However, the minimal length of the PCR-fragmentshould be at least 300 bp as shorter probes are less sensitive. We have
successfully applied the PCR-based approach to a number of cDNAs including
our recently published Xenopus Cadherin-6 (Xcad-6) clones (ref. 2), Xenopus
Reptin (ref. 3) as well as various novel clones isolated using the yeast twohybrid-
methodology. Excellent results were also obtained when fluoresceine
labelled probes were used for hybridization and when transcription was
performed via a T7 promoter introduced in the forward primer. The latter
approach enabled simultaneous synthesis of antisense and sense probes
from the same PCR-template, which is shown for Xcad-6 (ref. 2). The
antisense probe revealed Xcad-6-transcripts in the brain, the eye, the
peripheral nervous system and in neurogenic placodes (Fig. 2G) and as
expected no signal was observed using the corresponding sense probe (Fig.
2H).