Submitted on January 24, 2008
Revised on March 25, 2008
Directed Expression of Transgenes to Alveolar Type I Cells in the Mouse
Jeff N Vanderbilt1*, Lennell Allen1, Robert F Gonzalez1, Zachary Tigue1, Jess Edmondson1, Daniel Ansaldi1, Anne Marie Gillespie1, and Leland G Dobbs2
1 University of California San Francisco, Cardiovascular Research Institute, San Francisco, CA, USA,
2 University of California San Francisco, Cardiovascular Research Institute, San Francisco, CA, USA; Department of Medicine, University of California San Francisco, San Francisco, CA, USA; Department of Pediatrics, University of California San Francisco, San Francisco, CA, USA
* To whom correspondence should be addressed. E-mail: jeff.vanderbilt{at}ucsf.edu.
Podoplanin (RTI40, aggrus, T1
, hT1-2, E11, PA2.26, RANDAM-2, gp36, gp38, gp40, OTS8) is a type I cell marker in rat lung. We show that a bacterial artificial chromosome vector containing the rat podoplanin gene (RTIbac) delivers a pattern of transgene expression in lung that is more restricted to mouse type I cells than that of the endogenous mouse podoplanin gene. RTIbac transgenic mice expressed rat podoplanin in type I cells; type II cells, airways and vascular endothelium were negative. A modified BAC containing IRES-GFP sequences in the podoplanin 3[[rad]]UTR expressed rat podoplanin and transgenic GFP in type I cells. RTIbac transgene expression was absent or reduced in pulmonary pleura, lymphatic endothelium and putative lymphoid-associated stromal tissue, all of which contained abundant mouse podoplanin. Rat podoplanin mRNA levels in normal rat lung and RTIbac transgenic lung were 25-fold higher than in corresponding kidney and brain samples. On Western blots, transgenic rat and endogenous mouse podoplanin displayed very similar patterns of protein expression in various organs. Highest protein levels were observed in lung with 10 to 20 fold less in brain; there were low levels in thymus and kidney. Both GFP and rat podoplanin transgenes were expressed at extrapulmonary sites of endogenous mouse podoplanin gene expression including choroid plexus, eye ciliary epithelium and renal glomerulus. Because their pulmonary expression is more restricted than endogenous mouse podoplanin, RTIbac derivatives should be useful for mouse type I cell-specific transgene delivery.
