Structure–function analysis of the Drosophila retinal determination protein Dachshund

Abstract

Dachshund (Dac) is a highly conserved nuclear protein that is distantly related to the Ski/Sno family of corepressor proteins. In Drosophila, Dac is necessary and sufficient for eye development and, along with Eyeless (Ey), Sine oculis (So), and Eyes absent (Eya), forms the core of the retinal determination (RD) network. In vivo and in vitro experiments suggest that members of the RD network function together in one or more complexes to regulate the expression of downstream targets. For example, Dac and Eya synergize in vivo to induce ectopic eye formation and they physically interact through conserved domains. Dac contains two highly conserved domains, named DD1 and DD2, but no function has been assigned to either of them in an in vivo context. We performed structure-function studies to understand the relationship between the conserved domains of Dac and the rest of the protein and to determine the function of each domain during development. We show that only DD1 is essential for Dac function and while DD2 facilitates DD1, it is not absolutely essential in spite of more than 500 million years of conservation. Moreover, the physical interaction between Eya and DD2 is not required for the genetic synergy between the two proteins. Finally, we show that DD1 also plays a central role for nuclear localization of Dac.

Conserved role for the Dachshund protein with Drosophila Pax6 homolog Eyeless in insulin expression

“…Because Dac already is expressed in the IPC lineage at the embryonic stage (10, 11), we examined whether dac is required for the initial specification and neuronal differentiation of IPCs. dac 3 genetic-null homozygous mutants are lethal during the pupal stage, and these mutants exhibit severe defects in eye development (22,23). However, the cell number, neuronal morphology, and projection patterns in the dac-mutant larvae were indistinguishable from those in the control (Fig.…”

Evolution of sex comb from the primitive bristle pattern in drosophila is associated with modification in the developmental regulatory protein dachshund

“…Dachshund is a highly conserved nuclear protein shown to be important in eye, leg, and genital disc development (Keisman and Baker, 2001;Mardon et al, 1994;Martini et al, 2000;Shen and Mardon, 1997;Tavsanli et al, 2004). Studies on Montium like mutant of D. melanogaster described by Docquier (1997), and Docquier et al (1999) have shown that dachshund promotes sex comb formation by activating Scr expression.…”

“…Highly conserved DAC domain 1 (DD1 aa215-337 in D. melanogaster) and DAC domain 2 (DD2 aa 747-830 in D. melanogaster) (Davis et al 1999;Hammond et al, 1998). There are two nuclear localization domains NLS1 (aa353-359) and NLS2 (aa 803-819) identified in D. melanogaster (Tavsanli et al, 2004). Mutational and rescue construct analysis has shown that DD1 domain is critical for the function of DAC in leg and eye development where as DD2 facilitates but not absolutely essential (Tavsanli et al 2004).…”

“…There are two nuclear localization domains NLS1 (aa353-359) and NLS2 (aa 803-819) identified in D. melanogaster (Tavsanli et al, 2004). Mutational and rescue construct analysis has shown that DD1 domain is critical for the function of DAC in leg and eye development where as DD2 facilitates but not absolutely essential (Tavsanli et al 2004). The long sequence of aa 337-747 extending between DD1 and DD2 is designated as middle domain.…”

“…Some of the changes localize to the helices and sheets, which form usual interactive interfaces of the protein. DD2 and Middle domain were not found to be critical for DAC function as shown by Tavsanli et al (2004). But, they had considered the eye and leg phenotypes as markers for analysis.…”