cues. In mice (and humans), the Robo1 locus has alternative promoters producing two
transcript isoforms, Robo1 and Dutt1. These isoforms have unique 5′ termini, predicted to
encode distinct N-terminal amino acids, but share the rest of their 3′ exons. To determine
the spatial expression of the Robo1 and Dutt1 isoforms, we generated isoform-specific RNA
probes, and carried out in situ hybridization on E10. 5 mouse embryos, the stage in early …