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Fig. 1. Generation of splice site mutation to abolish Fgf8b expression
in mouse. (A) Schematic representation of mutations in the
Fgf8 locus. The change of sequences (bottom; mutations are shown in
red) at the junction of intron (lowercase letters) and exon (capital letters)
mutates the 5' alternative splice acceptor and creates an NdeI
site (underlined). (B) Southern blot analysis to identify targeted
embryonic stem (ES) cell clones. Asterisks indicate non-specific signals.
(C) PCR and restriction digestion analysis to verify the point
mutation. (D) Schematic representation of Fgf8 (top),
Fgf8
b-neo (middle, left),
Fgf8
b (middle, right) and
Fgf8neo (bottom) loci, and alterations in RNA splicing due
to the point mutation and neo insertion. The Fgf8-neo hybrid
transcript results from a cryptic splice donor and acceptor in the
neo gene and in the intronic region 360 bp downstream to the
neo gene, respectively. (E) Reverse transcriptase (RT)-PCR
analysis of different Fgf8 splice variants in E7.5 embryos of
indicated genotypes using primers 1 and 2 (shown in E). Fgf8 splice
variants (a-h and unknown) are marked to the left. Notice that
Fgf8b (asterisk) is missing in
Fgf8
b-neo/
b-neo
and
Fgf8
b/
b
embryos, whereas the neo insertion has no effect on the alternative
splicing of the first four exons. (F) RT-PCR assay using primers 3 and
4 (indicated in D) reveals that the insertion of neo results in the
production of Fgf8-neo hybrid transcripts. B, BamHI; E,
EcoRI; X, XbaI.