Lgr5 CGNs are non-proliferative and post-mitotic.

<p><b>a, b</b>) Cerebellar sections from <i>Lgr5^EGFP-CreERT2</i> mice were stained for the proliferation marker Ki67 and Lgr5-EGFP at both <b>a</b>) early (P7) and <b>b</b>) late (P14) stages of Lgr5 expression. Lgr5+ cells were uniformly negative for Ki67. Scale bars 50 microns. <b>c</b>) Lineage tracing was initiated at P4 in <i>Lgr5^EGFP-CreERT2; R26R^tdTomato</i> mice and cerebella analyzed for Ki67 at P10. Many other lineage trace time points were also analyzed (data not shown). Cells post-Lgr5 expression (tdTomato+) were uniformly negative for Ki67 in every time point analyzed. Note that immature granule neurons in the EGL in A-C were Ki67+, as expected. Scale bars for C <i>top</i>: 400 microns, <i>bottom</i>: 100 microns. <b>d</b>) <i>Lgr5^EGFP-CreERT2</i> mice were crossed with <i>Catnb^flox(exon3)</i> mice to yield <i>Lgr5^EGFP-CreERT2</i>; <i>Catnb^flox(exon3)</i> mice. Upon tamoxifen administration, Cre recombinase initiates expression of a constitutively active form of β-catenin in cells with an active <i>Lgr5</i> locus. <b>e</b>) Tamoxifen was administered at P4 and cerebella were analyzed at P25, when these mice die of other complications related to transgene expression. β-catenin over-activity led to prolonged Lgr5 expression in the IGL in <i>Lgr5^EGFP-CreERT2</i>; <i>Catnb^flox(exon3</i> mice (center panel), but not wild type (right panel). The normal architecture of the cerebellum was maintained in both conditions. Scale bars 400 microns. <b>f, g</b>) Lgr5+ CGNs from P25 <i>Lgr5^EGFP-CreERT2</i>; <i>Catnb^flox(exon3)</i> mice with tamoxifen administration at P4 were <b>f</b>) positive for Gabra6 and <b>g</b>) negative for Ki67. Scale bars, <i>bottom left</i>: 200 microns, <i>other 5 panels</i>: 25 microns.