Susan V Bryant - US grants

limbs; histogenesis; mammalian embryology; transplantation; skin; chromosome aberrations; cell cycle; intercellular connection; apical membrane; mesoderm; molecular genetics; dissection; laboratory mouse; autoradiography; electron microscopy;

limbs; histogenesis; mammalian embryology; transplantation; skin; chromosome aberrations; cell cycle; intercellular connection; apical membrane; mesoderm; molecular genetics; dissection; laboratory mouse; autoradiography; electron microscopy;

Pattern formation is the process that controls the spatial ordering of organs and differentiated cell types during development. Features of the mechanism of pattern formation are revealed when developing systems undergo pattern regulation. Developing and regenerating limbs show extensive regulative abilities and thus have long been used as models for pattern formation in vertebrates. The proposed experiments on regenerating axolotl limbs use a combination of in vivo and invitor approaches to investigate the ability of cells form one limb position to induce patterning and growth responses in cells at a different position. The induction of supernumerary pattern and growth will be used to investigate whether limb cells retain their positional properties in vitro, and whether the molecules associated with these properties can be detected in membranes, extracellular matrix or culture medium conditioned by cells from particular limb positions. We will examine the ability of retinoic acid to change anterior limb cells that function as posterior cells using both in vivo and in vitro approaches. Finally, the effects of TGF beta and a and b FGF, which have known effects on limb development, will be investigated for their role in pattern formation and position-dependent growth. It is anticipated that an understanding of pattern formation will allow for the development of strategies to stimulate controlled growth and pattern (regeneration); to inhibit unpatterned, uncontrolled growth (cancer) and to correct abnormal pattern (birth defects).

All vertebrates develop limbs by similar mechanisms, but only one group, urodele amphibians (salamanders and newts) have the remarkable ability to regenerate their limbs. Our goal is to understand the molecular events that occur when differentiated limb cells reenter the developmental pathway to reengage in pattern formation. During limb development, flank cells must first be specified as fore- or hind limb, and establish anterior-posterior and dorsal-ventral polarity prior to generating the proximal-distal axis. In contrast, during regeneration only the proximal- distal axis has to be re-developed. In all animals, genes of the Hox clusters are involved in pattern formation, both along the main head to tail axis and within the limbs. The expression patterns and functional analyses of genes of one Hox cluster, the HoxA genes, indicate their involvement in patterning of the proximal-distal limb axis in development. Since limb regeneration is the process of reforming the proximal-distal axis, we hypothesize that these genes will have a key regulatory function in limb regeneration. For this reason, we propose to analyze the expression and function of HoxA genes in regenerating axolotl limbs. In preliminary studies, we have discovered that HoxA genes are reexpressed in the initiation phase of regeneration. Both HoxA13 and A9 are reexpressed in the limb stump as an early response to amputation, prior to formation of the blastema that gives rise to the new structures. Our data suggest that HoxA genes do not obey the rules of temporal and spatial colinearity that are the hallmark of their expression during limb development. The order in which HoxA genes are reexpressed, and how the combinatorial domains of gene expression that characterize each limb segment (the Hox code) arise, will be investigated in our experiments. We will use information from classical experiments combined with experimental manipulations of gene expression (overexpression and inhibition of expression) to investigate how events in the regeneration cascade are causally linked to HoxA gene expression. We will find out whether activation of HoxA genes is unique to regeneration by studying non- regenerating wounds. We will examine the role of the epidermis (and FGF) and nerves in the initiation and maintenance of HoxA expression. We will study the role of HoxA genes in the formation of specific limb segments along the proximal-distal axis. We will investigate the relationship between the effects of retinoic acid on the pattern of regenerating limbs and its effects on HoxA gene expression. We will study the relationship between differential adhesiveness of cells from different proximal-distal limb levels and their different HoxA codes. With an understanding of the role of HoxA genes in regeneration, we will further our understanding of why limbs of other vertebrates, including humans, are unable to initiate the regeneration cascade, thus providing insights into future strategies for therapy.

DESCRIPTION (appended verbatim from investigator's abstract): Alone among vertebrates, urodele amphibians are able to regenerate lost body parts as adults. Our strategy is to use axolotls (Ambvstoma mexicanum! to discover the signals that trigger the regeneration response, in the belief that these signals have enormous potential and consequences for human health. Our long term goals are to identify the regeneration enabling signals in limbs, in order to support progress towards the eventual application of these molecules to the Specific Aims. In the first, we will use assays derived from the extensive experimental history of regeneration of limbs, to test the roles of several signaling molecules known to be essential for limb development. These assays will use virally driven ectopic expression to examine the signals that initiate regeneration, those that are needed to establish a blastema, as well as those that are required for intercalary growth between the new limb tip and the amputation plane. We will test the role of fibroblast growth factors in the initiation of outgrowth, the role of bone morphogenetic proteins in promoting healing and inhibiting regeneration, the role of sonic hedgehog in providing the asymmetry needed to establish the blastema, and the role on Wnt factors in intercalary growth. In the second Specific Aim, we will generate a library of cDNAs made from regenerating limbs at different stages, and screen it with forward and reverse subtracted probes to enrich it for genes expressed differentially during regeneration. The library will be arrayed for efficient use, and screened with stage specific probes to identify genes expressed at different times in regeneration; We are especially interested in any novel factors that might be involved in transforming the differentiated limb stump into a blastema. Candidate genes will be assayed as described for known signaling molecules. The tools and knowledge are in place to attack complex systems, and understanding regeneration is likely to lead to new approaches and therapies for replacing or repairing lost, damaged or diseased parts of the body.

The goal of this project is to contribute to the development of a national science and engineering academic workforce that includes the full participation of women in all levels of faculty and academic administration, particularly at the senior academic ranks through the transformation of institutional practices, policies, climate and culture. The central administration of UCI is committed to diversity and equity and realizes that to maintain and increase its competitive edge the problems contributing to the low representation of women in academic science and engineering need to be addressed. This sense of urgency is compounded by the impending growth of the campus as a result of 'Tidal Wave II'. With the influx of new students comes a rare opportunity to hire up to 50 new faculty, which added to the turnover in hiring, results in a projection of more than 80 new hires a year for the next decade. UCI intends to seize this opportunity to transform UCI into a diverse campus with flexible approaches and innovative solutions to problems that affect both science and the training of the workforce of the future.

UCI's goals are: to increase the recruitment of women into Science, Mathematics, Engineering and Technology (SMET) disciplines, provide a network of support and guidance through to tenure, monitor progress by collecting and analyzing data about the objective and subjective aspects of equity, promote networking and mentoring activities for tenured women to ensure that they develop to their fullest potential, including facilitating nominations for awards at the local, national and international levels. To accomplish these goals, UCI will appoint a senior faculty member as an Equity Advisor in each of the 8 SMET schools, to tailor an equity program for that school that meets its particular needs. Their involvement in recruiting will include assisting search committees to develop diverse candidate pools containing highly qualified women. They will also set up a mentoring program for junior faculty based on a successful UCI model. To increase awareness among administrators and search committees of the ways in which our judgment of individuals is altered by their gender, UCI will make use of workshops successfully implemented in the corporate world by one of the faculty. To encourage networking among women scientists, UCI will organize a series of scientific conferences, focused on different scientific disciplines, at which women scientists will be invited to speak about their research. Workshops will allow an exploration of the issues standing in the way of full participation of women in academia, and all faculty, students, and postdoctoral fellows will be invited to participate. Finally, to provide a tangible demonstration of the value of activities that promote gender equity, UCI will establish two ADVANCE Chairs, to be awarded to tenured faculty in the sciences with both excellent academic credentials as well as demonstrated commitment to gender equity. These Chairs will be continued after the period of the grant by funds raised from private donations. To evaluate the success of these strategies, UCI's annual self-assessment surveys will be complemented by two assessments by external evaluators to be conducted in years three and five.

This project is supported by the NSF ADVANCE Program. The overall mission of the ADVANCE Program is to increase the participation of women in the scientific and engineering workforce through the increased representation and advancement of women in academic science and engineering careers.

Through FOCUS (Faculty Outreach Collaborations Uniting Scientists, Students and Schools), the University of California, Irvine (UCI) unites the efforts of mathematics, science, education and research library faculty and staff with educators from local community colleges, school districts and local educational support agencies. The partnership builds on prior established relationships between UCI and three high-need California school districts: Compton Unified, Santa Ana Unified and the Westside of Newport-Mesa Unified. These schools serve 106,695 students of whom 82% are Hispanic and 11% are African American.

The work of FOCUS will include the construction of a "future teacher highway" to increase the number, quality and diversity of preK-12 teachers of mathematics and science; involvement of math and science professionals in "Discipline Dialogues" that cross segmental boundaries, and the creation of systemic reform in the professional development of preK-12 teachers of mathematics and science. FOCUS will ultimately impact the number of new mathematics and science teachers; the number of high school students prepared for and enrolled in advanced mathematics and science coursework; the achievement gap between the general student population and English Language Learners; and the number of higher education faculty engaged in efforts with preK-12 educational systems.