Studying the clonal relationships among the cells in an organ or organism is the ‘holy grail’ of developmental biology. The degree of clonal dispersion of cerebral cortical neurons has been a highly debated topic in neuroscience over the last five decades. There are several methods available to label the entire progeny of a given stem or progenitor cell, but all of them have some drawbacks and could suffer from either underestimating or overestimating the actual size of the clones. To minimize such inaccuracies, most existing methods should be used with very few clones in a given specimen, impeding the investigations on generation, integration and relationship of multiple clones.
The groups of García-Moreno, Begbie and Molnár (all from DPAG) have recently published a paper in the journal Development reporting CLoNe, a new method for clonal cell labelling in vivo. This method is based on the combined labelling (electroporation) of progenitor cells with three types of plasmids encoding (a) multiple fluorescent reporters, (b) a Cre driver and (c) a transposase. The method is developed so it allows the reliable tracing to specific progenitor populations, and the approach was tested in the mouse and chick embryonic telencephalon and in the chick limb bud. It is shown to permit long-term tracing through somatic integration of the reporter plasmids into the host cell genome, and to generate an unbiased colour distribution to maximize clone assignment.
CLoNe was developed specifically for comparative analysis of forebrain progenitor cells across mammals and birds, but it is suitable for various tissues, as evidenced in muscular and epithelial tissue, and systems across several vertebrate species.