The main suspect

The institute's scientists are investigating one of the mysterious "side effects" of Down syndrome

It is common to think that the doctor's role is to treat patients, and not necessarily to get to the bottom of the causes that cause diseases. But the medical student Niv Pankovitz, who is currently completing his Ph.D. research work at the Weizmann Institute of Science, strives to understand the disease - in the "know the enemy" test. For the past three years, he can be found in the laboratory of Prof. Yoram Groner, from the department of molecular genetics, where he traces the differentiation processes of certain blood cells, with the aim of understanding the causes of blood cancer, of the type common among patients with Down syndrome.

Niv Pankovitz's relationship with the institute started by chance, when at the end of the second year of medical studies he came to Prof. Gruner's laboratory as part of a summer program for students. Prof. Gruner's laboratory is engaged in researching the molecular basis of Down syndrome. Pankovitz saw that it was good, and after another year - during which he continued his research at the Institute at the same time as his studies at the Tel Aviv University School of Medicine - he took a three-year break from medical studies, received MD/Ph.D status, and devoted all his time to scientific research .

Pankowitz's research deals with one of the mysterious "side effects" of Down syndrome: its patients also suffer from a certain type of blood cancer (leukemia) in their infancy - the uncontrolled growth of blood cells responsible for the creation of blood platelets, called megakaryocytes. In most cases, fortunately, this is a transient phenomenon, but in a quarter of the patients the cancer relapses, and its late effect is much more devastating. The incidence of blood cancer in the population suffering from Down's syndrome is 500 times greater than in the general population, but the relationship between the two phenomena is unknown, as are the causes of the appearance of the cancer, its disappearance, and its renewed outbreak.

Previous studies by Prof. Gruner put the spotlight on a central suspect, who may be the link between Down syndrome and cancer of megakaryocytes. The suspect protein, called Runx1, functions as a transcription factor - that is, it binds to DNA and thus regulates the expression of genes - by determining the timing when RNA molecules will be produced from them, which are translated into the creation of proteins. Thus he controls, among other things, the differentiation process of blood cells of the megakaryocyte type. The incriminating evidence against Runx1 includes its suspicious location on chromosome 21 - a chromosome found in excess in Down syndrome patients, as well as the fact that leukemia patients express large amounts of a "shortened" form of Runx1, which disrupts the activity of the long, normal form.

How does Runx1 direct the differentiation of megakaryocytes? And what does it have to do with leukemia? To try to answer these questions, Pankowitz set out to map the genetic program that Runx1 activates at several time points throughout the differentiation process, by comparing normal cells, in which the transcription factor Runx1 functions properly, and transgenic cells, in which the activity of the Runx1 gene has been inhibited. In the first step, Pankowitz located the places where Runx1 binds to DNA, and determined the sequence of their bases. Later he looked for the genes whose degree of expression changes in the engineered cells compared to the normal cells.

The combination of the two methods makes it possible to determine the identity of the genes activated by Runx1 in each of the stages of differentiation that lead to the creation of megakaryocytes, but at the same time produces a huge volume of data. To analyze the large amount of information received, Pankovitz teamed up with research student Ram Ishak, from the group of Dr. Amos Tani from the Department of Computer Science and Applied Mathematics. Ishak, whose research tries to answer general questions concerning the control of gene expression, is engaged in the development of methods for handling genomic information through spatial analysis, based on a technique for identifying multidimensional patterns. For the purpose of the current research, Ishak developed new algorithms and methods, adapted to the task.

The research findings, published in the journal Blood, showed that the transcription factor Runx1 is a key factor in the differentiation process, and that it binds to a huge amount of sites on the genome - over 10,000. Detailed mapping of the binding sites of Runx1 at different stages of differentiation revealed several interesting insights. Thus, for example, it turned out that in the early stages of differentiation, Runx1 works in collaboration with another transcription factor, called GATA1. In the past, it was found that Down syndrome patients suffering from leukemia carry a defective copy of the GATA1 gene, which causes the formation of a shorter than normal protein. The scientists hypothesize that disruptions in the joint work of the two transcription factors may contribute to the development of leukemia. In addition, hundreds of suspect proteins controlled by Runx1 were discovered, which may also be involved in the development of the disease. The scientists were able to explain how Runx1 succeeds in performing different roles at different stages of differentiation: it turned out that this variation is achieved by joint activity with additional transcription factors, and characteristic lines were determined for this joint activity. According to Ishak, it is very possible that the principles discovered regarding the interaction with transcription factors and other factors may be relevant to other cases.

Pankowitz later created transgenic mice, which express the short form of Runx1 and the defective form of GATA1 - similar to Down syndrome patients. These mice showed symptoms similar to Down syndrome patients suffering from transient leukemia, and the scientists hope that it will be possible to use them as a model to understand the mysterious disease, as well as the reasons for its appearance - and its inexplicable disappearance. In his next studies - which he will carry out as part of post-doctoral research at the same time as completing his medical studies - Pankovitz plans to use these mice to investigate the molecular mechanisms underlying the activity of GATA1 and Runx1, as well as the involvement of Runx1 in other types of leukemia.

Doctors and researchers
A conference that took place recently at the institute at the initiative of Niv Pankovitz brought together students from all the medical schools in Israel, who are simultaneously pursuing a research doctorate in the physician-researcher track (MD/Ph.D). The conference was attended by nearly 50 students who were invited to present their research works, with the aim of encouraging acquaintance and cooperation, and expanding the common denominator. Pankovitz says that he initiated the conference because he felt that there was not enough contact between the students, despite the broad common denominator between them, in order to create a cohesive core of doctors who exchange ideas, information and experiences. In addition to the student lectures, veteran doctor-researchers gave lectures at the conference, who shared their experience with the students - both from the professional-scientific aspect, and from the personal aspect. Pankovitz hopes that the conference will become an annual tradition, which will help create a cohesive community of physician-researchers in Israel.