Publications

Domoic acid is a rigid analog of the neurotransmitter glutamate and a potent agonist of kainate subtype glutamate receptors. Persistent activation of these receptor subtypes results in rapid excitotoxicity, calcium dependent cell death and neuronal lesions in areas of the brain where kainate pathways are concentrated. To better understand responses to domoic acid induced excitotoxicity, microarrays were used to profile gene expression in mouse brain following domoic acid exposure. Adult female mice were subjected intraperitoneally to domoic acid at the lethal dose 50, killed and dissected at 30, 60 and 240 min post-injection. Total brain RNA from treated mice was compared with time-matched controls on Agilent 22K feature microarrays. Real-time PCR was performed on selected genes. For the 30, 60 and 240 min time points, 3.96%, 3.94% and 4.36% of the genes interrogated were differentially expressed (P-value < or = 0.01), respectively. Rigorous filtering of the data resulted in a set of 56 genes used for trending analysis and K-medians and agglomerative clustering. The earliest genes induced consisted primarily of early response gene families (Jun, Fos, Ier, Egr, growth arrest and DNA damage 45) and the inflammatory response element cyclooxygenase 2. Some later responding genes involved glucocorticoid responses (Gilz, Sgk), cold inducible proteins (Cirbp, Rbm3), Map kinases (Map3k6) and NF-kappaB inhibition. Real-time PCR in male mice from an additional study confirmed the expression of several of these genes across gender. The transcriptional profile induced by domoic acid shared similarity with expression profiles of brain ischemia and other excitotoxins, suggesting a common transcriptional response.

Estrogens exert their effect on the breast through the estrogen receptor. We prospectively investigated breast cancer risk associated with 2 polymorphic sites in the estrogen receptor alpha gene (ESR1). A total of 4,248 Caucasian women from the Study of Osteoporotic Fractures were genotyped for the -401 T/C and -354 A/G polymorphisms in ESR1. Cox proportional hazards models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI) for the associations between genotypes and breast cancer. During a mean follow-up of 12.4 years, 252 (5.9%) women developed breast cancer. The HR (95% CI) for breast cancer were 0.928 (0.708, 1.22) and 0.834 (0.538, 1.29) for the -354 A/G and A/A genotypes, respectively. Interactions with -354 variant were observed for smoking (HR = 1.52 and 1.56 for A/G and A/A smokers, respectively; HR = 0.74 and 0.60 for A/G and A/A non-smokers, respectively; interaction p = 0.03) and walking (HR = 0.75 and 1.15 for A/G and A/A walkers, respectively; HR = 0.18 and 0.49 for A/G and A/A non-walkers, respectively; interaction p = 0.01). There were no differences in the HR for the -401 T/C genotypes. An interaction between parity and carriage of the T allele was found (HR = 0.60 vs. 1.12 for nulliparous vs. parous women; interaction p = 0.03). ESR1 polymorphisms in combination with lifestyle factors may be associated with breast cancer risk in older Caucasian women.

RATIONALE

As the smallest free-living bacteria and a frequent cause of respiratory infections, mycoplasmas are unique pathogens. Mice infected with Mycoplasma pulmonis can develop localized, life-long airway infection accompanied by persistent inflammation and remodeling.

OBJECTIVE

Because mast cells protect mice from acute septic peritonitis and gram-negative pneumonia, we hypothesized that they defend against mycoplasma infection. This study tests this hypothesis using mast cell-deficient mice.

METHODS

Responses to airway infection with M. pulmonis were compared in wild-type and mast cell-deficient Kit(W-sh)/Kit(W-sh) mice and sham-infected control mice.

MEASUREMENTS AND MAIN RESULTS

Endpoints include mortality, body and lymph node weight, mycoplasma antibody titer, and lung mycoplasma burden and histopathology at intervals after infection. The results reveal that infected Kit(W-sh)/Kit(W-sh) mice, compared with other groups, lose more weight and are more likely to die. Live mycoplasma burden is greater in Kit(W-sh)/Kit(W-sh) than in wild-type mice at early time points. Four days after infection, the difference is 162-fold. Titers of mycoplasma-specific IgM and IgA appear earlier and rise higher in Kit(W-sh)/Kit(W-sh) mice, but antibody responses to heat-killed mycoplasma are not different compared with wild-type mice. Infected Kit(W-sh)/Kit(W-sh) mice develop larger bronchial lymph nodes and progressive pneumonia and airway occlusion with neutrophil-rich exudates, accompanied by angiogenesis and lymphangiogenesis. In wild-type mice, pneumonia and exudates are less severe, quicker to resolve, and are not associated with increased angiogenesis.

CONCLUSIONS

These findings suggest that mast cells are important for innate immune containment of and recovery from respiratory mycoplasma infection.

Population stratification may confound the results of genetic association studies among unrelated individuals from admixed populations. Several methods have been proposed to estimate the ancestral information in admixed populations and used to adjust the population stratification in genetic association tests. We evaluate the performances of three different methods: maximum likelihood estimation, ADMIXMAP and Structure through various simulated data sets and real data from Latino subjects participating in a genetic study of asthma. All three methods provide similar information on the accuracy of ancestral estimates and control type I error rate at an approximately similar rate. The most important factor in determining accuracy of the ancestry estimate and in minimizing type I error rate is the number of markers used to estimate ancestry. We demonstrate that approximately 100 ancestry informative markers (AIMs) are required to obtain estimates of ancestry that correlate with correlation coefficients more than 0.9 with the true individual ancestral proportions. In addition, after accounting for the ancestry information in association tests, the excess of type I error rate is controlled at the 5% level when 100 markers are used to estimate ancestry. However, since the effect of admixture on the type I error rate worsens with sample size, the accuracy of ancestry estimates also needs to increase to make the appropriate correction. Using data from the Latino subjects, we also apply these methods to an association study between body mass index and 44 AIMs. These simulations are meant to provide some practical guidelines for investigators conducting association studies in admixed populations.