title: Development of posterior hypothalamic neurons enlightens a switch in the prosencephalic basic plan.
abstract: In rats and mice, ascending and descending axons from neurons producing melanin-concentrating hormone (MCH) reach the cerebral cortex and spinal cord. However, these ascending and descending projections originate from distinct sub-populations expressing or not "Cocaine-and-Amphetamine-Regulated-Transcript" (CART) peptide. Using a BrdU approach, MCH cell bodies are among the very first generated in the hypothalamus, within a longitudinal cell cord made of earliest delaminating neuroblasts in the diencephalon and extending from the chiasmatic region to the ventral midbrain. This region also specifically expresses the regulatory genes Sonic hedgehog (Shh) and Nkx2.2. First MCH axons run through the tractus postopticus (tpoc) which gathers pioneer axons from the cell cord and courses parallel to the Shh/Nkx2.2 expression domain. Subsequently generated MCH neurons and ascending MCH axons differentiate while neurogenesis and mantle layer differentiation are generalized in the prosencephalon, including telencephalon. Ascending MCH axons follow dopaminergic axons of the mesotelencephalic tract, both being an initial component of the medial forebrain bundle (mfb). Netrin1 and Slit2 proteins that are involved in the establishment of the tpoc and mfb, respectively attract or repulse MCH axons.We conclude that first generated MCH neurons develop in a diencephalic segment of a longitudinal Shh/Nkx2.2 domain. This region can be seen as a prosencephalic segment of a medial neurogenic column extending from the chiasmatic region through the ventral neural tube. However, as the telencephalon expends, it exerts a trophic action and the mfb expands, inducing a switch in the longitudinal axial organization of the prosencephalon.
authors.affiliation: EA3922, Faculté de Médecine et de Pharmacie, Université de Franche-Comté, Besançon, France.
authors.forename: Sophie
authors.initials: S
authors.lastname: Croizier
authors.forename: Clotilde
authors.initials: C
authors.lastname: Amiot
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Chen
authors.forename: Françoise
authors.initials: F
authors.lastname: Presse
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Nahon
authors.forename: Jane Y
authors.initials: JY
authors.lastname: Wu
authors.forename: Dominique
authors.initials: D
authors.lastname: Fellmann
authors.forename: Pierre-Yves
authors.initials: PY
authors.lastname: Risold
mesh_terms: D000818:Animals; D001369:Axons / Q000378:metabolism; D001973:Bromodeoxyuridine / Q000378:metabolism; D002454:Cell Differentiation; D004622:Embryo, Mammalian / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D049452:Green Fluorescent Proteins / Q000378:metabolism; D053823:Hedgehog Proteins / Q000378:metabolism; D000090322:Homeobox Protein Nkx-2.2; D007028:Hypothalamic Hormones / Q000378:metabolism; D007031:Hypothalamus / Q000166:cytology* / Q000378:metabolism*; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D008543:Melanins / Q000378:metabolism; D008636:Mesencephalon / Q000166:cytology / Q000378:metabolism; D051379:Mice; D008954:Models, Biological; D009414:Nerve Growth Factors / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000378:metabolism; D000075388:Netrin-1; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D010641:Phenotype; D010907:Pituitary Hormones / Q000378:metabolism; D051381:Rats; D011971:Receptors, Immunologic / Q000378:metabolism; D013687:Telencephalon / Q000166:cytology / Q000378:metabolism; D013997:Time Factors; D025521:Tumor Suppressor Proteins / Q000378:metabolism; D000098552:Slit Homolog 2 Protein; D000097905:Roundabout Proteins
chemical_list: D001973:Bromodeoxyuridine; D049452:Green Fluorescent Proteins; D053823:Hedgehog Proteins; D000090322:Homeobox Protein Nkx-2.2; D007028:Hypothalamic Hormones; D036341:Intercellular Signaling Peptides and Proteins; D008543:Melanins; D009414:Nerve Growth Factors; D009419:Nerve Tissue Proteins; D000075388:Netrin-1; D010907:Pituitary Hormones; D011971:Receptors, Immunologic; D025521:Tumor Suppressor Proteins; D000098552:Slit Homolog 2 Protein; C000715627:Nkx2-2 protein, mouse; C000715628:Nkx2-2 protein, rat; C498888:Robo2 protein, mouse; D000097905:Roundabout Proteins; C465570:Shh protein, mouse; C019463:melanin-concentrating hormone