Nicholas Gaiano - US grants

DESCRIPTION (provided by applicant): How the mammalian brain develops from a proliferating progenitor pool into the most intricate structure in the body is a fundamental question facing modern biology. The work proposed here investigates this question in the telencephalon, the embryonic structure that gives rise to the cerebral cortex and other areas of higher brain function. In addition, these studies will consider the relationship between embryonic neural progenitors and those present in the postnatal brain. Our specific objectives are to understand in depth how the Notch and FGF signaling pathways influence telencephalic progenitors. Previous studies have shown that these pathways play critical roles during progenitor maintenance, proliferation, and differentiation. A defining feature of our approach is an emphasis on characterizing progenitors in vivo. Using our uniquely powerful gain-of-function system, we will genetically modify neural progenitors in the mouse embryo in utero, and examine the fate of those cells during development and in the adult. By combining this approach with in vitro proliferation and developmental potential assays, we will gain insight into the endogenous mechanisms regulating neural progenitors. These studies will also seek to determine specifically which receptors and downstream effectors mediate the effects of Notch signaling in telencephalic progenitors. This work will be complemented by loss-of-function studies focused on understanding the effects of deleting Notch and FGF receptors in telencephalic progenitors. Furthermore, using a novel transgenic approach we will prospectively isolate and characterize telencephalic progenitors containing endogenous Notch activation. By advancing an understanding of the basic mechanisms that regulate mammalian neural progenitors we hope to uncover fundamental principles with potential medical utility. In particular, these studies are likely to facilitate the manipulation of stem cells for therapeutic use in the nervous system and elsewhere.

The mechanisms regulating cell fate specification in the mammalian brain remain only partially understood. The Notch signaling pathway is known to regulate neural stem cells, although the function of Notch signaling in distinct proliferative neural subtypes remains unclear. Our recent findings have created a new foundation on which to investigate the regulation of neural progenitor heterogeneity, in particular with respect to Notch signaling. We have identified two molecularly distinct proliferative cell types in the neocortical ventricular zone (VZ), referred to hereafter as neural stem cells (NSCs) and intermediate neural progenitors (INPs). NSCs and INPs differentially utilize the Notch pathway, with the former signaling robustly through the canonical CBF1/Hes cascade, and the later possessing a stable attenuation and/or redirection of that cascade. The proposed studies will continue this novel line of investigation, with an emphasis on probing the differential regulation of Notch signaling in NSCs and INPs. In addition, as a new and exciting component of this work, we will examine a recently identified Notch pathway modulator, Pokemon (LRF/Zbtb7a), which has been shown to regulate Notch signaling in the immune system, and is expressed in the VZ of the developing brain. The proposed studies will employ a wide range of experimental approaches, including in vivo gain-of-function and loss-of-function, flow cytometry, chromatin immuno-precipitation (ChiP), and in vitro progenitor culturing and differentiation. These studies will greatly enhance our understanding of mammalian forebrain development. In addition, this work will contribute to the treatment of nervous system disorders, including brain cancer and neurodegenerative diseases, and to the treatment of traumatic brain injury.