Imaging heart development using high-resolution episcopic microscopy.
Bottom Line: Development of the heart in vertebrate embryos is a complex process in which the organ is continually remodelled as chambers are formed, valves sculpted and connections established to the developing vascular system.A recurrent challenge in this work is how to integrate studies as diverse as those of cardiac gene function and regulation with an appreciation of the localised interactions between cardiac tissues not to mention the manner in which both may be affected by cardiac function itself.Meeting this challenge requires an accurate way to analyse the changes in 3D morphology of the developing heart, which can be swift or protracted and both dramatic or subtle in consequence.
Affiliation: MRC National Institute for Medical Research, London, UK. email@example.comShow MeSH
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Mentions: 3D modelling of gene expression patterns has had an important impact on our understanding of heart morphogenesis by revealing the contributions of different cell lineages either directly (using CRE-mediated recombination to activate reporter genes) or indirectly (using endogenous gene expression patterns as a surrogate for lineage marking). As more marker genes for cardiac cells and tissues are identified, such studies will increasingly allow all aspects of cardiac development to be reassessed. Gene expression studies have almost exclusively relied on staining individual sections, since this has yielded the most sensitive results and allowed investigation of several gene patterns simultaneously. However, as with studies of morphology, reconstruction of the expression data into 3D models inevitably results in significant loss of resolution, in part from the limited frequency of sections but also from the constraints imposed by poor section registration. The finding that HREM can be adapted to detect localised patterns of gene expression revealed by colourimetric stains is therefore potentially important [25••]. Of course, the gains obtained from episcopic imaging may be offset by the loss of signal sensitivity resulting from wholemount rather than section staining procedures. This is undoubtedly the case for later stages of heart development in the mouse where penetration of staining reagents into dense cardiac tissue can be problematic. However, for stages of development up to E11.5–12.5, covering much of the period during which the heart is formed, reasonable staining appears possible and the resulting data can be combined with morphology to produce highly detailed 3D models (Figure 3a).
Affiliation: MRC National Institute for Medical Research, London, UK. firstname.lastname@example.org