The bHLH Factor Olig3 Coordinates the Specification of Dorsal Neurons in the Spinal Cord

Neurons found in the dorsal horn of the spinal cord play a key role in transmitting somatosensory information. It is known that during early embryonic development, two classes of neurons arise, class A and class B, respectively. While class A neurons are primarily responsible for transmitting information about the position of the body and limbs, class B neurons relay data about touch, temperature, and pain as perceived via the skin.

However, while the functional differences between class A and class B neurons have been well described, little was known about the fate-determining factors involved which give rise to these two distinct cell types. Now, Thomas Müller (laboratory of Carmen Birchmeier) and Katrin Anlag (laboratory of Mathias Treier) and colleagues report that the bHLH factor gene, Olig3, is essential for the proper specification of class A neurons in the dorsal spinal cord. Furthermore, Olig3 suppresses the specification of class B neurons. (Genes & Development 2005 19: 733-743).

Olig3 is expressed in progenitor cells that generate class A (dI1-dI3) neurons. The scientists generated Olig3 mutant mice and showed that all three subtypes of class A neurons do not develop correctly in the mutants: dI1 numbers were significantly reduced and both dI2 and dI3 neurons incorrectly assumed class B neuron identity. Conversely, the ectopic expression of Olig3 in the chick spinal cord repressed the emergence of class B neurons. The authors conclude that Olig3 expression distinguishes the two major classes of progenitors in the dorsal spinal cord and determines the distinct specification program of class A neurons. 

Contact:

Pamela Cohen
p.cohen@mdc-berlin.de
+49 30 9406 2121