Cell transplantation

Why transplant cells ?
Cell transplantation is a powerful tool for studying cell fate determination during development. It allows the study of cells of known origin in various kinds of environments. Thus, cell transplantation can be used to address several types of questions. For example:

• Isotopic and isochronic transplantation of precursor cells (same position and stage in donor and host) has been used to study their normal fate (see also DiI labelling technique).
  
• Heterotopic transplantation of cells (different positions in donor and host) adresses their regional determination and their ability to communicate with the surrounding tissue.
  
• Heterochronic transplantation (different developmental stage of donor and host) allows testing for the reversibility of the determination of the transplanted cells or for the time period in which particular cell communication processes are active.
  
• Using heterogenetic transplantations (transplantation of mutant cells into wild-type hosts or vice versa) it is possible to test for the cell-autonomous versus non-autonomous requirements of a gene.
  
• Interspecific transplantations of cells (between different species) can be used to study the functional compatibility, i.e. evolutionary conservation of mechanisms that involve intercellular communication.
  
• Finally, transplantation of pole cells can be used for the generation of germ line clones (e.g. in order to test the role of the maternal contribution of a particular gene).

How to transplant cells
In order to identify the transplanted cells after the transplantation experiment, individual cells are usually transplanted from labelled donors into unlabelled hosts (postblastodermal stages). Labelling of donors can be achieved by the injection of cell lineage markers (like HRP or Fluorescent dyes) at the syncytial blastoderm stage. The tracer is incorporated into all cells during cellularization. Alternatively, or in addition, donors can be labelled by genetic markers. Upon cellularization (from stage 7 onwards) cells can be removed from particular positions of donors and singly transplanted into a particular position of the host. During further development of the host the entire cell lineage originating from the transplanted precursor is detectable by the marker (being exclusively transferred to the progeny of the transplanted cells) and the clonal phenotype can be analysed in permanent preparations. The method can also be used for the transplantation of genetically labelled nuclei (mosaic analysis).

Prerequisites for applying this approach

• Fate maps are required to identify the anlagen from/into which cells are transplanted. For example, a detailed fate map exists for the early gastrula stage. The wildtype lineages of the various types of progenitor cells must be known in order to be able to detect and interpret phenotypic changes resulting from the respective experimental manipulation (exposure to a different spatial, temporal or genetic environment). Detailed descriptions of the wildtype lineages exist for precursors from all germ layers, and in particular for the entire set of neuroblasts forming the ventral nerve cord (Interactive Neuroblasts).
• Equipment: Inverted microscope (equipped with Nomarski optics and epifluorescence); micromanipulator; electrode puller; capillary tip grinder
  
  
  

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