The localization of proteins encoded by CRYM, KIAA1199, UBA52, COL9A3, and COL9A1, genes highly expressed in the cochlea.

Genes that are highly expressed in the inner ear, as revealed by cDNA microarray analysis, may have a crucial functional role there. Those that are expressed specifically in auditory tissues are likely to be good candidates to screen for genetic alterations in patients with deafness, and several genes have been successfully identified as responsible for hereditary hearing loss. To understand the detailed mechanisms of the hearing loss caused by the mutations in these genes, the present study examined the immunocytochemical localization of the proteins encoded by Crym, KIAA1199 homolog, Uba52, Col9a3, and Col9a1 in the cochlea of rats and mice. Confocal microscopic immunocytochemistry was performed on cryostat sections. Ultrastructurally, postembedding immunogold cytochemistry was applied using Lowicryl sections. Crym protein was predominantly distributed in the fibrocytes in the spiral ligament, as well as the stria vascularis in rats. KIAA1199 protein homolog was localized in various supporting cells, including inner phalangeal, border, inner and outer pillar, and Deiters' cells. Uba52 protein was restrictedly localized within the surface of the marginal cells of the stria vascularis. Collagen type IX was found within the tectorial membrane as well as fibrocytes in the spiral ligament. The present results showed cell-specific localization of the encoded proteins of these highly expressed genes, indicating that the coordinated actions of various molecules distributed in different parts of the cochlea are essential for maintenance of auditory processing in the cochlea.

Distribution and frequencies of CDH23 mutations in Japanese patients with non-syndromic hearing loss.

Mutations in the CDH23 gene are known to be responsible for both Usher syndrome type ID (USH1D) and non-syndromic hearing loss (DFNB12), and the molecular confirmation of the CDH23 gene has become important in the diagnosis of these conditions. The present study was performed to find whether the CDH23 mutations are also responsible for non-syndromic hearing loss in patients in the Japanese population. A total of 51 sequence variants were found in 64 Japanese probands with non-syndromic sensorineural hearing impairment from autosomal recessive families. Among them, at least four missense mutations in six patients from five families were confirmed to be responsible for deafness by segregation study. All mutations detected were missense mutations, corroborating the previous reports regarding DFNB12. The present data confirmed that CDH23 mutations are frequently found and significantly responsible in Japanese. Interestingly, the CDH23 mutation spectrum in Japanese is very different from that found in Caucasians. This Japanese spectrum may be representative of those in Eastern Asian populations and its elucidation is expected to facilitate the molecular diagnosis of DFNB12 and USH1D.

Association of erythrocyte aldose reductase activity with diabetic complications in type 1 diabetes mellitus.

Erythrocyte aldose reductase was isolated and its activity measured in 72 Type 1 (insulin dependent) diabetic patients and 21 age and sex matched non-diabetic subjects. The diabetic patients were categorized into two groups in terms of presence (n = 29) or absence (n = 43) of severe diabetic complications. Age, sex, duration of diabetes and HbA1c levels were matched between the diabetic groups. Erythrocyte aldose reductase (mean +/- SEM) was increased in patients with Type 1 diabetes compared to the non-diabetic subjects (7.22 +/- 0.24 vs 5.66 +/- 0.19 Ul-erythrocytes-1, < 0.0001). There was a four-fold variation in its activity among the diabetic patients (3.38-12.23 Ul-erythrocytes-1). The enzyme activity was significantly higher in patients with complications than those without (8.17 +/- 0.39 vs 6.58 +/- 0.26 Ul-erythrocytes-1, p < 0.002). When the patients were stratified by duration of the disease, the enzyme activity was highest in patients who had developed complications with a duration of less than 20 years and lowest in those without complications for 20 years or longer (8.54 +/- 0.48 vs 6.46 +/- p +/- 0.33 Ul-erythrocytes-1, p < 0.002). Patients who had an aldose reductase activity greater than the mean +/- 2SD of that seen in non-diabetic controls were four times more likely to have diabetic complications than those whose enzyme activity fell within 2SD of non-diabetic individuals (p < 0.0005).(ABSTRACT TRUNCATED AT 250 WORDS)

Crucial role of aldose reductase activity and plasma glucose level in sorbitol accumulation in erythrocytes from diabetic patients.

Increased sorbitol levels have been demonstrated in tissues of diabetic patients. Although tissue sorbitol levels correlate with plasma glucose levels, a large variability in sorbitol levels has been observed among diabetic patients with similar plasma glucose levels. This variability in tissue sorbitol levels may be due to differences in the activity of aldose reductase, the enzyme that converts glucose to sorbitol. In this study, we isolated aldose reductase from erythrocytes of 31 diabetic patients and 6 nondiabetic control subjects, measured its activity, and compared it to simultaneously measured erythrocyte sorbitol levels. The activity of erythrocyte aldose reductase was increased in diabetic patients compared with control subjects (28.1 +/- 1.4 vs. 22.4 +/- 1.7 nmol.min-1.g-1 Hb, P less than 0.05), but there was an approximately threefold variation in aldose reductase activity among diabetic patients. Erythrocyte aldose reductase activity and fasting plasma glucose levels significantly correlated with the erythrocyte sorbitol level in all individuals (r = 0.48, P less than 0.005 and r = 0.63, P less than 0.005, respectively). The sorbitol level was higher in patients with high aldose reductase activity than in those who had low enzyme activity for any given level of glycemia. The sorbitol production rate calculated from Km and Vmax values showed a better correlation with the erythrocyte sorbitol level (r = 0.80, P less than 0.005), and there was also a good correlation between the erythrocyte sorbitol level and the product of aldose reductase activity by plasma glucose level (r = 0.70, P less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)