ADSSL1 mutation relevant to autosomal recessive adolescent onset distal myopathy.

OBJECTIVE: Distal myopathy is a heterogeneous group of muscle diseases characterized by predominant distal muscle weakness. A study was done to identify the underlying cause of autosomal recessive adolescent onset distal myopathy. METHODS: Four patients from 2 unrelated Korean families were evaluated. To isolate the genetic cause, exome sequencing was performed. In vitro and in vivo assays using myoblast cells and zebrafish models were performed to examine the ADSSL1 mutation causing myopathy pathogenesis. RESULTS: Patients had an adolescent onset distal myopathy phenotype that included distal dominant weakness, facial muscle weakness, rimmed vacuoles, and mild elevation of serum creatine kinase. Exome sequencing identified completely cosegregating compound heterozygous mutations (p.D304N and p.I350fs) in ADSSL1, which encodes a muscle-specific adenylosuccinate synthase in both families. None of the controls had both mutations, and the mutation sites were located in well-conserved regions. Both the D304N and I350fs mutations in ADSSL1 led to decreased enzymatic activity. The knockdown of the Adssl1 gene significantly inhibited the proliferation of mouse myoblast cells, and the addition of human wild-type ADSSL1 reversed the reduced viability. In an adssl1 knockdown zebrafish model, muscle fibers were severely disrupted, which was evaluated by myosin expression and birefringence. In these conditions, supplementing wild-type ADSSL1 protein reversed the muscle defect. INTERPRETATION: We suggest that mutations in ADSSL1 are the novel genetic cause of the autosomal recessive adolescent onset distal myopathy. This study broadens the genetic and clinical spectrum of distal myopathy and will be useful for exact molecular diagnostics.

Development of bifunctional stilbene derivatives for targeting and modulating metal-amyloid-ß species.

Amyloid-ß (Aß) peptides and their metal-associated aggregated states have been implicated in the pathogenesis of Alzheimer's disease (AD). Although the etiology of AD remains uncertain, understanding the role of metal-Aß species could provide insights into the onset and development of the disease. To unravel this, bifunctional small molecules that can specifically target and modulate metal-Aß species have been developed, which could serve as suitable chemical tools for investigating metal-Aß-associated events in AD. Through a rational structure-based design principle involving the incorporation of a metal binding site into the structure of an Aß interacting molecule, we devised stilbene derivatives (L1-a and L1-b) and demonstrated their reactivity toward metal-Aß species. In particular, the dual functions of compounds with different structural features (e.g., with or without a dimethylamino group) were explored by UV-vis, X-ray crystallography, high-resolution 2D NMR, and docking studies. Enhanced bifunctionality of compounds provided greater effects on metal-induced Aß aggregation and neurotoxicity in vitro and in living cells. Mechanistic investigations of the reaction of L1-a and L1-b with Zn(2+)-Aß species by UV-vis and 2D NMR suggest that metal chelation with ligand and/or metal-ligand interaction with the Aß peptide may be driving factors for the observed modulation of metal-Aß aggregation pathways. Overall, the studies presented herein demonstrate the importance of a structure-interaction-reactivity relationship for designing small molecules to target metal-Aß species allowing for the modulation of metal-induced Aß reactivity and neurotoxicity.