| 1. |
- Bernhardt, Nadine Rabe, et al.
(författare)
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Genetic analysis of left-right coordination of locomotion
- 2013
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Ingår i: Frontiers in Bioscience. - : IMR Press. - 1093-9946 .- 1093-4715. ; 18, s. 20-35
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Tidskriftsartikel (refereegranskat)abstract
- While there is a rather large amount of data from pharmacological and anatomical studies of the murine locomotor CPG network, comprehensive information regarding the cellular and functional properties of the neuronal populations is lacking. Here, we describe concepts arising from genetic studies of the locomotor network with a focus on commissural interneurons regulating left-right coordination. In particular, this involves several families of axon guidance molecules relevant for midline crossing. We also describe recent advances within the field of neural circuit analysis, including imaging, genetic inactivation and optogenetic strategies, which are applicable to locomotor circuits. Such efforts, for example by using available genetic markers, should substantially increase our possibilities to decipher the functionality of spinal cord neuronal networks.
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| 2. |
- Lundell, Ingrid, et al.
(författare)
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Internalization studies of chimeric neuropeptide Y receptors Y1 and Y2 suggest complex interactions between cytoplasmic domains
- 2011
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Ingår i: Regulatory Peptides. - : Elsevier BV. - 0167-0115 .- 1873-1686. ; 168:1-3, s. 50-58
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Tidskriftsartikel (refereegranskat)abstract
- Agonist stimulation readily internalizes neuropeptide Y receptor Y1 while there are contradictory results for the Y2 receptor. In order to explore putative functional differences between the Y1 and Y2 receptors we generated reciprocal chimeras by swapping the third intracellular loop, the carboxy terminus or both between human Y1 and Y2. Internalization was studied in a quantitative radioligand binding assay with removal of surface-bound ligand in an acidic-wash procedure. The internalization assay revealed a lower degree of internalization as well as slower kinetics for the Y2 receptor. Generally, reciprocal exchange of receptor segments did not convey properties of the donor receptor but tended to enhance internalization. Surprisingly, insertion of the Y2 carboxy terminus into Y1 gave almost complete internalization (92%), rather than reduced internalization, while the insertion of both segments resulted in internalization equal to the native Y1 receptor. These findings were confirmed by fluorescence microscopy of immuno-stained receptors tagged with a C-terminal FLAG epitope. However, after exposure to high agonist concentrations (100 nM) Y2 was internalized. Studies of Y2 and the closely related Y7 receptor confirmed low internalization for Y2 from chicken and teleost fishes as well as Y7 from two teleosts. The conservation across species of low internalization at physiological concentrations suggests that this is an ancient feature and of vital importance for Y2 function. We propose that amino acid motifs in the third intracellular loop as well as the C terminus of both Y1 and Y2 are able to drive agonist-promoted internalization and that there may be constraining motifs in the Y2 receptor.
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| 3. |
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| 4. |
- Rabe Bernhardt, Nadine, 1978-, et al.
(författare)
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DCC mediated axon guidance of spinal interneurons is essential for normal locomotor central pattern generator function
- 2012
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Ingår i: Developmental Biology. - : Elsevier BV. - 0012-1606 .- 1095-564X. ; 366:2, s. 279-289
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Tidskriftsartikel (refereegranskat)abstract
- Coordinated limb rhythmic movements take place through organized signaling in local spinal cord neuronal networks. The establishment of these circuitries during development is dependent on the correct guidance of axons to their targets. It has previously been shown that the well-known axon guidance molecule netrin-1 is required for configuring the circuitry that provides left-right alternating coordination in fictive locomotion. The attraction of commissural axons to the midline in response to netrin-1 has been shown to involve the netrin-1 receptor DCC (deleted in Colorectal Cancer). However, the role of DCC for the establishment of CPG coordination has not yet been resolved. We show that mice carrying a null mutation of DCC displayed an uncoordinated left-right activity during fictive locomotion accompanied by a loss of interneuronal subpopulations originating from commissural progenitors. Thus, DCC plays a crucial role in the formation of spinal neuronal circuitry coordinating left-right activities. Together with the previously published results from netrin-1 deficient mice, the data presented in this study suggest a role for the most ventral originating V3 interneurons in synchronous activities over the midline. Further, it provides evidence that axon crossing in the spinal cord is more intricately controlled than in previously suggested models of DCC-netrin-1 interaction.
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| 5. |
- Rabe Bernhardt, Nadine, 1978-, et al.
(författare)
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Hop Mice Display Synchronous Hindlimb Locomotion and a Ventrally Fused Lumbar Spinal Cord Caused by a Point Mutation in Ttc26
- 2022
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Ingår i: eNeuro. - : Society for Neuroscience. - 2373-2822. ; 9:2
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Tidskriftsartikel (refereegranskat)abstract
- Identifying the spinal circuits controlling locomotion is critical for unravelling the mechanisms controlling the production of gaits. Development of the circuits governing left-right coordination relies on axon guidance molecules such as ephrins and netrins. To date, no other class of proteins have been shown to play a role during this process. Here, we have analyzed hop mice, which walk with a characteristic hopping gait using their hindlimbs in synchrony. Fictive locomotion experiments suggest that a local defect in the ventral spinal cord contributes to the aberrant locomotor phenotype. Hop mutant spinal cords had severe morphologic defects, including the absence of the ventral midline and a poorly defined border between white and gray matter. The hop mice represent the first model where, exclusively found in the lumbar domain, the left and right components of the central pattern generators (CPGs) are fused with a synchronous hindlimb gait as a functional consequence. These defects were associated with abnormal developmental processes, including a misplaced notochord and reduced induction of ventral progenitor domains. Whereas the underlying mutation in hop mice has been suggested to lie within the Ttc26 gene, other genes in close vicinity have been associated with gait defects. Mouse embryos carrying a CRISPR replicated point mutation within Ttc26 displayed an identical morphologic phenotype. Thus, our data suggest that the assembly of the lumbar CPG network is dependent on fully functional TTC26 protein.
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