To understand the role that the ParaHox genes may have played in animal evolution, and whether they have been as vital as the famous Hox genes, their organisation and expression must be understood in a much greater variety of taxa than have currently been investigated.
In particular flies and nematodes are of limited value in this endeavour since they have broken up the ParaHox cluster and lost some of the genes. Alternative protostome models are required, such as the polychaetes, which have retained all three ParaHox genes.
- Hui, J.H.L., Raible, F., Korchagina, N., Dray, N., Samain, S., Magdelenat, G., Jubin, C., Segurens, B., Balavoine, G., Arendt, D., and Ferrier, D.E.K. Features of the ancestral bilaterian inferred from Platynereis dumerilii ParaHox genes. BMC Biology (2009) 7:43.