Gene expression profiles of a mouse congenic strain carrying an obesity susceptibility QTL under obesigenic diets

Genetic factors are strongly involved in the development of obesity, likely through the interactions of susceptibility genes with obesigenic environments, such as high-fat, high-sucrose (HFS) diets. Previously, we have established a mouse congenic strain on C57BL/6 J background, carrying an obesity quantitative trait locus (QTL), tabw2, derived from obese diabetic TALLYHO/JngJ mice. The tabw2 congenic mice exhibit increased adiposity and hyperleptinemia, which becomes exacerbated upon feeding HFS diets. In this study, we conducted genome-wide gene expression profiling to evaluate differentially expressed genes between tabw2 and control mice fed HFS diets, which may lead to identification of candidate genes as well as insights into the mechanisms underlying obesity mediated by tabw2. Both tabw2 congenic mice and control mice were fed HFS diets for 10 weeks beginning at 4 weeks of age, and total RNA was isolated from liver and adipose tissue. Whole-genome microarray analysis was performed and verified by real-time quantitative RT–PCR. At False Discovery Rate adjusted P < 0.05, 1026 genes were up-regulated and 308 down-regulated in liver, whereas 393 were up-regulated and 187 down-regulated in adipose tissue in tabw2 congenic mice compared to controls. Within the tabw2 QTL interval, 70 genes exhibited differential expression in either liver or adipose tissue. A comprehensive pathway analysis revealed a number of biological pathways that may be perturbed in the diet-induced obesity mediated by tabw2.     

Study protocol to investigate the effects of testosterone therapy as an adjunct to exercise rehabilitation in hypogonadal males with chronic heart failure

Background

Most studies on risk factors for development of coronary heart disease (CHD) have been based on the clinical outcome of CHD. Our aim was to identify factors that could predict the development of ECG markers of CHD, such as abnormal Q/QS patterns, ST segment depression and T wave abnormalities, in 70-year-old men, irrespective of clinical outcome.

Methods

Predictors for development of different ECG abnormalities were identified in a population-based study using stepwise logistic regression. Anthropometrical and metabolic factors, ECG abnormalities and vital signs from a health survey of men at age 50 were related to ECG abnormalities identified in the same cohort 20 years later.

Results

At the age of 70, 9% had developed a major abnormal Q/QS pattern, but 63% of these subjects had not been previously hospitalized due to MI, while 57% with symptomatic MI between age 50 and 70 had no major Q/QS pattern at age 70. T wave abnormalities (Odds ratio 3.11, 95% CI 1.18–8.17), high lipoprotein (a) levels, high body mass index (BMI) and smoking were identified as significant independent predictors for the development of abnormal major Q/QS patterns. T wave abnormalities and high fasting glucose levels were significant independent predictors for the development of ST segment depression without abnormal Q/QS pattern.

Conclusion

T wave abnormalities on resting ECG should be given special attention and correlated with clinical information. Risk factors for major Q/QS patterns need not be the same as traditional risk factors for clinically recognized CHD. High lipoprotein (a) levels may be a stronger risk factor for silent myocardial infarction (MI) compared to clinically recognized MI.     

Regulation of early events in integrin signaling by protein tyrosine phosphatase SHP-2

The nontransmembrane protein tyrosine phosphatase SHP-2 plays a critical role in growth factor and cytokine signaling pathways. Previous studies revealed that a fraction of SHP-2 moves to focal contacts upon integrin engagement and that SHP-2 binds to SHP substrate 1 (SHPS-1)/SIRP-1alpha, a transmembrane glycoprotein with adhesion molecule characteristics (Y. Fujioka et al., Mol. Cell. Biol. 16:6887-6899, 1996; M. Tsuda et al., J. Biol. Chem. 273:13223-13229). Therefore, we asked whether SHP2-SHPS-1 complexes participate in integrin signaling. SHPS-1 tyrosyl phosphorylation increased upon plating of murine fibroblasts onto specific extracellular matrices. Both in vitro and in vivo studies indicate that SHPS-1 tyrosyl phosphorylation is catalyzed by Src family protein tyrosine kinases (PTKs). Overexpression of SHPS-1 in 293 cells potentiated integrin-induced mitogen-activated protein kinase (MAPK) activation, and potentiation required functional SHP-2. To further explore the role of SHP-2 in integrin signaling, we analyzed the responses of SHP-2 exon 3(-/-) and wild-type cell lines to being plated on fibronectin. Integrin-induced activation of Src family PTKs, tyrosyl phosphorylation of several focal adhesion proteins, MAPK activation, and the ability to spread on fibronectin were defective in SHP-2 mutant fibroblasts but were restored upon SHP-2 expression. Our data suggest a positive-feedback model in which, upon integrin engagement, basal levels of c-Src activity catalyze the tyrosyl phosphorylation of SHPS-1, thereby recruiting SHP-2 to the plasma membrane, where, perhaps by further activating Src PTKs, SHP-2 transduces positive signals for downstream events such as MAPK activation and cell shape changes.     

Relating foliar dehydration tolerance of mycorrhizal Phaseolus vulgaris to soil and root colonization by hyphae

Mycorrhizal symbiosis can modify plant response to drying soil, but little is known about the relative contribution of soil vs. root hyphal colonization to drought resistance of mycorrhizal plants. Foliar dehydration tolerance, characterized as leaf and soil water potential at the end of a lethal drying episode, was measured in bean plants (Phaseolus vulgaris) colonized by Glomus intraradices or by a mix of arbuscular mycorrhizal fungi collected from a semi-arid grassland. Path analysis modeling was used to evaluate how colonization rates and other variables affected these lethal values. Of several plant and soil characteristics tested, variation in dehydration tolerance was best explained by soil hyphal density. Soil hyphal colonization had larger direct and total effects on both lethal leaf water potential and soil water potential than did root hyphal colonization, root density, soil aggregation, soil glomalin concentration, leaf phosphorus concentration or leaf osmotic potential. Plants colonized by the semi-arid mix of mycorrhizal fungi had lower lethal leaf water potential and soil water potential than plants colonized by G. intraradices. Our findings support the assertion that external, soil hyphae may play an important role in mycorrhizal influence on the water relations of host plants.     

Etoposide exposure during male mouse pachytene has complex effects on crossing-over and causes nondisjunction

In experiments involving different germ-cell stages, we had previously found meiotic prophase of the male mouse to be vulnerable to the induction of several types of genetic damage by the topoisomerase-II inhibitor etoposide. The present study of etoposide effects involved two end points of meiotic events known to occur in primary spermatocytes--chromosomal crossing-over and segregation. By following assortment of 13 microsatellite markers in two chromosomes (Ch 7 and Ch 15) it was shown that etoposide significantly affected crossing-over, but did not do so in a uniform fashion. Treatment generally changed the pattern for each chromosome, leading to local decreases in recombination, a distal shift in locations of crossing-over, and an overall decrease in double crossovers; at least some of these results might be interpreted as evidence for increased interference. Two methods were used to explore etoposide effects on chromosome segregation: a genetic experiment capable of detecting sex-chromosome nondisjunction in living progeny; and the use of FISH (fluorescence in situ hybridization) technology to score numbers of Chromosomes X, Y, and 8 in spermatozoa. Taken together these two approaches indicated that etoposide exposure of pachytene spermatocytes induces malsegregation, and that the findings of the genetic experiment probably yielded a marked underestimate of nondisjunction. As indicated by certain segregants, at least part of the etoposide effect could be due to disrupted pairing of achiasmatic homologs, followed by precocious sister-centromere separation. It has been shown for several organisms that absent or reduced levels of recombination, as well as suboptimally positioned recombination events, may be associated with abnormal segregation. Etoposide is the only chemical tested to date for which living progeny indicates an effect on both male meiotic crossing-over and chromosome segregation. Whether, however, etoposide-induced changes in recombination patterns are direct causes of the observed malsegregation requires additional investigation.     

Predisposition locus for major depression at chromosome 12q22-12q23.2

Major depression disorder is a common psychiatric disease with a major economic impact on society. In many cases, no effective treatment is available. The etiology of major depression is complex, but it is clear that the disease is, to a large extent, determined genetically, especially among individuals with a familial history of major depression, presumably through the involvement of multiple predisposition genes in addition to an environmental component. As a first step toward identification of chromosomal loci contributing to genetic predisposition to major depression, we have conducted a genomewide scan by using 628 microsatellite markers on 1,890 individuals from 110 Utah pedigrees with a strong family history of major depression. We identified significant linkage to major depression in males at marker D12S1300 (multipoint heterogeneity LOD score 4.6; P=.00003 after adjustment for multiple testing). With additional markers, the linkage evidence became highly significant, with the multipoint heterogeneity LOD score at marker D12S1706 increasing to 6.1 (P=.0000007 after adjustment for multiple testing). This study confirms the presence of one or more genes involved in psychiatric diseases on the q arm of chromosome 12 and provides strong evidence for the existence of a sex-specific predisposition gene to major depression at 12q22-q23.2.     

KLP-18, a Klp2 kinesin,is required for assembly of acentrosomal meiotic spindles in Caenorhabditis elegans

The proper segregation of chromosomes during meiosis or mitosis requires the assembly of well organized spindles. In many organisms, meiotic spindles lack centrosomes. The formation of such acentrosomal spindles seems to involve first assembly or capture of microtubules (MTs) in a random pattern around the meiotic chromosomes and then parallel bundling and bipolar organization by the action of MT motors and other proteins. Here, we describe the structure, distribution, and function of KLP-18, a Caenorhabditis elegans Klp2 kinesin. Previous reports of Klp2 kinesins agree that it concentrates in spindles, but do not provide a clear view of its function. During prometaphase, metaphase, and anaphase, KLP-18 concentrates toward the poles in both meiotic and mitotic spindles. Depletion of KLP-18 by RNA-mediated interference prevents parallel bundling/bipolar organization of the MTs that accumulate around female meiotic chromosomes. Hence, meiotic chromosome segregation fails, leading to haploid or aneuploid embryos. Subsequent assembly and function of centrosomal mitotic spindles is normal except when aberrant maternal chromatin is present. This suggests that although KLP-18 is critical for organizing chromosome-derived MTs into a parallel bipolar spindle, the order inherent in centrosome-derived astral MT arrays greatly reduces or eliminates the need for KLP-18 organizing activity in mitotic spindles.