Prkci is required for a non-autonomous signal that coordinates cell polarity during cavitation.
Polarized epithelia define boundaries, spaces, and cavities within organisms. Cavitation, a process by which multicellular hollow balls or tubes are produced, is typically associated with the formation of organized epithelia. In order for these epithelial layers to form, cells must ultimately establish a distinct apical-basal polarity. Atypical PKCs have been proposed to be required for apical-basal polarity in diverse species. Here we show that while cells null for the Prkci isozyme exhibit some polarity characteristics, they fail to properly segregate apical-basal proteins, form a coordinated ectodermal epithelium, or participate in normal cavitation. A failure to cavitate could be due to an overgrowth of interior cells or to an inability of interior cells to die. Null cells however, do not have a marked change in proliferation rate and are still capable of undergoing cell death, suggesting that alterations in these processes are not the predominant cause of the failed cavitation. Overexpression of BMP4 or EZRIN can partially rescue the phenotype possibly by promoting cell death, polarity, and differentiation. However, neither is sufficient to provide the required cues to generate a polarized epithelium and fully rescue cavitation. Interestingly, when wildtype and Prkci(-/-) ES cells are mixed together, a polarized ectodermal epithelium forms and cavitation is rescued, likely due to the ability of wildtype cells to produce non-autonomous polarity cues. We conclude that Prkci is not required for cells to respond to these cues, though it is required to produce them. Together these findings indicate that environmental cues can facilitate the formation of polarized epithelia and that cavitation requires the proper coordination of multiple basic cellular processes including proliferation, differentiation, cell death, and apical-basal polarization.
Keck School of Medicine, University of Southern California, Broad CIRM Center for Regenerative Medicine & Stem Cell Research, BCC-407, MC9080 1425 San Pablo St., Los Angeles, CA 90033, United States.
In Kyoung
IK
Mah
Department of Biological Sciences, University of California, San Diego, La Jolla, CA 92093-0377, United States.
Rachel
R
Soloff
Keck School of Medicine, University of Southern California, Broad CIRM Center for Regenerative Medicine & Stem Cell Research, BCC-407, MC9080 1425 San Pablo St., Los Angeles, CA 90033, United States.
Audrey K
AK
Izuhara
Keck School of Medicine, University of Southern California, Broad CIRM Center for Regenerative Medicine & Stem Cell Research, BCC-407, MC9080 1425 San Pablo St., Los Angeles, CA 90033, United States.
Daniel L
DL
Lakeland
Loma Linda University School of Medicine, 11021 Campus Street, Alumni Hall, Room 121, Loma Linda, CA 92350, United States.
Charles
C
Wang
Keck School of Medicine, University of Southern California, Broad CIRM Center for Regenerative Medicine & Stem Cell Research, BCC-407, MC9080 1425 San Pablo St., Los Angeles, CA 90033, United States. Electronic address: fmariani@usc.edu.
Francesca V
FV
Mariani
D055415:Bone Morphogenetic Protein 4 / Q000378:metabolism; D015815:Cell Adhesion Molecules / Q000378:metabolism; D016923:Cell Death; D002460:Cell Line; D016764:Cell Polarity; D049109:Cell Proliferation; D003598:Cytoskeletal Proteins / Q000502:physiology; D004848:Epithelium / Q000196:embryology*; D020869:Gene Expression Profiling; D006801:Humans; D007527:Isoenzymes / Q000235:genetics / Q000502:physiology*; D009024:Morphogenesis; D010641:Phenotype; D011493:Protein Kinase C / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction; D000099149:Ezrin; D000099293:Protein Kinase C-lambda
D055415:Bone Morphogenetic Protein 4; D015815:Cell Adhesion Molecules; D003598:Cytoskeletal Proteins; D007527:Isoenzymes; D011493:Protein Kinase C; D000099149:Ezrin; D000099293:Protein Kinase C-lambda; C525810:Bmp4 protein, mouse
Cavitation; EB development; Epithelia; Polarity; Prkci; Stem cell