 While at the NINDS, Fischbach researched the effects of neuregulin, which is a family of proteins including heregulin, neu differentiation factor, ARIA, and glial growth factor that are critical for vertebrate embryogenesis and specifically for the formation of vertebrate spinal cord oligodendrocytes. Fischbach and his colleagues noticed that oligodendrocytes failed to form in mice that were homozygous for the mutant neuregulin gene. However, when wild-type neuregulin was added to homozygous mutant neuregulin explants (isolated tissue cell cultures) nine days after conception of the embryos, normal oligodendrocyte development occurred. This indicated that neuregulin is not necessary for the proliferation of oligodendrocyte multipotent precursor cells. Additionally, when IgB4, a neuregulin inhibitor, is added to wild-type explants, oligodendrocyte development failed to occur.
