New research reveals how the pattern of different cells in the
spinal cord are produced in time and space.
Dr James Briscoe of the Medical Research Council's National
Institute for Medical Research (now part of the Francis Crick
Institute) explained: "The spinal cord contains many
different types of cells. For nerve circuits to form correctly,
these have to be produced at the right time and place during embryo
development.
"The production of the different cell types is controlled by
only a few signals. We found that the signals function in different
combinations to control the type of cells produced.
"These combinations change during embryo development and,
interestingly, it is the growth of the embryo that gradually
changes the location of signal production. This alters the location
at which signals intersect, resulting in the successive production
of different cell types at different positions in the embryo."
For their work, the scientists combined well-established
developmental biology methods, such as controlling the activity of
specific genes in chick embryos and growing tiny segments of
embryonic spinal cord tissue, with new genomic technologies that
allowed them to measure gene activity in tissues grown in specific
conditions.
This also enabled them to identify some of the genes that
function within cells downstream of the signals to make the
different cell types.
"How the large diversity of cell types that make an individual
are produced and organised in embryos is a fundamental question in
developmental biology. The spinal cord is often seen as a useful
example where general principles of tissue formation can be worked
out. The current work adds to our understanding of the strategies
employed to increase the variety of cell types while maintaining
control over the position where they form," added Dr Briscoe.
His team's findings are also likely to be relevant in other
developing tissues, and could evetually help in the design of
methods to produce specific cell types from stem cells.
The paper, Integration of Signals along Orthogonal Axes of the Vertebrate
Neural Tube Controls Progenitor Competence and Increases Cell
Diversity, is published in the PLOS
Biology.