Is spine head growth an "artifact"?

A visiting seminar speaker to my department recently told that he thought that the rapid and permanent increase in spine head size we have reported was an artifact of 2-photon uncaging (of glutamate). At this years SfN annual conference in San Diego, two labs are finally catching up and reporting similar phenomena. Karel Svoboda gave the Presidential address on the saturday evening (3rd November) of the conference. In the final part of his talk he showed all unpublished data using 2-photon uncaging of MNI-Glu. Using a Ras indicator, he showed that tetanic photo-stimulation of single spine heads a la Matsuzaki, produced enlargement (see pic). Activated Ras was seen to spread from the spine into the dendrite and remain active for several minutes. Hayashi's lab (MIT) had a poster (363.11/M23) showing spine head enlargement using photochemical tetanus as well.

So now with a n=3, perhaps spine head enlargement is not an "artifact" after all?

Matsuzaki et al. Nature Neurosci. (2001) 4: 1086-1092, & Nature (2004) 429:761-766.

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All the colours of the rainbow.

So the "brainbow" paper is finally out. Sanes & Lichtman and co-workers published a paper in Nature (1st Nov 2007) with beautiful images of what might be called their "second generation" GFP mice. In 2000 they introduced their "simple" GFP mice in which they created mice lines with different populations of neurons stained. Now they have created multi-coloured neurons using mixing of RFP, YFP and CFP in a random way. The results are visually stunning (see pic from Supp Fig 2). Unfortunately most of us do not have the microscopes which will allow us to see these colours. You will need 3 PMTs or a CCD colour camera. These mice are a revolution.

Livet J, Weissman TA, Kang H, Draft RW, Lu J, Bennis RA, Sanes JR, Lichtman JW Transgenic strategies for combinatorial expression of fluorescent proteins in the nervous system. Nature (2007) 450 (7166):56-62.

Feng G, Mellor RH, Bernstein M, Keller-Peck C, Nguyen QT, Wallace M, Nerbonne JM, Lichtman JW, Sanes JR Imaging neuronal subsets in transgenic mice expressing multiple spectral variants of GFP. Neuron (2000) 28:41-51