Molecular Recognition in Biological Systems and Bioinformatics

Protein structure and function; cell development; proteomics; gene regulation.

The major area in which Dr. Free has made a contribution is the Molecular Genetics of filamentous fungi. His recent work has focused on the process of cell fusion between specialized fungal cells called fusion pegs. He is also currently studying the process of fungal cell wall biogenesis. As part of his work on cell wall biogenesis, Dr. Free has identified and characterized several genes that function in the synthesis of the GPI anchor that attaches many cell wall proteins to the plasma membrane.

Much of his earlier work focused on the regulation of Neurospora asexual development. He cloned the Neurospora grg-1 (ccg-1) gene and characterized two cis-acting regulatory elements that are essential for its expression during early asexual development (conidiation). Dr. Free identified and characterized three genes from the MAP kinase pathway that function to regulate fungal development. These genes encode a MAPKK kinase (nrc-1), a serine/threonine protein kinase (nrc-2) and the regulatory subunit of calcineurin (cnb-1).

Dr. Free's laboratory also contributed to our understanding of organellar biogenesis. He demonstrated that the prepore vesicle, a specialized secretory vesicle that builds the Dictyostelium spore wall is derived from pre-existing lysosomes. As part of this work, Dr. Free isolated and characterized Dictyostelium mutants that were defective in post-translational modification of secreted enzymes.

Neurospora crassa, Dictyostelium discoidium, Candida albicans

MAP kinase pathway genes; Genes involved in the biosynthesis of the GPI anchor structure; Genes involved in the synthesis of the fungal cell wall

Fungal infections in immuno-suppressed patients

Molecular and classical genetics; Chemical digestion of cell walls, fluorescent microscopy; proteomics

Trifluoromethanesulphonic acid for the digestion of fungal cell walls

Aspergillosis and Candidiasis

Bowman, S.M., Piwowar, A., Al Dabbous, M., Vierula, J., and Free, S.J. (2006) Mutational analysis of the Glycosylphosphatidylinositol (GPI) anchor pathway demonstrates that GPI-anchored proteins are required for cell wall biogenesis and normal hyphal growth in Neurospora crassa. Euk. Cell 5:587-600.

Bowman, S.M., Piwowar, A., Ciocca, M. and Free, S.J. (2005) Mannosyltransferase is required for cell wall biosynthesis, morphology, and control of asexual development in Neurospora crassa. Mycol. 97:872-879.

Bowman, S.M. and Free, S.J. (2006) The structure and synthesis of the fungal cell wall. BioEssays 28:799-808.

Gupta, G.D., Free, S.J., Levina, N.N., Keranen, S., and Heath, I.B. (2003) Two divergent plasma membrane snytaxin-like SNAREs, nsyn1 and nsyn2, contribute to hyphal tip growth and other developmental processes in Neurospora crassa. Fungal Genet. Biol. 40:271-286.

Kothe, G.O. and Free, S.J. (1998) The isolation and characterization of nrc-1 and nrc-2, two genes encoding protein kinase homologs that control growth and development in Neurospora crassa. Genetics 149:117-130.