Fig. 7: Schema of the proposed hypothesis on the photoperiodic regulation of gonadotrope cell mitosis via melatoinin, Tsh, and folliculostellate cells. | Communications Biology

Fig. 7: Schema of the proposed hypothesis on the photoperiodic regulation of gonadotrope cell mitosis via melatoinin, Tsh, and folliculostellate cells.

From: Day length regulates gonadotrope proliferation and reproduction via an intra-pituitary pathway in the model vertebrate Oryzias latipes

Fig. 7

In summer photoperiod (right panel), melatonin levels are suppressed, allowing Tsh cells to stimulate gene expression and mitosis of gonadotrope cells, via folliculostellate cells. As a result, an increasing number of gonadotrope cell due to mitosis participates in the increase in gonadotropin production necessary for gametogenesis and steroidogenesis, which allow the fish to reproduce. In winter photoperiod condition (left panel), high melatonin levels indirectly suppress tshba expression. In absence of Tsh stimulation, gene expression and mitosis of gonadotrope cells remain low. By contrast, melatonin indirectly upregulates tshbb expression that might inhibit Fsh and Lh, but this needs to be confirmed.

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