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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.

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Related in: MedlinePlus

In Situ hybridization pattern of Semaphorin 6a and Semaphorin 7a in the cervical spinal cord.In situ hybridization of Semaphorin 6a (A) mRNA in the unlesioned cervical spinal cord. Strong signal for Semaphorin 6a (A) is detected with the anti-sense probe. No signal is detected with the sense probe (B). (C) Confocal picture of double-labeled neurons in the ventral horn (NeuN: green; Semaphorin 6a: red). (D-F) Co-localization of Semaphorin 6a mRNA in glycinergic neurons (D; GlyT2: green, Semaphorin6a: red), LPSN (E; LPSN: green, Semaphorin 6a: red, NT435: blue), and SPSN (F; SPSN: green, Semaphorin 6a: red, NT435: blue) in the cervical spinal cord. In situ hybridization of Semaphorin 7a (G) mRNA in the unlesioned cervical spinal cord. Moderate signals for semaphorin 7a in inter- and motoneurons for Semaphorin 7a (G) is detected with the anti-sense probe. No signal is detected with the sense probes (H). (I) Confocal image of double-labeled neurons in the ventral horn (NeuN : green; Semaphorin 7a: red). (J-L) Co-localization of Semaphorin 7a mRNA in glycinergic neurons (D; GlyT2: green, Semaphorin 7a: red), LPSN (E; LPSN: green, Semaphorin 7a: red, NT435: blue), and SPSN (F, SPSN: green, Semaphorin 7a: red, NT435: blue) in the cervical spinal cord. (M, N) Quantification of the number of GlyT2, LPSN and SPSN expressing Semaphorin 6a (M) and semaphorin 7a (N) in unlesioned and lesioned cervical spinal cord. DH: dorsal horn; VH: ventral horn. Arrows in D and J show double-labeled glycinergic neurons. Scale bars in A, B, G, H: 250 µm; Scale bars in C, I: 25 µm; Scale bars in E, F, K, L: 25 µm; Scale bars in D, J: 50 µm.
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pone-0088449-g003: In Situ hybridization pattern of Semaphorin 6a and Semaphorin 7a in the cervical spinal cord.In situ hybridization of Semaphorin 6a (A) mRNA in the unlesioned cervical spinal cord. Strong signal for Semaphorin 6a (A) is detected with the anti-sense probe. No signal is detected with the sense probe (B). (C) Confocal picture of double-labeled neurons in the ventral horn (NeuN: green; Semaphorin 6a: red). (D-F) Co-localization of Semaphorin 6a mRNA in glycinergic neurons (D; GlyT2: green, Semaphorin6a: red), LPSN (E; LPSN: green, Semaphorin 6a: red, NT435: blue), and SPSN (F; SPSN: green, Semaphorin 6a: red, NT435: blue) in the cervical spinal cord. In situ hybridization of Semaphorin 7a (G) mRNA in the unlesioned cervical spinal cord. Moderate signals for semaphorin 7a in inter- and motoneurons for Semaphorin 7a (G) is detected with the anti-sense probe. No signal is detected with the sense probes (H). (I) Confocal image of double-labeled neurons in the ventral horn (NeuN : green; Semaphorin 7a: red). (J-L) Co-localization of Semaphorin 7a mRNA in glycinergic neurons (D; GlyT2: green, Semaphorin 7a: red), LPSN (E; LPSN: green, Semaphorin 7a: red, NT435: blue), and SPSN (F, SPSN: green, Semaphorin 7a: red, NT435: blue) in the cervical spinal cord. (M, N) Quantification of the number of GlyT2, LPSN and SPSN expressing Semaphorin 6a (M) and semaphorin 7a (N) in unlesioned and lesioned cervical spinal cord. DH: dorsal horn; VH: ventral horn. Arrows in D and J show double-labeled glycinergic neurons. Scale bars in A, B, G, H: 250 µm; Scale bars in C, I: 25 µm; Scale bars in E, F, K, L: 25 µm; Scale bars in D, J: 50 µm.

Mentions: The repulsive membrane associated Sema6a has been shown to control axon guidance in different parts of the nervous system [25]-[27] and specifically to affect the growth of the developing CST at multiple choice points [28]. We now investigated the expression pattern of Sema6a in the cervical spinal cord of healthy mice by in situ hybridization. While Sema6a mRNA is specifically present throughout the spinal gray matter (Fig. 3A,B) the hybridization signals are more intense in the middle and ventral laminae (IV – IX) of the spinal cord than in the dorsal horn (Fig. 3A and Table 2). Morphology analysis after counterstaining with NeuN suggests that in the gray matter Sema6a is primarily expressed by neurons and in particular by interneurons (Fig. 3C). Sema6a mRNA is also present in cells in the dorsal and ventral white matter (Table 2), consistent with the reported expression of Sema6a in oligodendrocytes, [25].


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 Semaphorin 6a and Semaphorin 7a in the cervical spinal cord.In situ hybridization of Semaphorin 6a (A) mRNA in the unlesioned cervical spinal cord. Strong signal for Semaphorin 6a (A) is detected with the anti-sense probe. No signal is detected with the sense probe (B). (C) Confocal picture of double-labeled neurons in the ventral horn (NeuN: green; Semaphorin 6a: red). (D-F) Co-localization of Semaphorin 6a mRNA in glycinergic neurons (D; GlyT2: green, Semaphorin6a: red), LPSN (E; LPSN: green, Semaphorin 6a: red, NT435: blue), and SPSN (F; SPSN: green, Semaphorin 6a: red, NT435: blue) in the cervical spinal cord. In situ hybridization of Semaphorin 7a (G) mRNA in the unlesioned cervical spinal cord. Moderate signals for semaphorin 7a in inter- and motoneurons for Semaphorin 7a (G) is detected with the anti-sense probe. No signal is detected with the sense probes (H). (I) Confocal image of double-labeled neurons in the ventral horn (NeuN : green; Semaphorin 7a: red). (J-L) Co-localization of Semaphorin 7a mRNA in glycinergic neurons (D; GlyT2: green, Semaphorin 7a: red), LPSN (E; LPSN: green, Semaphorin 7a: red, NT435: blue), and SPSN (F, SPSN: green, Semaphorin 7a: red, NT435: blue) in the cervical spinal cord. (M, N) Quantification of the number of GlyT2, LPSN and SPSN expressing Semaphorin 6a (M) and semaphorin 7a (N) in unlesioned and lesioned cervical spinal cord. DH: dorsal horn; VH: ventral horn. Arrows in D and J show double-labeled glycinergic neurons. Scale bars in A, B, G, H: 250 µm; Scale bars in C, I: 25 µm; Scale bars in E, F, K, L: 25 µm; Scale bars in D, J: 50 µm.
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Related In: Results  -  Collection

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

pone-0088449-g003: In Situ hybridization pattern of Semaphorin 6a and Semaphorin 7a in the cervical spinal cord.In situ hybridization of Semaphorin 6a (A) mRNA in the unlesioned cervical spinal cord. Strong signal for Semaphorin 6a (A) is detected with the anti-sense probe. No signal is detected with the sense probe (B). (C) Confocal picture of double-labeled neurons in the ventral horn (NeuN: green; Semaphorin 6a: red). (D-F) Co-localization of Semaphorin 6a mRNA in glycinergic neurons (D; GlyT2: green, Semaphorin6a: red), LPSN (E; LPSN: green, Semaphorin 6a: red, NT435: blue), and SPSN (F; SPSN: green, Semaphorin 6a: red, NT435: blue) in the cervical spinal cord. In situ hybridization of Semaphorin 7a (G) mRNA in the unlesioned cervical spinal cord. Moderate signals for semaphorin 7a in inter- and motoneurons for Semaphorin 7a (G) is detected with the anti-sense probe. No signal is detected with the sense probes (H). (I) Confocal image of double-labeled neurons in the ventral horn (NeuN : green; Semaphorin 7a: red). (J-L) Co-localization of Semaphorin 7a mRNA in glycinergic neurons (D; GlyT2: green, Semaphorin 7a: red), LPSN (E; LPSN: green, Semaphorin 7a: red, NT435: blue), and SPSN (F, SPSN: green, Semaphorin 7a: red, NT435: blue) in the cervical spinal cord. (M, N) Quantification of the number of GlyT2, LPSN and SPSN expressing Semaphorin 6a (M) and semaphorin 7a (N) in unlesioned and lesioned cervical spinal cord. DH: dorsal horn; VH: ventral horn. Arrows in D and J show double-labeled glycinergic neurons. Scale bars in A, B, G, H: 250 µm; Scale bars in C, I: 25 µm; Scale bars in E, F, K, L: 25 µm; Scale bars in D, J: 50 µm.
Mentions: The repulsive membrane associated Sema6a has been shown to control axon guidance in different parts of the nervous system [25]-[27] and specifically to affect the growth of the developing CST at multiple choice points [28]. We now investigated the expression pattern of Sema6a in the cervical spinal cord of healthy mice by in situ hybridization. While Sema6a mRNA is specifically present throughout the spinal gray matter (Fig. 3A,B) the hybridization signals are more intense in the middle and ventral laminae (IV – IX) of the spinal cord than in the dorsal horn (Fig. 3A and Table 2). Morphology analysis after counterstaining with NeuN suggests that in the gray matter Sema6a is primarily expressed by neurons and in particular by interneurons (Fig. 3C). Sema6a mRNA is also present in cells in the dorsal and ventral white matter (Table 2), consistent with the reported expression of Sema6a in oligodendrocytes, [25].

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