Figure 4

Analysis of cytokeratin expression pattern in bone marrow and tracheal epithelial cells. Reverse transcriptase PCRs for actin, CD45 or cytokeratin (CK) were carried out on RNA extracted from various samples. Cells were dissociated from adult mouse trachea, adult bone marrow (BM), side population cells isolated from BM as described[1](SP), bone marrow from which the SP has been removed (-SP). Equal numbers of cells were used for the RNA extractions in each case. No cytokeratin signal was detectable in the SP cytokeratin RT-PCR. The lower panel shows cytokeratin RT-PCR on human bronchial epithelial (HBE) cell RNA and ROSA (Rosa 26 bone marrow cells) as positive and negative controls respectively. The dilution series (where the ratio of HBE to Rosa 26 marrow cells is varied) indicates that the cytokeratin signal can be amplified and visualised using ethidium bromide from an RNA sample extracted from 1 HBE cell seeded into 2000 ROSA bone marrow cells. Greater sensitivity is obtained by blotting and probing with an internal oligonucleotide (data not shown).