Lmx1b is required at multiple stages to build expansive serotonergic axon architectures
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ABSTRACT:
PROVIDER: PRJNA540504 | ENA |
REPOSITORIES: ENA
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Project description:Formation of long-range axons occurs over multiple stages of morphological maturation. However, the intrinsic transcriptional mechanisms that temporally control different stages of axon projection development are unknown. Here, we addressed this question by studying the formation of mouse serotonin (5-HT) axons, the exemplar of long-range profusely arborized axon architectures. We report that LIM homeodomain factor 1b (Lmx1b)-deficient 5-HT neurons fail to generate axonal projections to the forebrain and spinal cord. Stage-specific targeting demonstrates that Lmx1b is required at successive stages to control 5-HT axon primary outgrowth, selective routing, and terminal arborization. We show a Lmx1b→Pet1 regulatory cascade is temporally required for 5-HT arborization and upregulation of the 5-HT axon arborization gene, Protocadherin-alphac2, during postnatal development of forebrain 5-HT axons. Our findings identify a temporal regulatory mechanism in which a single continuously expressed transcription factor functions at successive stages to orchestrate the progressive development of long-range axon architectures enabling expansive neuromodulation.
2019-08-02 | GSE130514 | GEO
Project description:Formation of long-range axons occurs over multiple stages of morphological maturation. However, the intrinsic transcriptional mechanisms that temporally control different stages of axon projection development are unknown. Here, we addressed this question by studying the formation of mouse serotonin (5-HT) axons, the exemplar of long-range profusely arborized axon architectures. We report that LIM homeodomain factor 1b (Lmx1b)-deficient 5-HT neurons fail to generate axonal projections to the forebrain and spinal cord. Stage-specific targeting demonstrates that Lmx1b is required at successive stages to control 5-HT axon primary outgrowth, selective routing, and terminal arborization. We show a Lmx1b→Pet1 regulatory cascade is temporally required for 5-HT arborization and upregulation of the 5-HT axon arborization gene, Protocadherin-alphac2, during postnatal development of forebrain 5-HT axons. Our findings identify a temporal regulatory mechanism in which a single continuously expressed transcription factor functions at successive stages to orchestrate the progressive development of long-range axon architectures enabling expansive neuromodulation.
| S-EPMC6685705 | biostudies-literature
Project description:Neurons must function for decades of life but how these non-dividing cells are preserved is poorly understood. Using mouse serotonin (5-HT) neurons as a model, we discovered a novel adult-stage transcriptional program specialized to ensure the preservation of serotonergic connectivity. We uncover a switch in Lmx1b and Pet1 transcription factor function from controlling embryonic axonal growth to sustaining a transcriptomic signature of serotonergic connectivity comprising functionally diverse synaptic and axonal genes. Adult-stage deficiency of Lmx1b and Pet1 caused slowly progressive degeneration of 5-HT synapses and axons, increased susceptibility of 5-HT axons to neurotoxic injury, and abnormal stress responses. Axon degeneration occurred in a die back pattern and was accompanied by accumulation of alpha-synuclein and APP in spheroids and mitochondrial fragmentation without cell body loss. Our findings suggest neuronal connectivity is transcriptionally protected by maintenance of connectivity transcriptomes; progressive decay of such transcriptomes may contribute to age-related diseases of brain circuitry.
2022-03-24 | GSE189052 | GEO
Project description:Neuronal programming by forced expression of transcription factors (TFs) holds promise for clinical applications of regenerative medicine. However, the mechanisms by which TFs coordinate their activities on the genome and control distinct neuronal fates remain obscure. Using direct neuronal programming of embryonic stem cells, we dissected the contribution of a series of TFs to specific neuronal regulatory programs. We deconstructed the Ascl1-Lmx1b-Foxa2-Pet1 TF combination that has been shown to generate serotonergic neurons and found that stepwise addition of TFs to Ascl1 canalizes the neuronal fate into a diffuse monoaminergic fate. The addition of pioneer factor Foxa2 represses Phox2b to induce serotonergic fate, similar to in vivo regulatory networks. Foxa2 and Pet1 appear to act synergistically to upregulate serotonergic fate. Foxa2 and Pet1 co-bind to a small fraction of genomic regions but mostly bind to different regulatory sites. In contrast to the combinatorial binding activities of other programming TFs, Pet1 does not strictly follow the Foxa2 pioneer. These findings highlight the challenges in formulating generalizable rules for describing the behavior of TF combinations that program distinct neuronal subtypes.
2022-06-09 | GSE199314 | GEO
Project description:Neuronal programming by forced expression of transcription factors (TFs) holds promise for clinical applications of regenerative medicine. However, the mechanisms by which TFs coordinate their activities on the genome and control distinct neuronal fates remain obscure. Using direct neuronal programming of embryonic stem cells, we dissected the contribution of a series of TFs to specific neuronal regulatory programs. We deconstructed the Ascl1-Lmx1b-Foxa2-Pet1 TF combination that has been shown to generate serotonergic neurons and found that stepwise addition of TFs to Ascl1 canalizes the neuronal fate into a diffuse monoaminergic fate. The addition of pioneer factor Foxa2 represses Phox2b to induce serotonergic fate, similar to in vivo regulatory networks. Foxa2 and Pet1 appear to act synergistically to upregulate serotonergic fate. Foxa2 and Pet1 co-bind to a small fraction of genomic regions but mostly bind to different regulatory sites. In contrast to the combinatorial binding activities of other programming TFs, Pet1 does not strictly follow the Foxa2 pioneer. These findings highlight the challenges in formulating generalizable rules for describing the behavior of TF combinations that program distinct neuronal subtypes.
2022-06-09 | GSE199313 | GEO
Project description:Lmx1b is a homeodomain transcription factor responsible for limb dorsalization. Despite striking double-ventral (loss-of-function) and double-dorsal (gain-of-function) limb phenotypes, no direct downstream gene targets in the limb have been confirmed. To determine direct targets of Lmx1b during limb dorsalization (E12.5), we performed chromatin immunoprecipitation followed by next generation sequencing (ChIP-seq). Nearly 84% (n=617) of the Lmx1b-bound genomic fragments or intervals (LBIs) identified by two Lmx1b-ChIP-seqs overlap with chromatin regulatory marks indicative of potential cis-regulatory modules (PCRMs). In addition, 73 LBIs mapped to known cis-regulatory modules (CRMs) active during limb development. We compared Lmx1b-bound PCRMs to genes differentially expressed by Lmx1b at E12.5 and found 292 PCRMs within 1 Mb of 254 Lmx1b-regulated genes. Gene ontology analysis of these associated genes suggests that Lmx1b mediates dorsalization through the regulation of extracellular matrix production, bone/joint formation, axonal guidance, vascular development, cell proliferation and cell movement. We validated the functional activity of 2 PCRMs associated to Lmx1b-regulated genes, demonstrating activity and overlap with the associated gene during limb development. This is the first report to describe the genome-wide distribution of Lmx1b binding during limb development, directly linking Lmx1b to targets that accomplish limb dorsalization.
2017-05-06 | GSE84064 | GEO
Project description:A control vs. genetic knockout experiment aimed at determining what RNAs are upregulated or downregulated in e11.5 mouse proximal limb tissue lacking the Lmx1b gene. Because Lmx1b is required for dorsal-ventral patterning of the limb, this screen gives insight into what putative downstream targets of Lmx1b contribute to dorsal-ventral patterning. Keywords: Genetic allele comparison
2008-02-15 | GSE10516 | GEO
Project description:A control vs. genetic knockout experiment aimed at determining what RNAs are upregulated or downregulated in E13.5 mouse limb tissue lacking the Lmx1b gene. Because LMX1B is required for dorsal-ventral patterning of the limb, this screen gives insight into what putative downstream targets of Lmx1b contribute to dorsal-ventral patterning.
2010-07-06 | GSE21446 | GEO
Project description:Mammalian digit tip regeneration is linked to the presence of nail tissue, but a nail-explicit model is missing. Here, we report that nail-less double-ventral digits of ΔLARM1/2 mutants that lack limb-specific Lmx1b enhancers, fail to regenerate. To separate the nail’s effect from the lack of DV polarity, we also interrogate double-dorsal double-nail digits and show that they regenerate. Thus, DV polarity is not a prerequisite for regeneration and the nail requirement is supported. Transcriptomic comparison between wild-type and non-regenerative ΔLARM1/2 mutant blastemas reveals differential up-regulation of vascularization and connective tissue functional signatures in wild-type versus upregulation of inflammation in the mutant. These results, together with the finding of Lmx1b expression in the postnatal dorsal dermis underneath the nail and uniformly in the regenerative blastema opens the possibility of additional Lmx1b roles in the progression of digit tip regeneration, in addition to the indirect effect of mediating the formation of the nail.
2022-12-02 | GSE202223 | GEO
Project description:LMX1B is a LIM-homeodomain transcription factor essential for development. Putative LMX1B target genes have been identified through mouse gene targeting studies; however, in the absence of in vivo molecular characterization of their regulation, their identity as direct LMX1B targets remains hypothetical. We describe here the first molecular characterization of LMX1B target gene regulation. A tetracycline-inducible expression system and microarray analysis showed that a subset of NF-kappa B target genes, including IL-6 and IL-8 are upregulated in LMX1B-expressing HeLa cells. Chromatin immunoprecipitation assays revealed that LMX1B binds to the proximal promoter region of IL-6 and IL-8 in vivo, in the vicinity of the characterized kappa B site, and that LMX1B recruitment correlates with an increased NF-kappa B DNA association. Inhibition of NF-kappa B activity by short interfering RNA-mediated knock-down of p65 impairs LMX1B-dependent induction of NF-kappa B target genes, while activation of NF-kappa B activity by TNF-alpha results in a synergistic induction of these genes by LMX1B. IL-6 promoter-driven reporter assays showed that the kappa B site and an adjacent putative LMX1B binding motif are both involved in LMX1B-mediated transcription. Expression of a number of NF-kappa B target genes is affected in the kidney of Lmx1b-/- knock-out mice, thus supporting the biological relevance of the data obtained in the human cell line. Together, these data demonstrate for the first time that LMX1B directly regulates transcription of a subset of NF-kappa B target genes in cooperation with nuclear p50/p65 NF-kappa B.
2008-12-04 | GSE12008 | GEO