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Theory of Living Matter Group

Second meeting of the TLM group


Schedule

In this informal meeting we will have two talks, a theoretical talks and an experimental talk. Both talks are intended to be understandable for a broad audience. Henrik Boije (Department of Physiology, Development and Neuroscience) will give a talk on Building a retina: Extrinsic and intrinsic factors regulating cell fate in the developing retina.

We use the zebrafish retina as a model to understand how a pool of equipotent stem cells can create a complex organ of the correct size and cell type distribution. Analysis of cell lineages of retinal progenitor cells reveals a large variation in size and cell type composition suggesting an element of stochasticity during proliferation and cell fate assignment. However, stochasticity does not mean that these events are uncontrolled or random but rather that they operate according to defined probabilities creating statistically well-behaved ensembles. How environmental cues (extrinsic factors) and cell-autonomous decisions (intrinsic factors) regulate cell proliferation and differentiation remains elusive. We experimentally study intrinsic and extrinsic influences by combining cell transplantation with cell lineage tracing technologies. Our experiments reveal the fate changes that occur when the translation of key fate determinants is blocked by “morpholinos”. Based on these experiments and with knowledge of the transcriptional hierarchies during retina development we were able to develop a stochastic model, which takes into account the proliferative capacity and fate assignment of retinal progenitor cells.

Then, after a short break, Joel Peck (Department of Genetics) will talk about Is Life Impossible? Information, Sex, and the Origin of Complex Organisms.

Eigen’s Paradox is a logical puzzle concerned with the origin of complex life. It is presumed that, early in the history of life, mutation rates were much higher than they are in contemporary organisms. According to Manfred Eigen, this implies that the maximum amount of information that could have been stably encoded in the genomes of early organisms must have been severely limited. In contemporary organisms, the mechanisms of error prevention and correction are quite complex. This leads to a “chicken-and-egg problem.” How could life that is complex enough to allow the suppression of mutation to low levels have evolved while mutation rates were quite high? Eigen’s calculations are based on the idea that, if the genome with the best-possible fitness can not be maintained in a population, then “The information ... would slowly seep away until it is entirely lost.” However, this idea is not obviously based on any firm information-theoretic foundation. What really matters is whether, in a stable population, organisms are able to generate phenotypes that are complex enough to allow for highly effective error-prevention-and-correction mechanisms. This talk will present a re-analysis of the problem using this phenotypic-complexity criterion. The findings show that there are conditions where much more information can be stably encoded in the genome than would follow from Eigen’s criterion, despite the existence of relatively high mutation rates. The highest levels of information content are obtained when recombination occurs, and when each possible phenotype is produced by many different genotypes. The talk will also contain a few speculative comments about the possible role of information theory for other evolutionary problems, and in the life sciences in general.

After the talks there will be plenty of time for informal discussions. We will serve some snacks and there will be opportunities to order food and drinks.


Date and venue

Date: Wednesday, 30th July from 6-8pm

Venue: The Brew House, 1 King St, CB1 1LH Cambridge, top floor

The Brew House is located between Christ's College and Jesus College. There will be signs which will guide the way.


Registration

To judge attendance please briefly register here in case you plan to take part:
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Do you think your experimental work might benefit from theoretical insights? Are you a theorist who would like to present his work to an interdisciplinary audience? Then why not give a talk in one of our meetings? Just send us an email at .