA. (Deltcheva et al., 2011) The collaboration between Dr. Doudna and Dr. Charpentier saw the unison of expertise in microbiology, structural biology and biochemistry. Along with their post-doctoral fellows, Dr. Martin Jinek and graduate student Dr. Krysztof Chylinski, their labs detailed how the CRISPR/Cas9 system provides bacteria with viral immunity. 

It was discovered that the Cas9 endonuclease enzyme is guided by two RNA molecules: crRNA and tracrRNA (Jinek et al, 2012). During the viral attack of bacteria, the viral DNA is incorporated into the CRISPR loci. RNA complementary to this region is made by the bacterial cell, termed the cRNA. A part of this RNA base pairs with a tracrRNA, which is used as a handle by the Cas9 endonuclease. This complex of cRNA and tracrRNA forms the fully-functional guide RNA (gRNA). Cas9 then uses this dual-RNA guiding system to locate viral sequences matching the crRNA, where gRNA-DNA base pairing occurs. This is followed by the introduction of precise cuts in the dsDNA by the Cas9 endonuclease. Homology-Directed repair (HDR) and Nonhomologous end-joining (NHEJ) are two mechanisms by which this cut can be repaired. HDR integrates homologous donor DNA into the break while NHEJ simply ligates the strands. (Miyaoka et al., 2016) It became apparent that the former repair system could be used to integrate desired DNA into the precise cuts made by the CRISPR/Cas9 system. 

Doudna and Charpentier also designed a single RNA-guided system, with tracrRNA and crRNA linked into one entity. This accompanied by a single endonuclease protein formed a simplified model. They published their findings in a paper describing the relevance of such a model as a gene editing tool (Jinek et al, 2012). Their work took the world by storm, becoming the buzzword in science overnight. While there exist other gene editing tools like Zinc Finger Nucleases and TAL effector Nucleases, they are protein guided and require protein engineering. But with the CRISPR/Cas9 system, the guide is a single RNA strand that is easier to construct and of the investigator’s choice. The precision of changes that can be made also differs, with CRISPR capable of making extremely targeted cuts in DNA. This is owing to the use of gRNA-DNA base pairing as a recognition mechanism.   

CRISPR is a molecular tool that is now used in labs all over the world. It has found applications in cell and gene therapy, diagnostics, industrial biotechnology and food and agriculture. (Barrangou & Doudna, 2016). The potential it holds continues to excite the world with new applications often unveiling themselves. 

Dr. Doudna is currently the President of Innovative Genomics Institute and an investigator at Howard Hughes Medical Institute and Gladstone Institutes. (Jennifer Doudna, 2022) Her lab currently focuses on unveiling the mechanisms of CRISPR action, whilst also finding innovative applications for the same. These applications mainly include ventures into therapeutic and agricultural avenues. She also continues her search for the next best gene-editing tool, by surveying microbial communities for novel proteins of use. Besides her academic pursuits, she also leads important discussions on the ethical battles faced in the use of CRISPR and promotes the development of policies surrounding safe usage of the same. (Jennifer Doudna, 2022) 

Dr. Doudna currently holds the Li Ka Shing Chancellor’s chair in Biomedical and Health Sciences at Berkeley. The Nobel Prize in Chemistry in 2020 was awarded to Dr. Doudna and her collaborator Dr. Emmanuelle Charpentier for their work on CRISPR. She has also been awarded many other awards for the same, such as the Breakthrough Prize in Life Sciences in 2015 and the L’Oréal-UNESCO Award for Women in Science in 2016. She holds a position in the National Academy of Sciences and the American Academy of Arts and Sciences. She currently resides in Berkeley with her husband, Dr. Jamie Cate, a biochemistry professor at UC Berkeley and her son, Andrew. 

Much like her mentor Dr. Sharon Panasenko was to her, Dr. Jennifer Doudna is now a stellar example to young women scientists all over the world of how women can thrive in the male-dominant arena of STEM. The Nobel Prize in Chemistry, awarded to Dr. Doudna and Dr. Charpentier, is the first of its kind to be jointly awarded to two women. This landmark Nobel Prize win is guaranteed to have dissolved some of the intimidation young women feel surrounding a career in STEM. It may also help increase the percentage of women making up the STEM workforce, which according to a 2018 survey, is 28%. (STEM Statistics: Workforce, 2021) Her contribution to the world of science is immeasurable and will continue to inspire for many years to come. 

Did you enjoy reading this? Let us know what you thought of this article in the comments section below!

ABOUT THE AUTHOR

Diya K Prasad 

The Author is in her third year at St. Xavier’s College, studying Life Science and Biochemistry.

We would like to thank Dr.Kartik Soni, A Post Doctorate, an expertise in Molecular Biology and Stem cell biology from The Institut Pasteur, France for reviewing the article and for his valuable inputs.

-The Boffin Bloggers

References:

  1. Barrangou, R., & Doudna, J. A. (2016). Applications of CRISPR technologies in research and beyond. Nature Biotechnology, 34(9), 933–941. https://doi.org/10.1038/nbt.3659 
  2. Cate, J. H., Gooding, A. R., Podell, E., Zhou, K., Golden, B. L., Kundrot, C. E., Cech, T. R., & Doudna, J. A. (1996). Crystal Structure of a Group I Ribozyme Domain: Principles of RNA Packing. Science, 273(5282), 1678–1685. https://doi.org/10.1126/science.273.5282.1678 
  3. Deltcheva, E., Chylinski, K., Sharma, C. M., Gonzales, K., Chao, Y., Pirzada, Z. A., Eckert, M. R., Vogel, J., & Charpentier, E. (2011). CRISPR RNA maturation by trans-encoded small RNA and host factor RNase III. Nature, 471(7340), 602–607. https://doi.org/10.1038/nature09886  
  4. Doudna, J. A., & Sternberg, S. H. (2017). A crack in creation: Gene editing and the unthinkable power to control evolution. Boston: Houghton Mifflin Harcourt.
  5. Doudna, J. A., & Szostak, J. W. (1989). RNA-catalysed synthesis of complementary-strand RNA. Nature, 339(6225), 519–522. https://doi.org/10.1038/339519a0 
  6. Ferré-D’Amaré, A. R., Zhou, K., & Doudna, J. A. (1998). Crystal structure of a hepatitis delta virus ribozyme. Nature, 395(6702), 567–574. https://doi.org/10.1038/26912  
  7. iBiology. (2018, October 4). Genome Engineering with CRISPR-Cas9: Birth of a Breakthrough Technology [Video]. YouTube. https://www.ibiology.org/genetics-and-gene-regulation/crispr-cas9/   
  8. Jennifer Doudna. (2022, August 23). Innovative Genomics Institute (IGI). https://innovativegenomics.org/people/jennifer-doudna/
  9. Laureates of the 2016 L’Oréal-UNESCO For Women In Science Awards. (2022, April 21). UNESCO. https://www.unesco.org/en/articles/laureates-2016-loreal-unesco-women-science-awards 
  10. Life Sciences Breakthrough Prize Laureates – Jennifer A. Doudna. (n.d.). Life Sciences Breakthrough Prize. https://breakthroughprize.org/Laureates/2/L63  
  11. Marino, M. (2004). Biography of Jennifer A. Doudna. Proceedings of the National Academy of Sciences, 101(49), 16987–16989. https://doi.org/10.1073/pnas.0408147101 
  12. Rajagopal, J., Doudna, J. A., & Szostak, J. W. (1989). Stereochemical course of catalysis by the Tetrahymena ribozyme. Science, 244(4905), 692–694. https://doi.org/10.1126/science.2470151 
  13. STEM Statistics: Workforce. (2021, December 27). National Girls Collaborative Project. https://ngcproject.org/resources/stem-statistics-workforce
  14. Thomas R. Cech- Facts. (n.d.). The Nobel Prize. https://www.nobelprize.org/prizes/chemistry/1989/cech/facts/ 
  15. Trans-activating CRISPR RNA (tracrRNA). (2020, September 28). Innovative Genomics Institute (IGI). https://innovativegenomics.org/glossary/tracrrna/
  16. Wonder Collaborative. (2019, October 7). Discovery Story: Genome Engineering with CRISPR-Cas9 (Doudna, Jinek, Charpentier) [Video]. YouTube. https://www.youtube.com/watch?v=jm5QqxN7Hkw 
  17. Yale. (n.d.). Jennifer Doudna. Gruber Foundation. https://gruber.yale.edu/genetics/jennifer-doudna#:%7E:text=Jennifer%20Doudna%20was%20born%20in,at%20a%20local%20community%20college

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