Altering a Histone H3K4 Methylation Pathway in Glomerular Podocytes Promotes a Chronic Disease Phenotype

Methylation of specific lysine residues in core histone proteins is essential for embryonic development and can impart active and inactive epigenetic marks on chromatin domains. The ubiquitous nuclear protein PTIP is encoded by the Paxip1 gene and is an essential component of a histone H3 lysine 4 (H3K4) methyltransferase complex conserved in metazoans. In order to determine if PTIP and its associated complexes are necessary for maintaining stable gene expression patterns in a terminally differentiated, non-dividing cell, we conditionally deleted PTIP in glomerular podocytes in mice. Renal development and function were not impaired in young mice. However, older animals progressively exhibited proteinuria and podocyte ultra structural defects similar to chronic glomerular disease. Loss of PTIP resulted in subtle changes in gene expression patterns prior to the onset of a renal disease phenotype. Chromatin immunoprecipitation showed a loss of PTIP binding and lower H3K4 methylation at the Ntrk3 (neurotrophic tyrosine kinase receptor, type 3) locus, whose expression was significantly reduced and whose function may be essential for podocyte foot process patterning. These data demonstrate that alterations or mutations in an epigenetic regulatory pathway can alter the phenotypes of differentiated cells and lead to a chronic disease state

Epidemiology of basal-like breast cancer

Risk factors for the newly identified “intrinsic” breast cancer subtypes (luminal A, luminal B, basal-like and human epidermal growth factor receptor 2-positive/estrogen receptor-negative) were determined in the Carolina Breast Cancer Study, a population-based, case–control study of African-American and white women. Immunohistochemical markers were used to subtype 1,424 cases of invasive and in situ breast cancer, and case subtypes were compared to 2,022 controls. Luminal A, the most common subtype, exhibited risk factors typically reported for breast cancer in previous studies, including inverse associations for increased parity and younger age at first full-term pregnancy. Basal-like cases exhibited several associations that were opposite to those observed for luminal A, including increased risk for parity and younger age at first term full-term pregnancy. Longer duration breastfeeding, increasing number of children breastfed, and increasing number of months breastfeeding per child were each associated with reduced risk of basal-like breast cancer, but not luminal A. Women with multiple live births who did not breastfeed and women who used medications to suppress lactation were at increased risk of basal-like, but not luminal A, breast cancer. Elevated waist-hip ratio was associated with increased risk of luminal A in postmenopausal women, and increased risk of basal-like breast cancer in pre- and postmenopausal women. The prevalence of basal-like breast cancer was highest among premenopausal African-American women, who also showed the highest prevalence of basal-like risk factors. Among younger African-American women, we estimate that up to 68% of basal-like breast cancer could be prevented by promoting breastfeeding and reducing abdominal adiposity

BRCT Domain-Containing Protein PTIP Is Essential for Progression through Mitosis

The Pax transactivation domain-interacting protein (PTIP) is a large nuclear protein with multiple BRCT domains that was identified on the basis of its interaction with transcription factors of the Pax and Smad families. To address the function of PTIP during mouse development, we generated a constitutive null allele. Homozygous PTIP mutants are developmentally retarded, disorganized, and embryonic lethal by day 9.5 of embryonic development (E9.5). PTIP mutant cells appear to replicate DNA but show reduced levels of mitosis and widespread cell death by E8.5. DNA damage appears to precede nuclear condensation at E7.5, suggesting a defect in DNA repair. Neither embryonic fibroblast nor embryonic stem cells from PTIP mutants proliferate in culture, suggesting a fundamental defect in cell proliferation. Trophoblast cells from PTIP mutants are more sensitive to DNA-damaging agents. Condensation of chromatin and expression of phospho-histone H3 are also affected in PTIP mutants, and this may underlie the inability of PTIP mutants to progress through mitosis. Given the role of BRCT domain proteins in DNA repair and cell cycle control, we propose that PTIP is an essential element of the cell proliferation machinery, perhaps by functioning in the DNA repair pathways

Elimination of Mycobacterium avium subspecies paratuberculosis from dairy farms: fact or fiction?

ABSTRACT In this key note paper, we discuss whether elimination of Mycobacterium avium subspecies paratuberculosis (MAP) from dairy farms is a realistic option for modern dairy farms. Longitudinal observational studies have shown that farms may have low apparent prevalence of MAP for long periods of time. This is remarkable as it may be expected that a low prevalence would result in infection fade out from a substantial proportion of the farms. We present data that would indicate that the true MAP prevalence on dairy farms is much higher. Data from tissues collected at slaughter in cows from longitudinally studied herds show an apparent prevalence of infection in culled cows of approximately twenty-five percent. The reasons for this high prevalence are discussed. The impact of this high prevalence for control programs is evaluated using both mathematical, economical and molecular tools. We conclude that elimination of MAP for most dairy farms is more fiction than fact

IRB perspectives on the return of individual results from genomic research

PURPOSE: Return of individual research results from genomic studies is a hotly debated ethical issue in genomic research. However, the perspective of key stakeholders—Institutional Review Board (IRB) reviewers—has been missing from this dialogue. This study explores the positions and experiences of IRB members and staff regarding this issue. METHODS: In depth interviews with 31 IRB professionals at six sites across the United States. RESULTS: IRB professionals agreed that research results should be returned to research participants when results are medically actionable but only if the participants wanted to know the result. Many respondents expected researchers to address the issue of return of results (ROR) in the IRB application and informed-consent document. Many respondents were not comfortable with their expertise in genomics research, and only a few described actual experiences in addressing ROR. Although participants agreed that guidelines would be helpful, most were reticent to develop them in isolation. Even where IRB guidance exists (e.g., CLIA lab certification required for return), in practice, the guidance has been overruled to allow return (e.g., no CLIA lab performs the assay). CONCLUSION: An IRB-researcher partnership is needed to help inform responsible and feasible institutional approaches to returning research results

The Borrelia burgdorferi Integrin Ligand P66 Affects Gene Expression by Human Cells in Culture ▿

Borrelia burgdorferi, an agent of Lyme disease, establishes persistent infection in immunocompetent animals and humans. Although the infection in humans can be cleared by antibiotic therapy, persistence in reservoir animals is necessary for the maintenance of the bacterium in the natural reservoir host⇔tick vector infectious cycle. B. burgdorferi binds to β1- and β3-chain integrins, and the P66 outer membrane protein is responsible for at least some of the integrin binding activity of the spirochete. Because integrins are transmembrane, bidirectional signaling molecules, integrin binding may alter the nature of the host response to the bacteria. We used isogenic B. burgdorferi p66+ and Δp66 strains to analyze the responses of cultured human cells to P66-integrin interaction during infection. Microarray results suggest that the response differs according to the cell type, infection time, and experimental conditions. Clusters of genes in functionally related categories that showed significant changes included proteins involved in cell-extracellular matrix interactions, actin dynamics, stress response, and immune responses. Integrin binding by P66 may therefore help B. burgdorferi establish infection by facilitating tissue invasion and modulating the activation of the immune system to other components of the bacteria, e.g., lipoproteins. These results provide insight into how B. burgdorferi is able to establish infection in immunocompetent hosts