Division of Molecular and Developmental Biology・Kawakami Group

The spatio-temporal regulation of muscle contractions that generate body movements critically depends on the exquisitely precise innervation of each muscle type by the appropriate motoneuron subtype. Therefore, delineating the identities of motoneurons and their connectivity to target muscles is fundamental to an understanding of the motor control by the central nervous system. In this study, by taking advantage of the optical and genetic accessibility, we dissected the spinal cord motor column of zebrafish larvae at the cellular level. By using the BAC for the Mnx homeodomain gene mnr2b, we established the mnGFF7 transgenic line expressing the Gal4FF transcription factor in a large part of the motor column. Single cell labelling of Gal4FF-expressing cells in the mnGFF7 larvae enabled a detailed investigation of the morphological characteristics of individual spinal motoneurons, as well as the overall organisation of the motor column in a spinal segment. The transgenic fish established here should facilitate an understanding of the cellular and molecular architecture of the spinal cord motor column and its connection to muscles in vertebrates.

Lateral view of a zebrafish larva (top). Eleven different types of spinal motoneurons identified in the single cell labeling experiment.