Frank Buchholz

Functional genomics in mammalian cells: applications to cancer- and stem cell- biology

Previous and current research

Sequencing of whole genomes has provided new perspectives into the blueprints of diverse organisms. Knowing the sequences, however, does not always tell us much about the function of the genes that regulate development and homeostasis. Our laboratory is using different strategies to dissect gene function in mammalian cells relevant to cancer biology and stem cell research.

Loss-of-function screens in mammalian cells with esiRNA

RNA interference is becoming the method of choice for gene function analysis in cells and whole organisms. Our lab has developed innovative technology to perform large scale RNAi experiments in mammalian cells and in mice. We use enodibonuclease prepared siRNA (esiRNA) for the efficient and specific knock down in genome wide screens to identify and characterize genes relevant to cancer biology and differentiation.

Normal and malignant haematopoiesis

Haematopoietic and endothelial cells arise from a common precursor, commonly referred to as the haemangioblast. The decision whether the cells differentiate into the blood- or vessel- lineage seems to correlate with the expression of certain "master switch genes". One of these important genes for lineage specification is the runx1 gene. Runx1 seems to participate in the fate decision in favor of haematopoietic development. Its pivotal role during development makes runx1 also a good candidate to play an important role in adult stem cells. Interestingly, runx1 is also one of the most frequently mutated genes in human leukemias, supporting that runx1 plays an important role in the adult. We study the role of runx1 during development and in adult mice. A better understanding of this master switch regulator may help to understand, how cells that have a common origin take on a specific fate in the body to build an organ and may also help to understand the development of certain leukemias.

Advanced genome engineering

The need for fluent and precise genomic manipulation strategies has been exacerbated by the increasing pace of published genome sequences. Beyond the reading of complete genomes, the precise manipulation of the encoded information is becoming more important in modern molecular biology. Site specific recombinases are prominent genetic engineering tools that allow the genetic manipulation of whole organisms. In order to expand the usefulness of these enzymes we are designing novel recombinases through directed molecular evolution and test them for their usefulness in biology and medicine.

Future prospects and goals

• Improve esiRNA technology for functional genomic studies.
• Perform RNAi screens in mouse ES cells to identify and characterize factors involved in self renewal and differentiation.
• Perform phenotypic profiling of cancer cell lines and identify and characterize candidate genes with therapeutic potential.
• Study the role of Runx1 in the developing and adult mouse.
• Develop and apply tools that allow flexible and precise genomic manipulations.
  

About

1997: PhD in Biology, University of Heidelberg 1997-1998: Post-doctoral training at EMBL, Heidelberg 1998-2000: Post-doctoral training at the University of California San Francisco (UCSF), the G.W. Hooper Foundation since 2001: Group Leader at the Max Planck Institute of Molecular Cell Biology and Genetics

Selected publications

Kittler, R., Surendranath, V.,  Heninger,A.K., Slabicki, M., Theis, M., Putz, G., Franke,K., Caldareli, A., Grabner, H., Kozak, K., Wagner, J., Rees, E., Korn, B., Sachse, C., Sönnichsen, B., Guo, J., Schelter, J., Burchard, J., Linsley, P.S., Jackson, A.L., Habermann, B., and Buchholz, F. (2007):Genome-wide resources of endoribonuclease-prepared short interfering RNAs for specific loss-of-function studies.
Nat Methods, in press.

Riedel , C.G., Katis, V.L., Katou ,Y., Mori, S., Itoh, T., Helmhart, W., Galova,  M., Petronczki , M., Gregan, J., Cetin, B., Mudrak, I., Ogris, E., Mechtler, K., Pelletier,  L., Buchholz , F., Shirahige,  K., Nasmyth, K. (2006):Protein phosphatase 2A protects centromeric sister chromatid cohesion during meiosis I. Nature, 441(7089):53-61.

Putz, G., Rosner, A., Nuesslein, I., Schmitz, N., and Buchholz, F. (2006): AML1 deletion in adult mice causes splenomegaly and lymphomas.
Oncogene,  25(6):929-39.

Kittler R, Pelletier L, Ma C, Poser I, Fischer S, Hyman AA, Buchholz F. (2005): "RNA interference rescue by bacterial artificial chromosome transgenesis in mammalian tissue culture cells." Proc Natl Acad Sci U S A. 2005 Feb 15;102(7):2396-401.

Ralf Kittler, Gabi Putz, Laurence Pelletier, Ina Poser, Anne K. Heninger, David Drechsel, Steffi Fischer, Irena Konstantinova, Bianka Habermann, Hannes Grabner, Marie L. Yaspo, Heinz Himmelbauer, Bernd Korn, Karla Neugebauer, Maria T. Pisabarro, Frank Buchholz: “An endoribonuclease-prepared siRNA screen in human cells identifies genes essential for cell division.” Nature 432: 1036 -1040

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