Competence to epithelialise coincides with competence to differentiate in pluripotent cells

SummaryPluripotent cells reorganise themselves into an epithelium before they initiate differentiation, but it is not clear how these two events are mechanistically linked. Here we use quantitative imaging approaches to measure cellular rearrangements that accompany exit from naive pluripotency. We show that competence to epithelialise, like competence to differentiate, is a regulated process. The pro-differentiation transcription factor Tcf15 prospectively identifies cells that are competent to epithelialise. We identify early upregulation of the laminin receptor integrin alpha3 prior to differentiation and show that Tcf15 helps to regulate this change. Finally, we show that Tcf15 identifies and is required for efficient differentiation of a primed subpopulation of pluripotent cells. We conclude that competence to epithelialise is actively regulated and linked to differentiation-competence through the transcription factor Tcf15.

Synergistic activities of alpha3 and alpha6 integrins are required during apical ectodermal ridge formation and organogenesis in the mouse

Integrins alpha6beta1 and alpha6beta4 are cell surface receptors for laminins. Integrin alpha6-null mice die at birth with severe skin blistering and defects in the cerebral cortex and in the retina. Integrin alpha3beta1 can associate with laminins and other ligands. Integrin alpha3-null mice also die at birth, with kidney and lung defects at late stages of development, and moderate skin blistering. To investigate possible overlapping functions between alpha3 and alpha6 integrins, we analyzed the phenotype of compound alpha3−/−/alpha6−/− mutant embryos. Double homozygous mutant embryos were growth-retarded and displayed several developmental defects not observed in the single mutant animals. First, limb abnormalities characterized by an absence of digit separation and the fusion of preskeletal elements were observed. Further analyses indicated a defect in the apical ectodermal ridge, an essential limb organizing center. In the double mutant, the ridge appeared flattened, and ridge cells did not show a columnar morphology. A strong reduction in ridge cell proliferation and alterations of the basal lamina underlying the ectoderm were observed. These results suggest that alpha3 and alpha6 integrins are required for the organization or compaction of presumptive apical ectodermal ridge cells into a distinct differentiated structure. Additional defects were present: an absence of neural tube closure, bilateral lung hypoplasia, and several abnormalities in the urogenital tract. Finally, an aggravation of brain and eye lamination defects was observed. The presence of novel phenotypes in double mutant embryos demonstrates the synergism between alpha3 and alpha6 integrins and their essential roles in multiple processes during embryogenesis.

Reduced integrin alpha3 expression as a factor of poor prognosis of patients with adenocarcinoma of the lung.

PURPOSE We investigated the possible association between integrin alpha3 and motility-related protein (MRP-1), cluster of differentiation antigen 9 (CD9) gene expression in non-small-cell lung cancer (NSCLC) and evaluated the prognostic significance of integrin alpha3 expression. PATIENTS AND METHODS We performed a retrospective study of integrin alpha3 and MRP-1/CD9 expression in resected tumor tissues from 151 NSCLC patients using quantitative reverse-transcriptase polymerase chain reaction (RT-PCR) and immunohistochemistry. RESULTS The ratio of integrin alpha3/beta-actin expression ranged from 0 to 5.87 (mean was 0.80; median, 0.70). Using the cutoff value of 0.7, there were 78 (52%) integrin alpha3-positive tumors and 73 (48%) tumors with reduced integrin alpha3 expression. The immunohistochemical results agreed well with those of the RT-PCR assays, and 88% had no discrepancy. In case of discrepancy, the results of RT-PCR were used in specimen classification. Integrin alpha3 gene expression was independent from MRP-1/CD9 gene expression. No significant association was found between integrin alpha3 expression and the patients' clinical characteristics. The overall survival rate of patients with integrin alpha3-positive NSCLCs was only slightly better than that of individuals whose tumors had reduced integrin alpha3 expression (55.9% v 47.1%; P = .085). By comparison, the overall survival rate of patients with integrin alpha3-positive adenocarcinomas was strikingly greater than in those whose tumors had reduced gene expression (54.4% v 35.2%; P = .004). Multivariate analysis with the Cox regression model of NSCLC and adenocarcinoma indicated that integrin alpha3 expression correlated better (P = .0188 and P = .0008, respectively) with the overall survival rate than other variables, except lymph node status. CONCLUSION No significant association was found between integrin alpha3 and MRP-1/CD9 gene expression in lung cancer. However, reduced integrin alpha3 expression is a poor prognosis factor in patients with adenocarcinomas.