Arcadis (Switzerland)

Abstract The establishment of tissue axes is fundamental during embryonic development. In the Drosophila wing, the anterior/posterior (AP) and the dorsal/ventral (DV) compartment boundaries provide the basic coordinates around which the tissue develops. These boundaries arise as a result of two lineage decisions, the acquisition of posterior fate by the selector gene engrailed ( en) and dorsal fate by the selector gene apterous ( ap ). While the en expression domain is set up during embryogenesis, ap expression begins only during early wing development. Thus, the correct establishment of the ap expression pattern relative to en must be tightly controlled. Here, we functionally investigate the transcriptional inputs integrated by the early ap enhancer (apE) and their requirement for correct boundary formation. Detailed mutational analyses using CRISPR/Cas revealed a role for apE in positioning the DV boundary relative to the AP boundary, with apE mutants often displaying mirror-image anterior wing duplications. We then designed and applied methods to accomplish tissue-specific enhancer disruption via dCas9 expression. This approach allowed us to dissect the spatiotemporal requirement for apE function, clarifying the mechanism by which apE misregulation leads to AP defects. Base-pair-resolution analyses of apE uncovered a single HOX binding site essential for wing development that, when mutated, led to wingless flies. We demonstrated that the transcription factors Pointed (Pnt), Homothorax (Hth), and Grain (Grn) are required for apE function, and the HOX gene Antennapedia (Antp) contributes to early wing development. Together, our results provide a comprehensive molecular basis of early ap activation and the developmental consequences of its misregulation, shedding light on how compartmental boundaries are set up during development.

International audience

In-vitro diagnostic assays involve various substances that may be released into the environment via a sewage treatment plant if the effluent from diagnostic instruments is discharged into the drains. Because the release of liquid waste into the public sewer system is regulated at national and/or local levels, a risk assessment per site should be performed to determine whether the release of the effluent from in-vitro diagnostic equipment is compliant with applicable regulations.To facilitate the assessment, we developed a screening tool to generate exposure scenarios for chemical substances used in in-vitro diagnostic assays. This screening tool helps in determining a) whether release of the effluent into the sewer system would be allowed from a regulatory point of view and b) whether such release would result in potential risks to surface water.The screening tool is based on conditions encountered at typical usage sites in Switzerland and Germany, with the option to adapt them to other local settings. In addition, measured analytical results of liquid waste together with typical operational parameters of diagnostic equipment were defined as default input parameters. The resulting concentrations in liquid waste and predicted environmental concentrations (PEC) are compared with regulatory limit values for release into the sewer system and predicted no-effect concentrations (PNEC) for surface water for risk estimation.The functioning of the presented screening tool is demonstrated by two assessments performed for fictitious but typical hospitals in Switzerland and Germany. It identified substances that cause potential concern for which a more advanced assessment is required.