Lila Solnica-Krezel Lab
Research Description
We are interested in the cellular and molecular genetic mechanisms underlying vertebrate gastrulation, a crucial period of embryogenesis during which the germ layers are formed and then shaped into the vertebrate body plan. Gastrulation entails a combination of inductive events that specify cell identities with massive cell movements and rearrangements that generate and shape the germ layers. The complex and dynamic nature of gastrulation makes it a challenging but intellectually fascinating object of study. In humans, 25-50% of pregnancies end in early miscarriages of largely unknown genetic origin. Moreover, recent studies demonstrate that the molecular regulation of tumor growth and metastasis is strikingly similar to that of morphogenetic processes such as gastrulation, underscoring the practical significance of gastrulation research. We are addressing the mechanisms of gastrulation in the zebrafish (Danio rerio), a system that affords a powerful combination of forward and reverse genetic analyses with embryological and molecular methods.
Current Projects:
• Gastrula Organizer: During early vertebrate development, of particular significance is the Spemann-Mangold gastrula organizer, a specialized dorsal region of the gastrula that patterns germ layers and coordinates gastrulation movements. We have demonstrated that Bozozok transcriptional repressor acts at the top of a hierarchy of zygotic genes that specify development of dorso-anterior embryonic structures. Currently, we employ microarray and genetic methods to unravel the gene regulatory network Bozozok is involved in to pattern the embryo.
• Forebrain Patterning & Morphogenesis: Forebrain is the most anterior part of the central nervous system from which cerebral cortex develops. Holoprosencephaly is failure to separate the forebrain into hemispheres and is the most common forebrain defect in humans. We are studying the genetic regulation of normal forebrain morphogenesis and defects underlying holoprosencephaly with particular focus on the transcription factor Six3.
• Convergence & Extension Movements: During vertebrate gastrulation convergence and extension are key processes that narrow embryonic tissues along the mediolateral embryonic axis while extending them from head to tail. Studies from our and other groups have shown that these movements are driven by several cell behaviors, including directed migration and intercalation of mediolaterally elongated cells. Furthermore, we implicated several pathways in regulation of convergence and extension movements of entire germ layers (non-canonical Wnt signaling, Bone Morphogenetic Proteins, Prostaglandins, G-protein Coupled Receptors). Current projects delineate the cellular and molecular mechanisms via which these pathways determine the specific gastrulation cell movement behaviors.
• Interplay between Tissue Mechanics and Gene Expression during Gastrulation: This collaborative project with the Farge group (Paris, France) and Sanson group (Cambridge, UK) funded by Human Frontiers in Science Program aims to apply physics tools to investigate zebrafish embryo mechanics. More specifically, our objectives are: 1) To describe the mechanical phenotypes of WT and zebrafish embryos using particle image velocimetry; 2) To search for mechanosensitive genes during zebrafish embryonic development; and 3) To investigate the pathways linking mechanical forces to gene expression in zebrafish.
• G-protein Coupled Receptors: We have recently provided the first evidence that G-protein coupled receptors are required for gastrulation movements of discrete cell populations. Zebrafish homologs of the Agtrl1b receptor and its ligand, Apelin, previously implicated in physiology and angiogenesis, control movements of heart precursors and heart field formation. We are now working towards identification of additional G-protein coupled receptors that regulate gastrulation movements.
• Forward Genetics: One of the main strengths of the zebrafish model is that genetic screens can be used to identify, in an unbiased way, genes essential for developmental processes. Our lab is engaged in screens for mutations that impair gastrulation and early patterning. We are also currently working on the phenotypic and molecular characterization of several mutants with defective gastrulation.
• Reverse Genetics: To identify mutations in known genes of interest, we employ the TILLING (Targeting Induced Local Lesions in Genomes) method, which involves random induction of point mutations using standard ENU chemical mutagenesis methods followed by screening DNA from mutagenized animals by a gene-specific PCR polymorphism detection method. We have already identified 19 nonsense mutations in several genes of interest to our work and that of our colleagues in the zebrafish community.
