Encystation commitment in Giardia duodenalis: a long and winding road.

Cholesterol and bile salts are relevant modulators of Giardia encystation. Although several molecules within signaling cascades have been identified, and changes in their expression observed during giardial encystation, their underlying interactions leading to expression of cyst wall markers (CWPs and precursors of the GalNAc homopolymer) are not well defined. Recent experimental data and the completion of the Giardia Genome Project Database (GiardiaDB) allow us now to consider the role of bile salts as "natural stimuli" and the potential involvement of a Raf/MEK/ERK pathway mediating cholesterol-regulated expression of cyst-specific genes. These new findings may provide promising targets for diagnostics, drug design and prophylactic intervention against giardiasis.