Deformation of the Outer Hair Cells and the Accumulation of Caveolin-2 in Connexin 26 Deficient Mice

BackgroundMutations in GJB2, which encodes connexin 26 (Cx26), a cochlear gap junction protein, represent a major cause of pre-lingual, non-syndromic deafness. The degeneration of the organ of Corti observed in Cx26 mutant—associated deafness is thought to be a secondary pathology of hearing loss. Here we focused on abnormal development of the organ of Corti followed by degeneration including outer hair cell (OHC) loss.MethodsWe investigated the crucial factors involved in late-onset degeneration and loss of OHC by ultrastructural observation, immunohistochemistry and protein analysis in our Cx26-deficient mice (Cx26^f/fP0Cre).ResultsIn ultrastructural observations of Cx26^f/fP0Cre mice, OHCs changed shape irregularly, and several folds or notches were observed in the plasma membrane. Furthermore, the mutant OHCs had a flat surface compared with the characteristic wavy surface structure of OHCs of normal mice. Protein analysis revealed an increased protein level of caveolin-2 (CAV2) in Cx26^f/fP0Cre mouse cochlea. In immunohistochemistry, a remarkable accumulation of CAV2 was observed in Cx26^f/fP0Cre mice. In particular, this accumulation of CAV2 was mainly observed around OHCs, and furthermore this accumulation was observed around the shrunken site of OHCs with an abnormal hourglass-like shape.ConclusionsThe deformation of OHCs and the accumulation of CAV2 in the organ of Corti may play a crucial role in the progression of, or secondary OHC loss in, GJB2-associated deafness. Investigation of these molecular pathways, including those involving CAV2, may contribute to the elucidation of a new pathogenic mechanism of GJB2-associated deafness and identify effective targets for new therapies.     

Unraveling the complex maternal history of Southern African Khoisan populations

The Khoisan populations of southern Africa are known to harbor some of the deepest‐rooting lineages of human mtDNA; however, their relationships are as yet poorly understood. Here, we report the results of analyses of complete mtDNA genome sequences from nearly 700 individuals representing 26 populations of southern Africa who speak diverse Khoisan and Bantu languages. Our data reveal a multilayered history of the indigenous populations of southern Africa, who are likely to be the result of admixture of different genetic substrates, such as resident forager populations and pre‐Bantu pastoralists from East Africa. We find high levels of genetic differentiation of the Khoisan populations, which can be explained by the effect of drift together with a partial uxorilocal/multilocal residence pattern. Furthermore, there is evidence of extensive contact, not only between geographically proximate groups, but also across wider areas. The results of this contact, which may have played a role in the diffusion of common cultural and linguistic features, are especially evident in the Khoisan populations of the central Kalahari. Am J Phys Anthropol 153:435–448, 2014. © 2013 Wiley Periodicals, Inc.     

NMR analyses on the interactions of the yeast Tim50 C-terminal region with the presequence and Tim50 core domain

The mitochondrial targeting signal in the presequence of mitochondrial precursor proteins is recognized by Tom20 and subsequently by Tim50 in mitochondria. Yeast Tim50 contains two presequence binding sites in the conserved core domain and in the fungi-specific C-terminal presequence binding domain (PBD). We report the NMR analyses on interactions of a shorter variant of PBD (sPBD), a shorter variant of PBD, with presequences. The presequence is recognized by sPBD in a similar manner to Tom20. sPBD can also bind to the core domain of Tim50 through the presequence binding region, which could promote transfer of the presequence from sPBD to the core domain in Tim50.     

Ortho-azo substituted phenylboronic acids for colorimetric sugar sensors

The phenylboronic acids substituted with an azo group on the ortho-position show a significant change in UV-vis spectra upon sugar binding. A new mechanism for the spectral change of the dyes is proposed based on the formation and cleavage of B-N dative bond between boronic acid group and azo group.     

Sex-associated difference in estrogen receptor β expression in N-methyl-N'-nitro-N-nitrosoguanidine-induced gastric cancers in rats

Epidemiologic studies indicate that the incidence of gastric cancer is higher in males than in females. Although the mechanisms mediating this difference are unclear, a role for estrogens has been proposed. We used Western blotting to evaluate the role of estrogen receptor (ER) subtypes ERα and ERβ and proliferating cell nuclear antigen (PCNA) in N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced gastric carcinogenesis in Wistar rats; ERα and ERβ mRNA levels also were analyzed by quantitative real-time RT-PCR analysis. The incidence of gastric cancer was significantly higher in male than female rats. In both sexes, ERα expression was similar in MNNG-treated cancerous and noncancerous tissues and normal gastric tissue. However, ERβ expression in MNNG-treated cancerous and noncancerous tissues was significantly lower in male rats and higher in female rats than that in normal gastric tissue; MNNG-induced cancerous tissue showed the highest ERβ expression. PCNA expression in MNNG-treated cancerous tissues was higher than that in noncancerous tissues, and was higher in male rats than female rats. Western blotting results were consistent with the mRNA changes determined by quantitative real-time RT-PCR. The present study provides evidence of a sex-associated difference in ERβ and PCNA expression in MNNG-induced gastric cancers in Wistar rats.     

Electrochemical studies of danthron and the DNA-danthron interaction

Danthron is an important natural occurring component in laxative drugs. In this paper, electrochemical investigation of danthron and its interaction with DNA is reported. Via the electrochemical approach assisted by ultraviolet-visible (UV-Vis) spectroscopy, we have proved that danthron intercalates into DNA strands forming some nonelectroactive complexes, which results in the decrease of redox peak currents of danthron. In addition, the decrease of the peak currents is proportional to the concentration of DNA. The difference between the interaction of danthron with double-stranded DNA (dsDNA) and with single-stranded DNA (ssDNA) has also been studied. This character implies the potential of danthron to discriminate dsDNA and ssDNA.     

Disintegration of layer-by-layer assemblies composed of 2-iminobiotin-labeled poly(ethyleneimine) and avidin

A layer-by-layer thin film composed of avidin and 2-iminobiotin-labeled poly(ethyleneimine) (ib-PEI) was prepared and their sensitivity to the environmental pH and biotin was studied. The avidin/ib-PEI multilayer assemblies were stable at pH 8-12, whereas the assemblies were decomposed at pH 5-6 due to the low affinity of the protonated iminobiotin residue to avidin. The avidin/ib-PEI assemblies can be disintegrated upon addition of biotin and analogues in the solution as a result of the preferential binding of biotin or analogues to the binding site of avidin. The decomposition rate was arbitrarily controlled by changing the type of stimulant (biotin or analogues) and its concentration. The avidin/ib-PEI assemblies were disintegrated rapidly by the addition of biotin or desthiobiotin, whereas the rate of decomposition was rather slow upon addition of lipoic acid or 2-(4'-hydroxyphenylazo)benzoic acid. The present system may be useful for constructing the stimuli-sensitive devices that can release drug or other functional molecules.     

Crystal structure of the endonuclease domain encoded by the telomere-specific long interspersed nuclear element, TRAS1

The telomere-specific long interspersed nuclear element, TRAS1, encodes an endonuclease domain, TRAS1-EN, which specifically cleaves the telomeric repeat targets (TTAGG)n of insects and (TTAGGG)n of vertebrates. To elucidate the sequence-specific recognition properties of TRAS1-EN, we determined the crystal structure at 2.4-A resolution. TRAS1-EN has a four-layered alpha/beta sandwich structure; its topology is similar to apurinic/apyrimidinic endonucleases, but the beta-hairpin (beta10-beta11) at the edge of the DNA-binding surface makes an extra loop that distinguishes TRAS1-EN from cellular apurinic/apyrimidinic endonucleases. A protein-DNA complex model suggests that the beta10-beta11 hairpin fits into the minor groove, enabling interaction with the telomeric repeats. Mutational studies of TRAS1-EN also indicated that the Asp-130 and beta10-beta11 hairpin structure are involved in specific recognition of telomeric repeats.     

A Novel Transporter of SLC22 Family Specifically Transports Prostaglandins and Co-localizes with 15-Hydroxyprostaglandin Dehydrogenase in Renal Proximal Tubules

We identified a novel prostaglandin (PG)-specific organic anion transporter (OAT) in the OAT group of the SLC22 family. The transporter designated OAT-PG from mouse kidney exhibited Na⁺-independent and saturable transport of PGE₂ when expressed in a proximal tubule cell line (S₂). Unusual for OAT members, OAT-PG showed narrow substrate selectivity and high affinity for a specific subset of PGs, including PGE₂, PGF_2α, and PGD₂. Similar to PGE₂ receptor and PGT, a structurally distinct PG transporter, OAT-PG requires for its substrates an α-carboxyl group, with a double bond between C13 and C14 as well as a (S)-hydroxyl group at C15. Unlike the PGE₂ receptor, however, the hydroxyl group at C11 in a cyclopentane ring is not essential for OAT-PG substrates. Addition of a hydroxyl group at C19 or C20 impairs the interaction with OAT-PG, whereas an ethyl group at C20 enhances the interaction, suggesting the importance of hydrophobicity around the ω-tail tip forming a “hydrophobic core” accompanied by a negative charge, which is essential for substrates of OAT members. OAT-PG-mediated transport is concentrative in nature, although OAT-PG mediates both facilitative and exchange transport. OAT-PG is kidney-specific and localized on the basolateral membrane of proximal tubules where a PG-inactivating enzyme, 15-hydroxyprostaglandin dehydrogenase, is expressed. Because of the fact that 15-keto-PGE₂, the metabolite of PGE₂ produced by 15-hydroxyprostaglandin dehydrogenase, is not a substrate of OAT-PG, the transport-metabolism coupling would make unidirectional PGE₂ transport more efficient. By removing extracellular PGE₂, OAT-PG is proposed to be involved in the local PGE₂ clearance and metabolism for the inactivation of PG signals in the kidney cortex.     

Renal elimination of p-aminohippurate (PAH) in response to three days of biliary obstruction in the rat. The role of OAT1 and OAT3

Pharmacokinetic studies of the drugs administered to subjects with mechanical cholestasis are scarce. The purpose of the present study was to examine the effects of bile duct ligation of 3 days (peak of elevation of serum bile acids and bilirubin) on the systemic and renal PAH clearance and on the expression of cortical renal OAT1 and OAT3 in a rat model. PAH is the prototypical substrate of the renal organic anion transport system. Male Wistar rats underwent a bile duct ligation (BDL rats). Pair-fed sham-operated rats served as controls. BDL rats displayed a significantly lower systemic PAH clearance. Renal studies revealed a reduction in the renal clearance and in the excreted and secreted load of PAH in BDL rats. The OAT1 protein expression in kidney homogenates was not modified, but it decreased in the basolateral membranes from BDL rats. In contrast, OAT3 abundance in both kidney cortex homogenates and in basolateral membranes increased by 3 days after the ligation. Immunocytochemical studies (light microscopic and confocal immunofluorescence microscopic analyses) confirmed the changes in the renal expression of these transport proteins. The present study demonstrates the key role of OAT1 expression in the impaired elimination of PAH after 3 days of obstructive cholestasis.