Mouse transgenic research suggests that lymphocyte development requires a robust chromatin remodeling. Turkova et al. found that although the chromatin-remodeling enzyme known as Smarca5 was thought to be a general factor, lymphocyte development in stem cells is most sensitive to its decrease.

The production of blood cells relies on coordinated regulation of gene expression, timing of the cell cycle, and suppression of inappropriate processes by apoptosis. Like any stem cell, the hematopoietic stem cell deals with the balance between stemness and differentiation, but also with the quantitative requirements for the production of different elements at specific stages of development and during everyday situations that might include bleeding or infections. The different decisions in the cell nucleus of stem cells are related to the structure of the DNA, which is wrapped in a bun of histone proteins. Different critical sequences have to be made available, and this is done by an enzymatic motor that releases DNA from the histone octamer, called the nucleosome, with the expenditure of energy, creating a region of freely accessible DNA, while other unnecessary DNA sequences are twisted like a thread around a spool. The unwinding of the DNA strand from the nucleosome is called the process of chromatin remodeling. It is generally accepted that stem cells have very little gene expression and replication, and thus we were interested in how dependent the various blood subtypes are on the function of the chromatin remodeling enzymatic engine in stem cells during their early differentiation. Specifically, we tested how the ISWI ATPase SMARCA5 (SNF2H), which represents an absolutely essential and unique enzyme, effects the production of lymphoid, erythroid and myeloid cells.

This type of project involves mouse transgenic models that we have gradually developed over the past 20 years. My lab group took up the project around 2005 in Prague, Czech Republic, but the roots go back to 1998 when we cloned the mouse mRNA for Smarca5 and found that Smarca5 is very important for blood production. In 2003, we published with Art Skoultchi (Albert Einstein College of Medicine, Bronx, NY) a mouse knockout for Smarca5 that showed its indispensability for early embryonic development. Further research led to the development of a mouse model of Smarca5 conditional inactivation that demonstrated the importance of Smarca5 for hematopoietic stem cell, lymphoid and erythroid development.

When we used up the possibilities of the knockout mouse and decided to create a conditional transgenic model for Smarca5. Although we created models for human as well as murine Smarca5, a publication now coming out in Communications Biology covers the first results with the transgene for human SMARCA5 entitled: Differential requirements for Smarca5 expression during hematopoietic stem cell commitment. We observed that the transgenic allele only provides about 10% of the expression of the normal allele. Therefore, we crossed the transgenic model with the previous model with a knockout allele to generate a set of supermodels in which the different Smarca5 expression levels exist. This allowed us to show that the hypomorphic (producing lower protein levels) SMARCA5 allele (S5tg) is fully functional and can rescue, in a dose-dependent manner, the gene inactivation phenotypes from previous k.o. projects, i.e. defects in lymphoid and erythroid development. In addition, transgenic Smarca5 binds all canonical complexes that have been incrementally discovered. Once we express low level of Smarca5 in stem cells, we see that progenitors entering lymphoid T and B development are the most sensitive to Smarca5 reduction, while other progenitors are less or not affected (see figure & legend).

Figure legend: Hematopoietic stem cells in bone marrow regulate the expression of the epigenetic regulator Smarca5, which influences the development of blood elements through ATP-dependent effects on nucleosome architecture. Our data show that the development of lymphoid progenitors of both the B and T lineages is most dependent on Smarca5 levels, erythropoiesis is less dependent, while a very low level of the studied ISWI ATPase is sufficient for myeloid cell development. Created with BioRender.com.








To support our hypothesis that SMARCA5 expression level has a direct effect on development at stem cell level, we employed competitive transplantation experiment of transgenic and normal stem cells into normal but also transgenic recipients. Both of these experiments confirmed our hypothesis that it is primarily lymphocyte development that is strongly dependent on Smarca5 levels and that the defect originates in stem cells. Low SMARCA5 levels lead to significant permissiveness of the bone marrow niche for wild type stem cells. Transgenic hematopoietic stem cells were not able to produce lymphocytes, indicating that these lymphoid early progenitors are most sensitive to SMARCA5 levels. You think that's the end of the story? But no. Our current results show that Smarca5 is indeed a very important factor that affects the life of cancer stem cells. Therefore, we are also focusing on the question of how to effectively get rid of these cancer stem cells and one of the mechanisms is to focus on the biology of Smarca5 in this regard.

Authors: Tereza Turková a Tomáš Stopka

Publication: Turkova, T., Kokavec, J., Zikmund, T. et al. Differential requirements for Smarca5 expression during hematopoietic stem cell commitment. Commun Biol 7, 244 (2024). https://doi.org/10.1038/s42003-024-05917-z

Co se událo na poli české a světové hematologie? ZDE 

2. místo

Knizkova D, Pribikova M, Draberova H, Semberova T, Trivic T, Synackova A, Ujevic A, Stefanovic J, Drobek A, Huranova M, Niederlova V, Tsyklauri O, Neuwirth A, Tureckova J, Stepanek O, Draber P. CMTM4 is a subunit of the IL-17 receptor and mediates autoimmune pathology. Nat Immunol. 2022 Nov;23(11):1644-1652. doi: 10.1038/s41590-022-01325-9. (PubMed)

5. místo

Stopka T, Minařík L, Dusilková N, Pešta M, Kulvait V, Špaček M, Zemanová Z, Kalousová M, Jonášová A. G-CSF plus azacitidine versus azacitidine alone for patients with high-risk myelodysplastic syndrome: academic, open label, randomized trial. Blood Cancer J. 2022 Jul 7;12(7):105. doi: 10.1038/s41408-022-00698-2. (PubMed)

9. místo

Pimkova K, Jassinskaja M, Munita R, Ciesla M, Guzzi N, Cao Thi Ngoc P, Vajrychova M, Johansson E, Bellodi C, Hansson J. Quantitative analysis of redox proteome reveals oxidation-sensitive protein thiols acting in fundamental processes of developmental hematopoiesis. Redox Biol. 2022 Jul;53:102343. doi: 10.1016/j.redox.2022.102343. (PubMed)

A team of researchers and physicians from the BIOCEV Centre, 1^st Department of Medicine - Hematology (the First Faculty of Medicine of Charles University) and the General University Hospital in Prague has designed a new approach for the treatment of acute leukaemia. This innovative method involves the combination of two medicines that, when administered together, have significantly prolonged the survival of patients. The clinical trial lasted five years and included 76 patients from the Czech Republic. Information about the new type of treatment was published by the prestigious Blood Cancer Journal from the Nature Publishing Group. At the moment, negotiations are underway to expand the trial to the European-wide level.

Doc. Anna Jonášová and Prof. Tomáš Stopka  

Myelodysplastic syndrome (MDS) is a cancer of the bone marrow causing a low production of non-functioning blood cells. As a result, patients are deficient in both red and white blood cells, which are crucial for the body’s immunity, as well as platelets for blood coagulation. Patients suffering from this anaemia suffer from bruising, frequent internal bleeding and are less resistant to bacterial and viral infections, for example pneumonia.

Depending on the severity of the disease, antibiotics or repeated blood transfusions are given as treatment. In exceptional cases, patients can be treated with a bone marrow transplant. In Europe, four MDS patients per 100,000 people are diagnosed annually. In the Czech Republic, the General University Hospital registers approximately 80 patients each year. The critical phase of MDS is the transition to acute myeloid leukaemia (AML), characterised with a very short survival time.

"The current globally applied treatment for MDS patients during their transition to AML is based on 5-azacytidine, a medicine which was invented in the 1970s by the Czechoslovak Academy of Sciences. Azacytidine is an inhibitor of nuclear enzymes, referred to as DNA methylases, which are genetically and functionally disrupted in leukemic cells, and therefore, their activity helps to eliminate leukemic cells. Based on previous research, much of which has been published in reputable journals, our MDS/AML group has come up with the concept of “differentiation therapy for MDS”. We propose combining azacytidine with another substance called G-CSF, which promotes the formation and development of white blood cells in the bone marrow. We have been able to demonstrate the therapeutic effects of the new combination, and, above all, its safe effect on patients, but we have also been able to prolong their survival by months,” says Prof. Tomáš Stopka, head of research from the First Faculty of Medicine, Charles University, and Biocev. “At the same time, we have discovered that the combination of these agents induced significantly more treatment responses, which is ground-breaking and essential for further research and clinical testing in patients.”

A clinical trial demonstrating the benefit of the new treatment method in high-risk MDS was approved by the State Institute for Drug Control in 2017. The coordinator of the clinical trial was the Head of MDS and AML Treatment and Diagnosis, Doc. Anna Jonášová from the 1st Internal Clinic – Haematology, First Faculty of Medicine, Charles University in Prague: “We had to make a huge effort even before the trial itself was launched as we had to secure an application with the State Institute for Drug Control and have the trial pass through the ethics committees. The proposed therapeutic combination advances the use of the cytokine G-CSF in AML therapy, while its synergistic activity with azacytidine makes this treatment more effective and safer for patients, representing a proven strategy that is immediately applicable in practice. We would not have achieved the results if it had not been for the great willingness of the patients who participated in the trial."

At the moment, intensive negotiations are underway for a new European-wide trial in which another medicine, Venetoclax, will be investigated alongside 5-azacytidine and G-CSF. "I am happy that we are successfully linking genetic and clinical data in the Czech Republic and thanks to this, we are able to determine how acute leukaemia will be treated in the near future," adds Prof. Tomáš Stopka.

Link to the publication: HERE

Rozhovor pro UK FORUM: Nová kombinace léčiv prodlužuje život pacientů s leukémií (ukforum.cz)