Cell culture and animal models:

NMuMG cells were purchased from ATCC (CRL-1636). C57BL/6 itgβ4^flox/flox mice were generated as described (13). C57BL/6 WAP-Cre mice (11) and B6.129 ROSA26^mT/mG mice (12) were obtained from Ingolf Bach and Jaime Rivera, respectively at the University of Massachusetts Medical School (11, 12). All of the animal breeding and procedures were approved by the Institutional Animal Care and Use Committee of the University of Massachusetts Medical School.