Evidence for a Novel Multipotent Mammary Progenitor with Pregnancy-Specific Activity

The mouse mammary gland has emerged as a model system for studying processes involved in the development of epithelial tissues. Current evidence suggests the existence of a differentiation hierarchy in the mammary gland, consisting of a stem cell capable of reconstituting the tissue, progenitors with the capacity to produce specific functional cell types, and differentiated cells with limited or no repopulation potential. Although markers for mammary stem cells and progenitors have been identified, these populations have not been isolated to purity and our understanding of how they function in different stages of mammary development remains incomplete. Many adult stem cells are mitotically quiescent and can therefore retain a DNA or histone label significantly longer than differentiated cells. In an attempt to identify mammary stem cells/progenitors by histone label retention, I crossed a mouse carrying the tetracycline-inducible histone 2b/eGFP (H2BGFP) gene with tetracycline transactivator strains expected to induce H2BGFP in the mammary gland. H2BGFP expression was induced in the mammary gland until puberty and then chased for 6-8 weeks; $H2BGFP^+$ label retaining cells were isolated and assayed. Transplantation experiments comparing MMTVrtTA/H2BGFP MECs isolated after induction to MMTVrtTA/H2BGFP MECs retaining label post-chase failed to prove that label retention enriches for stem cells/progenitors in the MMTVrtTA/H2BGFP system. During the course of these experiments, I unexpectedly discovered that MMTVrtTA induced H2BGFP expression exclusively in the $CD24^+/CD29^+$ and $CD24^+/CD29^{lo}$ populations, which contain stem cells and progenitors, respectively. Interestingly, I also discovered that H2BGFP+/CD24+/CD29lo MECs developed limited mammary outgrowths in vivo and that pregnancy increased the repopulation ability of these cells by 5-10-fold. H2BGFP+/CD24+/CD29lo outgrowths contained all mammary lineages and produced milk, but were unable to self-renew in serial transplant assays. Furthermore, $H2BGFP^+/CD24^+/CD29^{lo}$ and $H2BGFP^-/CD24^+/CD29^{lo}$ MECs had distinct gene expression profiles, with H2BGFP+/CD24+/CD29lo MECs expressing lower levels of transcripts involved in mammary development and differentiation. These data provide evidence for the existence of a multipotent, pregnancy-activated mammary progenitor and suggests that different progenitor populations are responsible for mammary expansion during puberty and pregnancy. Future studies may identify FACS markers for purification of pregnancy-activated progenitors and further elucidate the role of different mammary cell types during pregnancy

Evidence for a multipotent mammary progenitor with pregnancy-specific activity

Introduction: The mouse mammary gland provides a powerful model system for studying processes involved in epithelial tissue development. Although markers that enrich for mammary stem cells and progenitors have been identified, our understanding of the mammary developmental hierarchy remains incomplete. Methods: We used the MMTV promoter linked to the reverse tetracycline transactivator to induce H2BGFP expression in the mouse mammary gland. Mammary epithelial cells (MECs) from virgin mice were sorted by flow cytometry for expression of the mammary stem cell/progenitor markers CD24 and CD29, and H2BGFP. Sorted populations were analyzed for in vivo repopulation ability, expression of mammary lineage markers, and differential gene expression. Results: The reconstituting activity of CD24+/CD29+ cells in cleared fat pad transplantation assays was not distinguished in GFP+ compared to GFP- subpopulations. However, within the CD24+/CD29lo luminal progenitor-enriched population, H2BGFP+, but not H2BGFP-, MECs formed mammary structures in transplantation assays; moreover, this activity was dramatically enhanced in pregnant recipients. These outgrowths contained luminal and myoepithelial mammary lineages and produced milk, but lacked the capacity for serial transplantation. Transcriptional microarray analysis revealed that H2BGFP+/CD24+/CD29lo MECs are distinct from H2BGFP-/CD24+/CD29lo MECs and enriched for gene expression signatures with both the stem cell (CD24+/CD29+) and luminal progenitor (CD24+/CD29lo/CD61+) compartments. Conclusions: We have identified a population of MECs containing pregnancy-activated multipotent progenitors that are present in the virgin mammary gland and contribute to the expansion of the mammary gland during pregnancy

Belonging: identity, emotion work, and agency of intercountry Korean adoptees

Department Head: Jack Brouillette.2009 Summer.Includes bibliographical references (pages 166-176).This phenomenological study examines the experiences of adult Intercountry Korean Adoptees who lived in Seoul, Korea and Colorado at the time of the study. The research draws upon data gathered through participant observation and 31 in-depth semistructured interviews. Through an inductive theoretical approach, this study attempts to fill the gaps in the existing literature by providing a conceptual framework to better understand the complexity and the dynamics of intercountry identity formation. Unlike the identity development literature on racial minorities, intercountry adoptees cannot rely on the most basic membership criteria by which non-adoptees may define identity such as family, community, ethnicity, or culture. For intercountry adoptees, none of these taken-for-granted membership criteria is stable enough to claim ownership. In their struggle to anchor the shifting identity markers, intercountry adoptees assume different roles and play the part that is consistent with it. However, their unique status as adoptees fundamentally conflicts with societal norms about belonging, complicated by the socially ascribed master statuses, such as race, class, gender and other constructions of difference, which accentuate their "unbelongingness." Building on the sociology of emotions, this study posits that the intercountry adoptees' struggle for acceptance and a sense of belonging elicits much emotion work. I situate the varied emotional management efforts in the context of culture and structures that mediate rationally-conceived emotional responses tailored appropriately to certain interaction contexts. In the process of managing conflicting emotions between socially-ascribed feeling rules and true emotions, intercountry adoptees undergo transformative experiences that frame their sense of identity. This dissertation analyzes the ways that intercountry adoptees navigate through their identity formation and how this in turn shapes their actions and agency. The goal is to improve social theory regarding the identity formation of intercountry adoptees using adult rather than children’s voices. It also suggests identity is dynamic rather than linear or progressive. Further, the research introduces some contextual issues influencing identity formation

haPtic Intuitive N-scalable System : a haptic computer interface system

Thesis (M. Eng. and S.B.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2004.Includes bibliographical references (p. 73-74).The research goal was to develop a dense array of discreet vertical actuators as an input and output device with haptic feedback for Human Computer Interaction (HCI). This expands upon the current research of table surfaces as medium for HCI by adding a third dimension that both a user and a computer can control. The use of vertical actuation makes possible new kinds of physical interactions with virtual objects and allows a computer to maintain constancy with the physical representation and the digital information. This requires the design and constructions of an elegant, reliable, and economically reasonable actuator array. Each array element requires autonomy to quickly and accurately move to a precise height. As an array, combined elements must provide enough resolution so that the user perceives the array as a continuously morphing, three-dimensional surface. Shape transformations are accomplished either indirectly by digital means or directly by user touch. The proposed research will focus on development of a real-time haptic actuation arrays supporting technology. The process includes working on the design, function, appearance, response, and implementation.by Bradley C. Kaanta.M.Eng.and S.B

Design of a Personal Health Monitor Interface for Wireless, IP-based, Data Logging

Collaborating with the Enterprise Research Centre at the University of Limerick (UL) in Ireland, we designed, developed, and implemented a proof-of-concept glucose meter adapter that allows blood glucose level readings to be securely transmitted to a remote database via existing WiFi technology. By using open source software and embedded components, we have created a highly flexible platform that allows healthcare professionals to monitor patients in near real-time. Our device aims to simplify the lifestyle of diabetics while providing new opportunities for statistical research and analysis of diabetes