Microarray analysis of Foxa2 mutant mouse embryos reveals novel gene expression and inductive roles for the gastrula organizer and its derivatives

<p>Abstract</p> <p>Background</p> <p>The Spemann/Mangold organizer is a transient tissue critical for patterning the gastrula stage vertebrate embryo and formation of the three germ layers. Despite its important role during development, there are still relatively few genes with specific expression in the organizer and its derivatives. Foxa2 is a forkhead transcription factor that is absolutely required for formation of the mammalian equivalent of the organizer, the node, the axial mesoderm and the definitive endoderm (DE). However, the targets of Foxa2 during embryogenesis, and the molecular impact of organizer loss on the gastrula embryo, have not been well defined.</p> <p>Results</p> <p>To identify genes specific to the Spemann/Mangold organizer, we performed a microarray-based screen that compared wild-type and <it>Foxa2 </it>mutant embryos at late gastrulation stage (E7.5). We could detect genes that were consistently down-regulated in replicate pools of mutant embryos versus wild-type, and these included a number of known node and DE markers. We selected 314 genes without previously published data at E7.5 and screened for expression by whole mount <it>in situ </it>hybridization. We identified 10 novel expression patterns in the node and 5 in the definitive endoderm. We also found significant reduction of markers expressed in secondary tissues that require interaction with the organizer and its derivatives, such as cardiac mesoderm, vasculature, primitive streak, and anterior neuroectoderm.</p> <p>Conclusion</p> <p>The genes identified in this screen represent novel Spemann/Mangold organizer genes as well as potential Foxa2 targets. Further investigation will be needed to define these genes as novel developmental regulatory factors involved in organizer formation and function. We have placed these genes in a Foxa2-dependent genetic regulatory network and we hypothesize how Foxa2 may regulate a molecular program of Spemann/Mangold organizer development. We have also shown how early loss of the organizer and its inductive properties in an otherwise normal embryo, impacts on the molecular profile of surrounding tissues.</p

Structural and electronic information drawn from the circularly polarized luminescence spectra: Many questions and some answers for simple organic molecules, polymers, and molecular aggregates

In the last ten years, circularly polarized luminescence (CPL) has greatly advanced: Lots of data have been collected and many compounds have been synthesized with the aim of enhancing this chiroptical response. We review here a few aspects with illustrative examples. After examination of the relation of circular dichroism (CD) and CPL signals, we investigate how CPL can be used to probe environment: Aggregation phenomena or the presence of metal ions or pH variations. We also study the CPL of inherently dissymmetric chromophores and of metal complexes. We finally touch upon whether CPL originates from molecules or from aggregated inhomogeneous systems

The Netherlands : from diversity celebration to a colorblind approach

This chapter offers a systematic review of sociological research in the Netherlands on the relationship between race/ethnicity and educational inequality between 1980 and 2017. Six major research traditions are identified: (1) political arithmetic; (2) racism and ethnic discrimination; (3) school characteristics; (4) school choice; (5) family background and (6) an institutional approach, with research on ‘family background’ and ‘political arithmetic’ being the most dominant research traditions. Most of the research conducted in the Netherlands focuses on explaining ‘underachievement’ in relationship to ‘Turkish’, ‘Moroccan’ and ‘Surinamese’ minority students and is characterized by the use of quantitative research methods and a more positivistic approach to social sciences. This rich body of research is written mainly in Dutch and developed in a context characterized by a close collaborative relationship between educational sociologists and the government in conducting research in this area and a shift in policy that emphasises assimilation over multiculturalism