Figure 6

Ezh2 and HMGA2 proteins are more highly expressed in Dicer null cortical progenitor cells during development. Over the course of development neural progenitors become restricted to the generation of upper layer neuron types and this coincides with a decrease in Ezh2 and Hmga2 protein levels but the Dicer null cortex showed increased expression of both proteins compared to wild-type. (A) Hmga2+ foci were located along the ventricular surface in the wild-type and Dicer null E15.5 cortex confirming that Hmga2 is expressed in neural progenitor cells. (B) Magnification of boxed area in (A) showing overlap of Hmga2+ foci with the mitotic marker phospho-histone H3. (C) The number of Hmga2+ foci per 100 μm of ventricular zone was significantly increased in the Dicer null (P = 0.01) compared to the wild-type but despite the reduction in size of the ventricular zone, there was no difference in the number of mitotic cells. A total of three sections from three Dicer null and three wild-type littermate cortices were analysed. (D) Western blot of Ezh2 protein levels in the Dicer null cortex at E13.5 and E15.5 compared to the wild-type. Protein was extracted from two wild-type and two Dicer null brains at each time point. (E) Quantification of Ezh2 protein expression normalised to β-actin. (F) Expression of six let-7 family members in the E13.5 Dicer null cortex, compared with littermate controls. Expression is expressed as % of wild-type levels. Scale bars: 50 μm.