Cell Migration

In general, we are interested in understanding how extracellular signals, including cell-extracellular (ECM) and cell-cell adhesive events, are transduced inside cells to influence the cellular cytoskeleton so as to effect cell motility or cell migration. Our approach to this problem has been biochemical and cellular imaging – both static and dynamic, in 2- and 3-dimensional systems. More recently we are developing computational models of signaling pathways that regulate cell migration and are amenable to experimental manipulation, so as to identify and quantify the interactions between these processes during cell migration.

Bone osteosarcoma cells (U2OS) stained with Phalloidin to identify actin filaments (red),and an antibody to vinculin (green) that identifies Focal Adhesions. The cellis migrating to the right. <<<

Epithelia Biogenesis and Morphogenesis

Epithelia are cellular barriers established to protect our bodies (inside and out) from environmental insults. As such their development, organization, and maintenance are critical for normal homeostasis. We are interested in understanding how epithelia form and remodel during development, how they are organized (polarity, cell-cell adhesion), and how they are maintained in the adult. To study this problem we employ multidisciplinary approaches - Cell Biology, Development Biology and Genetics, and make use of multiple experimental organisms (Xenopus, drosophila, and mouse).

Polarized kidney epithelial cells (MDCK) stained with antibodies to the LIM protein Ajuba (green) and the tight junction protein Occludin (red). The Z-stack reconstruction at the top shows that the cellular localization of these 2 proteins overlap (yellow). <<<

MARCM clones in the eye of a drosophila pupa (40h) stained with antibodies to E-cadherin (red – identifies adherens junction), and Discs large (blue – identifies the septate junction). GFP (green) positive cells are homozygous for a lethal mutation. The MARCM system allows for the analysis of the role of lethal genes in epithelial morphogenesis and whether they exhibit cell autonomous or cell-cell functions. <<<

Epithelial Mesenchymal Transitions (EMT) and Cancer Metastasis

During epithelia-derived cancer invasion and spread (metastasis), early well-differentiated epithelial tumors de-adhere from one another and acquire the capacity to migrate or invade through the basement membrane, leading to spread to other organs throughout the body. This process has been morphologically, functionally, and genetically described as an epithelial-mesenchymal transition or EMT. While EMT is a normal process during development, in the adult it has been associated with wound healing, and pathologic conditions such as organ fibrosis in response to injury, and cancer metastasis. We are interested in understanding the molecular and cellular mechanisms regulating EMT. Specifically, how cell surface adhesive events communicate with nuclear responses to initiate, maintain, and terminate EMT changes. We study EMT processes in normal development and cancer metastasis.

+ XSlug + XWTIP	+ XSlug morpholino + XWTIP morpholino
Ajuba LIM proteins are Snail/Slug co-repressors, required for developmental EMT (neural crest development/migration)
Xenopus embryos (2 cell stage) are injected with Slug or WTIP (Ajuba family LIM protein) mRNA (left) or morpholinos to knock down expression (right). Embryos are then stained at stage 18 for neural crest markers (dark stain). B-gal staining (blue) identifies the injected side. Note the expansion of neural crest progenitors in XSlug and XWTIP injected embryos, while knockdown of either blocks neural crest development.

 

 

lung cancer

Loss of heterozygosity (LOH) and homozygous deletions at chromosome 3p21.3 are common in both small and non-small cell lung cancers, indicating the likely presence of tumor suppressor genes (TSG). We found that expression of the 3p21.3 gene, LIMD1, a LIM domain containing adapter protein that has the potential to communicate cell extrinsic or environmental cues with nuclear responses by virtue of its localization to E-cadherin cell-cell adhesive junctions and nuclear translocation, is frequently down-regulated in human lung tumors. Human genetic analyses has revealed that loss of LIMD1 expression occurs through a combination of gene deletion, LOH, and epigenetic silencing of transcription without evidence for coding region mutations. Experimentally LIMD1 is a bona fide TSG as Limd1-/- mice are predisposed to chemical-induced lung adenocarcinoma, and genetic inactivation of Limd1 in mice heterozygous for oncogenic K-RasG12D markedly increase tumor initiation, promotion, as well as mortality. Future work is directed at determining whether there is clinical predictive value of loss of LIMD1 in lung cancer patients (i.e., can LIMD1 serve as a clinical biomarker). Secondly we are determining the cellular mechanism whereby LIMD1 functions as a tumor suppressor in lung cancer and then testing these results in mouse models of lung cancer with reagents developed in our lab (Limd1-/- mice).

 

BLIMD1 expression in human lung cancer. Immunohistochemical stained lung normal bronchiolar tissue (A) and normal alveolar tissue (C) with matched adjacent squamous cell carcinoma tissue section (B) and matched adjacent adenocarcinoma section (D) respectively. Original magnification x100. <<<