Figure 5.

PRC1 subunits localize to restricted OE subpopulations. (A) PRC1 complexes are highly diverse, owing to the multiple variants that exist for each subunit. For instance, a canonical PRC1 contains one of five possible CBX variants and one of six known PCGF variants. (B) Gene expression assays by RT–qPCR from expansion–competent basal cell cultures reveal heterogeneous expression of multiple PRC1 subunits. The PRC2 gene Ezh2, expressed in basal cells, is included for comparison. Gene expression is normalized to RPO, n=3 replicates, bars=SD. (C, D) The PCGF proteins BMI1 (PCGF4) and MEL18 (PCGF2) have complementary expression patterns in adult OE tissue. MEL18 (C) is widely present in globose basal cells (BCs) and immature neurons (iOSN), as well as weakly expressed in the apical sustentacular and microvillar cell layers (Sus/mV); BMI1 (D) is present in mature neurons (mOSN) as well as occasional upstream globose cells (arrows), previously reported to be the SOX2⁺ subset; note the absence of BMI1 label in the thin iOSN region in D, in contrast to MEL18 label in C. (E, F) CBX8 is a neuron–specific PRC1 subunit in the OE; CBX8 is restricted to the neuronal layers by immunohistochemistry (E); Western blot (F) confirms antigen of correct size is detected by anti–CBX8 from OE extracts. Nuclei are stained with DAPI (blue) C–E, Bar=10μm in C, 50μm in E.