The P-body protein 4E-T represses translation to regulate the balance between cell genesis and establishment of the postnatal NSC pool.

Here, we ask how developing precursors maintain the balance between cell genesis for tissue growth and establishment of adult stem cell pools, focusing on postnatal forebrain neural precursor cells (NPCs). We show that these NPCs are transcriptionally primed to differentiate and that the primed mRNAs are associated with the translational repressor 4E-T. 4E-T also broadly associates with other NPC mRNAs encoding transcriptional regulators, and these are preferentially depleted from ribosomes, consistent with repression. By contrast, a second translational regulator, Cpeb4, associates with diverse target mRNAs that are largely ribosome associated. The 4E-T-dependent mRNA association is functionally important because 4E-T knockdown or conditional knockout derepresses proneurogenic mRNA translation and perturbs maintenance versus differentiation of early postnatal NPCs in culture and in vivo. Thus, early postnatal NPCs are primed to differentiate, and 4E-T regulates the balance between cell genesis and stem cell expansion by sequestering and repressing mRNAs encoding transcriptional regulators.

Immunohistochemical analysis of the developing mouse cortex.

The cerebral cortex is the most complex structure in the mammalian brain, whose development requires coordinated proliferation of neural stem/precursor cells (NPCs) and their differentiation into neurons and glia. Perturbations in NPC homeostasis can lead to abnormal cortical development which is frequently seen in neurodevelopmental disorders. In this chapter, we describe the preparation of cortical tissues from mice and step-by-step protocol for immunohistochemistry to study cortical development. With this technique, we employ commonly used molecular markers and thymidine analog methods to analyze NPC populations. We also discuss assay conditions that can be optimized according to the specific needs to improve experimental outcomes.