Augmented expression of macrophage migration inhibitory factor (MIF) in the telencephalon of the developing rat brain

Macrophage migration inhibitory factor (MIF) has been characterized as a proinflammatory cytokine, hormone, and immunomodulator. We previously demonstrated the distribution of MIF in the adult rat brain and revealed its expression in neurons as well as glial cells. In this study, we investigated the localization of MIF in the developing rat brain from embryonic day (ED) 13 to ED19, and after birth from postnatal day (PD) 1 to PD28 using both immunohistochemistry and in situ hybridization. On ED16, the signals of MIF mRNA were high in the ventricular, subventricular, and intermediate zones of the telencephalon, in which 'neuropoietic' progenitor cells proliferate and migrate from the ventricular zone to the superficial layer in the cerebral cortex. The mRNA expression was detected throughout the postnatal period, and intense signals of the transcript were seen in the ventricle and in layers I, II and III of the cerebral cortex at PD5. Similarly, positive staining of MIF protein was seen in the ventricular zone by immunohistochemical analysis, although the positively stained area appeared to be smaller than the mRNA expression. Taken together, these results suggest that the increase in MIF mRNA in the developing brain reflects the growth and maturation of neurons and glial cells.