Figure 7: CLCb is upregulated in invasive extravillous trophoblast cells.

(a) Microarray analysis of mRNA in human trophoblast cells showing relative gene expression levels in extravillous trophoblast (EVT) cells compared with villous trophoblast (VT) cells. Genes encoding clathrin subunits and their transcript levels are indicated in red. CLTB encodes CLCb, CLTA encodes CLCa, CLTC encodes CHC17 and CLTCL1 encodes CHC22. For three genes encoding clathrin subunits, more than one probe was used to detect splice variants and these are numbered. Probes CLTB-1, CTLA-2, CLTA-3 and CLTCL1-1 detect all variants, CLTB-2 and CLTA-1 detect the neuronal splice variants of CLCs and CLTCL1-2 detects a second splice variant encoded by this gene. (b) Serial sections of normal, non-cancerous human placental tissue were stained for CLCb, CLCa, CHC17 and trophoblast markers, as indicated. Cytokeratin staining depicts cytotrophoblast cell columns (columnar) and invading extravillous trophoblast cells developing from placental villi. Extravillous trophoblast was distinguished from villous trophoblast on the basis of HLA-G expression. Arrowheads depict extravillous trophoblast cells with high CLCb expression. Intensities of the staining are quantified as arbitrary units (a.u.) and illustrated on the right as line profiles across each box shown at the far left. V, villous; C, columnar; EV, extravillous trophoblast. Scale bars, 500 μm.