Fig. 6. Effect of the expression of T7-tagged WT1 (–KTS) and EGR1 on transcription from lampbrush chromosomes. For immunostaining, expression plasmids were co-injected with BrUTP (0.1 µg) or [³H]-labelled uridine (0.1 µCi) into the GVs of stage IV oocytes. (A-C) Immunostaining of a chromosome bivalent from oocytes expressing WT1 with anti-BrU showing extensive labelling of lateral loops (A); the DAPI-stained DNA axes (B) and the phase-contrast image (C) are shown. (D-F) Immunostaining of a chromosome bivalent from oocytes expressing EGR1, with anti-BrU showing compacted chromosomes and limited labelling of lateral loops (D). The DAPI-stained DNA axes (E) and the phase-contrast image (F) are also shown. Bar, 10 µm. (G) Incorporation of [³H]-labelled uridine into noninjected oocytes (open circles), noninjected oocytes incubated in the presence of 5 µg/ml actinomycin D (black circles), and oocytes expressing WT1 (open squares) and EGR1 (black squares). Each time-point represents incorporation per oocyte averaged from five oocytes.