Somatic motoneurone specification in the hindbrain: the influence of somite-derived signals, retinoic acid and Hoxa3

• Published in: Development (Cambridge) Vol. 130; no. 13; pp. 2981 - 2996
• Main Authors: Guidato, Sonia, Prin, Fabrice, Guthrie, Sarah
• Format: Journal Article
• Language: English
• Published: England The Company of Biologists Limited 01.07.2003
• Subjects: Animals; Brain Tissue Transplantation; Cell Lineage; Chick Embryo; Chimera; Electroporation; Embryonic Induction; Gene Expression Regulation, Developmental; Homeodomain Proteins - genetics; Homeodomain Proteins - metabolism; Humans; In Situ Hybridization; LIM-Homeodomain Proteins; Mesoderm - physiology; Microspheres; Motor Neurons - cytology; Motor Neurons - physiology; Nerve Tissue Proteins - genetics; Nerve Tissue Proteins - metabolism; Quail - embryology; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - metabolism; Rhombencephalon - cytology; Rhombencephalon - embryology; Rhombencephalon - growth & development; Rhombencephalon - transplantation; Somites - physiology; Transcription Factors - genetics; Transcription Factors - metabolism; Tretinoin - metabolism; Zebrafish Proteins
• ISSN: 0950-1991; 1477-9129
• DOI: 10.1242/dev.00496

We have investigated the mechanisms involved in generating hindbrain motoneurone subtypes, focusing on somatic motoneurones, which are confined to the caudal hindbrain within rhombomeres 5-8. Following heterotopic transplantation of rhombomeres along the rostrocaudal axis at various developmental stages, we have found that the capacity of rhombomeres to generate somatic motoneurones is labile at the neural plate stage but becomes fixed just after neural tube closure, at stage 10-11. Grafting of somites or retinoic acid-loaded beads beneath the rostral hindbrain induced the formation of somatic motoneurones in rhombomere 4 only, and Hox genes normally expressed more caudally ( Hoxa3, Hoxd4 ) were induced in this region. Targeted overexpression of Hoxa3 in the rostral hindbrain led to the generation of ectopic somatic motoneurones in ventral rhombomeres 1-4, and was accompanied by the repression of the dorsoventral patterning gene Irx3. Taken together, these observations suggest that the somites, retinoic acid and Hox genes play a role in patterning somatic motoneurones in vivo.