Identification and characterization of genes and signaling pathways involved in proliferation and differentiation of mammary epithelial cells

The mammary gland is a perfect system to study the pathways regulating organogenesis during development of an individual. The proper development of the mammary gland requires a tight coordination of expression of many genes involved in proliferation and differentiation. The aim of this work was to identify novel genes and pathways involved in the development of the mammary gland and to find possible correlations between the signaling pathways and their downstream targets that are activated during proliferation and functional differentiation of mammary epithelial cells. In this study rapamycin has been used to inhibit the mTOR protein to analyze its role during mammary gland development. Further a genomic approach was used to identify genes differently expressed during this process. The analysis of the effects caused by the inhibition of the mTOR signaling pathway by using rapamycin on mammary epithelial cells for the first time demonstrate that mTOR plays central role in the coordination of pathways governing the proliferation and differentiation of epithelial cells during mammary gland development. More detailed analysis led to the identification of Id1 and Id2 as two major downstream effectors of the mTOR signaling pathway regulating proliferation and differentiation respectively. The genomics analysis revealed several interesting genes involved in the regulation of a proliferative or secretory phenotype of normal epithelial cells in vitro. Various genes identified by microarray analysis are of high interest and to determine their role in mammary gland development. Among the identified genes some contribute to process of proliferation like Nol5 and Kpna2, whereas other genes are required for proper functional differentiation such as Nkd2 and Cited4. Importantly, the mentioned candidate genes are also interesting regarding cancer development, since deregulation of their expression might contribute to tumor formation. The findings described in this work clearly contribute to our better understanding of the mTOR signaling pathway regulating expression of the genes involved in the development of mammary gland. In addition, the presented results should allow broadening our view of the events that contribute to breast cancer development and help to design better anticancer therapies in the future.In der vorliegenden Promotionsarbeit wurde die Funktion des Proteins mTOR (mammalian target of rapamycin) in der Organentwicklung am Modellsystem der murinen Brustdrüse untersucht. Der mTOR-Signalweg ist in die Regulation vieler zellulärer Prozesse involviert. Die Rolle des Proteins in der Organogenese scheint bis heute jedoch noch unklar zu sein. Hierbei wurde ein einzigartiges Organ (die murine Brustdrüse) verwendet, das im Laufe der Individualentwicklung verschiedene Stadien mit unterschiedlichen Proliferations- und Differenzierungseigenschafien durchläuft. Dadurch war es möglich, die Rolle von mTOR am adulten Tier unabhängig von der Embryonalentwicklung zu studieren. Um die Funktion des mTOR-Signalweges während des Wachstums und der Differenzierung zu untersuchen, wurden diverse Studien mit der Brustepithelzelllinie HC111 durchgeführt. Die Vorläufer dieser Zellen wurden ursprünglich aus einer schwangeren Maus in der Mitte der Schwangerschaft isoliert und für eine in vitro Kultivierung optimiert. Die HC11 Zellen proliferierten als adhärente Zellen in einer Plastikkulturschale. Durch eine laktogene Hormon-Mischung aus Dexamethason, Insulin und Prolaktin (DIP) konnte in diesen Zellen die Expression von ß-Casein induziert werden. Aus der Expression dieses Milchproteins ließ sich ableiten, dass sich die Zellen im Stadium der vollen funktionellen Differenzierung befanden. Die Zusammenfassung der Promotionsarbeit gibt einen Überblick über die erhaltenen Ergebnisse und die möglichen Schlussfolgerungen. Zu Beginn wurde die Aktivität von mTOR und vom Differenzierungsmarkerprotein ß-Casein mit und ohne Inhibitor-Behandlung (Rapamycin) untersucht. Anschließend wurden Versuche durchgeführt, die zeigen, wie mTOR die Proliferation und die funktionelle bzw. morphologische Differenzierung der Brustepithelzellen durch Regulation sogenannter Idb-Proteine kontrolliert. Um die in vitro Daten in einem in vivo ähnlichen System zu bestätigen, wurden primäre, murine Brustepithelzellen einer Rapamycin-Behandlung unterzogen und die Auswirkungen auf ihre Differenzierung bestimmt. In einem weiteren Schritt wurden die Effekte einer Rapamycin-Behandlung auf die Entwicklung der murinen Brustdrüse und auf die Neugeborenen in einem Mausmodell in vivo analysiert. Ferner wurde die Rolle von mTOR in der Laktation von Brustepithelzellen in vivo untersucht. ..

Long-Wavelength Modes of Cosmological Scalar Fields

We give a numerical analysis of long-wavelength modes in the WKB approximation of cosmological scalar fields coupled to gravity via $\xi\phi^{2}R$. Massless fields are coupled conformally at $\xi=1/6$. Conformality can be preserved for fields of nonzero mass by shifting $\xi$. We discuss implications for density perturbations.Comment: 10 pages, 10 figures, several stylistic improvement

Space-Time Foam and Cosmic-Ray Interactions

It has been proposed that propagation of cosmic rays at extreme-energy may be sensitive to Lorentz-violating metric fluctuations (``foam''). We investigate the changes in interaction thresholds for cosmic-rays and gamma-rays interacting on the CMB and IR backgrounds, for a class of stochastic models of spacetime foam. The strength of the foam is characterized by the factor (E/M_P)^a, where ``a'' is a phenomenological suppression parameter. We find that there exists a critical value of ``a'' (dependent on the particular reaction), below which the threshold energy can only be lowered, and above which the threshold energy may be raised, but at most by a factor of two. Thus, it does not appear possible in this class of models to extend cosmic-ray spectra significantly beyond their classical absorption energies. However, the lower thresholds resulting from foam may have signatures in the cosmic-ray spectrum. We also find that cosmic-ray energies cannot exceed the fundamental Planck scale, and so set a lower bound of 10^8 TeV on the context of this model for the scale of gravity. Finally, we comment in the apparent non-conservation of particle energy-momentum, and speculate on its re-emergence as dark energy in the foamy vacuum.Comment: 27 pages, 13 figures. Author added (Buniy), appendix added, and new section added, corrections made. To appear in Astroparticle Physic

Transformations among large c conformal field theories

We show that there is a set of transformations that relates all of the 24 dimensional even self-dual (Niemeier) lattices, and also leads to non-lattice objects that however cannot be interpreted as a basis for the construction of holomorphic conformal field theory. In the second part of this paper, we extend our observations to higher dimensional conformal field theories build on extremal partition functions, where we generate c=24k theories with spectra decomposable into the irreducible representations of the Fischer-Griess Monster. We observe interesting periodicities in the coefficients of extremal partition functions and characters of the extremal vertex operator algebras.Comment: 14 pages, minor corrections, new references adde

Multimodal magnetic resonance neuroimaging measures characteristic of early cART-treated pediatric HIV: A feature selection approach

Children with perinatally acquired HIV (CPHIV) have poor cognitive outcomes despite early combination antiretroviral therapy (cART). While CPHIV-related brain alterations can be investigated separately using proton magnetic resonance spectroscopy