RNA-binding protein that plays a central role in myelinization. Binds to the 5'-NACUAAY-N(1,20)-UAAY-3' RNA core sequence. Acts by regulating pre-mRNA splicing, mRNA export, mRNA stability and protein translation. Required to protect and promote stability of mRNAs which promotes oligodendrocyte differentiation. Participates in mRNA transport by regulating the nuclear export of MBP mRNA. Also involved in regulation of mRNA splicing of some pre-mRNA. Acts as a translational repressor (By similarity). Homodimer. Does not require RNA to homodimerize (By similarity). Maternally and zygotically expressed. Ubiquitously expressed during cleavage and blastula periods, and then it accumulates in the dorsal midline of the body trunk during gastrulation. During segmentation and pharyngula periods it is expressed in the neural tissue of the head region, and in the paraxial mesoderm of the body trunk. Subsequently expression diminishes until the hatching period, when it is expressed only in the cardiac sac and pectoral finbuds. Isoform 2 localizes in neural tissue in the head region, but not in the paraxial mesoderm in the body trunk.