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Paul Heid

Graduate Student, Biochemistry Program

B.S. in Biochemistry, University of Iowa, 1991

Address: Developmental Studies Hybridoma Bank; 41BB; University of Iowa, Iowa City, IA

Phone: 319/335-2883

Research Interests:

I am interested in understanding the mechanism by which cell movements occur in the developing embryo, how these movements are regulated, and what they accomplish. One means by which cells reorganize in developing embryos is through mediolateral intercalation, or convergent extension. Convergent extension involves the movement of groups of cells toward a common axis. The cells converge toward this axis, which results in extension of the tissue along the axis. Convergent extension is known to be important in many developmental events, including: notochord formation in vertebrates, gastrulation movements in frogs and sea urchins, and germ-band extension in Drosophila. However, little is known about how these movements are controlled at the molecular level.

The hypodermis (skin) of C. elegans provides an excellent system for studying a convergent extension-like process which is called dorsal intercalation. The hypodermis of C. elegans initially forms as a patch of six rows of cells on the dorsal surface of the embryo. The inner two rows (dorsal hypodermis) interdigitate, or intercalate, to form a single row of cells. These movements are very similar to what occurs in convergent extension in other systems. Advantages to studying these movements in C. elegans include: 1) Cell movements that occur during intercalation have been described, and can easily be followed at the level of single cells since the embryos are transparent and the process involves only 20 cells. 2) C. elegans is amenable to genetic and molecular analysis, which allows us to generate mutants that are defective in intercalation, and to clone and analyze genes required for this process. 3) A variety of GFP (Green Fluorescent Protein) and antibody markers for C. elegans hypodermis exist, allowing us to monitor the formation and organization of hypodermis.

I am studying a recessive lethal mutation called die-1 (dorsal intercalation and elongation defective). Dorsal hypodermal cells in homozygous mutants fail to intercalate. Other aspects of hypodermal development appear relatively normal, including formation and initial organization of hypodermis, and enclosure of the entire embryo with hypodermis. die-1 embryos do display other defects such as the failure to elongate into a worm shape, and disorganization of some of the muscle cells.

die-1 was mapped and cloned, and determined to encode a zinc-finger protein. Therefore, it is likely to act as a transcription factor. I have generated a die-1::GFP fusion gene which when transformed into die-1 embryos rescues them to viability. When expression was monitored with anti-GFP antibodies, nuclear staining was observed in embryos as young as 12-cells, through the completion of intercalation. Expression was no longer observed in embryos shortly after completion of intercalation. Staining was primarily confined to the posterior half of the embryo and staining was observed in the posterior dorsal epidermal cells while they were intercalating. Sequencing of the mutant allele indicates that the existing allele of die-1 is likely a null (complete loss of function) allele.

My current interests are to develop antibodies to DIE-1 to determine when and where the protein is present. I also plan to perform mosaic analysis of die-1 to determine which cells in the embryo can tolerate loss of die-1 activity and in which cells activity is necessary. Finally, I would like to begin to determine what some of the genes are that are regulated by DIE-1. This may allow us to identify genes that are directly involved in cell movements that occur during intercalation.

Publications:

Williams-Masson, E.M., Heid, P.J., Lavin, C.A. and Hardin, J. (1998) The Cellular mechanism of epithelial rearrangement during morpogenesis of the c.elegnas dorsl hypodermis. In press.

Heid, P.J. and Hardin, J. (1998) Cell Line Analysis: Videomicroscopy Techniques. Methods in Molecular Biology, in press.

Zhu, J., Hill, R.J., Heid, P.J., Fukuyama, M., Sugimoto, A., Priess, J.R. and Rothman, J.H. (1997). end-1 encodes an apparent GATA factor that specifies the endoderm precursor in Caenorhabditis elegans embryos. Genes and Development. 11, 2883-2896.

Ferguson, K.F., Heid, P.J. and Rothman, J.H. (1996). The SL1 trans-spliced leader RNA performs an essential embryonic function in Caenhorhabditis elegans that can also be supplied by SL2 RNA. Genes and Development. 10, 1543-1556.

Shalongo, W., Heid, P.J. and Stellwaqen, E. (1993). Kinetic analysis of the hydrodynamic transition accompanying protein folding using size exclusion chromatography. 1. Denaturant dependent baseline changes. Biopolymers. 33, 127-134.

Shalongo, W., Jagannadham, M.V., Heid, P.J. and Stellwagen, E. (1992). A kinetic study of the folding of staphylococcal nuclease using size-exclusion chromatography. Biochem. 31(46), 11390-11396.

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