Aurora controls sister kinetochore mono-orientation and homolog bi-orientation in meiosis-I

Aurora-B kinases are important regulators of mitotic chromosome segregation, where they are required for the faithful bi-orientation of sister chromatids. In contrast to mitosis, sister chromatids have to be oriented toward the same spindle pole in meiosis-I, while homologous chromosomes are bi-oriented. We find that the fission yeast Aurora kinase Ark1 is required for the faithful bi-orientation of sister chromatids in mitosis and of homologous chromosomes in meiosis-I. Unexpectedly, Ark1 is also necessary for the faithful mono-orientation of sister chromatids in meiosis-I, even though the canonical mono-orientation pathway, which depends on Moa1 and Rec8, seems intact. Our data suggest that Ark1 prevents unified sister kinetochores during metaphase-I from merotelic attachment to both spindle poles and thus from being torn apart during anaphase-I, revealing a novel mechanism promoting monopolar attachment. Furthermore, our results provide an explanation for the previously enigmatic observation that fission yeast Shugoshin Sgo2, which assists in loading Aurora to centromeres, and its regulator Bub1 are required for the mono-orientation of sister chromatids in meiosis-I.     

Actin-related protein Arp4 functions in kinetochore assembly

The actin-related proteins (Arps) comprise a conserved protein family. Arp4p is found in large multisubunits of the INO80 and SWR1 chromatin remodeling complexes and in the NuA4 histone acetyltransferase complex. Here we show that arp4 (arp4S23A/D159A) temperature-sensitive cells are defective in G2/M phase function. arp4 mutants are sensitive to the microtubule depolymerizing agent benomyl and arrest at G2/M phase at restrictive temperature. Arp4p is associated with centromeric and telomeric regions throughout cell cycle. Ino80p, Esa1p and Swr1p, components of the INO80, NuA4 and SWR1 complexes, respectively, also associate with centromeres. The association of many kinetochore components including Cse4p, a component of the centromere nucleosome, Mtw1p and Ctf3p is partially impaired in arp4 cells, suggesting that the G2/M arrest of arp4 mutant cells is due to a defect in formation of the chromosomal segregation apparatus.     

On the carapacial ridge in turtle embryos: its developmental origin, function and the chelonian body plan

The chelonian carapace is composed of dorsolaterally expanded ribs; an evolutionary change in the rib-patterning program is assumed to be related to this novelty. Turtle embryos exhibit a longitudinal ridge called the carapacial ridge (CR) on the flank, and its histological resemblance to the apical ectodermal ridge of the limb bud implies its inductive activity in the unique patterning of the ribs. We studied the Chinese soft-shelled turtle, Pelodiscus sinensis, and confirmed by labeling with a lipophilic dye, DiI, that the CR contains the somite-derived dermis and that it is a unique structure among amniotes. Using electroporation of a dominant-negative form of LEF-1, the CR-specific gene, we showed that CR-specific genes function in the growth and maintenance of the CR. Microcauterization or implantation of the CR did not change the dorsoventral pattern of the ribs, and only their fan-shaped pattern was arrested by CR removal. We conclude that the CR is a true embryonic novelty among amniotes and, because of the specific expression of regulatory genes, it functions in the marginal growth of the carapacial primordium, thereby inducing the fan-shaped arrangement of the ribs.     

Alterations in mRNA Expression of Myelin Proteins in the Sciatic Nerves and Brains of Streptozotocin-induced Diabetic Rats

Diabetic neuropathy is the most common complication of diabetes. We examined the levels and the mRNA expression of myelin proteins in the sciatic nerves and the brains of streptozotocin-induced diabetic rats. The diabetic rats exhibited a decrease in body weight, elevation of the blood glucose level and a decrease in motor nerve conduction velocity at 2 weeks after streptozotocin injection. In the sciatic nerves of diabetic rats, the level of P0 protein and its mRNA expression were markedly reduced at 20 weeks after the injection. In the brains, the levels of proteolipid protein and myelin-associated glycoprotein and their mRNA expression were selectively decreased at 20 weeks after the injection. This affected expression of myelin proteins was found even when no histological abnormalities were detectable. Considering the functional significance of myelin proteins, this impairment of protein expression is possibly involved in the pathogenesis of diabetic neuropathy, including that in brain disorders.     

A Small-Scale Field Trial of Pyriproxyfen-Impregnated Bed Nets against Pyrethroid-Resistant Anopheles gambiae s.s. in Western Kenya

Pyrethroid resistance is becoming a major problem for vector control programs, because at present, there are few suitable chemical substitutes for pyrethroids, as when used on bed nets the insecticide must have low mammalian toxicity as well as high activity to mosquitoes. Pyriproxyfen (PPF) is one of the most active chemicals among the juvenile hormone mimic (JHM) group. Sterilizing mosquitoes by using PPF could be a potential control measure for pyrethroid-resistant malaria vectors. We investigated the sterilizing effects of two types of PPF-impregnated bed nets – a 1% PPF-impregnated net and a 1% PPF +2% permethrin-impregnated net (Olyset Duo) – to pyrethroid-resistant wild population of Anopheles gambiae s.s. in western Kenya. High mortality of blood-fed mosquitos was observed 3 days post-collection, in the houses where PPF-impregnated nets were used, indicating the effect of PPF on the longevity of mosquitos that came in contact with the net. Reduction in the number of ovipositing females, number of eggs, and number of progeny per female were also observed in the houses in which both Olyset Duo and PPF-impregnated nets were used. This is the first field study showing the high sterilizing efficacy of PPF against wild pyrethroid-resistant An. gambiae s.s. population. In addition, we recognized the necessity of combined use of permethrin with PPF, in order to reduce the risk of mosquito bites and provide a level of personal protection. Further studies on wild pyrethroid-resistant mosquito populations such as An. arabiensis and An. funestus s.s. would provide more information on the practical use of the PPF-impregnated bed nets.     

Identification of a Novel Hypocholesterolemic Protein,Major Royal Jelly Protein 1, Derived from Royal Jelly

Royal jelly (RJ) intake lowers serum cholesterol levels in animals and humans, but the active component in RJ that lowers serum cholesterol level and its molecular mechanism are unclear. In this study, we set out to identify the bile acid-binding protein contained in RJ, because dietary bile acid-binding proteins including soybean protein and its peptide are effective in ameliorating hypercholesterolemia. Using a cholic acid-conjugated column, we separated some bile acid-binding proteins from RJ and identified the major RJ protein 1 (MRJP1), MRJP2, and MRJP3 as novel bile acid-binding proteins from RJ, based on matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Purified MRJP1, which is the most abundant protein of the bile acid-binding proteins in RJ, exhibited taurocholate-binding activity in vitro. The micellar solubility of cholesterol was significantly decreased in the presence of MRJP1 compared with casein in vitro. Liver bile acids levels were significantly increased, and cholesterol 7α-hydroxylase (CYP7A1) mRNA and protein tended to increase by MRJP1 feeding compared with the control. CYP7A1 mRNA and protein levels were significantly increased by MRJP1 tryptic hydrolysate treatment compared with that of casein tryptic hydrolysate in hepatocytes. MRJP1 hypocholesterolemic effect has been investigated in rats. The cholesterol-lowering action induced by MRJP1 occurs because MRJP1 interacts with bile acids induces a significant increase in fecal bile acids excretion and a tendency to increase in fecal cholesterol excretion and also enhances the hepatic cholesterol catabolism. We have identified, for the first time, a novel hypocholesterolemic protein, MRJP1, in RJ. Interestingly, MRJP1 exhibits greater hypocholesterolemic activity than the medicine β-sitosterol in rats.     

Co-occurrence of Point Mutations in the Voltage-Gated Sodium Channel of Pyrethroid-Resistant Aedes aegypti Populations in Myanmar

Background

Single amino acid substitutions in the voltage-gated sodium channel associated with pyrethroid resistance constitute one of the main causative factors of knockdown resistance in insects. The kdr gene has been observed in several mosquito species; however, point mutations in the para gene of Aedes aegypti populations in Myanmar have not been fully characterized. The aim of the present study was to determine the types and frequencies of mutations in the para gene of Aedes aegypti collected from used tires in Yangon City, Myanmar.

Methodology/Principal Findings

We determined high pyrethroid resistance in Aedes aegypti larvae at all collection sites in Yangon City, by using a simplified knockdown bioassay. We showed that V1016G and S989P mutations were widely distributed, with high frequencies (84.4% and 78.8%, respectively). By contrast, we were unable to detect I1011M (or I1011V) or L1014F mutations. F1534C mutations were also widely distributed, but with a lower frequency than the V1016G mutation (21.2%). High percentage of co-occurrence of the homozygous V1016G/S989P mutations was detected (65.7%). Additionally, co-occurrence of homozygous V1016G/F1534C mutations (2.9%) and homozygous V1016G/F1534C/S989P mutations (0.98%) were detected in the present study.

Conclusions/Significance

Pyrethroid insecticides were first used for malaria control in 1992, and have since been constantly used in Myanmar. This intensive use may explain the strong selection pressure toward Aedes aegypti, because this mosquito is generally a domestic and endophagic species with a preference for indoor breeding. Extensive use of DDT for malaria control before the use of this chemical was banned may also explain the development of pyrethroid resistance in Aedes aegypti.