Editors' ChoiceDevelopmental Biology

Seeing Hedgehog at a Distance

Science's STKE  07 Aug 2001:
Vol. 2001, Issue 94, pp. tw14
DOI: 10.1126/stke.2001.94.tw14

Gritli-Linde et al. developed an improved fixation technique that allows visualization of mammalian Hedgehog proteins (Sonic Hedgehog and Indian Hedgehog) by immunohistochemistry at sites distant from the site of Hedgehog production. This represents an important advance in demonstrating that the acylation and cholesterol-modified signaling ligands can act directly on distant target cells to control differentiation and morphogenesis instead of exerting their effects through intermediary signals. Their method relies on fixation with ethanol-acetic acid solution, which precipitates and preserves proteoglycan (PGs) and glycosaminoglycans (GAGs) in the tissue. Experiments in which the tissues were treated with enzymes to increase PG and GAG solubility in aqueous solutions led to loss of staining for the Hedgehog proteins under one staining condition, but if the ethanol-acetic acid fixation solution was used the Hedgehog proteins could be visualized. These results suggest that Hedgehog may interact with PGs and GAGs and support experiments in Drosophila that suggested that proteoglycan synthesis is important for Hedgehog signaling.

A. Gritli-Linde, P. Lewis, A. P. McMahon, A. Linde, The whereabouts of a morphogen: Direct evidence for short- and graded long-range activity of Hedgehog signaling proteins. Dev. Biol. 236, 364-386 (2001). [Online Journal]