Putative transcription factor required for axon growth and guidance in the central and peripheral nervous systems. Repels CNS axons away from the midline by promoting the expression of the midline repellent sli and its receptor robo. Some isoforms may be generated by alternative trans-splicing of exons sequentially encoded by the same DNA strand. By stage 11, isoform F is expressed throughout the mesoderm whereas isoform T, and at low levels isoform I, is expressed throughout the ectoderm. Isoform K is expressed in both mesoderm and ectoderm. Expression becomes restricted during later stages; starting from stage 14 to 15, isoform F is expressed in the gut. Isoform I is expressed in the CNS. Isoform I and isoform F show expression in the epithelium starting at stage 14, though for isoform I the CNS expression remains predominant. Expression is also seen in specific types of cells in the embryo; isoform K is expressed in the ventral furrow at stage 5 and in a dynamic pattern in the ventral neurogenic region starting at stage 7. Isoform T is expressed around the tracheal pits at stage 11. Isoform F shows transient enrichment in a dorsal cell layer in the CNS at stages 13 and 14. Expressed both maternally and zygotically. At least one isoform is present at each developmental stage. Truncated N-terminus.