A possible interpretation of some colony forming assays: 'developmental tree' model

The characteristic form of the probability distributions of in vitro grown colonies is analysed and experimental results are shown to be well approximated by an exponential dependence. It is argued that this type of dependence is very frequent in nature and does not provide sufficient evidence to resolve the dilemma whether the development of haemopoietic lineages proceeds according to a schema of 'progressive and stochastic restriction' or more limiting 'developmental tree' with some random control process involved. Detailed analysis of the experimental conditions and results is needed to provide insight into collective phenomena in cellular proliferation and differentiation. At present, the complexity of the phenomena involved prevents unique interpretation of the experimental distributions. Nevertheless, one particular quantitative model, based on a developmental tree concept, yields a set of the theoretical probability distributions, which are in a very good agreement with the experimental results.