DOK7 Gene Therapy Enhances Neuromuscular Junction Innervation and Motor Function in Aged Mice

Abstract

Summary Muscle denervation at the neuromuscular junction (NMJ), the essential synapse between motor neuron and skeletal muscle, is associated with age-related motor impairment. Therefore, improving muscle innervation at aged NMJs may be an effective therapeutic strategy for treating the impairment. We previously demonstrated that the muscle protein Dok-7 plays an essential role in NMJ formation, and, indeed, its forced expression in muscle enlarges NMJs. Moreover, therapeutic administration of an adeno-associated virus vector encoding human Dok-7 ( DOK7 gene therapy) suppressed muscle denervation and enhanced motor activity in a mouse model of amyotrophic lateral sclerosis (ALS). Here, we show that DOK7 gene therapy significantly enhances motor function and muscle strength together with NMJ innervation in aged mice. Furthermore, the treated mice showed greatly increased compound muscle action potential (CMAP) amplitudes compared with the controls, suggesting enhanced neuromuscular transmission. Thus, therapies aimed at enhancing NMJ innervation have potential for treating age-related motor impairment.

The Impact of Milk Fat Globule Membrane with Exercise on Age-Related Degeneration of Neuromuscular Junctions

“…Since the combination of MFGM intake and exercise from a young age has been shown to attenuate the age-related decline in the expression of Dok-7, which promotes NMJ formation [ 22 , 23 , 24 , 32 , 33 ], we examined whether MFGM with exercise from an old age affects the expression of Dok-7. The expression of Dok-7 protein was significantly higher in the Ex-MFGM group than in the Cont group ( Figure S1 ).…”

“…By contrast, in the current study MFGM supplementation increased the protein expression of Dok-7 in muscles, which is consistent with the results of our previous studies [ 20 , 22 ]. We recently showed that the overexpression of Dok-7 in skeletal muscles ameliorated age-related NMJ denervation [ 32 ], and therefore MFGM may have secondary effects on the nervous system via muscles and NMJs. Further studies are needed to clarify whether MFGM directly affects the nervous system.…”

“…Since the combination of MFGM intake and exercise from a young age has been shown to attenuate the age-related decline in the expression of Dok-7, which promotes NMJ formation [22][23][24]32,33], we examined whether MFGM with exercise from an old age Since the combination of MFGM intake and exercise from a young age has been shown to attenuate the age-related decline in the expression of Dok-7, which promotes NMJ formation [22][23][24]32,33], we examined whether MFGM with exercise from an old age affects the expression of Dok-7. The expression of Dok-7 protein was significantly higher in the Ex-MFGM group than in the Cont group (Figure S1).…”

Micro‐ and nano‐tomography analysis of mouse soleus muscle using radiation

“…In this study, the soleus muscle was used to observe the muscle's detailed structure. This method is widely used to determine muscle structure in animal models (Zeller‐Plumhoff et al, 2017), and to determine the degree of damage and recovery of sensorimotor function through functional evaluation in animal models (Ueta et al, 2020).…”

The Neuromuscular Junction: Roles in Aging and Neuromuscular Disease

“…NMJ fragmentation and denervation, and consequent decreased skeletal muscle contractility in aging skeletal muscle have also been mitigated by stabilizing endplates: for example, via transgenic expression of LRP-4 and α-sarcoglycan (which delays LRP-4 degradation). Gene therapy to increase expression of Dok-7 (a cytoplasmic adapter protein, which is a substrate of MuSK and activates MuSK kinase activity) [ 144 ] in aging skeletal muscle also improves the acetylcholine receptor area, innervation and consequent skeletal muscle contractility, further implicating the role of NMJ pathology in sarcopenia [ 145 , 146 ]. An engineered agrin (a C-terminal fragment of mouse agrin) improved skeletal muscle strength in a sarcopenia-like murine muscle model (neurotrypsin-overexpression) [ 147 ].…”