Layer-specific differential regulation of transcription factors Zif268 and Jun-D in visual cortex V1 and V2 of macaque monkeys.

To investigate intracellular mechanisms of cortical layer-specific gene regulation, we quantitatively examined the expression of two transcription factors, Zif268 and JunD, and compared their expression levels in each layer of the primary visual cortex (VI) and visual area 2 (V2) of macaque monkeys (Macaca fuscata). The brain sections were immunohistochemically stained for determination of the percentage of Zif268- or JunD-expressing neurons in the total neuronal population. We found area- and layer-specific expression of these transcription factors; Zif268 tended to be expressed at high levels in layers on the parvocellular pathway in V1, whereas JunD did not show such an expression pattern. In V1, many Zif268-immunopositive neurons were observed in layers II/III, IVC beta and VI. The percentage of Zif268-immunopositive neurons was highest in layer IVC beta and lowest in layer IVC alpha. JunD-immunopositive neurons were fewest in layer IVC beta and most abundant in layer VI. In V2, the level of expression of Zif268 was almost the same as that of JunD in layer II/II. However, layer IV of V2 tended to contain more Zif268-immunopositive neurons than JunD-immunopositive neurons, whereas layer VI contained more JunD-immunopositive neurons than Zif268-immunopositive neurons. Although it has been reported that the same extracellular signals induce both Zif268 and JunD, the present results indicate that the expression of these transcription factors is differentially controlled in each layer of the primate visual cortical areas. Furthermore, the present results suggest that these transcription factors contribute to area- and layer-specific gene regulation by mediating transmission of extracellular signals to the nucleus via different intracellular signalling pathways.