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Research Spotlight: Nancy Fossett

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Laboratory of   Nancy Fossett 

Core Facilities used:  Microscopy Core  

The GATA factor Serpent cross-regulates lozenge and u-shaped expression during Drosophila blood cell development 

Selen Muratoglu, Barry Hough, Soe T. Mon and Nancy Fossett 

Center for Vascular and Inflammatory Diseases and the Department of Pathology, University of Maryland School of Medicine, Baltimore, MD 21201, USA 

Developmental Biology 

The Drosophila GATA factor Serpent interacts with the RUNX factor Lozenge to activate the crystal cell program, whereas SerpentNC binds the Friend of GATA protein U-shaped to limit crystal cell production. Here, we identified a lozenge minimal hematopoietic cis-regulatory module and showed that lozenge–lacZ reporter-gene expression was autoregulated by Serpent and Lozenge. We also showed that upregulation of u-shaped was delayed until after lozenge activation, consistent with our previous results that showed u-shaped expression in the crystal cell lineage is dependent on both Serpent and Lozenge. Together, these observations describe a feed forward regulatory motif, which controls the temporal expression of u-shaped. Finally, we showed that lozenge reporter-gene activity increased in a u-shaped mutant background and that forced expression of SerpentNC with U-shaped blocked lozenge- and u-shaped-lacZ reporter-gene activity. This is the first demonstration of GATA:FOG regulation of Runx and Fog gene expression. Moreover, these results identify components of a Serpent cross-regulatory sub-circuit that can modulate lozenge expression. Based on the sub-circuit design and the combinatorial control of crystal cell production, we present a model for the specification of a dynamic bi-potential regulatory state that contributes to the selection between a Lozenge-positive and Lozenge-negative state. 

Fossett Research Image

Fig. 4. lz–lacZ and Ush expression during crystal cell development.  

The lz ? 1236/? 737 CRM was used to assess lz expression and is depicted in green. Ush protein expression is depicted in red. Co-localized expression is depicted in yellow. The stage of embryogenesis is indicated at the top of each column. The enlarged area is marked by a white dotted box. Arrows mark the following: stage 9 cells expressing only lz–lacZ; stage 10 cells with co-localized expression of lz–lacZ and Ush; and stage 12 cells expressing only Ush. Abbreviations: lz–lacZ, lz ? 1236/? 747 lacZ; Ush, U-shaped; co, co-localization.