Biomedical subjects

Kitty Tang

Publications and source records attributed to Kitty Tang.

3 recordsLinked to original sources

PubMed2006

Morphological and biochemical analysis of Rac1 in three-dimensional epithelial cell cultures.

Rho GTPases are critical regulators of epithelial morphogenesis. A powerful means to investigate their function is three-dimensional (3D) cell culture, which mimics the architecture of epithelia in vivo. However, the nature of 3D culture requires specialized techniques for morphological and biochemical analyses. Here, we describe protocols for 3D culture studies with Madin-Darby Canine Kidney (MDCK) epithelial cells: establishing cultures, immunostaining, and expressing, detecting, and assaying Rho proteins. These protocols enable the regulation of epithelial morphogenesis to be explored at a detailed molecular level.

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PubMed2005

Formation of multicellular epithelial structures.

The kidney is primarily comprised of highly polarized epithelial cells. Much has been learned recently about the mechanisms of epithelial polarization. However, in most experimental systems the orientation of this polarity is determined by external cues, such as growth of epithelial cells on a filter support. When Madin-Darby canine kidney (MDCK) cells are grown instead in a three-dimensional (3D) collagen gel, the cells form hollow cysts lined by a monolayer of epithelial cells, with their apical surfaces all facing the central lumen. We have found that expression of a dominant-negative (DN) form of the small GTPase Rac1 causes an inversion of epithelial polarity, such that the apical surface of the cells instead faces the periphery of the cyst. This indicates that the establishment of polarity and the orientation of polarity can be experimentally separated by growing cells in a 3D collagen gel, where there is no filter support to provide an external cue for orientation. DN Rac1 causes a defect in the assembly of laminin into its normal basement membrane network, and addition of a high concentration of exogenous laminin rescues the inversion of polarity caused by DN Rac1.

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PubMed2004

ERK and MMPs sequentially regulate distinct stages of epithelial tubule development.

Epithelial cells undergo tubulogenesis in response to morphogens such as hepatocyte growth factor (HGF). To organize into tubules, cells must execute a complex series of morphogenetic events; however, the mechanisms that underlie the timing and sequence of these events are poorly understood. Here, we show that downstream effectors of HGF coordinately regulate successive stages of tubulogenesis. Activation of extracellular-regulated kinase (ERK) is necessary and sufficient for the initial stage, during which cells depolarize and migrate. ERK becomes dispensable for the latter stage, during which cells repolarize and differentiate. Conversely, the activity of matrix metalloproteases (MMPs) is essential for the late stage but not the initial stage. Thus, ERK and MMPs define two regulatory subprograms that act in sequence. By inducing these reciprocal signals, HGF directs the morphogenetic progression of tubule development.

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