European researchers locate spine growth control genes
Lissabon/Leicester/Oeiras/Strasbourg/Utrecht - A set of genes that is known to control many aspects of embryonic development is also involved in determining the number of vertebrae in the spine, according to the results of new EU-funded research published in the journal Developmental Cell (Vol. 17, Iss. 4, p. 516-526). In the study, scientists from France, the Netherlands, Portugal and the UK scrutinised the role of Hox genes in spinal development. EU support for the study came from the Cells Into Organs project (Cells Into Organs: functional genomics for development and disease of mesodermal organ systems'), which came to an end earlier this year and received 7.2 million euros in funding from the Sixth Framework Programme thematic area 'Life sciences, genomics and biotechnology for health'.
Hox genes, regulatory genes that play an important role throughout development, can be found throughout the animal kingdom, and are known to help ensure that the right kind of vertebrae grow in the right place. A family of regulatory genes, Cdx, is also known to be involved in the number of vertebrae. When the Cdx genes are disabled, some Hox genes are also rendered inactive, but to date this was assumed to be part of the Hox mechanism controlling vertebrate identity. Normally, switching off the Cdx genes halts the growth of the embryo at the tail end. However, this new research shows that the Hox genes are able to take over and restore growth, and ensure the production of the correct number of somites (and thus vertebrae).
“We now show that the activation of Hox genes is also part of how Cdx genes promote growth of the embryo at its tail end,” explained Moises Mallo from the Instituto Gulbenkian de Ciência in Portugal. “When the relevant Hox genes were activated in the Cdx mouse mutants [i.e. mice lacking the Cdx genes], the embryos recovered and were born with a quite normal vertebral column, proving that the Hox genes were able to compensate for the lack of Cdx. This is a novel role for Hox genes.”
“This paper provides an important addition to a long-standing view on the role of the Hox genes - one of the most-studied genes involved in embryonic development: that it controls not only identity, but also number of vertebrae,” added Dr Mallo. “Although these observations were made in the tail-end region of the embryo, it is very likely that similar mechanisms might be acting to determine the number of segments closer to the head.”