Posts Tagged ‘embryo’

2. Biological pattern formation

Currently, the most advanced topic in the lab is our work on biological pattern formation in developing fruit fly embryos; partly because this project evolves in an environment that has a long tradition at Princeton. How does an organism form a body axis, and how are the different body parts along this axis patterned and established is one of the most fundamental questions in developmental biology, and with current access to quantitative data the prospect of exposing general theoretical principles in the biological context, similar to our understanding of physical pattern formation, are conspicuous. My laboratory has chosen the earliest patterning events of the fly embryo for the conceptual reason that the blueprint for the future adult structure is determined entirely during this time, and for the practical reasons of ease of experimental access, and of the powerful scientific environment at Princeton in this field. Pattering at these early stages consists mainly in the differential expression of genes, where Princeton has been developing tools to quantify protein levels in living and fixed embryos since the early 2000s, both experimental and theoretical.

In the past 2.5 years my laboratory has focussed mainly on widening our tool chest to quantify patterning in the early embryo. The goal of these technical improvements is to obtain eventually a fully quantitative (absolute numbers) dynamic picture of the entire patterning process, and address issues such as reproducibility, precision or scaling of the patterning events. We have developed a method to count individual molecules of mRNA in whole fixed embryos, which gives us besides proteins an independent access into the transcriptional regulatory machinery and will hopefully allow us to quantify the ‚??central dogma‚?? at the molecular level in a natural multicellular context. We have made progress on expanding our investigation of patterning dynamics in living embryos (originally restricted to the maternal input gradient of Bicoid protein concentration) to other members of the regulatory network, which is formed by a cascade of interconnected genes that together with the input gradients determine the final body pattern within the first three hours of the embryo‚??s development. Using genetic engineering, we are in the process of labeling the gene products of this network with multicolored fluorescent proteins, for both mRNA and protein. In parallel we are developing microscopes that can track the concentrations of these differently colored molecules in living embryos, where we are facing challenges at the level of spectral unmixing, light exposure of the living specimen, and size constraints of our specimen that affect both spatial and temporal resolution of our data.

 

Diffusion and scaling during early embryonic pattern formation.

T. Gregor, W. Bialek, R. R. deRuyter van Steveninck, D. W. Tank, E. F. Wieschaus, PNAS 102, 18403-18407 (2005).

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