Project description:During development, two cell types born from closely related progenitor pools often express identical transcriptional regulators despite their completely distinct characteristics. This phenomenon implies the need for a mechanism that operates to segregate the identities of the two cell types throughout differentiation after initial fate commitment. To understand this mechanism, we investigated the fate specification of spinal V2a interneurons, which share important developmental genes with motor neurons (MNs). We demonstrate that the paired homeodomain factor Chx10 functions as a critical determinant for V2a fate and is required to consolidate V2a identity in postmitotic neurons. Chx10 actively promotes V2a fate, downstream of the LIM-homeodomain factor Lhx3, while concomitantly suppressing the MN developmental program by preventing the MN-specific transcription complex from binding and activating MN genes. This dual activity enables Chx10 to effectively separate the V2a and MN pathways. Our study uncovers a widely applicable gene regulatory principle for segregating related cell fates.
Project description:During development, two cell-types born from closely related progenitor pools often express the identical transcriptional regulators despite their completely distinct characteristics. This phenomenon highlights the necessity of the mechanism that operates to segregate the identities of the two cell-types throughout differentiation after initial fate commitment. To understand this mechanism, we investigated the fate specification of spinal V2a interneurons, which share important developmental genes with motor neurons (MNs). Here we demonstrate that the paired homeodomain factor Chx10 functions as a critical determinant for V2a fate and is required to consolidate V2a identity in postmitotic neurons. Chx10 actively promotes V2a fate, downstream of the LIM-homeodomain factor Lhx3, while concomitantly suppressing MN developmental program by preventing the MN-specific transcription complex from binding and activating MN genes. This dual activity enables Chx10 to effectively separate V2a and MN pathways. Together, our study uncovers a widely applicable gene regulatory principle for segregating related cell fates. ChIP DNA samples from Chx10-ESC-derived MNs were prepared for sequencing according to the Illumina protocol, and sequenced on the Illumina HiSeq 2000. The peak calling was conducted with MACS software (Zhang et al., 2008). MEME-ChIP Suite (Bailey et al., 2009; Machanick and Bailey, 2011) and TOMTOM algorithm (Gupta et al., 2007) was used for motif analysis.
Project description:During development, two cell-types born from closely related progenitor pools often express the identical transcriptional regulators despite their completely distinct characteristics. This phenomenon highlights the necessity of the mechanism that operates to segregate the identities of the two cell-types throughout differentiation after initial fate commitment. To understand this mechanism, we investigated the fate specification of spinal V2a interneurons, which share important developmental genes with motor neurons (MNs). Here we demonstrate that the paired homeodomain factor Chx10 functions as a critical determinant for V2a fate and is required to consolidate V2a identity in postmitotic neurons. Chx10 actively promotes V2a fate, downstream of the LIM-homeodomain factor Lhx3, while concomitantly suppressing MN developmental program by preventing the MN-specific transcription complex from binding and activating MN genes. This dual activity enables Chx10 to effectively separate V2a and MN pathways. Together, our study uncovers a widely applicable gene regulatory principle for segregating related cell fates. RNA samples from Chx10-ESC-derived MNs were prepared for sequencing according to the Illumina protocol, and sequenced on the Illumina HiSeq 2000. We will then compare the transcriptome changes between -Dox (no Chx10) and +Dox (Chx10) in order to identify genes rregulated by Chx10.
Project description:During development, two cell-types born from closely related progenitor pools often express the identical transcriptional regulators despite their completely distinct characteristics. This phenomenon highlights the necessity of the mechanism that operates to segregate the identities of the two cell-types throughout differentiation after initial fate commitment. To understand this mechanism, we investigated the fate specification of spinal V2a interneurons, which share important developmental genes with motor neurons (MNs). Here we demonstrate that the paired homeodomain factor Chx10 functions as a critical determinant for V2a fate and is required to consolidate V2a identity in postmitotic neurons. Chx10 actively promotes V2a fate, downstream of the LIM-homeodomain factor Lhx3, while concomitantly suppressing MN developmental program by preventing the MN-specific transcription complex from binding and activating MN genes. This dual activity enables Chx10 to effectively separate V2a and MN pathways. Together, our study uncovers a widely applicable gene regulatory principle for segregating related cell fates.
Project description:During development, two cell-types born from closely related progenitor pools often express the identical transcriptional regulators despite their completely distinct characteristics. This phenomenon highlights the necessity of the mechanism that operates to segregate the identities of the two cell-types throughout differentiation after initial fate commitment. To understand this mechanism, we investigated the fate specification of spinal V2a interneurons, which share important developmental genes with motor neurons (MNs). Here we demonstrate that the paired homeodomain factor Chx10 functions as a critical determinant for V2a fate and is required to consolidate V2a identity in postmitotic neurons. Chx10 actively promotes V2a fate, downstream of the LIM-homeodomain factor Lhx3, while concomitantly suppressing MN developmental program by preventing the MN-specific transcription complex from binding and activating MN genes. This dual activity enables Chx10 to effectively separate V2a and MN pathways. Together, our study uncovers a widely applicable gene regulatory principle for segregating related cell fates.
Project description:Chx10-expressing V2a (Chx10+V2a) spinal interneurons play a large role in the excitatory drive of motoneurons. Chemogenetic ablation studies have demonstrated the essential nature of Chx10+V2a interneurons in the regulation of locomotor initiation, maintenance, alternation, speed, and rhythmicity. The role of Chx10+V2a interneurons in locomotion and autonomic nervous system regulation is thought to be robust, but their precise role in spinal motor regulation and spinal cord injury have not been fully explored. The present paper reviews the origin, characteristics, and functional roles of Chx10+V2a interneurons with an emphasis on their involvement in the pathogenesis of spinal cord injury. The diverse functional properties of these cells have only been substantiated by and are due in large part to their integration in a variety of diverse spinal circuits. Chx10+V2a interneurons play an integral role in conferring locomotion, which integrates various corticospinal, mechanosensory, and interneuron pathways. Moreover, accumulating evidence suggests that Chx10+V2a interneurons also play an important role in rhythmic patterning maintenance, left-right alternation of central pattern generation, and locomotor pattern generation in higher order mammals, likely conferring complex locomotion. Consequently, the latest research has focused on postinjury transplantation and noninvasive stimulation of Chx10+V2a interneurons as a therapeutic strategy, particularly in spinal cord injury. Finally, we review the latest preclinical study advances in laboratory derivation and stimulation/transplantation of these cells as a strategy for the treatment of spinal cord injury. The evidence supports that the Chx10+V2a interneurons act as a new therapeutic target for spinal cord injury. Future optimization strategies should focus on the viability, maturity, and functional integration of Chx10+V2a interneurons transplanted in spinal cord injury foci.
Project description:LIM transcription factors bind to nuclear LIM interactor (Ldb/NLI/Clim) in specific ratios to form higher-order complexes that regulate gene expression. Here we examined how the dosage of LIM homeodomain proteins Isl1 and Isl2 and LIM-only protein Lmo4 influences the assembly and function of complexes involved in the generation of spinal motor neurons (MNs) and V2a interneurons (INs). Reducing the levels of Islet proteins using a graded series of mutations favored V2a IN differentiation at the expense of MN formation. Although LIM-only proteins (LMOs) are predicted to antagonize the function of Islet proteins, we found that the presence or absence of Lmo4 had little influence on MN or V2a IN specification. We did find, however, that the loss of MNs resulting from reduced Islet levels was rescued by eliminating Lmo4, unmasking a functional interaction between these proteins. Our findings demonstrate that MN and V2a IN fates are specified by distinct complexes that are sensitive to the relative stoichiometries of the constituent factors and we present a model to explain how LIM domain proteins modulate these complexes and, thereby, this binary-cell-fate decision.
Project description:V2a interneurons are located in the hindbrain and spinal cord, where they provide rhythmic input to major motor control centers. Many of the phenotypic properties and functions of excitatory V2a interneurons have yet to be fully defined. Definition of these properties could lead to novel regenerative therapies for traumatic injuries and drug targets for chronic degenerative diseases. Here we describe how to produce V2a interneurons from mouse and human pluripotent stem cells (PSCs), as well as strategies to characterize and mature the cells for further analysis. The described protocols are based on a sequence of small-molecule treatments that induce differentiation of PSCs into V2a interneurons. We also include a detailed description of how to phenotypically characterize, mature, and freeze the cells. The mouse and human protocols are similar in regard to the sequence of small molecules used but differ slightly in the concentrations and durations necessary for induction. With the protocols described, scientists can expect to obtain V2a interneurons with purities of ~75% (mouse) in 7 d and ~50% (human) in 20 d.