An extraordinary capacity of cells is their ability to modulate their shape, polarity and intracellular cytoskeletal organisation, according to the functions they need to perform. Our work seeks to identify the gene and protein networks that regulate these three processes and overall cell morphogenesis, in space and time.To that end we adopt a multi-disciplinary approach combining high- content and quantitative microscopy, genetics, biochemistry and computational methods.We use fission yeast as our primary model organism and plan to extend our scope to mammalian cells in the future.

We recently established a high-throughput/high-content microscopy platform for yeast-based functional genomics studies. Using that platform and systematic gene knock- outs, we recently completed the first comprehensive live cell-based screen for microtubule and cell shape regulators and discovered tens of potential novel regulators that
we are in the course of validating. With that screen, we hope to obtain the most exhaustive genomic map and spatiotemporal annotation of such regulators to date. Various other microscopy-based functional genomics projects are also ongoing in our group.

We have also developed, in collaboration with theoreticians, computational methods to simulate the collective interaction of microtubules and microtubule regulator recipes in 3D over time, in order to clarify the mechanisms that precisely pattern microtubules in cells. We find that, together with regulator abundance, cell geometry is a strong determinant of microtubule pattern, something we are actively investigating experimentally.
Lastly, we have begun characterising the dynamics and structure of the polarity machinery at high spatiotemporal resolution. Using live super-resolution microscopy and custom-made image analysis tools, we find that components of the machinery previously thought to regulate polarity by physically interacting at the cell cortex actually localise to separate, distinct complexes.This suggests novel layers of polarity regulation we are seeking to unravel.

High-resolution image of cells expressing GFP-tubulin, generated with an automated high-throughput spinning disc confocal microscope.

Polarity complexes visualised at superresolution. Live cells expressing two fluroscently-labelled (green:GFP, red:mCherry) polarity factors. Superresolution reveals that both factors, thought to regulate polarity by physically interacting, belong to separate 150mm-sized complexes. Left: cell visualized 'sideways'. Right: cell visualized 'head on'. Dotted lines: cell contours.

Plain English:
An extraordinary capacity of cells is the ability to adopt specialized shapes and growth modes according to the functions they need to perform. For example, neurons adopt defined growth patterns in order to properly innervate our bodies, epithelial cells become polarized to correctly function in our skin and tissues, and blood cells take a specific shape allowing them to flow uninterrupted in our bloodstream. Not surprisingly, when cells lose control over that capacity they begin to malfunction and this leads to many human pathologies, ranging from neuronal disorders to cancer. Our general aim is to identify the networks of genes and proteins that regulate polarity, shape and growth pattern in cells, and to understand how the networks act in a coordinated manner to regulate those processes or become uncoordinated in disease.

Selected publications:

• Carazo-Salas RE, and Nurse P (2007). Sorting out
interphase microtubules. Mol Syst Biol 3:95-6.

• Salinas S, Carazo-Salas RE, Proukakis C, Schiavo G, Warner TT (2007). Spastin and microtubules: Functions in health and disease. J Neurosci Res 85(12):2778-82.

• Carazo-Salas RE, and Nurse P (2006). Self-organization of interphase microtubule arrays in fission yeast. Nat Cell Biol 8(10):1102-7.

• Salinas S, Carazo-Salas RE, Proukakis C, Cooper JM, Weston AE, Schiavo G, Warner TT (2005). Human spastin has multiple microtubule-related functions. J Neurochem 95(5):1411-20.

• Carazo-Salas RE, Antony C, Nurse P (2005).The kinesin Klp2 mediates polarization of interphase microtubules in fission yeast. Science 309(5732):297-300.

A high-throughput/high-content microscopy workflow used to systematically screen through the genome for novel regulators of cell morphogenesis.

Fig 3: Snapshots from a computer simulation of microtubule organization in a virtual cell.