Formation Of Supernumerary Muscle Spindles At The Expense Of Golgi Tendon Organs In Er81-deficient Mice

Formation Of Supernumerary Muscle Spindles At The Expense Of Golgi Tendon Organs In Er81-deficient Mice

Kucera J; Cooney W; Que A; Szeder V; Stancz-Szeder H; Walro J

Developmental Dynamics

2002

2002-03

ER81, a member of the ETS family of transcription factors, is essential for the formation of connections between sensory and motor neurons in the spinal cord. Mice lacking Er81 genes exhibit reduced monosynaptic sensory-motoneuron connectivity in response to muscle nerve stimulation. Proximal muscle nerve stimulation elicits fewer monosynaptic potentials than stimulation of distal nerves in hind-limbs, a deficit that is paralleled by a paucity of muscle spindles in proximal muscles (Arber et al., 2000). We examined whether a presence of spindles innervated by afferents in distal muscles correlated with the increased preservation of monosynaptic sensory-motor potentials in distal muscle nerves. Not only were spindles and Ia afferents present, but also they were supernumerary in distal muscles such as the soleus, medial gastrocnemius, and extensor hallucis longus. Concomitantly, a deficiency of Golgi tendon organs (GTOs) and Ib afferents was observed in distal muscles, as if supernumerary spindles formed at the expense of tendon organs in the absence of Er81. Thus, ER81 may be involved in mechanisms that regulate acquisition of the Ia and Ib phenotypes by subsets of proprioceptive muscle afferents. Segmental differences in muscle spindle and GTO dependence on ER81 suggest that more than one ETS transcription factor may participate in the regulation of limb proprioceptive system assembly in the mouse. (C) 2002 Wiley-Liss, Inc.

Anatomy & Morphology; Developmental Biology; ETS transcription factors; expression; Golgi tendon organs; group; ia afferents; innervation; motor neurons; muscle spindles; mutant mice; myosin heavy-chain; neonatal rats; nerve growth-factor; neurotrophin-3; primary sensory neurons; proprioceptive afferents; transcription factors

Journal Article or Conference Abstract Publication

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