Suppressor of fused regulates neural progenitor cell cycle progression during mammalian hindbrain neurogenesis

Abstract

Hedgehog signaling is known for its mitogenic function. Suppressor of fused (Sufu) is a mediator of mammalian hedgehog signaling, majorly by negatively regulating Gli activities. However, the role of Sufu in the cell cycle of neural progenitors is unclear. It was previously observed that when Sufu was conditionally ablated in mouse hindbrain rhombomere 4 (r4), there was an expansion of Sox2+ neural progenitor pool. To explore possible contribution of the phenotype by any abnormalities in r4 neural progenitor cell cycle, a cumulative BrdU labelling scheme was applied to analyze cell cycle kinetics of hindbrain r4 at E11.5 in control and Sufu mutant. Since the expanded Sox2 domains in Sufu mutant primarily occupied the dorsal Pax6+ and Pax7+ regions, r4 was sub-divided into 4 progenitor domains along its dorsal-ventral axis to assess cell cycle individually. Preliminary data showed that Sufu mutant dorsal progenitors tended to extend their cell cycle length, with a lengthening of S-phase and a shortening of Gap phases compared to control. To temporally characterize the progenitor proliferation, 1hr BrdU labelling was performed to visualize S phase cells from E10.5 to E12.5. Normally the proportion of neural progenitors in S phase would decrease at E12.5 whereas Sufu mutant displayed an accumulation of S phase cells, especially in Pax6+ and Pax7+ domains, suggesting that Sufu might be required for the shortening of S phases during hindbrain neurogenesis. In summary, the data implied that Sufu is involved in the regulation of proper cell cycle progression in mammalian hindbrain neural progenitors.