During development of the vertebrate nervous system, neuronal precursors acquire distinct identities based on their position in the early neural tube. For motoneurons, a key component of this identity is the ability to recognize specific guidance cues in the periphery and to project to correct muscle target regions. The long-term objective of this application is to understand how the positional identity of motoneurons is encoded in the early neural tube and subsequently translated into a set of specific axon patterns.
The specific aims of this project center on the roles of Hox genes in the specification of motoneuron identity in limb innervating regions of the spinal cord. Hox genes encode transcription factors implicated in the early patterning of multiple structures including the central nervous system and its motoneuron populations. In humans, mutations in Hox genes are associated with limb and genital abnormalities. We have specifically chosen the avian lumbosacral (LS) spinal cord/hind limb as a model system because a substantial background exists on early motoneuron programming and crucial molecular and cellular steps in patterning the limb and spinal cord. Thus, this model provides an opportunity to precisely define the roles of Hox genes in the multistep process of motoneuron patterning. In preliminary studies, Hoxd10 has been ectopically expressed in thoracic segments via in ovo electroporation. Results indicate that the misexpression of this single gene can lead to a posteriorization of the molecular profile and axon trajectories of thoracic motoneurons. In this proposal, preliminary studies will be extended to more fully characterize motoneuron projections and temporal aspects of Hoxd10 function. In ovo electroporation will next be used to mis express Hoxd10 in mesoderm tissues normally encountered by motoneuron axons. Axon tracing will be used to define axon projection and to dissect central from peripheral effects of Hoxd10 expression. Similar approaches will be taken for Hoxa10, a combination of Hoxa10+ Hoxd10, and Hoxd11 to identify unique and cooperative functions of 5' Hox genes. In the above experiments, molecular markers of different types of motoneurons and target regions will be used to assess changes in regional identity following Hox misexpression and to search for potential downstream targets of Hox. Our studies will specifically search for links between Hox proteins and Eph/ephrin receptors and ligands, LIM-Homeodomain proteins, and Meis transcription factors. In addition to chick gain-of-function models, this last aim will take advantage of a loss-of-function model, a Hoxd10 null mouse. Project results will yield fundamental information on motoneuron development and provide insights into the origins of human patterning defects present at birth.

Agency
National Institute of Health (NIH)
Institute
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Type
Research Project (R01)
Project #
5R01HD025676-14
Application #
7417907
Study Section
Neurogenesis and Cell Fate Study Section (NCF)
Program Officer
Henken, Deborah B
Project Start
1989-07-01
Project End
2011-04-30
Budget Start
2008-05-01
Budget End
2011-04-30
Support Year
14
Fiscal Year
2008
Total Cost
$244,183
Indirect Cost
Name
University of Pittsburgh
Department
Biology
Type
Schools of Medicine
DUNS #
004514360
City
Pittsburgh
State
PA
Country
United States
Zip Code
15213
Misra, Mala; Sours, Emily; Lance-Jones, Cynthia (2012) Hox transcription factors influence motoneuron identity through the integrated actions of both homeodomain and non-homeodomain regions. Dev Dyn 241:718-31
Misra, Mala; Shah, Veeral; Carpenter, Ellen et al. (2009) Restricted patterns of Hoxd10 and Hoxd11 set segmental differences in motoneuron subtype complement in the lumbosacral spinal cord. Dev Biol 330:54-72
Shah, Veeral; Drill, Emily; Lance-Jones, Cynthia (2004) Ectopic expression of Hoxd10 in thoracic spinal segments induces motoneurons with a lumbosacral molecular profile and axon projections to the limb. Dev Dyn 231:43-56
Omelchenko, Natalia; Lance-Jones, Cynthia (2003) Programming neural Hoxd10: in vivo evidence that early node-associated signals predominate over paraxial mesoderm signals at posterior spinal levels. Dev Biol 261:99-115
Lance-Jones, C; Omelchenko, N; Bailis, A et al. (2001) Hoxd10 induction and regionalization in the developing lumbosacral spinal cord. Development 128:2255-68
Lin, J H; Saito, T; Anderson, D J et al. (1998) Functionally related motor neuron pool and muscle sensory afferent subtypes defined by coordinate ETS gene expression. Cell 95:393-407
Matise, M P; Lance-Jones, C (1996) A critical period for the specification of motor pools in the chick lumbosacral spinal cord. Development 122:659-69
Van Swearingen, J; Lance-Jones, C (1995) Slow and fast muscle fibers are preferentially derived from myoblasts migrating into the chick limb bud at different developmental times. Dev Biol 170:321-37
VanSwearingen, J M; Lance-Jones, C (1993) Spatial and temporal patterns of muscle formation in the limb of the avian embryo. Prog Clin Biol Res 383B:553-62
Lance-Jones, C; Dias, M (1991) The influence of presumptive limb connective tissue on motoneuron axon guidance. Dev Biol 143:93-110