Maternally transmitted non-syndromic deafness was described recently both in pedigrees with susceptibility to aminoglycoside ototoxicity and in a large Arab-Israeli pedigree. Because of the known action of aminoglycosides on bacterial ribosomes, we analysed the sequence of the mitochondrial rRNA genes of three unrelated patients with familial aminoglycoside-induced deafness. We also sequenced the complete mitochondrial genome of the Arab-Israeli pedigree. All four families shared a nucleotide 1555 A to G substitution in the 12S rRNA gene, a site implicated in aminoglycoside activity. Our study offers the first description of a mitochondrial rRNA mutation leading to disease, the first cases of non-syndromic deafness caused by a mitochondrial DNA mutation and the first molecular genetic study of antibiotic-induced ototoxicity.

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Introduction: Oxidative stress may contribute to the pathogenesis of periodontitis. However, the detailed molecular mechanism remains unclear. Both 8-hydroxydeoxyguanosine (8-OHdG) and mitochondrial DNA (mtDNA) deletion have been reported as early oxidative DNA damage markers. In this study, 8-OHdG levels in saliva and mtDNA deletions in gingival tissue of patients with chronic periodontitis (CP) were evaluated. Materials and Methods: Gingival tissue and whole saliva samples were collected from 32 patients with CP and 32 healthy control subjects. To determine the clinical condition of each subject, the plaque index, gingival index, clinical attachment level (CAL), and probing depth (PD) were measured. Using the ELISA and polymerase chain reaction methods, the salivary 8-OHdG levels and the 7.4-kbp and 5-kbp mtDNA deletions were examined. Results: The 5-kbp mtDNA deletion was detected in 20 of the 32 periodontitis patients (62.5%), but was not detected in the healthy controls. The mean value of 8-OHdG in the saliva of the periodontitis patients with deleted mtDNA was significantly higher than in the patients with non-deleted mtDNA (p<0.01). Also, significant correlation was found between the occurrence of the 5-kbp mtDNA deletion and salivary 8-OHdG levels (p<0.01). Similar correlations were detected between salivary 8-OHdG levels and age, PD, and CAL (p<0.01, p<0.05). Conclusion: Increased oxidative stress may lead to premature oxidative DNA damage in the gingival tissue of periodontitis patients and the salivary 8-OHdG level may signify premature oxidative mtDNA damage in diseased gingival tissue.

Two sisters presented with partial alopecia, primary hypergonadotropic hypogonadism and Mullerian hypoplasia associated with mild mental retardation, microcephaly, flat occiput, sparse eyebrows, absence of breast tissue, absent ovaries, mild-moderate dorsal kyphosis, thin upper lip and unilateral sensorioneural deafness in one of them. They were the product of a Turkish consanguineous marriage. The clinical course for our patients is similar to two families reported by Al-Awadi et al. [Al-Awadi et al. (1985) Am J Med Genet 22:619-622] and Megarbane et al. [Megarbane et al. (2003) Am J Med Genet Part A 119A:214-217]. This report supports the literature by proposing an autosomal recessive syndrome which was firstly reported by Al-Awadi et al. [Al-Awadi et al. (1985) Am J Med Genet 22:619-622]. This condition may be due to a founder mutation.

Background: Overproduction of reactive oxygen species (ROS) causes increased oxidative stress in gingival tissue. It has been generally accepted that increased oxidative stress might contribute to additional damage of lipids, proteins, and DNA molecules. The mitochondrial DNA (mtDNA) mutation is a superb biomarker of oxidative damage. The aim of the present study was to investigate the mtDNA deletions in the gingival tissue of patients with periodontitis and to explain the correlations between mtDNA deletion in gingival tissue and clinical parameters of periodontitis and age. Methods: Gingival tissue and blood samples were collected from 30 patients with chronic periodontitis (CP group) and 30 healthy control subjects (H group). To determine the clinical condition of each subject, the plaque index, gingival index, clinical attachment level, and probing depth were measured. Using the polymerase chain reaction (PCR) method, we examined the 7.4‐ and 5‐kbp mtDNA deletions in tissue and blood samples. Three different pairs of PCR primers were used in this study. Results: In this study, we did not detect any deletions in blood DNA samples in either the CP or H group. Also, the 7.4‐kbp mtDNA deletion was not detected in gingival tissues of subjects. However, the 5‐kbp mtDNA deletion was detected in 24 of the 30 subjects (80%) in the CP group and was not detected in the H group (0%). Significant correlations were found between the occurrence of the 5‐kbp mtDNA deletion and all clinical parameters (P <0.01). A similar correlation was found between the occurrence of the 5‐kbp mtDNA deletion and age (P <0.05). Conclusions: The overproduction of ROS by activated polymorphonuclear leukocytes in chronic inflammation may lead to premature oxidative damage of the mtDNA. In this study, the occurrence of the 5‐kbp mtDNA deletion in 24 periodontitis subjects may be evidence of premature oxidative DNA damage.