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. Isoform D interacts with JIL-1. Some isoforms may be generated by alternative trans-splicing of exons sequentially encoded by the same DNA strand. By stage 11, isoform B is expressed throughout the mesoderm, whereas isoform A, isoform D and isoform L are expressed throughout the ectoderm. Expression becomes restricted during later stages; starting from stage 14 to 16, isoform B is expressed in muscle. Isoform A, isoform D, and at low levels isoform B, are expressed in the CNS. Expression is also seen in specific types of cells in the embryo; isoform A and isoform L are expressed in a dynamic pattern in the ventral neurogenic region starting at stage 7. Isoform L is expressed around the tracheal pits at stage 11. Expressed both maternally and zygotically. At least one isoform is present at each developmental stage. Isoform D is restricted to early embryogenesis (at protein level). C-terminal exons may be joined by a trans-splicing event. The exons are coded by the same DNA strand.