Repulsive guidance molecule A (RGMA) is widely expressed in the CNS of the sea lamprey Petromyzon marinus during early development.

RGM interactions with its receptor Neogenin play an important role in the regulation of axonal guidance or cell death in the developing central nervous system. The sea lamprey RGMA transcript has been recently identified. However, its expression has been only studied in the spinal cord of mature (premetamorphic) larval sea lampreys. Here, we report the expression of the sea lamprey RGMA transcript in developing embryos and prolarvae by means of in situ hybridization. Our data show that the RGMA transcript is broadly expressed in the central nervous system of embryos and prolarvae and with a rostro-caudal gradient of expression.