semar4dPierre Semard (15 February 1887 – 7 March 1942) was a trade unionist, secretary general of the federation of railway-workers and leader of the French Communist Party (acting asSemaphorin 4D (Sema 4D) is an axon guidance molecule which is secreted by olodendrocytes and induces growth cone collapse in the central nervous system.By binding plexin B1 receptor