Maternal X chromosome expression in mouse chorionic ectoderm

An electrophoretic variant of the X-linked enzyme phosphoglycerate kinase (PGK-1) has been used to study regulation of X chromosome expression in the diploid derivatives of the trophectoderm at 8–8.5 days post coitum in the mouse. These derivatives included the chorionic ectoderm and the polar trophoblast. The biochemical analysis suggests that only the maternally derived X chromosome (X^m) is expressed in the diploid trophectoderm derivatives. Cell selection and maternal tissue contamination were ruled out as possible causes of the observed X^m expression. From these and other results, we conclude that all derivatives of the trophectoderm, along with the primitive endoderm, express only X^m, whereas derivatives of the primitive ectoderm show random X chromosome expression.     

犬瘟热病毒XJ株的分离鉴定

应用犬肺原代巨噬细胞,从新疆阿克苏送检的一只病死犬肺脏中分离出1株犬瘟热病毒,并对其进行了形态学、理化学、血清学、动物感染试验、分子生物学鉴定。结果证明所分离的XJ株为1株CDV的强毒株。     

Interaction of hepatitis B virus X protein with damaged DNA-binding protein p127: Structural analysis and identification of antagonists

The hepatitis B virus X protein is a multifunctional protein that is essential for natural infection and has also been implicated in liver cancer development. Previous studies have identified the DDB1 subunit of the damaged-DNA binding complex as a critical partner of X protein in the infection process, X-mediated cytotoxicity and stability of the viral protein. Here, we investigated the structural and functional constraints of X-DDB1 interaction using various mutational analyses. Our data show that the interaction interface of X with DDB1 is confined to a 15-residue epitope. All substitutions responsible for loss of binding mapped to this core-binding domain. In contrast, a marked increase in affinity for DDB1 resulted from substitutions at clustered positions lying close to the DDB1-binding epitope and correlated with loss of apoptotic potential. Selection of mutations in DDB1 that partially rescue the binding defect of an X mutant gave further insight into the contacts established between the two proteins. Importantly, both the core-binding domain of X and the gain-of-affinity X mutants inhibited DDB1-mediated stabilization of wild-type X protein. These X protein derivatives thus provide the basis for the development of therapeutic agents that antagonize X function through competitive inhibition of X-DDB1 interaction.     

Generation of a transgenic mouse model with chondrocyte-specific and tamoxifen-inducible expression of Cre recombinase

Postnatal cartilage development and growth are regulated by key growth factors and signaling molecules. To fully understand the function of these regulators, an inducible and chondrocyte-specific gene deletion system needs to be established to circumvent the perinatal lethality. In this report, we have generated a transgenic mouse model (Col2a1-CreER(T2)) in which expression of the Cre recombinase is driven by the chondrocyte-specific col2a1 promoter in a tamoxifen-inducible manner. To determine the specificity and efficiency of the Cre recombination, we have bred Col2a1-CreER(T2) mice with Rosa26R reporter mice. The X-Gal staining showed that the Cre recombination is specifically achieved in cartilage tissues with tamoxifen-induction. In vitro experiments of chondrocyte cell culture also demonstrate the 4-hydroxy tamoxifen-induced Cre recombination. These results demonstrate that Col2a1-CreER(T2) transgenic mice can be used as a valuable tool for an inducible and chondrocyte-specific gene deletion approach.     

Synergistic effect of conjugated linolenic acid isomers against induced oxidative stress,inflammation and erythrocyte membrane disintegrity in rat model

Background

α-Eleostearic acid and punicic acid, two typical conjugated linolenic acid (CLnA) isomers present in bitter gourd and snake gourd oil respectively, exhibit contrasting cis-trans configuration which made them biologically important.

Methods

Rats were divided into six groups. Group 1 was control and group 2 was treated control. Rats in the groups 3 and 4 were treated with mixture of α-eleostearic acid and punicic acid (1:1) (0.5% and 1.0% respectively) while rats in the groups 5 and 6 were treated with 0.5% of α-eleostearic acid and 0.5% of punicic acid respectively along with sodium arsenite by oral gavage once per day.

Results

Results showed that increase in nitric oxide synthase (NOS) activity, inflammatory markers expression, platelet aggregation, lipid peroxidation, protein oxidation, DNA damage and altered expression of liver X receptor-α (LXR-α) after arsenite treatment were restored with the supplementation of oils containing CLnA isomers. Altered activities of different antioxidant enzymes such as superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and ferric reducing ability of plasma (FRAP) also restored after oil supplementation. Altered morphology and fluidity of erythrocyte membrane studied by atomic force and scanning electron microscopy, after stress induction were significantly improved due to amelioration in cholesterol/phospholipid ratio and fatty acid profile of membrane. Oils treatment also improved morphology of liver and fatty acid composition of hepatic lipid.

Conclusions

Overall two isomers showed synergistic antioxidant and anti-inflammatory effect against induced perturbations and membrane disintegrity.

General significance

Synergistic antioxidant and anti-inflammatory role of these CLnA isomers were established by this study.     

Synaptic pattern of sex complements and sperm head malformation in X-autosome translocation carrier bulls

Testicular activity and semen characteristics of bulls carrying an X-autosome translocation t(Xp +;23q-) revealed all stages of spermatogenesis although their semen consisted of few and, exclusively, of malformed spermatozoa. Chromosome painting on metaphase spreads of their mother and synaptonemal complex analysis on these and normal bulls were carried out to test whether the location and meiotic pairing behaviour of the rearranged segments could have contributed to the sperm head malformation and oligospermia in our X-autosome translocation (X-AT) carrier bulls. Spermatocytes of X-AT carriers displayed the rearranged chromosomes in a univalent-trivalent association, with 23q- always remaining as a univalent and Xp + in synapsis with normal chromosome 23 and the Y chromosome. Chromosome painting studies to test whether the total absence of meiocytes showing a quadrivalent is due to the non-reciprocal nature of this translocation, identified Xp sequence homology with the distal end of 23q- confirming its relocation to the terminal segment of 23q-. Our synaptonemal complex analyses also confirmed that the bovine pseudo-autosomal region (PAR) is at the distal ends of Xq and Yp and further revealed that over 85% of spermatocytes of X-AT carriers (and up to 13% of spermatocytes of normal bulls) sustain a Y-axis break adjacent to the PAR. Although the exact cause of a Y-axis break in bovine spermatocytes is not known at present, we believe that the break and possible loss of Yq in such high proportions of spermatocytes of X-AT carriers could have contributed to the sperm head malformation and oligospermia in our X-AT carrier bulls.     

Insights into the potential function and membrane organization of the TP0435 (Tp17) lipoprotein from Treponema pallidum derived from structural and biophysical analyses

The sexually transmitted disease syphilis is caused by the bacterial spirochete Treponema pallidum. This microorganism is genetically intractable, accounting for the large number of putative and undercharacterized members of the pathogen's proteome. In an effort to ascribe a function(s) to the TP0435 (Tp17) lipoprotein, we engineered a soluble variant of the protein (rTP0435) and determined its crystal structure at a resolution of 2.42 Å. The structure is characterized by an eight‐stranded β‐barrel protein with a shallow “basin” at one end of the barrel and an α‐helix stacked on the opposite end. Furthermore, there is a disulfide‐linked dimer of the protein in the asymmetric unit of the crystals. Solution hydrodynamic experiments established that purified rTP0435 is monomeric, but specifically forms the disulfide‐stabilized dimer observed in the crystal structure. The data herein, when considered with previous work on TP0435, imply plausible roles for the protein in either ligand binding, treponemal membrane architecture, and/or pathogenesis.     

Local selection underlies the geographic distribution of sex-ratio drive in Drosophila neotestacea

"Selfish" genetic elements promote their own transmission to the next generation, often at a cost to the host individual. A sex-ratio (SR) driving X chromosome prevents the maturation of Y-bearing sperm, and as a result is transmitted to 100% of the offspring, all of which are female. Because the spread of a SR chromosome can result in a female-biased population sex ratio, the ecological and evolutionary consequences of harboring this selfish element can be severe. In this study, we show that the prevalence of SR drive in Drosophila neotestacea varies between 0% and 30% among populations, and is common in the south whereas rare in the north. The prevalence of SR is not associated with the presence of suppressors of drive, geographic distance, or genetic distance based on autosomal microsatellite loci. Instead, our results indicate that ecological selection on SR drive varies among populations, as the prevalence of SR is highly correlated with climatic factors, with the severity of winter the best determinant of SR frequency. Thus, ecological and demographic factors may have significant consequences for the short and long term evolutionary dynamics of selfish elements and the manner with which they coevolve with the rest of the genome.     

Role of nuclear receptor corepressor RIP140 in metabolic syndrome

Obesity and its associated complications, which can lead to the development of metabolic syndrome, are a worldwide major public health concern especially in developed countries where they have a very high prevalence. RIP140 is a nuclear coregulator with a pivotal role in controlling lipid and glucose metabolism. Genetically manipulated mice devoid of RIP140 are lean with increased oxygen consumption and are resistant to high-fat diet-induced obesity and hepatic steatosis with improved insulin sensitivity. Moreover, white adipocytes with targeted disruption of RIP140 express genes characteristic of brown fat including CIDEA and UCP1 while skeletal muscles show a shift in fibre type composition enriched in more oxidative fibres. Thus, RIP140 is a potential therapeutic target in metabolic disorders. In this article we will review the role of RIP140 in tissues relevant to the appearance and progression of the metabolic syndrome and discuss how the manipulation of RIP140 levels or activity might represent a therapeutic approach to combat obesity and associated metabolic disorders. This article is part of a Special Issue entitled: Translating nuclear receptors from health to disease.