BMP4 and spina bifida: RNA-seq analysis indicated alterations in BMP signaling earlier in gestation (E15); therefore, in order to determine the involvement of BMP signaling in accelerated astrogenesis in RA-induced spina bifida we assessed the expression of Sox9, Notch1, BMP2, and BMP4 in MMC fetal spinal cords compared to control and vehicle fetal spinal cords.