Jacob (Yaqub) H. Hanna (Arabic: Yaqub or Yaoub; born 26 August 1979) is a Palestinian biologist, born with Israeli citizenship, who is working as a Full Professor in the Department of Molecular Genetics at the Weizmann Institute of Science in Rehovot, Israel. An expert in embryonic stem cell research, he is most recognized for developing the first bona fide Structured Stem cell-derived Synthetic Embryo Models (SEMs) in the petri dish in mice and humans.
To achieve this, he first developed a technique for extended culturing mouse embryos outside the uterus (ex utero) in 2021 capturing normal development from before gastrulation until late organogenesis outside the uterus, subsequently applying his technique for making the first high-fidelity stem cell-derived whole embryo models of mice in 2022 (SEMs), and then of human in 2023 that can be made solely from embryonic pluripotent stem cells, without using egg or sperm and generated entirely outside the womb. SEMs are also known as "Stem-Cell-Based complete Embryo Models - SCBEMs", "Synthetic Embryos" or "High Fidelity Whole Embryo Models").
Hanna pioneered the extended static and dynamic post-implantation ex utero whole embryo growth platform that was critical for enabling the synthetic and structured embryo model establishment, and also pioneered developing the technology to generate alternative naive-like and naive pluripotent states in humans, that correspond to more early stages in development and retain an enhanced potential to make essential extra-embryonic tissue (e.g. placenta and yolk-sac), which proved essential for generating the first complete synthetic embryo models by his team and solely from such naive pluripotent cells.
Education Hanna has a PhD in microbiology and immunology and an MD in clinical medicine from the Hebrew University of Jerusalem. To train in stem cell research, he worked from 2007 to 2011 as a Helen Hay Whitney - Novartis postdoctoral fellow and a Genzyme postdoctoral fellow at the Whitehead Institute for Biomedical Research at MIT, Cambridge, Massachusetts, under Rudolf Jaenisch. In 2011, Hanna joined the Weizmann Institute of Science as an assistant professor in 2011, and has been there ever since. In 2018, Hanna received academic tenure and promotion at the Department of Molecular Genetics in the Weizmann Institute, and in 2023 became a Full Professor of Stem Cell Biology and Synthetic Embryology.
Hanna was listed in 2014 among top 40 under 40 leading international scientists by Cell journal and elected to the European Molecular Biology Organization in 2018. In 2021, he was announced as the top thinker of the year 2021 by Prospect magazine for his works on embryology. His extended ex utero embryo culture was selected among Science Magazine Breakthrough of the year 2021, and his mouse complete synthetic embryo models were selected by Nature magazine among seven technologies to watch in 2023. Human complete stem-cell derived embryo model generated by Hanna was selected by TIME in its featured list of inventions in 2023, and the generation of synthetic embryo models of development through using stem cells was selected as the method of the year 2023 by Nature Methods. He is the recipient of the 2025 Nakasone Award by the Human Frontiers Science Program – HFSP for " developing synthetic embryo models from naïve pluripotent stem cells, which provides a new foundation for developmental biology and regenerative medicine strategies."(Hanna's 2025 Nakasone Award Lecture)
Early life Hanna was born in Rameh, an Arab village in the Galilee region of Israel to a Palestinian Christian family. His father was a pediatrician and his mother was a high-school biology teacher. His grandfather was also a doctor in this village. He studied medical science at the Hebrew University of Jerusalem, obtaining a B.Sc. degree summa cum laude in 2001, and then continued to do an M.D.-Ph.D. degree at the same institute. He indicated in his interviews that his decision to undertake a career in research was heavily influenced and inspired by the success of his uncle, Nabil Hanna, who invented the first FDA-approved antibody therapy in humans (Rituxan, a blockbuster anti-CD20 mAb drug for treatment of non-Hodgkin lymphoma) while serving as chief scientific office of IDEC Pharmaceuticals. His Ph.D. research was supervised by and was on the roles of natural killer cells. In 2007, the Hebrew University awarded him both Ph.D. in microbiology and immunology and M.D. in clinical medicine summa cum laude. Hanna's three sisters also studied medicine in the Hebrew University.
Hanna decided not to go into practicing medicine but focus only on developing his research career in Academia. In 2007, he received the Helen Hay Whitney Foundation, and later a Genzyme-Whitehead Fellowship for outstanding postdoctoral fellows in 2009, by which he worked at the Whitehead Institute for Biomedical Research in Cambridge, Massachusetts. His research there till early 2011 under Rudolf Jaenisch helped him specialize in pluripotent stem cell research and induced pluripotent stem cell reprogramming.
Research and discoveries
Induced pluripotent stem cell reprogramming During his postdoctoral research at the Whitehead Institute, Hanna focused on studying embryonic stem cells (ESCs) and epigenetic reprogramming of somatic cells into ESC-like cells, called induced pluripotent stem cells (iPSCs). He developed transgenic mouse models to address problems in stem cell research. In 2007, he provided the first evidence that iPSCs could be used for a blood genetic disease, sickle cell anemia, by combined gene and cell therapy approach in mice. His supervisor, Jaenisch was awarded the Masri Prize and the Wolf Prize in 2011 for this research innovation, as the award citation read: "For demonstration that iPS cells can be used to cure genetic disease in a mammal, thus establishing their therapeutic potential".
Hanna made scientific contributions to understanding the iPSC phenomenon in its early days. He developed a novel inducible "reprogrammable mouse" transgenic models with drug controlled over expression of the Yamanaka reprogramming factors. This technique allowed him to create reprogrammed B lymphocytes carrying endogenous genetic rearrangements of the B-cell receptor (BCR) into iPSCs, thus providing definitive proof for the feasibility of reprogramming terminally differentiated cells to iPSCs that carried the original genetic rearrangement mark of the BCR.
Epigenetic reprogramming and naive pluripotency Initially, his independent group identified a number of key epigenetic regulators influencing iPSC derivation efficiency such as the role of H3K27 demethylase Utx in iPS formation, and first demonstrated the deterministic reprogramming efficiencies (up to 100% within 8 days) via optimized depletion of Gatad2a/Mbd3 core member-axis of the NuRD co-repressor complex. The latter work set the stage for others to show alternative methods to obtain deterministic reprogramming. For example, Thomas Graf group showed that transient activation of C/EBPα, previously highlighted by Hanna and Jaenisch as a booster for B cell reprogramming, can yield up to 100% deterministic iPSC reprogramming from B cells within 8 days. Hanna also identified SUMOylation of linker H1 histone as a major determinant for transition between totipotency and naïve pluripotency states.
From 2013, Hanna worked as the Robertson Stem Cell Investigator of The New York Stem Cell Foundation. His first major achievement under the NYSCF research was the demonstration that human naïve-like ES/iPS cell state tin NHSM naive-like conditions that he discovered (and later also in HENSM naive conditions), has additional unique functional properties compared to conventional primed iPS cells, which is the creation of sperm and egg stem cells from human skin cell derived naive-like iPSCs, which has not been possible thus far with conventional human iPSCs. The experiment, done in collaboration with Azim Surani's team at the University of Cambridge, was published in the journal Cell in 2015. David Cyranoski reported in Nature as "A feat achieved for the first time in humans".
In 2014, Hanna criticized Jaenisch, his former postdoctoral mentor at the Whitehead Institute - MIT, accusing his team of publishing unreliable "false" negative experimental results on inability to generate any cross-species mouse-human chimerism in a paper published by Jaenisch on the pluripotency of human embryonic stem cells in the journal Cell Stem Cell. Surprisingly, in 2016, Jaenisch and his team reported positive results on the same topic in the Proceedings of the National Academy of Sciences (PNAS) and reporting the ability to create chimeric embryo from a mixture of mouse and human cells. In light of the latter, Hanna again raised the same critical comments in PubMed, suggesting retraction of a section of the previous 2014 Jaenisch paper in Cell Stem Cell that reported negative results, in contrast to the newly reported 2016 PNAS positive results by the same team led by Jaenisch. Jaenisch published a correction in the same journal. Later findings independently reported by Jun Wu group and others supported mouse-human cross-species chimerism with human pluripotent cells as originally reported by Hanna in 2013 and expanded further by his group in 2021. Human PSCs expanded in Hanna lab naive-like RSeT media were also independently shown to contribute to dopamine neurons in postnatal mouse-human cross species chimeras, thus solidifying the earlier claims by Hanna and refuting those published by Jaenisch in 2014.
The Hanna team has also tackled pathways that resolve naive pluripotency programs and delineated a critical function for m6A RNA methylation in stem cell transitions in peri-implantation mouse development. Their study published in Science in 2015 provided the first evidence for the absolute essentiality of m6A mRNA epigenetic layer for mammalian embryo viability in vivo and uncovered opposing tolerance of epigenetic repressor depletion in naive and primed cells from the same species, that Hanna later used to optimize naive conditions in humans since only naive cells can tolerate genetic ablation or RNA and DNA methylation (deposited and maintained by METTL3 and DNMT1 enzymes, respectively). Hanna used the latter property to screen for conditions that allow survival of human pluripotent cells without these enzymes and termed the conditions human enhanced naive stem cell media (HENSM).
Hanna's lab also focused on deciphering the principles regulating naive pluripotency in different species and in 2013 his team was the first to derive human genetically unmodified MEK/ERK independent naïve-like pluripotent cells (termed NHSM conditions that were commercialized as RSeT by Stemcell Technologies). Hanna next developed engineered systems to screen for enhanced NHSM conditions that maintain human pluripotent ES cells that can tolerate removal of RNA or DNA methylation enzymes (by ablating METTL3 or DNMT1 genes, respectively), and identified enhanced NHSM conditions (termed HENSM), that can yield ESCs/iPSCs with more compelling characteristics of human pre-implantation blastocyst-morula stages.
From Naive Stem cells to synthetic complete embryo models developed ex utero - in mouse and human