El vistazo más cercano al tejido humano. Una poderosa técnica microscópica revela la organización estructural de la pielContributed by: Anonymous · Views: 999
Contributed by: Anonymous · December 07, 2007 @ 07:12 PM MST · Views: 999
The closest look ever at native human tissue
A powerful microscope technique reveals the molecular organisation of skin
This 3D reconstruction of a human skin cell was produced
by electron tomography and shows organelles in different
colours: regions of cell-cell contact [sandy brown], nucleus and nuclear
envelope [blue] with pores [red], microtubules [green],
mitochondria [purple], endoplasmic reticulum [steel blue].
3D visualisation of interacting cadherin molecules in their native arrangement. Known molecular structures of cadherins [grey and red ribbons] are fit into the electron tomogram [multicolour] of the complex.
So far, the only information available about a protein's position and interactions in a cell was based on either light microscopy images at poor resolution or techniques that remove proteins from their natural context. Frangakis and his group have been developing a technique called cryo-electron tomography, with which a cell or tissue is instantly frozen in its natural state and then examined with an electron microscope. Electron microscopy normally requires tissue to be treated with chemicals or coated in metal, a procedure that disturbs the natural state of a sample. With cyro-electron tomography, images are taken of the untreated sample from different directions and assembled into an accurate 3D image by a computer.
The researchers applied this technique to observe proteins that are crucial for the integrity of tissues and organs like the skin and the heart, but also play an important role in cell proliferation. These proteins, called cadherins, are anchored in cell membranes and interact with each other to bring cells close together and interlink them tightly.
"We could see the interaction between two cadherins directly, and this revealed where the strength of human skin comes from," says Ashraf Al-Amoudi, who carried out the work in Frangakis' lab. "The trick is that each cadherin binds twice: once to a molecule from the juxtaposed cell, and once to its next-door neighbour. The system works a bit like specialised Velcro and establishes very tight contacts between cells."
The new insights into the cadherin system broadens the understanding of structural aspects of cell adhesion and shed light on other crucial processes such as cell proliferation. The technical advances achieved in cryo-electron tomography of frozen sections open up new possibilities to study more systems at native conditions with molecular resolution.
A. Al-Amoudi, D. Castaño Díez, M.J. Betts, A.S. Frangakis. The Molecular Architecture of Cadherins in Native Epidermal Desmosomes. Nature, 6 December 2007
Credits: European Molecular Biology Laboratory (EMBL)