How to make a tapeworm
The Natural History Museum, Dept. of Life Sciences, Div. of Parasites & Vectors
Wednesday 20 November 11:00
Sir Neil Chalmers seminar room, Darwin Centre LG16 (below Attenborough studio)
The evolution of parasitic flatworms represented a major departure from the free-living platyhelminth form, with each group evolving fundamentally different key adaptations toward increased fecundity (i.e. extreme r-selection). Such radical departures in morphology make homology assessment difficult if not impossible and hence we are working to elucidate the molecular signals that underpin their morphological evolution.
Using the beetle/rodent tapeworm Hymenolepis microstoma as a laboratory model of a strobilate (i.e. segmented) tapeworm, we now have not only a full catalog of its genes, but also transcriptome (i.e. expressed gene) samples from different regions of the body and ontogenetic stages. These genome-wide transcriptome profiles provide both qualitative and quantitative data on gene expression within a given sample, and through comparison we can thus identify which genes are up- or down-regulated throughout their complex life cycle. Among these we have selected the comparatively small number (~50) of 'developmental genes' (i.e. signalling and transcription factors) and have begun to survey their spatial expression patterns through whole-mount in situ hybridisation.
Results show both stereotyped and novel spatial patterns and allow us to associate the genes with organs, such as the ovaries, which prove to be an important source of developmental signals in tapeworms, just as they are in other animals including ourselves. These data provide a comprehensive picture of the factors governing tapeworm development and offer an effective means of identifying the 'hidden synapomophies' that underpin key innovations in form.
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