Neuronal induction and migration are fundamental processes in nervous system development, and many human neurological disorders are caused by severe deficiencies in these processes. Our focus is the cranial motor neurons (CMNs), which control vital functions such as chewing, swallowing, and speech in humans. Our long-term goal is to elucidate the cellular and molecular mechanisms underlying the induction and migration of CMNs in the powerful model vertebrate, the zebrafish embryo. Secreted proteins of the sonic hedgehog (Shh) family are essential for vertebrate motor neuron induction. However, little is known about the mechanisms by which Shh signaling pathway components, including the Gli1 and Gli2 transcription factors, specify different types of motor neurons (CMNs and spinal motor neurons (SMNs)) along the anterior-posterior axis of the neural tube. The cellular mechanisms underlying tangential migration of CMNs following induction are equally obscure. Our preliminary studies demonstrate that the zebrafish detour (dtr/gli 1) and you-too (yot/gli2) genes have specific functions in CMN and SMN induction, and that mutations in the trilobite (tri) and valentino (val) genes disrupt particular events during tangential CMN migration. The studies we propose here will define the mechanisms of CMN specification and tangential migration. (1) We will determine whether Gli1 and Gli2 are necessary and sufficient for CMN and SMN induction (a) by characterizing motor neuron development in yot mutants, (b) by determining whether gli1 and gli2 are co-expressed in motor neurons, and (c) by analyzing CMN and SMN induction in dtr; yot double mutants, and following gli1 and gli2 overexpression in wildtype and dtr mutant embryos. (2) We will evaluate the function of Shh pathway components encoded by the chameleon (con) and iguana (igu) genes in CMN and SMN induction. (3) We will determine whether the CMN migration defects of tri and val mutants are caused by specific defects in dynamic cellular behaviors (a) by genetic mosaic analysis of tri mutants, and (b) by analyzing dynamic cellular behaviors of migrating CMNs in wildtype, and tri and val mutant embryos by time-lapse microscopy. The availability of key zebrafish mutants, the ability to employ gain- and loss-of-function approaches, the optical clarity of the zebrafish embryo, and the ability to perform genetic mosaic analysis and time-lapse microscopy represent a powerful combination of tools that will enable us to define the functions of particular genes in CMN development at the cellular and molecular levels. Our studies on motor neuron induction and migration will provide fundamental insights into the mechanisms underlying these processes essential for normal brain development and function.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS040449-03
Application #
6639684
Study Section
Special Emphasis Panel (ZRG1-MDCN-6 (01))
Program Officer
Leblanc, Gabrielle G
Project Start
2001-06-01
Project End
2005-05-31
Budget Start
2003-06-01
Budget End
2004-05-31
Support Year
3
Fiscal Year
2003
Total Cost
$215,609
Indirect Cost
Name
University of Missouri-Columbia
Department
Biology
Type
Schools of Arts and Sciences
DUNS #
153890272
City
Columbia
State
MO
Country
United States
Zip Code
65211
Gurung, Suman; Asante, Emilia; Hummel, Devynn et al. (2018) Distinct roles for the cell adhesion molecule Contactin2 in the development and function of neural circuits in zebrafish. Mech Dev 152:1-12
Allen, James R; Bhattacharyya, Kiran D; Asante, Emilia et al. (2017) Role of branchiomotor neurons in controlling food intake of zebrafish larvae. J Neurogenet 31:128-137
Glasco, Derrick M; Pike, Whitney; Qu, Yibo et al. (2016) The atypical cadherin Celsr1 functions non-cell autonomously to block rostral migration of facial branchiomotor neurons in mice. Dev Biol 417:40-9
Pan, Xiufang; Sittaramane, Vinoth; Gurung, Suman et al. (2014) Structural and temporal requirements of Wnt/PCP protein Vangl2 function for convergence and extension movements and facial branchiomotor neuron migration in zebrafish. Mech Dev 131:1-14
Sittaramane, Vinoth; Pan, Xiufang; Glasco, Derrick M et al. (2013) The PCP protein Vangl2 regulates migration of hindbrain motor neurons by acting in floor plate cells, and independently of cilia function. Dev Biol 382:400-12
Thoby-Brisson, Muriel; Bouvier, Julien; Glasco, Derrick M et al. (2012) Brainstem respiratory oscillators develop independently of neuronal migration defects in the Wnt/PCP mouse mutant looptail. PLoS One 7:e31140
Glasco, Derrick M; Sittaramane, Vinoth; Bryant, Whitney et al. (2012) The mouse Wnt/PCP protein Vangl2 is necessary for migration of facial branchiomotor neurons, and functions independently of Dishevelled. Dev Biol 369:211-22
Burroughs-Garcia, Jessica; Sittaramane, Vinoth; Chandrasekhar, Anand et al. (2011) Evolutionarily conserved function of Gbx2 in anterior hindbrain development. Dev Dyn 240:828-38
Qu, Yibo; Glasco, Derrick M; Zhou, Libing et al. (2010) Atypical cadherins Celsr1-3 differentially regulate migration of facial branchiomotor neurons in mice. J Neurosci 30:9392-401
Bouvrette, Denise J; Sittaramane, Vinoth; Heidel, Jerry R et al. (2010) Knockdown of bicaudal C in zebrafish (Danio rerio) causes cystic kidneys: a nonmammalian model of polycystic kidney disease. Comp Med 60:96-106

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