Figure 7. Ptbp1 and Rbfox Proteins Antagonistically Control Neural Progenitor Cell Differentiation.
A) Immunostaining of E18.5 Ptbp1 conditional knockout (cKO, Nestin-Cre) cerebral cortex showing typical PVNH (white arrow) and thinner ventricular layer of Pax6+ cells (brackets).
B) Western blot of Ptbp1 cKO and control MEF cells showing that proteins level of Ptbp1, Flna and Flnb are decreased in Ptbp1 cKO, while Ptbp2 level is increased.
C) RT-PCR results showing that Ptbp1 cKO in MEF cells de-represses the inclusion of Flna exonN and a 98-nt Flnb exon.
D) –E) Representative images and statistical analysis E) showing that Ptbp1 knockdown (green) at E13.5 results in reduced neural progenitors in the VZ at E15.5. The defect was partially rescued by co-expression of Ptbp1 coding sequence (CDS, red) or FLNA CDS. Numbers in parentheses indicate the number of embryos analyzed. Data are represented as mean +/− SD.
F) –G) Representative images and statistical analysis G) showing that introducing Rbfox3 expression into E13.5 mouse brains resulted in reduced progenitor cells in the VZ and reduced neurons in the CP at E16.5. Ectopic expression of Rbfox3 on top of Ptbp1 knockdown causes a more severe depletion of NPCs in the VZ. Data are represented as mean +/− SD.
H) A working model showing that Rbfox1/2/3 proteins are highly expressed in neurons and promote neuronal exon inclusion (red), while Ptbp1 is expressed in NPCs (blue, VZ) and represses neuronal exon inclusion. Sox2 binds to the promoter region of Ptbp1 (left). Dysregulation of Rbfox1/2/3 mediated AS may lead to brain disorders such as autism and intellectual disability. Mutations that de-represses neuronal exon inclusion in NPCs may result in PVNH (through FLNA).
See also Figure S7.