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Expression of Shh (Sonic hedgehog) upregulates the production of [[Bmi1]], a component of the PcG complex that recognizes H3K27me3. This occurs in a Gli-dependent manner, as [[Gli1]] and [[Gli2]] are downstream effectors of the [[Hedgehog signaling pathway]]. In culture, Bmi1 mediates the Hedgehog pathway’s ability to promote human mammary stem cell self-renewal.<ref name = "Liu">{{cite journal |pmid=16778178 |doi=10.1158/0008-5472.CAN-06-0054 |author=Liu S, ''et al'' |title=Hedgehog Signaling and Bmi-1 Regulate Self-renewal of Normal and Malignant Human Mammary Stem Cells |journal=Cancer Res |year=2006 |volume=66 |issue=12 |pages=6063–71}}</ref> In both humans and mice, researchers showed Bmi1 to be highly expressed in proliferating immature cerebellar granule cell precursors. When Bmi1 was knocked out in mice, impaired cerebellar development resulted, leading to significant reductions in postnatal brain mass along with abnormalities in motor control and behavior.<ref name = "Leung">{{cite journal |pmid=15029199 |doi=10.1038/nature02385 |author=Leung C, ''et al'' |title=Bmi1 is essential for cerebellar development and is overexpressed in human medulloblastomas |journal=Nature |year=2004 |volume=428 |issue=6980 |pages=337–41|bibcode = 2004Natur.428..337L }}</ref> A separate study showed a significant decrease in neural stem cell proliferation along with increased astrocyte proliferation in Bmi null mice.<ref name = "Zencak">{{cite journal |pmid=15958744 |doi=10.1523/JNEUROSCI.3452-04.2005 |author=Zencak D, ''et al'' |title=Bmi1 loss produces an increase in astroglial cells and a decrease in neural stem cell population and proliferation |journal=J Neurosci |year=2005 |volume=25 |issue=24 |pages=5774–83}}</ref>
 
En resumo, o papel da sinalización no control epixenético do destino de diferenciación da célula en mamíferos descoñécese en grande medida, mais hai varios exemplos que indican a probable existencia de tales mecanismos.
In summary, the role of signaling in the epigenetic control of cell fate in mammals is largely unknown, but distinct examples exist that indicate the likely existence of further such mechanisms.
 
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