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.

Quantification of lysophosphatidylcholines and phosphatidylcholines using liquid chromatography-tandem mass spectrometry in neonatal serum.

We established an improved method for quantification of phosphatidylcholine (PC) and lysophosphatidylcholine (LPC) molecular species in neonatal serum using high-performance liquid chromatography coupled tandem mass spectrometry (LC-MS/MS). A multiple reaction monitoring (MRM) mode of positive ionization for MS/MS was used. The method involved purification of phospholipids by solid phase extraction (SPE) from a 20-microl minimum specimen of serum. The assayed values of authentic 16:0-LPC and 18:0-LPC showed a linear response, and our quantitative results showed high precision for the all species of PC and LPC. Then, we quantified PC and LPC in adult and neonatal serum and compared them. Day 0-1 neonatal serum 16:0-, 18:0-, 18:1-, 18:2-LPC levels were significantly lower than adult ones. All species LPC levels in the day 0-1 neonates were significantly lower than day 4-8 neonates. Day 0-1 neonatal serum 16:0/18:2-, 18:0/18:2-PC levels were significantly lower than adult ones. Our method is advantageous for precise assessments of the relationships between PCs/LPCs levels and neonatal infectious diseases.

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.

Changes in regional cerebral blood volume in frontal cortex during mental work with and without caffeine intake: functional monitoring using near-infrared spectroscopy.

Near-infrared spectroscopy (NIRS) was used to measure frontal regional cerebral blood volume (rCBV) in a person whose brain was under the influence of pharmacological agents while the person was performing a complex task. Fourteen healthy participants were administered Uchida-Kraepelin psychodiagnostic (UKP) tests before and after caffeine intake, and the concentration of caffeine in the urine was measured. The average number of answers and the average number of correct answers given by the participants improved significantly following caffeine intake. During the UKP testing, changes in the rCBV in the inferior frontal cortex were continuously measured using NIRS. The volume during the rest periods decreased as a result of caffeine-induced constriction of the cerebral arteriola. The volume increased during the mental work, but the degree of the increase was the same before and after caffeine intake. Although the performance of the mental work improved following caffeine intake, the improvement was not reflected in the rCBV in the inferior frontal cerebral cortex. These results suggest that caffeine helps to protect the brain from excessive hyperemia in addition to activating the neurons in the prefrontal cortex.

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 an exon 7-skipped product. The +6C in SMN1 exon 7 proceeds to include exon 7 into mRNA, while the +6U in SMN2 causes skipping of exon 7. Here, approximately 45kD proteins bound to the SMN exon 7 RNA probe was found, and identified as hnRNP C1/C2. In gel-shift assay, hnRNP C1/C2 had a greater affinity for the RNA probe with +6C than for the RNA probe with +6U. In vitro splicing assay showed that anti-hnRNP C1/C2 antibody hampered splicing of SMN1 exon 7, but did not affect splicing of SMN2 exon 7. In conclusion, we showed the possibility that hnRNP C1/C2 enhanced SMN1 exon 7 splicing specifically.

Identification of N-acetyl Proline-Glycine-Proline (acPGP) in human serum of adults and newborns by liquid chromatography-tandem mass spectrometry.

BACKGROUND: N-acetyl Proline-Glycine-Proline (acPGP) is a novel neutrophil chemoattractant. However, no studies have been reported to identify the presence of acPGP in human serum. The purpose of our study was to establish a method for measuring acPGP, and to determine whether acPGP is present in human serum. METHODS: Serum samples were obtained from 22 healthy adults and 26 term and preterm newborns. For the sensitive analysis of acPGP, we utilized liquid chromatography-tandem mass spectrometry (LC-MS/MS) with a multiple reaction monitoring (MRM) positive ion mode. RESULTS: The major product ions of acPGP ([M+H](+) ion, m/z 312) appeared at 112 and 140. The MRM (transition: m/z 312/112) chromatogram in human serum showed a single peak with the same retention time as that of authentic acPGP. The calibration curve of authentic acPGP was linear, and our quantitative results indicated high precision. The mean serum acPGP levels in adults and newborns were 6.3 and 18.7 pg/ml, respectively. In newborns, lower birth weight infants had significantly higher serum acPGP levels. CONCLUSIONS: We established a method for the quantification of serum acPGP using LC-MS/MS, and this paper provides the first evidence for the presence of acPGP in human serum of adults and newborns.

Blood lysophosphatidylcholine (LPC) levels and characteristic molecular species in neonates: prolonged low blood LPC levels in very low birth weight infants.

Lysophosphatidylcholine (LPC) has various stimulatory effects on many types of immune cells. The purpose of our study was to characterize blood LPC levels and to determine the composition of LPC molecular species (LPCs) in the neonatal period. Thirty-six neonates were enrolled in this study and then grouped according to birth-weight as follows: non-very low birth weight (NVLBW); >or=1,500 g (n=17), and very low birth weight (VLBW); <1,500 g (n=19). Sixteen healthy normal adults were used as controls. Levels of total blood LPC and LPCs (16:0-, 18:0-, 18:1-, 18:2-, and 20:4-LPC species) were measured using HPLC coupled with tandem mass spectrometry. Total blood LPC levels at birth in neonates in both groups (NVLBW and VLBW) were significantly lower than those of adult levels. In NVLBW infants, LPC levels reached adult levels at postnatal day 3 compared with VLBW infants, who attained adult levels after postnatal day 57 (around full-term). The composition of the LPCs was different not only between neonates and adults, but between NVLBW and VLBW infants. These findings may be associated with the difference of immunity among adults, NVLBW, and VLBW infants.

Mutation analysis of the ornithine transcarbamylase (OTC) gene in five Japanese OTC deficiency patients revealed two known and three novel mutations including a deep intronic mutation.

Ornithine transcarbamylase (OTC) deficiency is the most common inborn error of the urea cycle. Although a combination of molecular methods have been used including DNA sequencing of all 10 exons and exon-intron boundaries of OTC gene, only approximately 80% of patients with OTC deficiency are found to have mutations. We report two known and three novel mutations of the OTC gene in five Japanese patients including two neonatal-onset, one late-onset, and two symptomatic female patients. Known nonsense mutations (c.578G>A and c.421C>T) were detected in a neonatal-onset male and a symptomatic female patient, respectively. Mutation analysis revealed two novel mutations including one splice site mutation (c.386+1G>C) in a symptomatic female patient and one missense mutation (c.515T>A) in a late-onset male patient. In the remaining case, which was a neonatal-onset male patient, no mutation was disclosed by direct sequencing of all 10 exons and their flanking intron sequences. Therefore, OTC mRNA in the liver was analyzed by RT-PCR, and remarkably, a 135-nt insertion was detected between exons 5 and 6. Genomic DNA analysis of intron sequences revealed a single nucleotide change at 265 bp downstream from the 3' end of exon 5, which created the novel splice acceptor site. Thereby, a 135-nt exon was created from the central part of an intron sequence. This is the first report of mutation deep in the intronic sequence in the OTC gene. Molecular analysis using genomic DNA and mRNA will increase the mutation detection ratio in the OTC gene.

Co-occurrence of mutations in both dystrophin- and androgen-receptor genes is a novel cause of female Duchenne muscular dystrophy.

Duchenne muscular dystrophy (DMD) is an X-linked recessive disorder. Here, we report a novel mechanism for the occurrence of DMD in females. In a Vietnamese DMD girl, conventional PCR amplification analysis disclosed a deletion of exons 12-19 of the dystrophin gene on Xp21.2, with a karyotype of 46, XY. Furthermore, a novel mutation in the androgen-receptor gene on Xq11.2-q12 was identified in this girl, which led to male pseudohermaphroditism. Co-occurrence of mutations of these two genes constitutes a novel mechanism underlying female DMD.