A regulatory network involving Foxn4, Mash1 and delta-like 4/Notch1 generates V2a and V2b spinal interneurons from a common progenitor pool

Harvard University, Cambridge, Massachusetts, United States
Development (Impact Factor: 6.46). 11/2007; 134(19):3427-36. DOI: 10.1242/dev.005868
Source: PubMed


In the developing central nervous system, cellular diversity depends in part on organising signals that establish regionally restricted progenitor domains, each of which produces distinct types of differentiated neurons. However, the mechanisms of neuronal subtype specification within each progenitor domain remain poorly understood. The p2 progenitor domain in the ventral spinal cord gives rise to two interneuron (IN) subtypes, V2a and V2b, which integrate into local neuronal networks that control motor activity and locomotion. Foxn4, a forkhead transcription factor, is expressed in the common progenitors of V2a and V2b INs and is required directly for V2b but not for V2a development. We show here in experiments conducted using mouse and chick that Foxn4 induces expression of delta-like 4 (Dll4) and Mash1 (Ascl1). Dll4 then signals through Notch1 to subdivide the p2 progenitor pool. Foxn4, Mash1 and activated Notch1 trigger the genetic cascade leading to V2b INs, whereas the complementary set of progenitors, without active Notch1, generates V2a INs. Thus, Foxn4 plays a dual role in V2 IN development: (1) by initiating Notch-Delta signalling, it introduces the asymmetry required for development of V2a and V2b INs from their common progenitors; (2) it simultaneously activates the V2b genetic programme.

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Available from: William David Richardson, Jan 06, 2016
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    • "For retinal and spinal cord progenitors, Dll1 and Dll4 are both involved in their proliferation. While Dll1 appears to regulate neurogenesis in a domain-specific manner in the spinal cord (Marklund et al., 2010; Ramos et al., 2010), Dll4 is additionally required for generating neuronal diversity (Del Barrio et al., 2007; Rocha et al., 2009; Luo et al., 2012). Dll4-mediated Notch signaling has been shown to be essential for vascular remodeling and arterial angiogenesis, T cell differentiation , and neural development (Liu et al., 2003; Corada et al., 2010; Billiard et al., 2011). "
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    ABSTRACT: Background: During retinal and spinal cord neurogenesis, Notch signaling plays crucial roles in regulating proliferation and differentiation of progenitor cells. One of the Notch ligands, Delta-like 4 (Dll4), has been shown to be expressed in subsets of retinal and spinal cord progenitors/precursors and involved in neuronal subtype specification. However, it remains to be determined whether Dll4 expression has any progenitor/precursor-specificity contributing to its functional specificity during neural development. Results: We generated a Dll4-Cre BAC transgenic mouse line that drives Cre recombinase expression mimicking that of the endogenous Dll4 in the developing retina and spinal cord. By fate-mapping analysis, we found that Dll4-expressing progenitors/precursors give rise to essentially all cone, amacrine and horizontal cells, a large portion of rod and ganglion cells, but only few bipolar and Müller cells. In the spinal cord, Dll4-expressing progenitors/precursors generate almost all V2a and V2c cells while producing only a fraction of the cells for other interneuron and motor neuron subtypes along the dorsoventral axis. Conclusions: Our data suggest that selective expression of Dll4 in progenitors/precursors contributes to its functional specificity in neuronal specification and that the Dll4-Cre line is a valuable tool for gene manipulation to study Notch signaling.
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    • "Analysis of mid-cervical ventral spinal cord revealed that at E10.5, which is when MNs emerge from the pMN domain, a cluster of Dll4-positive cells is located just dorsal of nascent Pou3f1+ Isl1/2+ MNs (Fig. 6A,B). Previous studies have mapped Dll4 expression to the p2 progenitor domain (Del Barrio et al., 2007; Peng et al., 2007). Furthermore, Notch1 protein is detectable on the most immature, medial MNs, and Pou3f1 expression in MNs overlaps with that of the Notch target gene Hey1 (supplementary material Fig. S11). "
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    Full-text · Article · Feb 2014 · Development
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    • "In the developing mouse spinal cord, Notch1 and Notch3 are mainly expressed in the ventricular zone, and Notch2 in the floor plate [11]. Interestingly, Notch1 signaling is selectively responsible for the differentiation of interneurons in the V2 domain and of motoneurons in the VMN domain [7], [11]. "
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    ABSTRACT: Members of the ADAM (a disintegrin and metalloprotease) family are involved in embryogenesis and tissue formation via their proteolytic function, cell-cell and cell-matrix interactions. ADAM10 is expressed temporally and spatially in the developing chicken spinal cord, but its function remains elusive. In the present study, we address this question by electroporating ADAM10 specific morpholino antisense oligonucleotides (ADAM10-mo) or dominant-negative ADAM10 (dn-ADAM10) plasmid into the developing chicken spinal cord as well as by in vitro cell culture investigation. Our results show that downregulation of ADAM10 drives precocious differentiation of neural progenitor cells and radial glial cells, resulting in an increase of neurons in the developing spinal cord, even in the prospective ventricular zone. Remarkably, overexpression of the dn-ADAM10 plasmid mutated in the metalloprotease domain (dn-ADAM10-me) mimics the phenotype as found by the ADAM10-mo transfection. Furthermore, in vitro experiments on cultured cells demonstrate that downregulation of ADAM10 decreases the amount of the cleaved intracellular part of Notch1 receptor and its target, and increases the number of βIII-tubulin-positive cells during neural progenitor cell differentiation. Taken together, our data suggest that ADAM10 negatively regulates neuronal differentiation, possibly via its proteolytic effect on the Notch signaling during development of the spinal cord.
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