Formation of supernumerary muscle spindles at the expense of golgi tendon organs in ER81‐deficient mice

Kučera, Jan; Cooney, William P.; Que, A.; Szeder, Viktor; Stancz-Szeder, H.; Walro, Jon M.

doi:10.1002/dvdy.10066

Cited by 22 publications

(23 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Our reported average of 11.3 ± 0.4 MS occupies the middle of the range of numbers from 10 to 12 MS reported elsewhere [17,33–38]. GTO numbers in mouse soleus have been less frequently quantified, but again numbers reported here (5.2 ± 0.2) agree with published reports [36,39]. Thus, the whole-mount muscle preparation used in these experiments allowed not only for rapid quantification of proprioceptive receptors and larger sample sizes, but also yielded equally accurate measures compared with more labor-intensive techniques.…”

Section: Discussionsupporting

confidence: 90%

Analysis of Proprioceptive Sensory Innervation of the Mouse Soleus: A Whole-Mount Muscle Approach

2017

View full text Add to dashboard Cite

Muscle proprioceptive afferents provide feedback critical for successful execution of motor tasks via specialized mechanoreceptors housed within skeletal muscles: muscle spindles, supplied by group Ia and group II afferents, and Golgi tendon organs, supplied by group Ib afferents. The morphology of these proprioceptors and their associated afferents has been studied extensively in the cat soleus, and to a lesser degree, in the rat; however, quantitative analyses of proprioceptive innervation in the mouse soleus are comparatively limited. The present study employed genetically-encoded fluorescent reporting systems to label and analyze muscle spindles, Golgi tendon organs, and the proprioceptive sensory neuron subpopulations supplying them within the intact mouse soleus muscle using high magnification confocal microscopy. Total proprioceptive receptors numbered 11.3 ± 0.4 and 5.2 ± 0.2 for muscle spindles and Golgi tendon organs, respectively, and these receptor counts varied independently (n = 27 muscles). Analogous to findings in the rat, muscle spindles analyzed were most frequently supplied by two proprioceptive afferents, and in the majority of instances, both were classified as primary endings using established morphological criteria. Secondary endings were most frequently observed when spindle associated afferents totaled three or more. The mean diameter of primary and secondary afferent axons differed significantly, but the distributions overlap more than previously observed in cat and rat studies.

show abstract

Section: Discussionsupporting

confidence: 90%

Analysis of Proprioceptive Sensory Innervation of the Mouse Soleus: A Whole-Mount Muscle Approach

2017

View full text Add to dashboard Cite

show abstract

“…This marked variability in Ia input to different MNs is unlikely to occur simply by chance. Each muscle nerve we used contains at least 30 -50 Ia axons (Kucera et al, 2002), which would tend to equalize synaptic input to each homonymous MN even if each Ia axon were making connections of random strength. Individual MNs within a single motor pool apparently have different receptivities to being innervated by their homonymous Ia axons.…”

Section: Discussionmentioning

confidence: 99%

Prenatal Exposure to Elevated NT3 Disrupts Synaptic Selectivity in the Spinal Cord

Wang¹,

Li²,

Taylor³

et al. 2007

J. Neurosci.

View full text Add to dashboard Cite

Monosynaptic connections between muscle spindle (Ia) afferents and motoneurons (MNs), the central portion of the stretch reflex circuit, are highly specific, but the mechanisms underlying this specificity are primarily unknown. In this study, we report that embryonic overexpression of neurotrophin-3 (NT3) in muscles disrupts the development of these specific Ia-MN connections, using transgenic (mlc/NT3) mice that express elevated levels of NT3 in muscles during development. In mlc/NT3 mice, there is a substantial increase in the amplitudes of monosynaptic EPSPs evoked by Ia afferents in MNs as measured with extracellular recordings from ventral roots. Despite this increased functional projection of Ia afferents, there is no obvious change in the anatomical density of Ia projections into the ventral horn of the spinal cord. Intracellular recordings from MNs revealed a major disruption in the pattern of Ia-MN connections. In addition to the normal connections between Ia afferents and MNs supplying the same muscle, there were also strong monosynaptic inputs from Ia afferents supplying unrelated muscles, which explains the increase seen in extracellular recordings. There was also a large variability in the strength of Ia input to individual MNs, both from correct and incorrect Ia afferents. Postnatal muscular administration of NT3 did not cause these changes in connectivity. These results indicate that prenatal exposure to elevated levels of NT3 disrupts the normal mechanisms responsible for synaptic selectivity in the stretch reflex circuit.

show abstract

“…-/-mice To clarify whether the decrease in the number of Runx3 -/-DRG neurons was due to the loss of specific neurons, we examined the number of proprioceptive DRG neurons using antibodies against selective markers PV, TrkC and calretinin [CR; calbindin 2 (Calb2)] (Copray et al, 1994;Honda, 1995;Kucera et al, 2002;Mu et al, 1993). In the wild-type mice, PV was expressed at a low level in the DRG (Th12) at E13.5 (data not shown), and subsequently PV expression increased.…”

Section: Cell Fate Specification Of Proprioceptive Drg Neurons In Runx3mentioning

confidence: 99%

Dynamic regulation of the expression of neurotrophin receptors by Runx3

et al. 2008

View full text Add to dashboard Cite

Sensory neurons in the dorsal root ganglion (DRG) specifically project axons to central and peripheral targets according to their sensory modality. However, the molecular mechanisms that govern sensory neuron differentiation and the axonal projections remain unclear. The Runt-related transcription factors, Runx1 and Runx3, are expressed in DRG neuronal subpopulations,suggesting that they might regulate the cell specification and the trajectories of specific axons. Here, we show that parvalbumin-positive DRG neurons fail to differentiate from the onset in Runx3-/-mice. By contrast, TrkC-positive DRG neurons differentiate normally at embryonic day (E) 11.5, but disappear by E13.5 in Runx3-/-mice. Subsequently, TrkC-positive DRG neurons reappear but in smaller numbers than in the wild type. In Runx3-/- mice, central axons of the TrkC-positive DRG neurons project to the dorsal spinal cord but not to the ventral and intermediate spinal cord, whereas the peripheral axons project to skin but not to muscle. These results suggest that Runx3 controls the acquisition of distinct proprioceptive DRG neuron identities, and that TrkC-positive DRG neurons consist of two subpopulations: Runx3-dependent early-appearing proprioceptive neurons that project to the ventral and intermediate spinal cord and muscle; and Runx3-independent late-appearing cutaneous neurons that project to the dorsal spinal cord and skin. Moreover,we show that the number of TrkA-positive DRG neurons is reduced in Runx3-/- mice, as compared with the wild type. These results suggest that Runx3 positively regulates the expression of TrkC and TrkA in DRG neurons.

show abstract

Formation of supernumerary muscle spindles at the expense of golgi tendon organs in ER81‐deficient mice

Cited by 22 publications

References 27 publications

Analysis of Proprioceptive Sensory Innervation of the Mouse Soleus: A Whole-Mount Muscle Approach

Analysis of Proprioceptive Sensory Innervation of the Mouse Soleus: A Whole-Mount Muscle Approach

Prenatal Exposure to Elevated NT3 Disrupts Synaptic Selectivity in the Spinal Cord

Dynamic regulation of the expression of neurotrophin receptors by Runx3

Contact Info

Product

Resources

About