l-Carnitine ameliorates congenital myopathy in a tropomyosin 3 de novo mutation transgenic zebrafish

Abstract

Background Congenital myopathy (CM) is a group of clinically and genetically heterogeneous muscle disorders, characterized by muscle weakness and hypotonia from birth. Currently, no definite treatment exists for CM. A de novo mutation in Tropomyosin 3-TPM3(E151G) was identified from a boy diagnosed with CM, previously TPM3(E151A) was reported to cause CM. However, the role of TPM3(E151G) in CM is unknown. Methods Histopathological, swimming behavior, and muscle endurance were monitored in TPM3 wild-type and mutant transgenic fish, modelling CM. Gene expression profiling of muscle of the transgenic fish were studied through RNAseq, and mitochondria respiration was investigated. Results While TPM3(WT) and TPM3(E151A) fish show normal appearance, amazingly a few TPM3(E151G) fish display either no tail, a crooked body in both F0 and F1 adults. Using histochemical staining for the muscle biopsy, we found TPM3(E151G) displays congenital fiber type disproportion and TPM3(E151A) resembles nemaline myopathy. TPM3(E151G) transgenic fish dramatically swimming slower than those in TPM3(WT) and TPM3(E151A) fish measured by DanioVision and T-maze, and exhibit weaker muscle endurance by swimming tunnel instrument. Interestingly, l-carnitine treatment on TPM3(E151G) transgenic larvae significantly improves the muscle endurance by restoring the basal respiration and ATP levels in mitochondria. With RNAseq transcriptomic analysis of the expression profiling from the muscle specimens, it surprisingly discloses large downregulation of genes involved in pathways of sodium, potassium, and calcium channels, which can be rescued by l-carnitine treatment, fatty acid metabolism was differentially dysregulated in TPM3(E151G) fish and rescued by l-carnitine treatment. Conclusions These results demonstrate that TPM3(E151G) and TPM3(E151A) exhibit different pathogenicity, also have distinct gene regulatory profiles but the ion channels were downregulated in both mutants, and provides a potential mechanism of action of TPM3 pathophysiology. Our results shed a new light in the future development of potential treatment for TPM3-related CM.

The genomic basis of reproductive and migratory behaviour in a polymorphic salmonid

“…Heterozygous SYNGAP1‐ knockout mice lines show impairment of working and reference spatial memory (Nakajima et al, 2019), the former affecting the capacity to hold information temporarily that is crucial in decision‐making, and the latter required to navigate through an environment. Transgenic zebrafish carrying mutations in TPM3 swim more slowly and show weaker muscle endurance than the wildtype, and in some cases do not develop a tail (Hsu et al, 2021). The functions of these candidate genes highlight how migration may require both neurological (e.g., decision‐making) and performance adaptations (e.g., ability to swim long distances across a long period of time).…”

Creatine and L-carnitine attenuate muscular laminopathy in the LMNA mutation transgenic zebrafish

“…To investigate the relationship between LMNA variants and muscular laminopathy, we assessed the muscle endurance of adult transgenic sh using a Brett-type intermittent-closed swimming tunnel (38 cm long, 10 cm wide and 9.5 cm deep; Loligo Systems ApS, Tjele, Denmark) at the Marine Research Station. After a one-minute habituation period, the sh were subjected to water ow resistance, and their U crit (critical swimming speed, represented as cm/s) was calculated using a formula based on maximum velocity and time to fatigue as described earlier 27 .…”

“…To identify potential drugs for the therapy of muscular laminopathy, we selected ve muscle-improving drugs for treatment of the larvae: L-tyrosine (10 µM in water), Taurine (1 mM in water), L-carnitine (10 µM in water), creatine (100 µM in water), and Terazosin (2.5 µM in diluted DMSO). The concentrations of those drugs were determined based on the previous studies 27,32,33 . We placed the larvae sh in Petri dishes and administered the different drugs at 28 hpf.…”

“…Based on our previous report, we selected ve chemical drugs, creatine, L-carnitine, taurine, tyrosine, and terazosin that have shown potential in improving neuromuscular diseases 27 . Since LMNA(E358K) which showed a slightly lower muscle endurance trend, we tested AB(WT), LMNA(WT), LMNA(L35P), LMNA(R453W), and LMNA(A539V) sh with these ve selected drugs (Figure 5).…”

“…Our previous study established transgenic sh expressing tropomyosin 3 (TPM3) mutations and demonstrated that TPM3(E151G) and TPM3(E151A) exhibit different pathogenicity. Furthermore, we identi ed L-Carnitine as a supplement that can ameliorate muscle endurance weakness in transgenic sh with TPM3 mutations 27 . This proof-of-concept study highlights the potential of zebra sh as a perfect model for congenital myopathy and drug screening.…”