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The Drosophila wing primordium is subdivided into a dorsal (D) and a ventral (V) compartment by the activity of the LIM-homeodomain protein Apterous in D cells. Cell interactions between D and V cells induce the activation of Notch at the DV boundary. Notch is required for the maintenance of the compartment boundary and the growth of the wing primordium. Beadex, a gain-of-function allele of dLMO, results in increased levels of dLMO protein, which interferes with the activity of Apterous and results in defects in DV axis formation. We performed a gain-of-function enhancer-promoter (EP) screen to search for suppressors of Beadex when overexpressed in D cells. We identified 53 lines corresponding to 35 genes. Loci encoding for micro-RNAs and proteins involved in chromatin organization, transcriptional control, and vesicle trafficking were characterized in the context of dLMO activity and DV boundary formation. Our results indicate that a gain-of-function genetic screen in a sensitized background, as opposed to classical loss-of-function-based screenings, is a very efficient way to identify redundant genes involved in a developmental process. I N multicellular organisms, initially homogenous sheets of cells are often subdivided into adjacent cell populations by the activity of certain transcription factors (reviewed in Irvine and Rauskolb 2001). In many cases, cell interactions between these populations lead to the restricted expression of signaling molecules at their boundaries, which organize growth and/or the pattern of nearby cells. The stability of these boundaries frequently relies on the acquisition of differential cell affinities between adjacent populations. When these boundaries behave as lineage restriction boundaries, these populations are called compartments (García-Bellido et al. 1973). The Drosophila wing primordium, a monolayered epithelium that gives rise to the adult wing and part of the thorax, is subdivided into an anterior and a posterior compartment by the activity of the homeodomain transcription factors Engrailed and Invected in posterior cells (García-Bellido and Santamaria 1972;Lawrence and Morata 1976;Tabata et al. 1995;Zecca et al. 1995). During larval development, the wing primordium suffers a secondary compartment subdivision. The activity of the LIMhomeodomain transcription factor Apterous (Ap) is responsible for this later subdivision into a dorsal (D) and a ventral (V) compartment (Diaz-Benjumea and Cohen 1993).Ap has three functions in wing development. It is responsible for the establishment of the Notch-dependent signaling center, the generation of a lineage restriction at the DV boundary, and the acquisition of a dorsal identity during cell differentiation. Ap exerts these functions through three classes of target genes. The complementary expression of Serrate and Delta, two ligands of the receptor Notch, to D and V cells, respectively, initiates a cascade of short-range cell interactions that lead to the activation of Notch at the DV boundary ( Figure 1B The activity of ...

A rapid, selective and sensitive ultra-performance liquid chromatography method has been developed for the detection and quantification of tocopherols and retinol in human plasma. Alpha-tocopherol, gamma-tocopherol and retinol are assayed using fluorescence detection. Excitation/emission wavelengths are 295/330 nm and 325/470 nm for the analysis of both tocopherols and retinol, respectively. Retinol acetate is employed as the internal standard. The reversed-phase method incorporates gradient elution with a mobile phase consisting of methanol and acetonitrile. Separation of vitamin compounds is achieved using a bridged ethyl hybrid C18 column. The retention times for retinol, retinol acetate, gamma-tocopherol and alpha-tocopherol are 1.6, 1.8, 3.9 and 4.3 min, respectively. The limits of quantification for retinol, gamma-tocopherol and alpha-tocopherol were 0.02, 0.02 and 0.1 µg/mL, respectively. The assay method is suitable for the analysis of tocopherols and retinol in human plasma. The method may be applied following the ingestion of foods fortified with these fat-soluble vitamins.

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