Conditional genetic labeling of the Renshaw cell population for functional studies of motor control
(English)Manuscript (preprint) (Other academic)
The Renshaw cells were among the first interneurons to be characterized in the mammalian spinal cord. Although the basic function of recurrent inhibition to motor neurons, as well as the Renshaw cell connectivity to other neurons have been thoroughly studied, the exact functional role of the Renshaw cells in motor control is still unknown. To further characterize the role of Renshaw cells in spinal cord circuitry, we searched for candidate genes useful in the Cre-loxP system. It has been reported that the mRNA expression of nicotinic cholinergic receptor alpha 2 (Chrna2) is found in a restricted number of cells at the ventral rim in adult rat and mouse spinal cord. In our own search for genes with distinct ventral expression, we noted a similar restricted Chrna2 mRNA expression pattern in the mouse spinal cord at postnatal day (P) 11 and during development at embryonic day 14.5. Based on the fact that the gene product is a cholinergic receptor and the pattern of expression, the neurons are predicted to be Renshaw cells. The possibility that these cells were motor neurons was excluded, since Chrna2 and Vesicular acetylcholine were not co-expressed at P11. To further study this cell population, we have generated a transgenic mouse expressing Cre recombinase (Cre) under the control of the Chrna2 promoter region. To visualize the Cre-expressing cells, the Chrna2-Cre transgenic mouse were bred with a reporter mouse expressing β-galactosidase (β-gal) in the nucleus after loxP excision. As expected, spinal cord β-gal immunoreactivity was observed in a limited number of ventrally located cells in the Cre-bearing offspring. Co-labeling of β-gal with calbindin-28K, a known marker for Renshaw cells, indicated that a majority of the calbindin positive cells were also β-gal positive at the ventral rim where calbindin is specific. In addition, β-gal positive cells without observable calbindin were also detected. It is conceivable that Chrna2 is expressed in additional cells apart from Renshaw cells or that a previously unidentified Renshaw cell subpopulation does not express calbindin. Nonetheless, a mouse with Cre-activity restricted to Chrna2-expressing cells opens the possibility to functionally study a limited population of spinal cord interneurons through genetic techniques, with the ambition to explore the specific role of Renshaw cells in spinal cord circuitry and motor control.
Renshaw cells, Spinal cord, Mouse, Nicotinic receptors, Cre recombinase
Cell and Molecular Biology Physiology Neurosciences
Research subject Developmental Neurosciences; Molecular Biology
IdentifiersURN: urn:nbn:se:uu:diva-109917OAI: oai:DiVA.org:uu-109917DiVA: diva2:274578