A Cre transgenic line for studying V2 neuronal lineages and functions in the spinal cord.

During spinal neurogenesis, the p2 progenitor domain generates at least two subclasses of interneurons named V2a and V2b, which are components of the locomotor central pattern generator. The winged-helix/forkhead transcription factor Foxn4 is expressed in a subset of p2 progenitors and required for specifying V2b interneurons. Here, we report the generation of a Foxn4-Cre BAC transgenic mouse line that drives Cre recombinase expression mimicking endogenous Foxn4 expression pattern in the developing spinal cord. We used this transgenic line to map neuronal lineages derived from Foxn4-expressing progenitors and found that they gave rise to all neurons of the V2a, V2b, and the newly identified V2c lineages. These data suggest that Foxn4 may be transiently expressed by all p2 progenitors and that the Foxn4-Cre line may serve as a useful genetic tool not only for lineage analysis but also for functional studies of genes and neurons involved in locomotion.