A key question in plant biology is
how different morphologies in plant shape were produced during evolution.
Plant leaves have remarkable morphological diversity, thus presenting
an attractive opportunity to investigate this problem. Both dissected
and simple leaves initiate as entire primordia from the shoot apical
meristem (SAM) but post-initiation, leaf morphology diverges through
mechanisms that are largely unknown. The Arabidopsis thaliana
close relative Cardamine hirsuta displays compound leaves and
has emerged as a powerful model system for studying processes responsible
for evolutionary diversification of leaf morphology. Leaflet formation
in C.hirsuta requires the establishment of growth foci that form
after leaf initiation at the leaf margin in response to an auxin activity
maxima organized via the PIN1 auxin efflux facilitator. However, the
the pathways that direct species-specific deployment of auxin activity
maxima that support leaflet formation are unclear. I propose to address
this problem by investigating whether regulated auxin biosynthesis by
the YUCCA pathway might contribute to species-specific leaflet
formation .

Non-small cell lung cancer (NSCLC) is a devastating disease carrying a 5 year overall survival of less than 5%. K-RAS is often mutated in human cancers, activating cell proliferation and survival signals. In vivo, oncogenic K-RAS triggers a potent oncogene induced replicative senescence response (OIS), a form of growth arrest that prevent cancer progression. In this setting, inactivation of the promyelocytic leukemia gene (PML), a tumor suppressor that is frequently lost in human NSCLC, leads to the development of a more aggressive phenotype due to OIS defect and up-regulation of the phosphorylated ribosomal S6 protein. It is of great interest that oncogenic K-RAS induced NSCLC completely regresses due to apoptosis when K-RAS expression is experimentally shut off. This observation implies that oncogenic K-RAS maintains an aberrant pro-survival signaling network upon which cancer cells are critically dependent, defined as “oncogene addiction”. I hypothesize that oncogene addiction plays a pivotal role in NSCLC pathogenesis and that OIS is a key tumor suppressor mechanism in K-RAS induced NSCLC tumorigenesis. To confirm these hypothesis I will: 1. test in vivo the anti-tumor effects of specific inhibitors of the RAS signaling cascade and whether Pml null tumors are more sensitive to this strategy 2. identify the apoptosis effector molecules responsible for tumor regression upon K-RAS withdrawal 3. characterize the mechanism of action of PML in OIS. The scope is to identify the cellular mechanisms required for tumor maintenance and shed light on the molecular networks governing OIS response providing the framework for the development of novel targeted anti-cancer drugs.

MicroRNAs (miRNAs) represent a new class of pivotal regulators of development and differentiation in animals and plants, by acting as negative controllers of specific target genes. Embryonic stem (ES) cells are derived from early stages of embryonic development and have unique characteristics that make them different from all other cell types. They are able both to indefinitely proliferate by self-renewal and to give rise to all cell types and tissues. The aim of my project is the characterization of miRNAs with important roles in human embryonic stem cells and early vertebrate development. Initially, I will obtain a profile of miRNAs specifically expressed or enriched in human ES cells by microarray analysis of miRNAs expressed in undifferentiated and differentiated ES cells. Then, bioinformatic predictions of the targets of ES specific microRNAs will be validated utilizing a reporter assay. Moreover, miRNAs promoters will be characterized in order to find transcriptional factors and pathways regulating their specific expression. The third part of the project is based on the ectopic expression and antisense-mediated knock-down of specific ES microRNAs. These experiments will assess the role of miRNAs in maintenance of the stemness or differentiation of the ES cells. The Xenopus laevis embryo represents a classic model system of vertebrate development. The role of miRNAs in early development will be evaluated by experiments of overexpression and inhibition of specific miRNAs in Xenopus embryos followed by analysis of the phenotype. This work will deepen our knowledge about molecular pathways regulating stem cell biology and early vertebrate development.

The vascular system is the first organ to form and function during embryonic development. Its correct development is essential for the proper formation of vertebrate embryos as well as for adulthood. Although much attention has been focused on the genetic requirements for early vascular development (vasculogenesis and angiogenesis), the mechanisms controlling later stages of blood vessel development (vascular maturation and blod vessel myogenesis) are largely unknown. In the past, I have successfully used the embryological and genetic attributes of the zebrafish model to study endothelial cell (EC) development: I identified regulators of blood vessel integrity and characterized vascular mural cells (MC). Here, I propose to identify new mechanisms involved in vascular maturation and blood vessel homeostasis focusing on the reciprocal relationship between EC and their surrounding microenvironment, including MC. Using a set of cellular, molecular, and genetic approaches as well as advanced microscopy techniques, I propose to elucidate how endothelial and mural cells cooperate to shape the vascular system and regulate vascular maturation and myogenesis. The long-term goal is to provide additional molecular entry points to further investigate EC maturation and MC development/differentiation in normal and pathological conditions. The HFSP long-term fellowship was essential in the establishment of my current research program. The CDA would offer me a unique opportunity as an independent young investigator to find the initial funding and scientific support to address new and important questions in vascular biology.