Limits...
Abundant expression of guidance and synaptogenic molecules in the injured spinal cord.

Jacobi A, Schmalz A, Bareyre FM - PLoS ONE (2014)

Bottom Line: To assign the expression of these molecules to distinct populations of interneurons we labeled short and long propriospinal neurons by retrograde tracing and glycinergic neurons using a transgenically expressed fluorescent protein.Overall the expression pattern of guidance and synaptogenic molecules in the cervical spinal cord appeared to be stable over time and was not substantially altered following a midthoracic spinal cord injury.Taken together, our study indicates that many of the guidance and synaptogenic cues that regulate neuronal circuit formation in development are also present in the adult CNS and therefore likely contribute to the remodelling of axonal connections in the injured spinal cord.

View Article: PubMed Central - PubMed

Affiliation: Institute of Clinical Neuroimmunology, Ludwig-Maximilians University Munich, Munich, Germany.

ABSTRACT

Background: Spinal interneurons have emerged as crucial targets of supraspinal input during post-injury axonal remodelling. For example, lesioned corticospinal projections use propriospinal neurons as relay stations to form intraspinal detour circuits that circumvent the lesion site and contribute to functional recovery. While a number of the molecules that determine the formation of neuronal circuits in the developing nervous system have been identified, it is much less understood which of these cues are also expressed in the injured spinal cord and can thus guide growing collaterals and initiate synaptogenesis during circuit remodelling.

Methodology/principal findings: To address this question we characterized the expression profile of a number of guidance and synaptogenic molecules in the cervical spinal cord of healthy and spinal cord-injured mice by in situ hybridization. To assign the expression of these molecules to distinct populations of interneurons we labeled short and long propriospinal neurons by retrograde tracing and glycinergic neurons using a transgenically expressed fluorescent protein. Interestingly, we found that most of the molecules studied including members of slit-, semaphorin-, synCAM-, neuroligin- and ephrin- families as well as their receptors are also present in the adult CNS. While many of these molecules were abundantly expressed in all interneurons examined, some molecules including slits, semaphorin 7a, synCAM4 and neuroligin 1 showed preferential expression in propriospinal interneurons. Overall the expression pattern of guidance and synaptogenic molecules in the cervical spinal cord appeared to be stable over time and was not substantially altered following a midthoracic spinal cord injury.

Conclusions: Taken together, our study indicates that many of the guidance and synaptogenic cues that regulate neuronal circuit formation in development are also present in the adult CNS and therefore likely contribute to the remodelling of axonal connections in the injured spinal cord.

Show MeSH

Related in: MedlinePlus

In Situ hybridization pattern of Robo-1,-2,-3 in the cortex.In situ hybridization of Robo-1 (A), Robo-2 (D) and Robo-3 (G) mRNA in the cortex. No signals are detected with the sense probes (B: Robo-1; E: Robo-2; H: Robo-3). Dotted lines in A, D, and G represent layer V. (C,F, I) Epifluorescence images of double-labeled neurons of layer V (Retrogradely-labeled CST neurons: green; In situ signal: red).Scale bars in A,B,D,E,G,H: 100 µm; Scale bars in C,F,I: 50 µm (25 µm in insets).
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3921160&req=5

pone-0088449-g002: In Situ hybridization pattern of Robo-1,-2,-3 in the cortex.In situ hybridization of Robo-1 (A), Robo-2 (D) and Robo-3 (G) mRNA in the cortex. No signals are detected with the sense probes (B: Robo-1; E: Robo-2; H: Robo-3). Dotted lines in A, D, and G represent layer V. (C,F, I) Epifluorescence images of double-labeled neurons of layer V (Retrogradely-labeled CST neurons: green; In situ signal: red).Scale bars in A,B,D,E,G,H: 100 µm; Scale bars in C,F,I: 50 µm (25 µm in insets).

Mentions: To determine whether the corticospinal collaterals that enter the spinal gray matter can respond to slits expressed by spinal interneurons we examined the expression of the corresponding slit-receptors (robo-1, -2, -3) in the mouse cortex by in situ hybridization . In the cortex, robo-1 can be detected in layer I to VI, with its strongest expression in the cells of layer V (Table 3 and Fig. 2A). Robo-2 is expressed from layer II to VI in the cortex, with a slightly more intense labelling in layer V (Fig. 2D). Additionally, robo-3 mRNA is detectable in layer II, V and VI although the expression level is very low (Fig. 2G). Specificity of the staining was validated by hybridization of the tissue with the sense probe which showed no signals (Fig. 2 B,E,H). Retrograde labelling with Texas Red® revealed that 90,2±3,4% of CST projection neurons in layer V express robo-1, 55,2±5,2% of CST projection neurons express robo-2 and that 26,4±1,9% of CST projection neurons express robo-3 (Fig. 2 C,F,I).


Abundant expression of guidance and synaptogenic molecules in the injured spinal cord.

Jacobi A, Schmalz A, Bareyre FM - PLoS ONE (2014)

In Situ hybridization pattern of Robo-1,-2,-3 in the cortex.In situ hybridization of Robo-1 (A), Robo-2 (D) and Robo-3 (G) mRNA in the cortex. No signals are detected with the sense probes (B: Robo-1; E: Robo-2; H: Robo-3). Dotted lines in A, D, and G represent layer V. (C,F, I) Epifluorescence images of double-labeled neurons of layer V (Retrogradely-labeled CST neurons: green; In situ signal: red).Scale bars in A,B,D,E,G,H: 100 µm; Scale bars in C,F,I: 50 µm (25 µm in insets).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3921160&req=5

pone-0088449-g002: In Situ hybridization pattern of Robo-1,-2,-3 in the cortex.In situ hybridization of Robo-1 (A), Robo-2 (D) and Robo-3 (G) mRNA in the cortex. No signals are detected with the sense probes (B: Robo-1; E: Robo-2; H: Robo-3). Dotted lines in A, D, and G represent layer V. (C,F, I) Epifluorescence images of double-labeled neurons of layer V (Retrogradely-labeled CST neurons: green; In situ signal: red).Scale bars in A,B,D,E,G,H: 100 µm; Scale bars in C,F,I: 50 µm (25 µm in insets).
Mentions: To determine whether the corticospinal collaterals that enter the spinal gray matter can respond to slits expressed by spinal interneurons we examined the expression of the corresponding slit-receptors (robo-1, -2, -3) in the mouse cortex by in situ hybridization . In the cortex, robo-1 can be detected in layer I to VI, with its strongest expression in the cells of layer V (Table 3 and Fig. 2A). Robo-2 is expressed from layer II to VI in the cortex, with a slightly more intense labelling in layer V (Fig. 2D). Additionally, robo-3 mRNA is detectable in layer II, V and VI although the expression level is very low (Fig. 2G). Specificity of the staining was validated by hybridization of the tissue with the sense probe which showed no signals (Fig. 2 B,E,H). Retrograde labelling with Texas Red® revealed that 90,2±3,4% of CST projection neurons in layer V express robo-1, 55,2±5,2% of CST projection neurons express robo-2 and that 26,4±1,9% of CST projection neurons express robo-3 (Fig. 2 C,F,I).

Bottom Line: To assign the expression of these molecules to distinct populations of interneurons we labeled short and long propriospinal neurons by retrograde tracing and glycinergic neurons using a transgenically expressed fluorescent protein.Overall the expression pattern of guidance and synaptogenic molecules in the cervical spinal cord appeared to be stable over time and was not substantially altered following a midthoracic spinal cord injury.Taken together, our study indicates that many of the guidance and synaptogenic cues that regulate neuronal circuit formation in development are also present in the adult CNS and therefore likely contribute to the remodelling of axonal connections in the injured spinal cord.

View Article: PubMed Central - PubMed

Affiliation: Institute of Clinical Neuroimmunology, Ludwig-Maximilians University Munich, Munich, Germany.

ABSTRACT

Background: Spinal interneurons have emerged as crucial targets of supraspinal input during post-injury axonal remodelling. For example, lesioned corticospinal projections use propriospinal neurons as relay stations to form intraspinal detour circuits that circumvent the lesion site and contribute to functional recovery. While a number of the molecules that determine the formation of neuronal circuits in the developing nervous system have been identified, it is much less understood which of these cues are also expressed in the injured spinal cord and can thus guide growing collaterals and initiate synaptogenesis during circuit remodelling.

Methodology/principal findings: To address this question we characterized the expression profile of a number of guidance and synaptogenic molecules in the cervical spinal cord of healthy and spinal cord-injured mice by in situ hybridization. To assign the expression of these molecules to distinct populations of interneurons we labeled short and long propriospinal neurons by retrograde tracing and glycinergic neurons using a transgenically expressed fluorescent protein. Interestingly, we found that most of the molecules studied including members of slit-, semaphorin-, synCAM-, neuroligin- and ephrin- families as well as their receptors are also present in the adult CNS. While many of these molecules were abundantly expressed in all interneurons examined, some molecules including slits, semaphorin 7a, synCAM4 and neuroligin 1 showed preferential expression in propriospinal interneurons. Overall the expression pattern of guidance and synaptogenic molecules in the cervical spinal cord appeared to be stable over time and was not substantially altered following a midthoracic spinal cord injury.

Conclusions: Taken together, our study indicates that many of the guidance and synaptogenic cues that regulate neuronal circuit formation in development are also present in the adult CNS and therefore likely contribute to the remodelling of axonal connections in the injured spinal cord.

Show MeSH
Related in: MedlinePlus