The acquisition and maintenance of cell division potential are important characteristics of tumorigenesis. Human telomerase reverse transcriptase (TERT) and telomerase RNA (TR) can immortalize cells through telomere maintenance, and telomerase activity is one factor that contributes to the in vitro transformation of normal cells. In vitro and in vivo evidence suggest that telomerase maintains telomeres as a functional multimer. In addition, hTERT may possess telomere maintenance-independent functions. To examine the effects of hTERT loss upon an in vitro generated tumorigenic cell line we created a tumorigenic cell line from human embryonic kidney cells through expression of the SV40 early region, H-RasG12V and a Cre-mediated excisable hTERT. These immortalized cells exhibited robust anchorage-independent colony growth and tumor formation in immuno-deficient mice. Cre recombinase expression resulted in the excision of hTERT from the tumorigenic cell lines, restoring cell mortality. A return to immortality was conferred by the re-introduction of wild-type hTERT, but not with hTERT point mutations in the N-terminus (hTEN) and reverse transcriptase (RT) domains that impair in vitro telomere elongation activity. The onset of cell mortality was not immediate, and the hTERT-excised tumorigenic cells exhibited clonal variation in the anchorage-independent colony growth assay and upon tumor formation in immuno-deficient mice. We hypothesized that tumorigenic potential was not related strictly to hTERT presence, but rather telomere length and/or integrity. To investigate this possibility we maintained the tumorigenic cell lines in the continuous presence of hTERT to permit telomere elongation prior to hTERT excision; subsequently, after hTERT excision tumor formation persisted, thus demonstrating a dependence on telomere length and not hTERT presence per se. To investigate the functional multimerization of hTERT in vivo we tested if two defective hTERT polypeptides with mutations in the hTEN and RT domains could restore telomere elongation activity in vivo. Unfortunately, during the course of these experiments an unanticipated recombination event occurred that restored a catalytically active hTERT transgene. Further in vivo analysis of hTERT multimerization should be carefully designed, accounting for the selective survival advantage bestowed by wild-type hTERT. This study provides compelling evidence that hTERT does not possess telomere maintenance-independent functions.

Many different approaches exist for engineering bacterial genomes. The most common current methods include transposons for random mutagenesis, recombineering for specific modifications in Escherichia coli, and targetrons for targeted knock-outs. Site-specific recombinases, which can catalyze a variety of large modifications at high efficiency, have been relatively underutilized in bacteria. Employing these technologies in combination could significantly expand and empower the toolkit available for modifying bacteria. Targetrons can be adapted to carry functional genetic elements to defined genomic loci. For instance, we re-engineered targetrons to deliver lox sites, the recognition target of the site-specific recombinase, Cre. We used this system on the E. coli genome to delete over 100 kilobases, invert over 1 megabase, insert a 12-kilobase polyketide-synthase operon, and translocate a 100 kilobase section to another site over 1 megabase away. We further used it to delete a 15-kilobase pathogenicity island from Staphylococcus aureus, catalyze an inversion of over 1 megabase in Bacillus subtilis, and simultaneously deliver nine lox sites to the genome of Shewanella oneidensis. This represents a powerful, versatile, and broad-host-range solution for bacterial genome engineering. We also placed lox sites on mariner transposons, which we leveraged to create libraries of millions of strains harboring rearranged genomes. The resulting data represents the most thorough search of the space of potential genomic rearrangements to date. While simple insertions were often most adaptive, the most successful modification found was an inversion that significantly improved fitness in minimal media. This approach could be pushed further to examine swapping or cutting and pasting regions of the genome, as well. As potential applications, we present work towards implementing and optimizing extracellular electron transfer in E. coli, as well as mathematical models of bacteria engineered to adhere to the principles of the economic concept of comparative advantage, which indicate that the approach is feasible, and furthermore indicate that economic cooperation is favored under more adverse conditions. Extracellular electron transfer has applications in bioenergy and biomechanical interfaces, while synthetic microbial economics has applications in designing consortia-based industrial bioprocesses. The genomic engineering methods presented above could be used to implement and optimize these systems. / text

Based on their highly bioactive properties in membrane phospholipids, there is growing recognition that dietary n-3 polyunsaturated fatty acids (PUFA) may be of significant benefit in the prevention and treatment of many lifestyle related pathologies, however direct evidence is lacking. The fat-1 transgenic mouse, a genetic model of n-3 PUFA enrichment, is a useful tool in nutritional research which has provided enhanced insight into the health effects of lifelong n-3 PUFA exposure. However, the influence of timing of n-3 PUFA exposure on health related outcomes remains unclear. This thesis describes the functional characterization of the novel Cre recombinase dependent inducible fat-1 (iFat-1) transgene. In the presence of Cre, the iFat-1 transgene was found to reduce phospholipid n-6/n-3 PUFA ratios both in vitro (100%) and in vivo (upwards of 70%), suggesting that the iFat-1 transgene has potential application to address temporal effects of n-3 PUFA in health and disease. / Canadian Institutes of Health Research - Frederick Banting and Charles Best Canada Graduate Scholarship, Sun Life Financial

Regensburg, Univ., Diss., 2009.

Univ., Diss., 2006--Giessen

Abstract The complete exon-intron organization of the gene coding for the mouse α1(XIII) collagen chain, Col13a1, was characterized from genomic clones and multiple transcription initiation points were determined. Detailed comparison of the human and mouse genes showed that the exon-intron structures are completely conserved between the species, and both genes have their 5' untranslated region preceded by a highly conserved putative promoter region. The chromosomal location of the mouse gene was determined to be at chromosome 10, band B4, between markers D10Mit5 – (2.3 ± 1.6 cM) – Col13a1 – (3.4 ± 1.9 cM) – D10Mit15. The location of the genes for both the catalytically important α-subunit of prolyl 4-hydroxylase (P4HA) and human type XIII collagen (COL13A1) were previously mapped to 10q21.3-23.1. Prolyl-4-hydroxylase catalyzes the formation of 4-hydroxyproline in collagens by the hydroxylation of peptide-bound proline and plays a crucial role in the synthesis of these proteins. The order and transcriptional orientation of the COL13A1 and P4HA was determined. These two genes were found to lie at tail to tail orientation on chromosome 10 and the distance between these genes was determined to be about 550 kbp. To study the function of type XIII collagen we used gene targeting in ES cells to generate a mouse line that carries a mutated type XIII collagen gene. Instead of normal protein, mutant mice express type XIII collagen with an altered amino-terminus in which the cytosolic and the transmembrane domains have been replaced with an unrelated sequence. The homozygous mice are fertile and viable but they show alterations in skeletal muscles, mainly wavy sarcolemma and increased variation in muscle fiber diameter. Ultrastructural studies revealed additional abnormalities such as streaming of z-disks, accumulation and enlargement of mitochondria, and disorganized myofilaments. The basement membranes of the muscle cells showed areas of detachment from the plasma membrane and the fibrillar matrix of the cells was less compact than in control animals. Fibroblasts cultured from mutant mice had normal levels of type XIII collagen but exhibited decreased adhesion to substratum which might be explained by a reduced anchoring strength of the altered protein.

Scleroderma (SSc) is an autoimmune disease characterized by dysfunctional immunity, vasculopathy, and fibrosis of the skin and internal organs. There is a poor prognosis for SSc patients and effective therapeutics have not yet been developed. Many mouse models have been developed, but most fail to recapitulate all of the symptoms seen in SSc patients. In this study we characterize a Fli1flox/flox mouse with CAG Cre under the beta-actin promoter. Based on what has been previously described in mice with deletion of Fli1 in specific cell types, we predicted that global postnatal deletion of Fli1 will result in systemic fibrosis, vasculopathy, and inflammation in these mice. The penetrance of a phenotype was highly variable; however, mice that developed a phenotype displayed disorganized vascular networks, fibrosis and proinflammatory cytokines and chemokines in the skin and lungs after 4 and 8 weeks of Fli1 deficiency. Increased macrophage and dendritic cell populations were observed in the lungs after 8 weeks. Fli1flox/flox CAG Cre mice exhibited hair loss after 5 months of Fli1 deletion. Since our experiments focus mainly on the lungs and skin, more experiments are required to characterize these mice to determine if they can be used as a novel animal model of SSc.

No description available.

No description available.

An estimated 70% of bacterial infections in the United States are resistant to first-line antibiotics. Of these, among the most difficult to treat are highly resistant to carbapenems, an antibiotic class used as a last resort. Septicemia, particularly when caused by a carbapenem-resistant organism, is among the most challenging clinical scenarios to treat, with an overall mortality rate of carbapenem-resistant septicemias 63.8%. Encouragingly, if effective antimicrobial treatment begins within 1-3 hours of septic shock onset, patient survival rates are around 80%. The first section of this work describes a real-time PCR-based assay that when coupled with existing bacteria-blood separation technology, can rapidly identify genes present in a multi-drug resistant bacterial sample at physiologically significant levels (<10 CFU/mL). Primers and probes were designed which identify all subtypes of the most common carbapenemase genes in carbapenem-resistant infections in the United States: Klebsiella pneumoniae Carbapenemase (KPC); New Delhi Metallo-beta-lactamase (NDM); Cefotaximase-Munich (CTX); Cephamycin AmpC beta-lactamase (CMY); and Oxacillinase-48 (OXA-48). The information provided by this assay will supply physicians with critical drug resistance information within two hours of septicemia onset and allow for timely prescription of effective antimicrobials which correspond to the resistance gene(s) present in the causative organism. Increased understanding of the mechanisms and evolution of carbapenem resistance; in particular, the phenomenon of heteroresistance, is of significant clinical import. As such, the second section of this work examines a clinical, carbapenem-resistant E. coli isolate that when cultured in the prolonged absence of antibiotic pressure, achieves clinically relevant levels of susceptibility to imipenem and doripenem through loss of its blaNDM-1-harboring transposon at the DNA level. Through full genomic sequencing of the highly resistant population, we theorize that the resistance level was achieved through loss of genomic regions whose maintenance either exerted fitness costs in the presence of doripenem, or which encoded genes whose expression inhibited doripenem resistance via pathways that influence outer membrane porin expression. Along with the disappearance and resurgence of carbapenem resistance, emergence of a highly carbapenem-heteroresistant population occurred early and remained throughout the duration of the study.