Analysis of the ratio of mitchondrial DNA with A1555G mutant to wild type in deaf patients of Fujian province in China by a new method and its relationship with the severity of hearing loss / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>It has been suggested that the ratio of mutant and wild type mitochondrial DNA may be related to its clinical phenotype. In this study, we developed a high sensitive real-time amplification refractory mutation system-quantitative polymerase chain reaction (RT-ARMS-qPCR) assay for quantitation of the mitochondrial DNA (mtDNA) with a mutated 1555 site, and explored the relationship between the ratio of mutated mtDNA and the severity of hearing loss of mitochondrial deafness (MD) patients of Fujian province in China.</p><p><b>METHODS</b>An amplified mtDNA fragment containing the 1555 site was ligated into a vector to construct a plasmid DNA standard. An RT-ARMS-qPCR system was used to measure the mtDNA copy number containing wild-type and mutant sequences in a cohort of 126 MD patients of Fujian province in China. Combined with the clinical data, we explored the relationship between the ratio of mutated mtDNA and the severity of hearing loss of MD.</p><p><b>RESULTS</b>The variation coefficient in the cohort was 1.21%, the interassay variation coefficient was 1.78%, and the linear range was 10(2) - 10(8) copies/µl for detecting a recombinant, wild-type plasmid. The primers amplified only the intended sequences. Mutation copy number correlated with the degree of deafness in sporadic cases with heteroplasmic mutations of mtDNA A1555G (R = 0.811, P = 0.003), but not in sporadic cases with homoplasmic mutations (R = 0.007, P = 0.989). The copy number of homoplasmic or heteroplasmic mutations of mtDNA A1555G in familial cases correlated with degree of deafness (R = 0.352, P = 0.023 and R = 0.90, P = 0.012, respectively).</p><p><b>CONCLUSIONS</b>The RT-ARMS-qPCR system is suitable for determining the copy number of mtDNA fragments containing the A1555G mutation. The ratio of mutated mtDNA correlates with the severity of hearing loss of MD.</p>

Mitochondrial DNA A1555G mutation of seven families with nonsyndromic hearing loss / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To study mitochondrial DNA (mtDNA) A1555G mutation in seven families with nonsyndromic hearing loss (NSHL).</p><p><b>METHODS</b>Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and real time-amplification refractory mutation system-quantitative PCR (ARMS-qPCR) were applied to detect mtDNA A1555G mutation in seven NSHL families. Related clinical data were also collected and analyzed.</p><p><b>RESULTS</b>The mtDNA A1555G mutation was detected in members from the maternal side, including heteroplasmy and homozygosis, others were negative for this mutation. The copy number of homoplasmic or heteroplasmic mutations of mtDNA A1555G correlated well with the degree of deafness (R = 0.341, P = 0.022 and R = 0.85, P = 0.015, respectively).</p><p><b>CONCLUSION</b>The mutation rate of the mtDNA A1555G is high in the NSHL patients, the mutation type include heteroplasmy and homozygosis. There is significant correlation between the mtDNA A1555G copy number and the severity of hearing loss.</p>

Novel mutation and polymorphism of PRSS1 gene in the Chinese patients with hereditary pancreatitis and chronic pancreatitis / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Mutations in the cationic trypsinogen gene (PRSS1) have been detected in patients with hereditary pancreatitis (HP). This study investigated the prevalence of the R122H (c.365 G > A), A121T (c.361 G > A) and D162D (c.488 C > T) mutations or polymorphisms in the common, non-hereditary forms of chronic pancreatitis and in an HP family.</p><p><b>METHODS</b>DNA was prepared from blood samples of 54 patients with chronic pancreatitis (35 alcoholic, 17 idiopathic and 2 hereditary) and 120 normal controls. The PRSS1 genes were amplified by polymerase chain reaction (PCR) and their products were analyzed by sequencing and related clinical data were also collected.</p><p><b>RESULTS</b>A new polymorphism (c.488 C > T) of PRSS1 was found in 25 patients with chronic pancreatitis (including one affected member of the HP family) and six members of the normal controls. The C/T genotype was significantly increased in chronic pancreatitis (OR: 16.379, 95% CI: 5.7522 - 52.3663), the frequency of c.488 C > T change was in according with the Hardy-Weinberg equilibrium, but it doesn't affect the clinical phenotype. The commonly reported change of R122H (c.365 G > A) was not detected in any of the study subjects. c.361 G > A was found in 2 affected members and one unaffected carrier in an HP family. One of the affected members of an HP family had c.361 G > A mutation and polymorphism (c.488 C > T) in the PRSS1 gene at the same time. The patient's clinical values (C3, C4, CA19-9 and HbA1c) were higher than those of the other patients with chronic pancreatitis. The two patients with HP developed diabetes mellitus and their father died with pancreatic cancer.</p><p><b>CONCLUSION</b>A new polymorphism (c.488 C > T) in the PRSS1 gene is associated with chronic pancreatitis, but it did not affect the clinical phenotype while the A121T (c.361 G > A) mutation in the gene shows a significant correlation in the patients with HP.</p>

Study of mitochondrial DNA A1555G mutation among nonsyndromic hearing impairment in Chinese population / 中华检验医学杂志

Objective To study the prevalence of the mtDNA A1555G gene mutation in Chinese population with nonsyndromic hearing impairment.Methods PCR-RFLP,directional sequencing of PCR products were applied in 325 patients with nonsyndromic hearing impairment and 50 normal controls.Results The mutation rate of the mtDNA A1555G was 14.5% (47/325),28 of 47 cases were homozygosis,19 of 47 cases were heterozygosis.The same mutation was not detected in the control subjects.Conclusion The mutation rate of the mtDNA A1555G is relatively high in the Chinese NSHI patients,the mutation type includes both heterozygosis and homozygosis.