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Separate transcriptionally regulated pathways specify distinct classes of sister dendrites in a nociceptive neuron.
O'Brien BMJ, Palumbos SD, Novakovic M, Shang X, Sundararajan L, Miller DM
(2017) Dev Biol 432: 248-257
MeSH Terms: Animals, Caenorhabditis elegans, Caenorhabditis elegans Proteins, DNA-Binding Proteins, Dendrites, Gene Expression Regulation, LIM-Homeodomain Proteins, Membrane Proteins, Nociceptors, Regulatory Elements, Transcriptional, Sensory Receptor Cells, Transcription Factors, Zinc Fingers
Show Abstract · Added March 26, 2019
The dendritic processes of nociceptive neurons transduce external signals into neurochemical cues that alert the organism to potentially damaging stimuli. The receptive field for each sensory neuron is defined by its dendritic arbor, but the mechanisms that shape dendritic architecture are incompletely understood. Using the model nociceptor, the PVD neuron in C. elegans, we determined that two types of PVD lateral branches project along the dorsal/ventral axis to generate the PVD dendritic arbor: (1) Pioneer dendrites that adhere to the epidermis, and (2) Commissural dendrites that fasciculate with circumferential motor neuron processes. Previous reports have shown that the LIM homeodomain transcription factor MEC-3 is required for all higher order PVD branching and that one of its targets, the claudin-like membrane protein HPO-30, preferentially promotes outgrowth of pioneer branches. Here, we show that another MEC-3 target, the conserved TFIIA-like zinc finger transcription factor EGL-46, adopts the alternative role of specifying commissural dendrites. The known EGL-46 binding partner, the TEAD transcription factor EGL-44, is also required for PVD commissural branch outgrowth. Double mutants of hpo-30 and egl-44 show strong enhancement of the lateral branching defect with decreased numbers of both pioneer and commissural dendrites. Thus, HPO-30/Claudin and EGL-46/EGL-44 function downstream of MEC-3 and in parallel acting pathways to direct outgrowth of two distinct classes of PVD dendritic branches.
Copyright © 2017 Elsevier Inc. All rights reserved.
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MeSH Terms
The LIM protein complex establishes a retinal circuitry of visual adaptation by regulating Pax6 α-enhancer activity.
Kim Y, Lim S, Ha T, Song YH, Sohn YI, Park DJ, Paik SS, Kim-Kaneyama JR, Song MR, Leung A, Levine EM, Kim IB, Goo YS, Lee SH, Kang KH, Kim JW
(2017) Elife 6:
MeSH Terms: Adaptation, Ocular, Animals, Cytoskeletal Proteins, DNA-Binding Proteins, Enhancer Elements, Genetic, Gene Expression Regulation, LIM Domain Proteins, LIM-Homeodomain Proteins, Mice, Mice, Knockout, PAX6 Transcription Factor, Retina, Transcription Factors
Show Abstract · Added February 14, 2018
The visual responses of vertebrates are sensitive to the overall composition of retinal interneurons including amacrine cells, which tune the activity of the retinal circuitry. The expression of is regulated by multiple cis-DNA elements including the intronic α-enhancer, which is active in GABAergic amacrine cell subsets. Here, we report that the transforming growth factor ß1-induced transcript 1 protein (Tgfb1i1) interacts with the LIM domain transcription factors Lhx3 and Isl1 to inhibit the α-enhancer in the post-natal mouse retina. mice show elevated α-enhancer activity leading to overproduction of Pax6ΔPD isoform that supports the GABAergic amacrine cell fate maintenance. Consequently, the mouse retinas show a sustained light response, which becomes more transient in mice with the auto-stimulation-defective mutation. Together, we show the antagonistic regulation of the α-enhancer activity by Pax6 and the LIM protein complex is necessary for the establishment of an inner retinal circuitry, which controls visual adaptation.
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13 MeSH Terms
Genetic chimeras reveal the autonomy requirements for Vsx2 in embryonic retinal progenitor cells.
Sigulinsky CL, German ML, Leung AM, Clark AM, Yun S, Levine EM
(2015) Neural Dev 10: 12
MeSH Terms: Animals, Cell Division, Chimera, Embryo Transfer, Female, Genes, Reporter, Homeodomain Proteins, LIM-Homeodomain Proteins, Male, Mice, Mice, Transgenic, Microphthalmia-Associated Transcription Factor, Mosaicism, Neural Stem Cells, Neurogenesis, Neuroglia, Organ Specificity, Retina, Retinal Ganglion Cells, Transcription Factors
Show Abstract · Added November 2, 2015
BACKGROUND - Vertebrate retinal development is a complex process, requiring the specification and maintenance of retinal identity, proliferative expansion of retinal progenitor cells (RPCs), and their differentiation into retinal neurons and glia. The homeobox gene Vsx2 is expressed in RPCs and required for the proper execution of this retinal program. However, our understanding of the mechanisms by which Vsx2 does this is still rudimentary. To define the autonomy requirements for Vsx2 in the regulation of RPC properties, we generated chimeric mouse embryos comprised of wild-type and Vsx2-deficient cells.
RESULTS - We show that Vsx2 maintains retinal identity in part through the cell-autonomous repression of the retinal pigment epithelium determinant Mitf, and that Lhx2 is required cell autonomously for the ectopic Mitf expression in Vsx2-deficient cells. We also found significant cell-nonautonomous contributions to Vsx2-mediated regulation of RPC proliferation, pointing to an important role for Vsx2 in establishing a growth-promoting extracellular environment. Additionally, we report a cell-autonomous requirement for Vsx2 in controlling when neurogenesis is initiated, indicating that Vsx2 is an important mediator of neurogenic competence. Finally, the distribution of wild-type cells shifted away from RPCs and toward retinal ganglion cell precursors in patches of high Vsx2-deficient cell density to potentially compensate for the lack of fated precursors in these areas.
CONCLUSIONS - Through the generation and analysis of genetic chimeras, we demonstrate that Vsx2 utilizes both cell-autonomous and cell-nonautonomous mechanisms to regulate progenitor properties in the embryonic retina. Importantly, Vsx2's role in regulating Mitf is in part separable from its role in promoting proliferation, and proliferation is excluded as the intrinsic timer that determines when neurogenesis is initiated. These findings highlight the complexity of Vsx2 function during retinal development and provide a framework for identifying the molecular mechanisms mediating these functions.
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20 MeSH Terms
Lhx2 balances progenitor maintenance with neurogenic output and promotes competence state progression in the developing retina.
Gordon PJ, Yun S, Clark AM, Monuki ES, Murtaugh LC, Levine EM
(2013) J Neurosci 33: 12197-207
MeSH Terms: Animals, Cell Differentiation, Female, Gene Expression Regulation, Developmental, Gene Knock-In Techniques, LIM-Homeodomain Proteins, Male, Mice, Mice, Mutant Strains, Neural Stem Cells, Neurogenesis, Pregnancy, Retina, Retinal Ganglion Cells, Retinal Rod Photoreceptor Cells, Transcription Factors
Show Abstract · Added November 2, 2015
The LIM-Homeodomain transcription factor Lhx2 is an essential organizer of early eye development and is subsequently expressed in retinal progenitor cells (RPCs). To determine its requirement in RPCs, we performed a temporal series of conditional inactivations in mice with the early RPC driver Pax6 α-Cre and the tamoxifen-inducible Hes1(CreERT2) driver. Deletion of Lhx2 caused a significant reduction of the progenitor population and a corresponding increase in neurogenesis. Precursor fate choice correlated with the time of inactivation; early and late inactivation led to the overproduction of retinal ganglion cells (RGCs) and rod photoreceptors, respectively. In each case, however, the overproduction was selective, occurring at the expense of other cell types and indicating a role for Lhx2 in generating cell type diversity. RPCs that persisted in the absence of Lhx2 continued to generate RGC precursors beyond their normal production window, suggesting that Lhx2 facilitates a transition in competence state. These results identify Lhx2 as a key regulator of RPC properties that contribute to the ordered production of multiple cell types during retinal tissue formation.
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16 MeSH Terms
Islet α-, β-, and δ-cell development is controlled by the Ldb1 coregulator, acting primarily with the islet-1 transcription factor.
Hunter CS, Dixit S, Cohen T, Ediger B, Wilcox C, Ferreira M, Westphal H, Stein R, May CL
(2013) Diabetes 62: 875-86
MeSH Terms: Animals, Cell Nucleus, DNA-Binding Proteins, Female, Gene Expression Regulation, Glucagon-Secreting Cells, Insulin-Secreting Cells, Islets of Langerhans, LIM Domain Proteins, LIM-Homeodomain Proteins, Male, Mice, Mice, Knockout, Mice, Mutant Strains, Mice, Transgenic, Organ Specificity, Organogenesis, Protein Isoforms, RNA, Messenger, Somatostatin-Secreting Cells, Transcription Factors
Show Abstract · Added December 5, 2013
Ldb1 and Ldb2 are coregulators that mediate Lin11-Isl1-Mec3 (LIM)-homeodomain (HD) and LIM-only transcription factor-driven gene regulation. Although both Ldb1 and Ldb2 mRNA were produced in the developing and adult pancreas, immunohistochemical analysis illustrated a broad Ldb1 protein expression pattern during early pancreatogenesis, which subsequently became enriched in islet and ductal cells perinatally. The islet-enriched pattern of Ldb1 was similar to pan-endocrine cell-expressed Islet-1 (Isl1), which was demonstrated in this study to be the primary LIM-HD transcription factor in developing and adult islet cells. Endocrine cell-specific removal of Ldb1 during mouse development resulted in a severe reduction of hormone⁺ cell numbers (i.e., α, β, and δ) and overt postnatal hyperglycemia, reminiscent of the phenotype described for the Isl1 conditional mutant. In contrast, neither endocrine cell development nor function was affected in the pancreas of Ldb2(-/-) mice. Gene expression and chromatin immunoprecipitation (ChIP) analyses demonstrated that many important Isl1-activated genes were coregulated by Ldb1, including MafA, Arx, insulin, and Glp1r. However, some genes (i.e., Hb9 and Glut2) only appeared to be impacted by Ldb1 during development. These findings establish Ldb1 as a critical transcriptional coregulator during islet α-, β-, and δ-cell development through Isl1-dependent and potentially Isl1-independent control.
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21 MeSH Terms
Six3 cooperates with Hedgehog signaling to specify ventral telencephalon by promoting early expression of Foxg1a and repressing Wnt signaling.
Carlin D, Sepich D, Grover VK, Cooper MK, Solnica-Krezel L, Inbal A
(2012) Development 139: 2614-24
MeSH Terms: Animals, Embryo, Nonmammalian, Eye Proteins, Homeodomain Proteins, LIM-Homeodomain Proteins, Nerve Tissue Proteins, Signal Transduction, Telencephalon, Transcription Factors, Zebrafish, Zebrafish Proteins
Show Abstract · Added March 7, 2014
Six3 exerts multiple functions in the development of anterior neural tissue of vertebrate embryos. Whereas complete loss of Six3 function in the mouse results in failure of forebrain formation, its hypomorphic mutations in human and mouse can promote holoprosencephaly (HPE), a forebrain malformation that results, at least in part, from abnormal telencephalon development. However, the roles of Six3 in telencephalon patterning and differentiation are not well understood. To address the role of Six3 in telencephalon development, we analyzed zebrafish embryos deficient in two out of three Six3-related genes, six3b and six7, representing a partial loss of Six3 function. We found that telencephalon forms in six3b;six7-deficient embryos; however, ventral telencephalic domains are smaller and dorsal domains are larger. Decreased cell proliferation or excess apoptosis cannot account for the ventral deficiency. Instead, six3b and six7 are required during early segmentation for specification of ventral progenitors, similar to the role of Hedgehog (Hh) signaling in telencephalon development. Unlike in mice, we observe that Hh signaling is not disrupted in embryos with reduced Six3 function. Furthermore, six3b overexpression is sufficient to compensate for loss of Hh signaling in isl1- but not nkx2.1b-positive cells, suggesting a novel Hh-independent role for Six3 in telencephalon patterning. We further find that Six3 promotes ventral telencephalic fates through transient regulation of foxg1a expression and repression of the Wnt/β-catenin pathway.
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11 MeSH Terms
Lhx2 links the intrinsic and extrinsic factors that control optic cup formation.
Yun S, Saijoh Y, Hirokawa KE, Kopinke D, Murtaugh LC, Monuki ES, Levine EM
(2009) Development 136: 3895-906
MeSH Terms: Animals, Body Patterning, Embryo, Mammalian, Eye, Fluorescent Antibody Technique, Direct, Homeodomain Proteins, Immunohistochemistry, In Situ Hybridization, LIM-Homeodomain Proteins, Mice, Mice, Knockout, Mice, Transgenic, Mutation, Organ Culture Techniques, Organogenesis, Transcription Factors
Show Abstract · Added November 2, 2015
A crucial step in eye organogenesis is the transition of the optic vesicle into the optic cup. Several transcription factors and extracellular signals mediate this transition, but whether a single factor links them into a common genetic network is unclear. Here, we provide evidence that the LIM homeobox gene Lhx2, which is expressed in the optic neuroepithelium, fulfils such a role. In Lhx2(-/-) mouse embryos, eye field specification and optic vesicle morphogenesis occur, but development arrests prior to optic cup formation in both the optic neuroepithelium and lens ectoderm. This is accompanied by failure to maintain or initiate the expression patterns of optic-vesicle-patterning and lens-inducing determinants. Of the signaling pathways examined, only BMP signaling is noticeably altered and Bmp4 and Bmp7 mRNAs are undetectable. Lhx2(-/-) optic vesicles and lens ectoderm upregulate Pax2, Fgf15 and Sox2 in response to BMP treatments, and Lhx2 genetic mosaics reveal that transcription factors, including Vsx2 and Mitf, require Lhx2 cell-autonomously for their expression. Our data indicate that Lhx2 is required for optic vesicle patterning and lens formation in part by regulating BMP signaling in an autocrine manner in the optic neuroepithelium and in a paracrine manner in the lens ectoderm. We propose a model in which Lhx2 is a central link in a genetic network that coordinates the multiple pathways leading to optic cup formation.
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16 MeSH Terms
Sonic hedgehog signaling regulates a novel epithelial progenitor domain of the hindbrain choroid plexus.
Huang X, Ketova T, Fleming JT, Wang H, Dey SK, Litingtung Y, Chiang C
(2009) Development 136: 2535-43
MeSH Terms: Animals, Animals, Newborn, Bone Morphogenetic Proteins, Cell Differentiation, Cell Proliferation, Choroid Plexus, Epithelial Cells, Gene Deletion, Growth Differentiation Factors, Hedgehog Proteins, Homeodomain Proteins, Integrases, Kruppel-Like Transcription Factors, LIM-Homeodomain Proteins, Mice, Models, Biological, Rhombencephalon, Signal Transduction, Stem Cells, Transcription Factors, Wnt Proteins, Zinc Finger Protein GLI1
Show Abstract · Added January 23, 2013
Choroid plexuses (ChPs) are vascularized secretory organs involved in the regulation of brain homeostasis, and function as the blood-cerebrospinal fluid (CSF) barrier. Despite their crucial roles, there is limited understanding of the regulatory mechanism driving ChP development. Sonic hedgehog (Shh), a secreted signal crucial for embryonic development and cancer, is strongly expressed in the differentiated hindbrain ChP epithelium (hChPe). However, we identify a distinct epithelial domain in the hChP that does not express Shh, but displays Shh signaling. We find that this distinct Shh target field that adjoins a germinal zone, the lower rhombic lip (LRL), functions as a progenitor domain by contributing directly to the hChPe. By conditional Shh mutant analysis, we show that Shh signaling regulates hChPe progenitor proliferation and hChPe expansion through late embryonic development, starting around E12.5. Whereas previous studies show that direct contribution to the hChPe by the LRL ceases around E14, our findings reveal a novel tissue-autonomous role for Shh production and signaling in driving the continual growth and expansion of the hindbrain choroid plexus throughout development.
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22 MeSH Terms
Single-stranded DNA-binding proteins regulate the abundance and function of the LIM-homeodomain transcription factor LHX2 in pituitary cells.
Cai Y, Xu Z, Nagarajan L, Brandt SJ
(2008) Biochem Biophys Res Commun 373: 303-8
MeSH Terms: Animals, Base Sequence, Cell Line, Chromatin Immunoprecipitation, DNA, Single-Stranded, DNA-Binding Proteins, Electrophoretic Mobility Shift Assay, Gene Expression Regulation, Glycoprotein Hormones, alpha Subunit, Homeodomain Proteins, LIM Domain Proteins, LIM-Homeodomain Proteins, Mice, Pituitary Gland, Promoter Regions, Genetic, Transcription Factors
Show Abstract · Added March 5, 2014
A family of single-stranded DNA-binding proteins (or SSBPs) has been shown to augment the function of LIM-homeodomain (LIM-HD) transcription factors in embryogenesis by interaction with LIM domain-binding protein-1 (LDB1). No DNA-binding complex has been described, however, containing a LIM-HD protein, LDB1, and SSBP, and the mechanism by which SSBPs affect LIM-HD function had not been elucidated. Through use of electrophoretic mobility shift, antibody supershift, and ChIP analyses, we show that an Lhx2-Ldb1-Ssbp3 complex binds a specific element in the Lhx2 target gene Cga (encoding the alpha subunit of glycoprotein hormones) in the alphaT3-1 pituitary cell line. Using overexpression and knockdown approaches, we demonstrate that SSBP3 inhibits Lhx2 and Ldb1 turnover, stimulates assembly of this DNA-binding complex, promotes its recruitment to the Cga promoter, and enhances Cga transcription. These studies provide novel insights into the regulation of pituitary gene expression and LIM-HD function more generally.
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16 MeSH Terms
Islet 1 (Isl1) expression is a reliable marker for pancreatic endocrine tumors and their metastases.
Schmitt AM, Riniker F, Anlauf M, Schmid S, Soltermann A, Moch H, Heitz PU, Klöppel G, Komminoth P, Perren A
(2008) Am J Surg Pathol 32: 420-5
MeSH Terms: Biomarkers, Tumor, CDX2 Transcription Factor, DNA-Binding Proteins, Gastrointestinal Neoplasms, Homeodomain Proteins, Humans, Immunohistochemistry, LIM-Homeodomain Proteins, Lung Neoplasms, Neoplasm Metastasis, Neuroendocrine Tumors, Pancreatic Neoplasms, Sensitivity and Specificity, Transcription Factors
Show Abstract · Added May 22, 2013
BACKGROUND - Tracing the origin of a metastasis of a neuroendocrine carcinoma is a challenge. The transcription factors Cdx2 and TTF1 have been found to be helpful in identifying well-differentiated neuroendocrine tumors of gastrointestinal and pulmonary origin, respectively. So far, such a marker is lacking for pancreatic neuroendocrine tumors (PETs) and metastases thereof. Islet1 (Isl1) is a transcription factor expressed in pancreatic islet cells. The aim of this study was (1) to test the specificity and sensitivity of Isl1 as a marker of PETs, and (2) to test the specificity and sensitivity of a panel of markers, including Isl1, Cdx2, and TTF1, for the localization of the primary.
DESIGN - One hundred eighty-eight primary gastroenteropancreatic and pulmonary endocrine tumors and 49 metastases thereof were examined. Immunohistochemistry using antibodies directed against Isl1, Cdx2, and TTF1 was performed and the staining results were scored semiquantitatively.
RESULTS - Isl1 proved to be a highly specific marker for pancreatic endocrine tumors. In 84 primary PET its specificity was 78.4% (sensitivity 74.3%) and in 18 metastases of PET the specificity reached 100% (sensitivity 77.8%). Strong Cdx2 staining showed a specificity for gastrointestinal origin of 83.9% (sensitivity 82%) in primary tumors and of 100% (sensitivity 40%) in metastases. Including weakly positive tumors lead to a decreased specificity but an increased sensitivity. TTF1 expression was detected in 2 PET and 1 ileal primary tumor only and was absent in all metastases of gastroenteropancreatic endocrine tumors.
CONCLUSIONS - Isl1 is a reliable marker of pancreatic endocrine tumors and metastases thereof. It shows a comparable sensitivity and specificity as Cdx2 as a marker of ileal and appendiceal neuroendocrine tumors and their metastases. TTF1 is very rarely expressed in well-differentiated gastroentero-PETs. Therefore, the panel of Isl1, Cdx2, and TTF1 seems useful for examining metastases of well-differentiated endocrine carcinomas of unknown origin.
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14 MeSH Terms