[Hearing loss may be associated with the novel mitochondrial tRNA(Asp) A7551G mutation in a Chinese family].

OBJECTIVE: We reported here the clinical and genetic evaluations as well as mutational analysis of mitochondrial DNA(mtDNA) in a Chinese family with maternally transmitted non-syndromic hearing loss and investigated the influence of the mitochondrial tRNA(Asp) A7551G mutation to the phenotypic manifestation of the deafness. METHODS: One Chinese Han pedigrees of maternally transmitted nonsyndromic hearing loss were collected. The proband and family members underwent clinical, genetic, and molecular evaluations, such as audiological examinations, mutational analysis of mitochondrial genome and mutational analysis of GJB2 gene. RESULTS: Six people of this pedigree suffered from hearing loss, including four matrilineal members, and others did not have significant clinical abnormalities. Sequence analysis of the complete mitochondrial genome in the proband showed that there were 28 mtDNA polymorphisms belonging to East -Asian haplogroup A4.In addition to the A7551G homogeneity mutation, there were no other functionally significant variants found in this family. The A7551G mutation located immediately at the three prime end to the anticodon, corresponding with the conventional position 37 of tRNA(Asp), and its' CI value was 100% compared with other 15 primate species. The A7551G mutation was absent in other Chinese controls. The mutations on GJB2 were detected by direct sequence analysis,GJB2 235delC and 299delAT which was associated with hearing loss were found in the genomic DNA of the proband and some matrilineal members. Clinical evaluation showed a variable phenotype of severity, age-at-onset and audiometric configuration of hearing loss in the matrilineal relatives in these families. CONCLUSIONS: The A7551G mutation may modify the secondary structure of the tRNA, and affect the stabilization of tRNA(Asp), produce non-normal functional tRNA(Asp) ultimately. And it may cause the phenotypic manifestation of the deafness that associated with A7551G mutation. Therefore, the mitochondrial tRNA(Asp) A7551G mutation may be a new mitochondrial mutation for hearing loss.

[DNA damage, Bcl-2, Bax expression and ultrastructure change in spermatogenic cell of mice exposed to cadmium].

OBJECTIVE: To study DNA damage, Bcl-2 and Bax expression, and ultrastructure change in spermatogenic cell of mice by cadmium exposure. METHODS: Twenty-four male mice were divided into 4 groups: 3 groups treated with cadmium chloride of 1, 5, 10 micromol x kg(-1) x d(-1) i.p. respectively for 5 days, and one normal saline control group. The DNA damage of spermatogenic cell by single-cell gel electrophoresis technology was detected. The expression positive rate of Bcl-2, Bax protein in spermatogenic cell by the immunohistochemical method was assayed, and the ultrastructural change of spermatogenic cell by the transmission electron microscope was observed. RESULTS: DNA damage rates of of spermatogenic cell in 1, 5, 10 micromol/kg cadmium chloride groups were higher than that of normal group (P < 0.001). Bcl-2 protein expression positive rates were lower than that of normal group (P < 0.001). Bax protein positive expression rate in 5 micromol/kg group was higher than those in normal group, and 1, 10 micromol/kg groups. The ultrastructure of karyotis, karyotheca, mitochondria, endoplasmic reticulum in three treated groups had different degree of damage and the degree of ultrastructural change was increasing with rising concentration of cadmium. CONCLUSION: Cadmium exposure will cause the DNA break, Bcl-2 and Bax protein abnormal expression and ultrastructural change in spermatogenic cell.

[The application of dual-color fluorescence in situ hybridization to the diagnosis of Klinefelter syndrome].

The objective of the work is to study the technique of dual-color fluorescence in situ hybridization(D-FISH) and its application value in the diagnosis of sex chromosomal count abnormality Klinefelter syndrome and establish an experimental approach to metaphase chromosome and interphase nucleus FISH technique. Biotin labeled alpha satellite X-chromosome DNA(pBamX7) probe and Digoxigenin labeled Y-chromosome long arm terminal repetitive sequence (pY3.4) probe were hybridized with pre-treated slides of peripheral blood chromosome and interphase nucleus in 19 cases of Klinefelter syndrome specimens. After being washed,the slides were treated with Avidin-FITC,Rhodamine-FITC and Anti-avidin,amplified with an additional layer and counter-stained with DAPI in an antifade solution. The hybridization signals,chromosomal or interphase nucleus settings were observed respectively with WIB, WIG and WU filters under fluorescence microscope Olympus AX-70,and the number of metaphase chromosome and interphase nucleus in the peripheral blood was counted. It was observed under the microscope that the Biotin labeled pBamX7 probe showed 2 green hybridization signals and that the Digoxigenin labeled pY3.4 probe showed 1 red hybridization signal. Chromosome or interphase nucleus counter-stained with DAPI showed blue. The average signal rate of chromosome and interphase nucleus hybridization was 95.89% and 95% respectively,significantly higher than the normal control (2.75%). Karyotype 47,XXY was confirmed,which agrees with the chromosomal findings. One case showed mosaic nuclei. XXY chromosome hybridization signal rate was 92% and XY hybridization signal rate was 6.7%, higher than the normal control rate of 4.17%. FISH is a valuable technique in diagnosing sex chromosomal count abnormality Klinefelter syndrome with the merits of fast speed, high sensitivity, strong signal,low background and multiple color. Therefore, FISH technique can find wide application and potential in prenatal diagnosis.