Cell cycle-regulated expression of Fam72a from the |Srgap2–Fam72a| master gene leads to Mis18a downregulation

The novel |Srgap2-Fam72a| master gene, comprising SLIT-ROBO Rho GTPase-activating protein 2 (Srgap2) and family with sequence similarity 72 member A (Fam72a), has attracted attention for its potential role in regulating brain plasticity and supporting advanced cognitive functions in humans. Moreover, recent studies have identified Fam72a as a new cell cycle-regulated gene. In this study, we investigated the activity of the intergenic region (IGR) between the native Srgap2 and Fam72a gene pair and the signaling pathways of Fam72a upon mitogen epidermal growth factor (Egf) stimulation. We found that, under mitogen Egf stimulation, the IGR functions as a divergent promoter, simultaneously driving the transcription of Srgap2 and Fam72a in opposite directions. Furthermore, Fam72a downregulates MIS18 kinetochore protein A (Mis18a), a tightly cell cycle-regulated gene, and interferes with the RAC-alpha serine/threonine-protein kinase (Akt1) signaling pathway by downregulating phosphorylated Akt1 at Serine 473, thereby favoring the more direct mitogen activated protein kinase 1 (Mapk1) route to promote cellular proliferation. These findings provide insight into the role of Fam72a during the cell cycle and suggest that it may contribute to the proliferation of neural stem cells (NSCs).