A novel ATTR L32V mutation causes familial amyloid polyneuropathy in a Bolivian family.

We report a new transthyretin (ATTR) gene c.272C>G mutation and variant protein, p.Leu32Val, in a kindred of Bolivian origin with a rapid progressive peripheral neuropathy and cardiomyopathy. Three individuals from a kindred with peripheral nerve and cardiac amyloidosis were examined. Analysis of the TTR gene was performed by Sanger direct sequencing. Neuropathologic examination was obtained on the index patient with mass spectrometry study of the ATTR deposition. Direct DNA sequence analysis of exons 2, 3, and 4 of the TTR gene demonstrated a c.272 C>G mutation in exon 2 (p.L32V). Sural nerve biopsy revealed massive amyloid deposition in the perineurium, endoneurium and vasa nervorum. Mass spectrometric analyses of ATTR immunoprecipitated from nerve biopsy showed the presence of both wild-type and variant proteins. The observed mass results for the wild-type and variant proteins were consistent with the predicted values calculated from the genetic analysis data. The ATTR L32V is associated with a severe course. This has implications for treatment of affected individuals and counseling of family members.

Fast skeletal myofibers of mdx mouse, model of Duchenne muscular dystrophy, express connexin hemichannels that lead to apoptosis.

Skeletal muscles of patients with Duchenne muscular dystrophy (DMD) show numerous alterations including inflammation, apoptosis, and necrosis of myofibers. However, the molecular mechanism that explains these changes remains largely unknown. Here, the involvement of hemichannels formed by connexins (Cx HCs) was evaluated in skeletal muscle of mdx mouse model of DMD. Fast myofibers of mdx mice were found to express three connexins (39, 43 and 45) and high sarcolemma permeability, which was absent in myofibers of mdx Cx43(fl/fl)Cx45(fl/fl):Myo-Cre mice (deficient in skeletal muscle Cx43/Cx45 expression). These myofibers did not show elevated basal intracellular free Ca(2+) levels, immunoreactivity to phosphorylated p65 (active NF-κB), eNOS and annexin V/active Caspase 3 (marker of apoptosis) but presented dystrophin immunoreactivity. Moreover, muscles of mdx Cx43(fl/fl)Cx45(fl/fl):Myo-Cre mice exhibited partial decrease of necrotic features (big cells and high creatine kinase levels). Accordingly, these muscles showed similar macrophage infiltration as control mdx muscles. Nonetheless, the hanging test performance of mdx Cx43(fl/fl)Cx45(fl/fl):Myo-Cre mice was significantly better than that of control mdx Cx43(fl/fl)Cx45(fl/fl) mice. All three Cxs found in skeletal muscles of mdx mice were also detected in fast myofibers of biopsy specimens from patients with muscular dystrophy. Thus, reduction of Cx expression and/or function of Cx HCs may be potential therapeutic approaches to abrogate myofiber apoptosis in DMD.