Sequence analysis of the connexin 26 genes from a deafness family with A1555G mutation in Huaiyin / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>To ascertain whether connexin 26 (Cx26) gene was a nuclear modifier gene in an extensive family with matrilineal nonsyndromic deafness associated with A1555G mutation in Huaiyin, China.</p><p><b>METHODS</b>Following PCR-restriction fragment length polymorphism (PCR-RFLP) with ApaI restriction enzyme, Cx26 genes from 26 cases, with A1555G mitochondrial mutations in this family, and 62 controls (including 2 patrilineal relatives, 10 spouse controls and 50 unrelated controls), were sequenced.</p><p><b>RESULTS</b>Compared with the reference sequence of Cx26 gene, totally four kinds of nucleotide changes,79G -->A, 109G-->A, 341G-->A and 235delC, were detected in a heterozygous form. However, the former three were previously reported polymorphisms, and only the 235delC was a previously described recessive mutation associated with most autosomal nonsyndromic sensorineural hearing loss in Japan and China. Further study showed that the heterozygous 235delC mutation existed in both one individual with mild hearing loss and two individuals with normal hearing. Clinical characterization showed that 235delC mutation did not seem to modify the deafness phenotype due to the A1555G mutation. Moreover, this 235delC mutation was deduced to derive from a married-in control. Finally, there were no co-segregation between the phenotypes of hearing loss and the genotypes for Cx26 genes based on the four kinds of nucleotide changes.</p><p><b>CONCLUSIONS</b>The heterozygous 235delC mutation of the Cx26 gene may not modulate the severity of hearing loss associated with A1555G mutation and Cx26 gene is unlikely to be a modifier gene for hearing loss due to A1555G mitochondrial mutation in this Chinese family.</p>

Analysis of germline mutations in the APC gene in familial adenomatous polyposis patients / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>This study was aimed at establishing an efficient mutation analysis technique system to screen the germline mutations in the adenomatous polyposis coli (APC) gene that predisposes the disease susceptibility in familial adenomatous polyposis (FAP) and to investigate the relationship between genotype and phenotype of APC gene.</p><p><b>METHODS</b>Genomic DNA was extracted from the peripheral blood lymphocytes of 22 patients with clinically diagnosed FAP and was forwarded to screening for germline mutations by using denaturing high-performance liquid chromatography(DHPLC), protein truncation test (PTT) and DNA sequencing in APC gene. Analysis of genotype-phenotype was also performed on the clinical data of the FAP patients.</p><p><b>RESULTS</b>Thirteen APC germline mutations were identified in 22 FAP patients. All of the mutations were nonsense or framshift mutations. Analysis of genotype-phenotype demonstrated that the FAP patients with mutations in the 5'or 3'extreme parts of the APC gene showed mild clinical symptoms. However, the FAP patients with mutations in the middle of the APC gene displayed typical or severe clinical symptoms.</p><p><b>CONCLUSION</b>The technique system established in this study can efficiently and sensitively detect the mutations in APC gene. It is useful in the molecular diagnosis of pre-symptomatic FAP cases in FAP family. The clinical features of FAP patients may be related to their genotypes of APC gene.</p>

Sequence analysis of the mitochondrial genome from a large family with maternally inherited nonsyndromic deafness / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To ascertain whether other variations coexist with 1555(A--> G) mutation in the mitochondrial DNA and may aggravate the severity of hearing loss or increase the penetrance of 1555(A--> G) mutation in a large family with maternally inherited nonsyndromic deafness in Huaiyin, Jiangsu province.</p><p><b>METHODS</b>PCR-restriction fragment length polymorphism (PCR-RFLP) was used to screen both the nt1555 and the nt7445 of the mitochondrial DNA from 27 maternal members in the core family; and then the mitochondrial genomes from two maternal members, and the 12S rRNA genes MTRNR1 and tRNA-Ser(UCN) gene MTTS1 from the others, were amplified by PCR-RFLP and were sequenced.</p><p><b>RESULTS</b>1555(A--> G) mutation in the mitochondrial DNA was reverified to be one of the major factors which cause maternally inherited nonsyndromic deafness and the cosegregation of 955-960(insC) and 1555(A--> G) was present in this family. Moreover, 7449 (insG), a novel homoplasmic mutation in the tRNA-Ser(UCN) gene, was found to co-exist with 1555(A--> G) mutation in two maternal members.</p><p><b>CONCLUSION</b>The cosegregation of 955-960(insC) and 1555(A--> G) implies that 955-960(insC) may synergistically cause hearing loss in the presence of an 1555(A--> G) mutation, serving as an aggravating factor to enhance the sensitivity to aminoglycosides, and may sometimes increase the penetrance of 1555(A--> G) mutation.</p>

The detection of microsatellite instability by ion-pair reversed-phase high performance liquid chromatography / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To set up a sensitive and stable technique which has high throughout to detect the instability of microsatellite DNA.</p><p><b>METHODS</b>Genomic DNA extracted from the cancer tissues and their normal tissues were subjected to microsatellite instability(MSI) analysis on five of DNA markers in 115 sporadic colorectal cancers by means of PCR and ion-pair reversed-phase high performance liquid chromatography. Genomic DNA extracted from lymphocytes in blood of 20 normal persons were analysed and used as the standard control.</p><p><b>RESULTS</b>Seventeen (14.8%) MSI-H and 23(20.0%) MSI-L were found in 115 sporadic colorectal cancers. The rates of MSI in the young patients and old patients were much higher than that in the middle-age patients (P<0.05). And the rate of MSI in low differentiation group was also much higher than that in high or middle differentiation groups (P<0.05).</p><p><b>CONCLUSION</b>The method the authors developed is a sensitive and accurate technique to detect MSI and has a high throughput.</p>