Discovery of a novel family of FKBP12 "reshapers" and their use as calcium modulators in skeletal muscle under nitro-oxidative stress.

The hypothesis of rescuing FKBP12/RyR1 interaction and intracellular calcium homeostasis through molecular "reshaping" of FKBP12 was investigated. To this end, novel 4-arylthioalkyl-1-carboxyalkyl-1,2,3-triazoles were designed and synthesized, and their efficacy was tested in human myotubes. A library of 17 compounds (10a-n) designed to dock the FKBP12/RyR1 hot-spot interface contact residues, was readily prepared from free α-amino acids and arylthioalkynes using CuAAC "click" protocols amenable to one-pot transformations in high overall yields and total configurational integrity. To model nitro-oxidative stress, human myotubes were treated with the peroxynitrite donor SIN1, and evidence was found that some triazoles 10 were able to normalize calcium levels, as well as FKBP12/RyR1 interaction. For example, compound 10 b at 150 nM rescued 46% of FKBP12/RyR1 interaction and up to 70% of resting cytosolic calcium levels in human myotubes under nitro-oxidative stress. All compounds 10 analyzed showed target engagement to FKBP12 and low levels of cytotoxicity in vitro. Compounds 10b, 10c, 10h, and 10iR were identified as potential therapeutic candidates to protect myotubes in muscle disorders with underlying nitro-oxidative stress, FKBP12/RyR1 dysfunction and calcium dysregulation.

A genotyping method combining primer competition PCR with HRM analysis to identify point mutations in Duchenne animal models.

Dystrophin-null sapje zebrafish is an excellent model for better understanding the pathological mechanisms underlying Duchenne muscular dystrophy, and it has recently arisen as a powerful tool for high-throughput screening of therapeutic candidates for this disease. While dystrophic phenotype in sapje larvae can be easily detected by birefringence, zebrafish genotyping is necessary for drug screening experiments, where the potential rescue of larvae phenotype is the primary outcome. Genotyping is also desirable during colony husbandry since heterozygous progenitors need to be selected. Currently, sapje zebrafish are genotyped through techniques involving sequencing or multi-step PCR, which are often costly, tedious, or require special equipment. Here we report a simple, precise, cost-effective, and versatile PCR genotyping method based on primer competition. Genotypes can be resolved by standard agarose gel electrophoresis and high-resolution melt assay, the latter being especially useful for genotyping a large number of samples. Our approach has shown high sensitivity, specificity, and reproducibility in detecting the A/T point mutation in sapje zebrafish and the C/T mutation in the mdx mouse model of Duchenne. Hence, this method can be applied to other single nucleotide substitutions and may be further optimized to detect small insertions and deletions. Given its robust performance with crude DNA extracts, our strategy may be particularly well-suited for detecting single nucleotide variants in poor-quality samples such as ancient DNA or DNA from formalin-fixed, paraffin-embedded material.

Insights into the mechanisms of copper dyshomeostasis in amyotrophic lateral sclerosis.

Amyotrophic lateral sclerosis (ALS) is a severe neuromuscular disease characterised by a progressive loss of motor neurons that usually results in paralysis and death within 2 to 5 years after disease onset. The pathophysiological mechanisms involved in ALS remain largely unknown and to date there is no effective treatment for this disease. Here, we review clinical and experimental evidence suggesting that dysregulation of copper homeostasis in the central nervous system is a crucial underlying event in motor neuron degeneration and ALS pathophysiology. We also review and discuss novel approaches seeking to target copper delivery to treat ALS. These novel approaches may be clinically relevant not only for ALS but also for other neurological disorders with abnormal copper homeostasis, such as Parkinson's, Huntington's and Prion diseases.

Calpain 3 deficiency affects SERCA expression and function in the skeletal muscle.

Limb-girdle muscular dystrophy type 2A (LGMD2A) is a form of muscular dystrophy caused by mutations in calpain 3 (CAPN3). Several studies have implicated Ca2+ dysregulation as an underlying event in several muscular dystrophies, including LGMD2A. In this study we used mouse and human myotube cultures, and muscle biopsies in order to determine whether dysfunction of sarco/endoplasmatic Ca2+-ATPase (SERCA) is involved in the pathology of this disease. In CAPN3-deficient myotubes, we found decreased levels of SERCA 1 and 2 proteins, while mRNA levels remained comparable with control myotubes. Also, we found a significant reduction in SERCA function that resulted in impairment of Ca2+ homeostasis, and elevated basal intracellular [Ca2+] in human myotubes. Furthermore, small Ankyrin 1 (sAnk1), a SERCA1-binding protein that is involved in sarcoplasmic reticulum integrity, was also diminished in CAPN3-deficient fibres. Interestingly, SERCA2 protein was patently reduced in muscles from LGMD2A patients, while it was normally expressed in other forms of muscular dystrophy. Thus, analysis of SERCA2 expression may prove useful for diagnostic purposes as a potential indicator of CAPN3 deficiency in muscle biopsies. Altogether, our results indicate that CAPN3 deficiency leads to degradation of SERCA proteins and Ca2+ dysregulation in the skeletal muscle. While further studies are needed in order to elucidate the specific contribution of SERCA towards muscle degeneration in LGMD2A, this study constitutes a reasonable foundation for the development of therapeutic approaches targeting SERCA1, SERCA2 or sAnk1.