Two novel missense mutations in the myostatin gene identified in Japanese patients with Duchenne muscular dystrophy

BACKGROUND: Myostatin is a negative regulator of skeletal muscle growth. Truncating mutations in the myostatin gene have been reported to result in gross muscle hypertrophy. Duchenne muscular dystrophy (DMD), the most common lethal muscle wasting disease, is a result of an absence of muscle dystrophin. Although this disorder causes a rather uniform pattern of muscle wasting, afflicted patients display phenotypic variability. We hypothesized that genetic variation in myostatin is a modifier of the DMD phenotype. METHODS: We analyzed 102 Japanese DMD patients for mutations in the myostatin gene. RESULTS: Two polymorphisms that are commonly observed in Western countries, p.55A>T and p.153K>R, were not observed in these Japanese patients. An uncommon polymorphism of p.164E>K was uncovered in four cases; each patient was found to be heterozygous for this polymorphism, which had the highest frequency of the polymorphism observed in the Japanese patients. Remarkably, two patients were found to be heterozygous for one of two novel missense mutations (p.95D>H and p.156L>I). One DMD patient carrying a novel missense mutation of p.95D>H was not phenotypically different from the non-carriers. The other DMD patient was found to carry both a novel mutation (p.156L>I) and a known polymorphism (p.164E>K) in one allele, although his phenotype was not significantly modified. Any nucleotide change creating a target site for micro RNAs was not disclosed in the 3' untranslated region. CONCLUSION: Our results indicate that heterozygous missense mutations including two novel mutations did not produce an apparent increase in muscle strength in Japanese DMD cases, even in a patient carrying two missense mutations

HnRNP C1/C2 May Regulate Exon 7 Splicing in the Spinal Muscular Atrophy Gene SMN1

Spinal muscular atrophy (SMA) is caused by loss of SMN1. A nearly identical gene,SMN2, fails to compensate for the loss of SMN1 because SMN2 produces mainly anexon 7-skipped product. The +6C in SMN1 exon 7 proceeds to include exon 7 intomRNA, while the +6U in SMN2 causes skipping of exon 7. Here, ∼45kD proteins boundto the SMN exon 7 RNA probe was found, and identified as hnRNP C1/C2. In gel-shiftassay, hnRNP C1/C2 had a greater affinity for the RNA probe with +6C than for theRNA probe with +6U. In vitro splicing assay showed that anti-hnRNP C1/C2 antibodyhampered splicing of SMN1 exon 7, but did not affect splicing of SMN2 exon 7. Inconclusion, we showed the possibility that hnRNP C1/C2 enhanced SMN1 exon 7splicing specifically

HnRNP C1/C2 May Regulate Exon 7 Splicing in the Spinal Muscular Atrophy Gene SMN1

Spinal muscular atrophy (SMA) is caused by loss of SMN1. A nearly identical gene,SMN2, fails to compensate for the loss of SMN1 because SMN2 produces mainly anexon 7-skipped product. The +6C in SMN1 exon 7 proceeds to include exon 7 intomRNA, while the +6U in SMN2 causes skipping of exon 7. Here, ∼45kD proteins boundto the SMN exon 7 RNA probe was found, and identified as hnRNP C1/C2. In gel-shiftassay, hnRNP C1/C2 had a greater affinity for the RNA probe with +6C than for theRNA probe with +6U. In vitro splicing assay showed that anti-hnRNP C1/C2 antibodyhampered splicing of SMN1 exon 7, but did not affect splicing of SMN2 exon 7. Inconclusion, we showed the possibility that hnRNP C1/C2 enhanced SMN1 exon 7splicing specifically

Evaluation of mutation effects on UGT1A1 activity toward 17beta-estradiol using liquid chromatography-tandem mass spectrometry

Mutations in the gene encoding UDP-glucuronosyltransferase 1A1 (UGT1A1) may reduce the glucuronidation of estradiol, bilirubin, etc. In the present study, we used a liquid chromatography-tandem mass spectrometry (LC/MS/MS) method to assay the activities of recombinant mutated UGT1A1 toward 17beta-estradiol (E2), by determining its glucuronide (E2G) content. Direct evidence for glucuronide formation was provided by E2G-specific ion peaks. The UGT1A1 activities of G71R (exon 1), F83L (exon 1), I322V (exon 2) and G493R (exon 5) mutants were 24, 30, 18 and 0.6% of the normal UGT1A1 activity, respectively. In conclusion, our study showed that LC/MS/MS enabled accurate evaluation of the effects of mutations on recombinant UGT1A1 activity towards E2