Prox1 regulates a transitory state for interneuron neurogenesis in the spinal cord

Misra, Kamana; Gui, Hongxing; Matise, Michael P.

doi:10.1002/dvdy.21519

Cited by 14 publications

(47 citation statements)

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“…This expression pattern is similar to p21 (Fig. 5J), which marks nascent INs as they undergo a transition from late G1 to early G0 phase (Misra et al, 2008).As Msx genes are known BMP signaling targets (Liu et al, 2004), our observations raised the possibility that BMP signaling may have a role in V2b IN specification. To test this possibility, we transfected a construct encoding the activated BMP receptor 1b (ABMPR) into chick SCs.…”

supporting

confidence: 75%

“…Smad4 shRNA plasmid was generated by inserting the already characterized region of Smad4 effective for gene silencing (Jazag et al, 2005) into the pBS/U6 (pU6) RNAi vector (Sui et al, 2002): 5′-GATCCGGCAGCCATAGTGAAGGACTGTTCAAGAGACAGTCCTTC -ACTATGGCTGCCTTTTTTTG-3′ and 5′-AATTCAAAAAAAGGCAGCC -ATAGTGAAGGACTGTCTCTTGAACAGTCCTTCACTATGGCTGCCG-3′. Scrambled control sequences generated by Genescript software were: 5′-GATCCGGAGTAAGCTACCGGTAAGGCTTCAAGAGAGCCTTACCG -GTAGCTTACTCCTTTTTTTG-3′ and 5′-AATTCAAAAAAAGGAGT -AAGCTACCGGTAAGGCTCTCTTGAAGCCTTACCGGT AGC T-TAC-TCCG-3′.Immunostaining, RNA in situ hybridization and BrdU labeling In-ovo BrdU labeling, immunostaining and in situ hybridization were performed as described previously Mo et al, 2004;Misra et al, 2008). The following primary antibodies were used: rabbit anti-Foxn4 Wang et al, 1996).…”

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confidence: 99%

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Asymmetric activation of Dll4-Notch signaling by Foxn4 and proneural factors activates BMP/TGFβ signaling to specify V2b interneurons in the spinal cord

Misra

Luo

et al. 2014

Development

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During development of the ventral spinal cord, the V2 interneurons emerge from p2 progenitors and diversify into two major subtypes, V2a and V2b, that play key roles in locomotor coordination. Dll4-mediated Notch activation in a subset of p2 precursors constitutes the crucial first step towards generating neuronal diversity in this domain. The mechanism behind the asymmetric Notch activation and downstream signaling events are, however, unknown at present. We show here that the Ascl1 and Neurog basic helix-loop-helix (bHLH) proneural factors are expressed in a mosaic pattern in p2 progenitors and that Foxn4 is required for setting and maintaining this expression mosaic. By binding directly to a conserved Dll4 enhancer, Foxn4 and Ascl1 activate Dll4 expression, whereas Neurog proteins prevent this effect, thereby resulting in asymmetric activation of Dll4 expression in V2 precursors expressing different combinations of proneural and Foxn4 transcription factors. Lineage tracing using the Cre-LoxP system reveals selective expression of Dll4 in V2a precursors, whereas Dll4 expression is initially excluded from V2b precursors. We provide evidence that BMP/TGFβ signaling is activated in V2b precursors and that Dll4-mediated Notch signaling is responsible for this activation. Using a gain-of-function approach and by inhibiting BMP/TGFβ signal transduction with pathway antagonists and RNAi knockdown, we further demonstrate that BMP/TGFβ signaling is both necessary and sufficient for V2b fate specification. Our data together thus suggest that the mosaic expression of Foxn4 and proneural factors may serve as the trigger to initiate asymmetric Dll4-Notch and subsequent BMP/TGFβ signaling events required for neuronal diversity in the V2 domain.KEY WORDS: V2 interneuron, Spinal cord, Foxn4, Ascl1, bHLH proneural factor, Dll4-Notch, BMP/TGFβ, Chick, Mouse INTRODUCTIONNeuronal diversity during spinal cord (SC) development is initially generated by activities of two competing signaling pathways: sonic hedgehog (Shh) ventrally and bone morphogenetic proteins (BMPs)/Wnt dorsally (Martí et al., 1995;Ericson et al., 1997 Edlund and Jessell, 1999;Jessell, 2000;Muroyama et al., 2002). Additional pathways subsequently get involved (Sockanathan and Jessell, 1998;Novitch et al., 2003;Mizuguchi et al., 2006;Wildner et al., 2006;Del Barrio et al., 2007;Peng et al., 2007). Themed on the traditional paradigm, Hh signals are localized to the ventral SC and Gli repressor forms restrict activity in the dorsal SC (Jacob and Briscoe, 2003;Meyer and Roelink, 2003;Matise and Wang, 2011). Similarly, Wnt ligands are mostly restricted to dorsal regions, whereas inhibitors such as secreted Frizzled related proteins (sFRPs) are expressed in the ventral SC (Wodarz and Nusse, 1998;Kim et al., 2001;Kawano and Kypta, 2003). BMP/TGFβ signaling, however, does not phenocopy this model. For instance, though implicated in dorsal fate specification, expression of Tgfβ2 is observed in notochord and floor plate (García-Campmany and Martí, 2007). Additiona...

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supporting

confidence: 75%

mentioning

confidence: 99%

Asymmetric activation of Dll4-Notch signaling by Foxn4 and proneural factors activates BMP/TGFβ signaling to specify V2b interneurons in the spinal cord

Misra

Luo

et al. 2014

Development

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“…Prox1 is a prospero-related homeodomain transcription factor, which is highly expressed in DG granule cells (10,15,16). Prox1 has previously been shown to be important for lens development, lymphangiogenesis, differentiation of certain spinal cord interneurons, and, very recently, in hippocampal granule cell genesis (17)(18)(19)(20). We analyzed the murine Prox1 promoter/enhancer regions for TCF/LEF sites and found two TCF/LEF consensus sites 49 kb and 43 kb upstream of the Prox1 start codon (Fig.…”

Section: Resultsmentioning

confidence: 99%

Prospero-related homeobox 1 gene (Prox1) is regulated by canonical Wnt signaling and has a stage-specific role in adult hippocampal neurogenesis

Karalay

Doberauer

Vadodaria

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

179

174

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Neural stem cells (NSCs) generate new granule cells throughout life in the mammalian hippocampus. Canonical Wnt signaling regulates the differentiation of NSCs towards the neuronal lineage. Here we identified the prospero-related homeodomain transcription factor Prox1 as a target of β-catenin–TCF/LEF signaling in vitro and in vivo. Prox1 overexpression enhanced neuronal differentiation whereas shRNA-mediated knockdown of Prox1 impaired the generation of neurons in vitro and within the hippocampal niche. In contrast, Prox1 was not required for survival of adult-generated granule cells after they had matured, suggesting a role for Prox1 in initial granule cell differentiation but not in the maintenance of mature granule cells. The data presented here characterize a molecular pathway from Wnt signaling to a transcriptional target leading to granule cell differentiation within the adult brain and identify a stage-specific function for Prox1 in the process of adult neurogenesis.

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“…During neurogenesis, the developing spinal cord is organized into a VZ and an MZ composed of proliferative NPCs and postmitotic and differentiating neurons, respectively (19,20). Cells moving out of the VZ and on their way to the MZ express NeuroM (13,31).…”

Section: Discussionmentioning

confidence: 99%

“…2C). Cells in the IZ are differentiating nascent neurons that undergo cell-cycle exit (19,20). Because Smad6 was expressed mainly in the IZ of dorsal neural tubes and was required for the neuronal differentiation, knockdown of Smad6 in this region may inhibit the differentiation of nascent neurons and result in the reduction in number of neurons that are migrating from the IZ to the MZ.…”

Section: Smad6 Is Required For Neuronal Differentiation Of Developingmentioning

confidence: 99%

Smad6 promotes neuronal differentiation in the intermediate zone of the dorsal neural tube by inhibition of the Wnt/β-catenin pathway

Xie

Chen

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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Proliferation of the neural/neuronal progenitor cells (NPCs) at the ventricular zone of the dorsal spinal cord requires the stimuli of Wnt and bone morphogenic protein (BMP). However, how these two signaling pathways are regulated to initiate differentiation in the NPCs as they enter the intermediate zone is not known. Here, we show that Smad6, a negative regulator of BMP signaling, is expressed in the intermediate zone of the chick dorsal spinal cord. Knockdown experiments show that Smad6 is required for promoting NPCs to exit the cell cycle and differentiate into neurons. Although we find that Smad6 inhibits BMP signaling, as expected, we also find that Smad6 unexpectedly inhibits the Wnt/β-catenin pathway. The inhibition of the Wnt/β-catenin pathway by Smad6 is independent of its effect on the BMP pathway. Rather, Smad6 through its N-terminal domain and link region enhances the interaction of C-terminal binding protein with the β-catenin/T cell factor (TCF) complex and the TCF-binding element to inhibit β-cateninmediated transcriptional activation. Our study provides evidence that transition of NPCs from a proliferative state to a differentiating state is controlled by the dual inhibitory role of Smad6 to both BMP and Wnt signaling at the level of transcription.intermediate zone | neurogenesis P recise spatial and temporal regulation of neural development is essential for generating the complex central nervous system (CNS) found in adult organisms (1, 2). In early neural development, neural progenitor cells are seemingly homogeneous (3, 4); as neurogenesis proceeds, cells acquire different developmental potentials and become located in different tissue compartments or zones (5). At midneurogenesis, the developing cerebral cortex is composed of the ventricular zone (VZ), subventricular zone (SVZ), intermediate zone (IZ), cortical plate (CP), and marginal zone (6). Cells located in the VZ are proliferative neural progenitor cells (7). These cells progressively initiate the expression of proneural genes, such as mouse achaete-scute complex homolog 1 (Mash1) and neurogenins in response to region-specific neurogenic signals (8-10). Proneural genes drive neural progenitor cells to become intermediate neuronal progenitor cells, and these cells migrate out from the VZ and localize to the SVZ (11, 12). Subsequently, neuronal progenitor cells exit the cell cycle, differentiate into nascent neurons in the IZ, and then migrate to the CP (11). It is generally accepted that in the developing spinal cord proliferative neural/ neuronal progenitor cells (NPCs) in the VZ produce postmitotic neurons that migrate directly into the mantle zone (MZ). However, in the developing chick spinal cord, a transition region similar to the IZ has been described between the VZ and MZ marked by expression of the neurogenic differentiation 4 (NeuroM) transcription factor at midneurogenesis (13). It is not clear whether other genes also are expressed in a similar pattern and are potentially involved in the transition between NPC proliferation a...

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Prox1 regulates a transitory state for interneuron neurogenesis in the spinal cord

Cited by 14 publications

References 0 publications

Asymmetric activation of Dll4-Notch signaling by Foxn4 and proneural factors activates BMP/TGFβ signaling to specify V2b interneurons in the spinal cord

Asymmetric activation of Dll4-Notch signaling by Foxn4 and proneural factors activates BMP/TGFβ signaling to specify V2b interneurons in the spinal cord

Prospero-related homeobox 1 gene (Prox1) is regulated by canonical Wnt signaling and has a stage-specific role in adult hippocampal neurogenesis

Smad6 promotes neuronal differentiation in the intermediate zone of the dorsal neural tube by inhibition of the Wnt/β-catenin pathway

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