development complexity and biased evolution n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Development, complexity and biased evolution PowerPoint Presentation
Download Presentation
Development, complexity and biased evolution

Loading in 2 Seconds...

play fullscreen
1 / 20

Development, complexity and biased evolution - PowerPoint PPT Presentation


  • 70 Views
  • Uploaded on

Development, complexity and biased evolution. Nic Geard SENSe, University of Southampton (formerly at: ARC Centre for Complex Systems, The University of Queensland, Australia). Background. Recently arrived in the UK to work with Seth Bullock at University of Southampton

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

Development, complexity and biased evolution


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
development complexity and biased evolution

Development, complexity and biased evolution

Nic Geard

SENSe, University of Southampton

(formerly at: ARC Centre for Complex Systems,

The University of Queensland, Australia)

background
Background
  • Recently arrived in the UK to work with Seth Bullock at University of Southampton
  • Prior to that, I obtained my PhD from the University of Queensland in Australia, advised by Professor Janet Wiles.
  • Thesis – Artificial Ontogenies: A Computational Model of the Control and Evolution of Development
evolution variation and selection

II. Gene Expression

III. Phenotype

I. Genome

..GTCATACTATAATCCTGGTCATCATGTCTGCTCTACATCGTGTCTACTCTGTTATACTTTACTGTCTTACTCTCACATATATCTCGTCACTGCATGCCATGTTACATCGTGTCTACTCTGTTATACTTTACTACATATATCTCGTCACTGCCTGT...

Anterior

Posterior

zygote

1st cleavage:

P

1

AB

2nd cleavage:

neurons

EMS

P

epidermis

2

pharynx

3rd cleavage:

MS

E

C

P

3

4th cleavage:

pharynx

intestine

epidermis

muscle

D

P

4

muscle

germ line

Sequence

Gene expressionNetwork Interactions

GrammarLineage trees

Mapping biology onto computation

Evolution: variation and selection

gene expression, development, environment, etc.

Organism

DNA Sequence

what role does development play in evolution
What role does development play in evolution?
  • Developmental reprogramming: mutational change affecting the developmental trajectory of an organism (Arthur 2002)
  • If reprogramming is more likely to produce some trajectories than others, then evolution may be biased towards those trajectories.
  • What is a good computational model for studying developmental reprogramming?

W. Arthur. The emerging conceptual framework of evolutionary developmental biology, Nature, 2002.

how to model developmental space
How to model developmental space?

Cell lineages:

  • Early development of some species is characterized by invariant patterns of cell division and differentiation (e.g. C. elegans)
  • Cell lineages provide a clear record of a developmental trajectory
  • An organizational, rather than a morphological, representation of development
modelling the control of development

gene regulatory network

cell dynamics

cell lineage

Modelling the control of development
  • Recurrent neural network model of gene regulation
  • Inputs = environmental context
  • Outputs = division and differentiation triggers
  • Each cell contains the same network, but with a different state
  • ‘Phenotype’ = terminal cells of lineage
measuring developmental complexity
Measuring developmental complexity

R. Azevedo et al. The simplicity of metazoan cell lineages, Nature, 2005.

how does developmental complexity vary
How does developmental complexity vary?
  • The space of possible developmental trajectories is vast
  • By parameterizing the model system, we can visualise ‘slices’ through this space
  • By making the visualisation interactive, we can efficiently identify major characteristics
  • LinMap – an interactive visualisation tool

N. Geard & J. Wiles. LinMap: Visualising complexity gradients in evolutionary space, Artificial Life, submitted.

different complexity measures
Different complexity measures

Number of

differentiated

cells

Number of

terminal cells

Weightedcomplexity

Non-deterministic

complexity

N=8, k=8

are all phenotypes equally available for natural selection
Are all phenotypes equally available for natural selection?

Traditional view

Developmental bias

W. Arthur. Biased Embryos and Evolution, 2004.

slide15
The gene network generates a very different distribution of frequent phenotypes compared to a stochastic (Markovian) model

# B cells

#A cells

what are the implications for evolution
What are the implications for evolution?
  • Adaptive task : Match a cell fate distribution derived from a biological cell lineage: e.g.
  • C. elegans (male) V6Lpap –
    • red = hypodermis; green = neuron;
    • blue = apoptosis; yellow = structural
summary
Summary
  • A tractable model of development.
  • Methods for measuring and visualising the structure of developmental space.
  • The intrinsic dynamics of the GRN model result in some lineages/phenotypes being generated more frequently than others.
  • This biased production of variation is reflected in the direction of adaptation.
  • A possible explanation for the complexity observed in real cell lineages … (?)
acknowledgements
Acknowledgements
  • Janet Wiles, Kai Willadsen and James Watson (UQ, Brisbane)
  • Ricardo Azevedo and Rolf Lohaus (UT, Houston)

Further Information

  • LinMap software (Java) and publications available from : http://www.itee.uq.edu.au/~nic
  • Geard, N., (2006). PhD Thesis.
  • Geard, N. & Wiles, J., (2006). Investigating ontogenetic space with developmental cell lineages, Artificial Life X.
  • Geard, N. & Wiles, J., (2005). A Gene Network Model for Developing Cell Lineages. Artificial Life11(3):249-268.