Fig. 6. Molecular characterisation of the Blimp1^gfp locus. (Top) An IRES-gfp reporter cassette inserted 3' to exon 6 predominantly leads to expression of truncated Blimp1 protein (Blimp-1^T) lacking the C-terminal zinc fingers (Z1-Z5) owing to the presence of inframe stop codons. Arrows indicate position of PCR primers used to amplify exon 6 (blue), exon 6-8 (green) and exon 8 (red) sequences. (A) RT-PCR analysis reveals correctly spliced transcripts containing exons 6,7 and 8. (B) Western blot experiments also demonstrate wild-type protein expression in homozygous Blimp1^gfp/gfp embryos. These results are representative of three independent experiments analysing individually genotyped wild-type (n=8), gfp/+ (n=8) and gfp/gfp (n=7) embryos. Molecular size markers in KDa are on the left. (C) COS cells transiently transfected with expression constructs encoding full-length (FL) or truncated (T) Blimp1 protein, were stained with monoclonal anti-Blimp1 antibody and analysed by confocal microscopy. In striking contrast to the wild-type protein, truncated Blimp1 lacking the C-terminal zinc fingers fails to enter the nucleus.