The development of tissues within a multi-cellular organism results from subdivision of homogeneous groups of cells into spatially patterned fields called compartments. In Drosophila, a series of 13 synchronous nuclear divisions produce a syncytial blastoderm with ~6000 totipotent nuclei at the cell cortex. Within an hour, the blastoderm cellularizes and begins gastrulation. Around this time, the embryo has established 28 compartments along the AP axis as demonstrated by the 14 stripes of engrailed (en) expression which determine the posterior compartment of each segment.

The homeobox (Hox) protein fushi tarzu (FTZ) is a pair-rule gene responsible for the development of alternate parasegments. The paradox of Hox proteins is their promiscuous DNA binding in vitro in comparison with their phenotypic specificity as they regulate cell fate and segmental identity throughout the animal kingdom. ftz is known to regulate alternate stripes of en, yet the question remains if ftz and the other pair-rule genes are simply responsible for drawing lines of engrailed to mark a border, or if they are painting segment-wide stripes and regulating additional segment realizator genes needed to establish each segment.

FTZ interacts with the orphan nuclear receptor FTZ-F1 to cooperatively bind DNA and synergistically regulate transcription. While ftz is zygotically expressed in seven stripes at the blastoderm stage, ftz-f1 is maternally deposited and ubiquitously expressed. The cuticle phenotypes of ftz and ftz-f1 null mutants are identical, demonstrating an in vivo requirement for their functional interaction in promoting the development of alternate parasegments. We have used Affymetrix micro-arrays on hand staged populations of embryos to address the Hox paradox and identify the segment realizator genes.

Only 25% of the cells used for RNA extraction were expected to vary between mutant and wild-type lines, however, hand staging of the embryos produced exceptionally high correlation coefficients between biological replicates. The regulation of target genes was as predicted for both developmental time-point and mutant condition. The high level of signal to noise achieved with this technique allows us to look for targets showing small but biologically significant changes in their expression levels. Those genes exhibiting expression patterns similar to en, the best known target, also show segmentally repeated expression patterns. We are validating the results by direct staining of mRNA expression patterns in wild-type, ftz and ftz-f1 mutant embryos. We are further identifying potential FTZ/FTZ-F1 binding sites near the transcriptional start sites of each validated target, and will design and test constructs for FTZ/FTZ-F1 responsive enhancer activity.

University of Maryland, College Park, MD

• Cell Biology and Molecular Genetics PhD Program 2003 to present
  University of Georgia, Athens, GA
  
• B.S., Biochemistry and Mathematics 2001 to 2003
  
• B.S., Computer Science 1990 to 1995
  

Anderson, W.R and Pick, L. (2007) Micro-array identification of FTZ-F1/FTZ targets in the early embryo. manuscript in preparation
 

Pick, L., Anderson, W.R., Shulz, J., and Woodard, C. (2006) The Ftz-F1 family: orphan nuclear receptors regulated by novel protein-protein interactions. in Nuclear receptors in development (Advances in Developmental Biology series). Reshma Taneja, editor. Elsevier.