Dear Professor Brun,

I am pleased to write this letter in support of Till Bretschneider's application for a faculty position in Systems Biology at Indiana University, Bloomington. Till and I were brought together late in 2003 by Günther Gerisch to investigate actin dynamics in Dictyostelium. This project turned into a highly productive and enjoyable collaboration which has produced 3 quality publications in 2 years, with a fourth manuscript near completion. I subsequently turned to Till for assistance on a project in my lab unrelated to the original work with Günther, which was published recently in the Journal of Cell Science. As a live-cell image acquisition specialist I am profoundly dependent on specialists in quantitative image analysis, as well as those who can integrate the resulting data into predictive models. Till has repeatedly demonstrated he can do both.

Our first project began with an attempt to image actin structure and dynamics at the cell surface of Dictyostelium using TIRF. We found actin patches, meshworks, and open networks which could not be explained by existing models of actin regulation. Based on meticulous data analysis, Till restricted our set of possible models to a minimum number and was vigorous in formulating experiments to distinguish among them. He could easily transfer complex ideas into language I understood. As we tried to interpret our data he confidently challenged existing ideas on the regulation of actin polymerization during protrusion of the plasma membrane, and was instrumental in our proposal that actin meshwork polymerization at the plasma membrane could be uncoupled from protrusion.

After the positive experience of working with Till on actin meshwork dynamics, I was quick to ask him for help with the analysis of the diffusion of fluorescent lipids in the plasma membrane. This required careful modification of standard methods of analysis used in fluorescence recovery after photo-bleaching (FRAP) to adapt them to our special experimental conditions of focal labeling and the observation of initial diffusion (FLOID). Till wrote custom software to perform the analysis and determine the diffusion constant of carbocyanine dyes by FLOID, which compared well with the diffusion constant value he derived from our FRAP data.

In summary Till is a promising scientist able to formulate and articulate novel ideas, who is also a pleasure to work with. Although his vision is impaired, this has had no significant impact on our interaction or on the quality of his contribution to our work. In fact I have been impressed by his innovative use of display methods to visualize multi-dimensional image data. Till would be an asset to any thriving research environment, and I fully recommend hiring him for this tenure track position.

Please do not hesitate to contact me if you would like any further information.

Yours sincerely,

Kurt Anderson

Group Leader, Actin Dynamics