CFTR is a tumor suppressor gene in murine and human intestinal cancer.

This corrects the article DOI: 10.1038/onc.2015.483.

Cystic Fibrosis Mice Develop Spontaneous Chronic Bordetella Airway Infections.

Chronic pulmonary disease and infection is the primary cause of morbidity and mortality in people with cystic fibrosis (CF). Though Pseudomonas aeruginosa, is most commonly found in the airways of individuals with CF, there is increasing appreciation for the diversity of the CF microbiome, including other taxa such as Bordetella. Here we describe the identification and impact of Bordetella pseudohinzii infection in CF mice, which previously have not been thought to develop spontaneous airway infections. We determined that CF mice are more susceptible to the B. pseudohinzii infections, and less able to resolve the infection than non-CF mice. Moreover, in both CF and non-CF mice, B. pseudohinzii infections lead to markedly reduced respiratory rates and a CF-specific immune response. These results establish the CF mouse model as an important tool for the study of CF-relevant infection and highlight the potential contribution of Bordetella to CF clinical pathology.

CFTR is a tumor suppressor gene in murine and human intestinal cancer.

CFTR, the cystic fibrosis (CF) gene, encodes for the CFTR protein that plays an essential role in anion regulation and tissue homeostasis of various epithelia. In the gastrointestinal (GI) tract CFTR promotes chloride and bicarbonate secretion, playing an essential role in ion and acid-base homeostasis. Cftr has been identified as a candidate driver gene for colorectal cancer (CRC) in several Sleeping Beauty DNA transposon-based forward genetic screens in mice. Further, recent epidemiological and clinical studies indicate that CF patients are at high risk for developing tumors in the colon. To investigate the effects of CFTR dysregulation on GI cancer, we generated Apc(Min) mice that carried an intestinal-specific knockout of Cftr. Our results indicate that Cftr is a tumor suppressor gene in the intestinal tract as Cftr mutant mice developed significantly more tumors in the colon and the entire small intestine. In Apc(+/+) mice aged to ~1 year, Cftr deficiency alone caused the development of intestinal tumors in >60% of mice. Colon organoid formation was significantly increased in organoids created from Cftr mutant mice compared with wild-type controls, suggesting a potential role of Cftr in regulating the intestinal stem cell compartment. Microarray data from the Cftr-deficient colon and the small intestine identified dysregulated genes that belong to groups of immune response, ion channel, intestinal stem cell and other growth signaling regulators. These associated clusters of genes were confirmed by pathway analysis using Ingenuity Pathway Analysis and gene set enrichment analysis (GSEA). We also conducted RNA Seq analysis of tumors from Apc(+/+) Cftr knockout mice and identified sets of genes dysregulated in tumors including altered Wnt ß-catenin target genes. Finally we analyzed expression of CFTR in early stage human CRC patients stratified by risk of recurrence and found that loss of expression of CFTR was significantly associated with poor disease-free survival.

Absence of the cystic fibrosis transmembrane regulator (Cftr) from myeloid-derived cells slows resolution of inflammation and infection.

The absence or reduction of CFTR function causes CF and results in a pulmonary milieu characterized by bacterial colonization and unresolved inflammation. The ineffectiveness at controlling infection by species such as Pseudomonas aeruginosa suggests defects in innate immunity. Macrophages, neutrophils, and DCs have all been shown to express CFTR mRNA but at low levels, raising the question of whether CFTR has a functional role in these cells. Bone marrow transplants between CF and non-CF mice suggest that these cells are inherently different; we confirm this observation using conditional inactivation of Cftr in myeloid-derived cells. Mice lacking Cftr in myeloid cells overtly appear indistinguishable from non-CF mice until challenged with bacteria instilled into the lungs and airways, at which point, they display survival and inflammatory profiles intermediate in severity as compared with CF mice. These studies demonstrate that Cftr is involved directly in myeloid cell function and imply that these cells contribute to the pathophysiological phenotype of the CF lung.

The cystic fibrosis transmembrane conductance regulator (Cftr) modulates the timing of puberty in mice.

BACKGROUND: Delayed puberty is common among individuals with cystic fibrosis (CF) and is usually attributed to chronic disease and/or poor nutrition. However, it has recently been recognised that pubertal delay can occur even in the setting of good nutritional and clinical status. This finding, along with evidence that Cftr is expressed in rat brain, human hypothalamus, and a gonadotropin releasing hormone secreting cell line, raises the possibility that some of the pubertal delay in CF could stem directly from alterations in Cftr function that affect the hypothalamic-pituitary-gonadal axis. METHODS: To examine this hypothesis, we investigated pubertal timing (as assessed by vaginal opening (VO)) in a mouse model of CF (Cftr(tm1Unc)) engineered to produce a truncated Cftr mRNA and referred to as S489X. Homozygous knockout, heterozygote, and wild type (WT) female mice were examined. RESULTS: As expected, the S489X-/S489X- knockout mice, which have chronic inflammation and gastrointestinal disease, grew more slowly and had later onset of puberty than WT animals. We anticipated that the S489X-/S489X+ heterozygotes, which have no clinical CF phenotype, might display an intermediate timing of puberty. Surprisingly, however, these mice had earlier VO than WT. These findings were confirmed in a second, independent model of CF engineered to generate the deltaF508 mutation in mice. Again, the homozygotes displayed later pubertal timing, while the heterozygotes displayed earlier VO than the WT animals. CONCLUSIONS: These data provide further evidence that Cftr can directly modulate the reproductive endocrine axis and raise the possibility that heterozygote mutation carriers may have a reproductive advantage.

Experimental evidence that changes in oocyte growth influence meiotic chromosome segregation.

BACKGROUND: It is well known that the fidelity of meiotic chromosome segregation is greatly reduced with increasing maternal age in humans. More recently, direct studies of human oocytes have demonstrated a striking age-related increase in oocytes exhibiting gross disturbances in chromosome alignment on the meiotic spindle. This abnormality, termed congression failure, has been postulated to be causally related to human non-disjunction and to result from subtle alterations in folliculogenesis that develop with advancing reproductive age. METHODS: Immunofluorescence staining, conventional cytogenetic analysis and spectral karyotyping of oocytes from mouse models were used to investigate the hypothesis that changes in the regulation of folliculogenesis induce meiotic defects. RESULTS: Mutations that affect oocyte growth were found to increase the frequency of congression failure at first meiotic metaphase. Importantly, increased congression failure was correlated with meiotic non-disjunction, suggesting a cause-and-effect relationship. CONCLUSIONS: Our findings support the hypothesis that congression failure results from disturbances in the complex interplay of signals regulating folliculogenesis and that these changes subtly alter the late stages of oocyte growth, increasing the risk of a non-disjunction error. These findings have important implications for human aneuploidy, since they suggest that it may be possible to develop prophylactic treatments for reducing the risk of age-related aneuploidy.

Coordinating the segregation of sister chromatids during the first meiotic division: evidence for sexual dimorphism.

Errors during the first meiotic division are common in our species, but virtually all occur during female meiosis. The reason why oogenesis is more error prone than spermatogenesis remains unknown. Normal segregation of homologous chromosomes at the first meiotic division (MI) requires coordinated behavior of the sister chromatids of each homolog. Failure of sister kinetochores to act cooperatively at MI, or precocious sister chromatid segregation (PSCS), has been postulated to be a major contributor to human nondisjunction. To investigate the factors that influence PSCS we utilized the XO mouse, since the chromatids of the single X chromosome frequently segregate at MI, and the propensity for PSCS is influenced by genetic background. Our studies demonstrate that the strain-specific differences in PSCS are due to the actions of an autosomal trans-acting factor or factors. Since components of the synaptonemal complex are thought to play a role in centromere cohesion and kinetochore orientation, we evaluated the behavior of the X chromosome at prophase to determine if this factor influenced the propensity of the chromosome for self-synapsis. We were unable to directly correlate synaptic differences with subsequent segregation behavior. However, unexpectedly, we uncovered a sexual dimorphism that may partially explain sex-specific differences in the fidelity of meiotic chromosome segregation. Specifically, in the male remnants of the synaptonemal complex remain associated with the centromeres until anaphase of the second meiotic division (MII), whereas in the female, all traces of synaptonemal complex (SC) protein components are lost from the chromosomes before the onset of the first meiotic division. This finding suggests a sex-specific difference in the components used to correctly segregate chromosomes during meiosis, and may provide a reason for the high error frequency during female meiosis.

Chromosomal influence on meiotic spindle assembly: abnormal meiosis I in female Mlh1 mutant mice.

In mouse oocytes, the first meiotic spindle is formed through the action of multiple microtubule organizing centers rather than a pair of centrosomes. Although the chromosomes are thought to play a major role in organizing the meiotic spindle, it remains unclear how a stable bipolar spindle is established. We have studied the formation of the first meiotic spindle in murine oocytes from mice homozygous for a targeted disruption of the DNA mismatch repair gene, Mlh1. In the absence of the MLH1 protein meiotic recombination is dramatically reduced and, as a result, the vast majority of chromosomes are present as unpaired univalents at the first meiotic division. The orientation of these univalent chromosomes at prometaphase suggests that they are unable to establish stable bipolar spindle attachments, presumably due to the inability to differentiate functional kinetochore domains on individual sister chromatids. In the presence of this aberrant chromosome behavior a stable first meiotic spindle is not formed, the spindle poles continue to elongate, and the vast majority of cells never initiate anaphase. These results suggest that, in female meiotic systems in which spindle formation is based on the action of multiple microtubule organizing centers, the chromosomes not only promote microtubule polymerization and organization but their attachment to opposite spindle poles acts to stabilize the forming spindle poles.

Mineral resources, environmental issues, and land use.

Contrary to predictions from the 1950s through the mid-1980s, persistent shortages of nonfuel minerals have not occurred, despite prodigious consumption, and world reserves have increased. Global availability of raw materials is relevant to policy decisions regarding mineral development and land use. Justification for environmental protection may exceed that for mining a specific ore body. Demand for environmental accountability is rising worldwide, and new technologies are enabling internalization of costs. Mineral-rich developing nations plagued by inefficient state-owned mining enterprises, high population growth rates, and environmental degradation could realize substantial benefit by reforming government policies to encourage foreign investment in resources and by appropriate allocation of mineral rents.

Prenatal exposure to ethanol alters the organization of hippocampal mossy fibers in rats.

Rats exposed to ethanol throughout their gestation were found to have abnormally distributed mossy fibers in temporal regions of the hippocampus. This demonstrates that prenatal exposure to ethanol causes alterations in neuronal circuitry that persist to maturity. Such defects may play a role in the mental retardation often observed in children with fetal alcohol syndrome.

Distal infrapyramidal granule cell axons possess typical mossy fiber morphology.

Using both the Timm's sulfide silver and anterograde horseradish peroxidase (HRP) histochemical techniques, we have demonstrated that granule cell in the dentate gyrus of the rat have topographical projections to both suprapyramidal and distal infrapyramidal terminal fields in the rostral one-third of the hippocampus. An anterograde HRP technique modified for visualization of axonal morphology indicated that intrapyramidal mossy fiber axons possess classic periodic swellings characteristic of suprapyramidal mossy fibers. Most distal infrapyramidal mossy fiber axons appear to be in position to make synaptic contact with deeper-lying neurons in the pyramidal cell layer.