An Appraisal of Nuclear Organisation in Interphase Embryonic Fibroblasts of Chicken, Turkey and Duck

Determining the nuclear 'addresses' of chromosome territories is a well-documented means of assaying for nuclear organisation in many cell types and species. Data in avian species are however limited at best, despite the pivotal role played by birds (particularly chickens) in agriculture, and as model organisms in developmental biology. That is, studies have hitherto focussed mostly on mammals (especially humans) and have demonstrated the importance of chromosome territory positioning in embryology, disease and evolution. Thus a detailed study of nuclear organisation in many species, many cell types and many developmental stages in birds is warranted, however, before this is achieved, 'baseline' needs to be established to determine precisely the relative locations of chromosome territories in at least 1 cell type of at least 1 bird. With this in mind we hybridised FISH probes from chicken chromosomes 1-28 to embryonic fibroblast nuclei, determining nuclear addresses using a newly developed plug-in to the image analysis package ImageJ. In our experience, evenly spaced representative BAC clones yielded more consistent results than hybridisation of chromosome paints. Results suggested that chromosome territory distribution best fitted a chromosome size-based (rather than gene density-based) pattern. Identical BAC clones were then hybridised to turkey and duck in a comparative genomic strategy. Observations were consistent with those seen in chicken (although, less well-defined in duck), providing preliminary evidence of conservation throughout evolution.