sentences:  In conjunction with the Robo receptor, Slit signaling played a role in determining tract positions parallel to the midline for longitudinal axons to follow during development.The loss of either Slit or Robo caused dysfunction in the development of longitudinal pioneer neurons in the midbrain and hindbrain of "Drosophila".Furthermore, it has been shown that Robo plays a diversified role in pioneer axon guidance in different areas of the brain during embryonic development.