Our lab is interested in the mechanisms by which tissues specify and measure spatial dimensions. What defines the “proper” size of developing organs at which they stop to grow? How are the species-specific sizes, shapes and proportions of organisms encoded and “realized” during development? Or during regeneration, how does the regenerative response replace exactly the tissues lost in to injury? We are using planarian flatworms of the species Schmidtea mediterranea as model system to tackle these long-standing questions from a new experimental angle. On first sight, these worms appear to be perfectly normal animals (A). Yet a number of quirks make them uniquely suited for addressing scale, shape and proportion: First, Planarians have amazing regenerative abilities- even when cut into tiny pieces, each piece will regenerate into a complete animal (B). Second, planarians grow when fed and literally shrink when starved, allowing experimental “tuning” of body size over a ~50-fold size range. And third, the shape and morphology even of adult animals responds dramatically to changes in patterning pathway activity.

We are approaching the mechanistic basis of size, shape and proportions via the signaling pathways patterning the planarian body plan. RNAi-screens based on the sequenced genome of Schmidtea mediterranea have already identified some of the underlying circuitry. For example, as in other animals, Wnt signaling plays a crucial role in determining head versus tail identity (C-E) and Bmp-signaling specifies “dorsal”. In the lab, we are now trying to understand how individual pathways interact to jointly specify the molecular coordinate system of the planarian body plan and how the coordinate system quantitatively adapts to changes in spatial dimensions during regeneration or growth. Current projects include:

1. Completion of the molecular coordinate system of the planarian body plan with genomic tools.
2. Localization of patterning reactions in the cell biological tissue landscape in terms of signal sources, -targets and –dynamics.
3. Third, understanding the “design logic” of the system, which allows regeneration of the coordinate system irrespective of the starting point.