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Randy L. Johnson - One of the best experts on this subject based on the ideXlab platform.

  • an LMX1B mir135a2 regulatory circuit modulates wnt1 wnt signaling and determines the size of the midbrain dopaminergic progenitor pool
    PLOS Genetics, 2013
    Co-Authors: Angela Anderegg, Hsin Pin Lin, Jun-an Chen, Natalya Cherepanova, Beth Yun, Milan Joksimovic, Jason R. Rock, Brian D. Harfe, Giuliana Caroniabrown, Randy L. Johnson
    Abstract:

    MicroRNAs regulate gene expression in diverse physiological scenarios. Their role in the control of morphogen related signaling pathways has been less studied, particularly in the context of embryonic Central Nervous System (CNS) development. Here, we uncover a role for microRNAs in limiting the spatiotemporal range of morphogen expression and function. Wnt1 is a key morphogen in the embryonic midbrain, and directs proliferation, survival, patterning and neurogenesis. We reveal an autoregulatory negative feedback loop between the transcription factor LMX1B and a newly characterized microRNA, miR135a2, which modulates the extent of Wnt1/Wnt signaling and the size of the dopamine progenitor domain. Conditional gain of function studies reveal that LMX1B promotes Wnt1/Wnt signaling, and thereby increases midbrain size and dopamine progenitor allocation. Conditional removal of LMX1B has the opposite effect, in that expansion of the dopamine progenitor domain is severely compromised. Next, we provide evidence that microRNAs are involved in restricting dopamine progenitor allocation. Conditional loss of Dicer1 in embryonic stem cells (ESCs) results in expanded Lmx1a/b+ progenitors. In contrast, forced elevation of miR135a2 during an early window in vivo phenocopies the LMX1B conditional knockout. When En1::Cre, but not Shh::Cre or Nes::Cre, is used for recombination, the expansion of Lmx1a/b+ progenitors is selectively reduced. Bioinformatics and luciferase assay data suggests that miR135a2 targets LMX1B and many genes in the Wnt signaling pathway, including Ccnd1, Gsk3b, and Tcf7l2. Consistent with this, we demonstrate that this mutant displays reductions in the size of the LMX1B/Wnt1 domain and range of canonical Wnt signaling. We posit that microRNA modulation of the LMX1B/Wnt axis in the early midbrain/isthmus could determine midbrain size and allocation of dopamine progenitors. Since canonical Wnt activity has recently been recognized as a key ingredient for programming ESCs towards a dopaminergic fate in vitro, these studies could impact the rational design of such protocols.

  • An LMX1B-miR135a2 Regulatory Circuit Modulates Wnt1/Wnt Signaling and Determines the Size of the Midbrain Dopaminergic Progenitor Pool
    PLoS genetics, 2013
    Co-Authors: Angela Anderegg, Hsin Pin Lin, Jun-an Chen, Giuliana Caronia-brown, Natalya Cherepanova, Beth Yun, Milan Joksimovic, Jason R. Rock, Brian D. Harfe, Randy L. Johnson
    Abstract:

    MicroRNAs regulate gene expression in diverse physiological scenarios. Their role in the control of morphogen related signaling pathways has been less studied, particularly in the context of embryonic Central Nervous System (CNS) development. Here, we uncover a role for microRNAs in limiting the spatiotemporal range of morphogen expression and function. Wnt1 is a key morphogen in the embryonic midbrain, and directs proliferation, survival, patterning and neurogenesis. We reveal an autoregulatory negative feedback loop between the transcription factor LMX1B and a newly characterized microRNA, miR135a2, which modulates the extent of Wnt1/Wnt signaling and the size of the dopamine progenitor domain. Conditional gain of function studies reveal that LMX1B promotes Wnt1/Wnt signaling, and thereby increases midbrain size and dopamine progenitor allocation. Conditional removal of LMX1B has the opposite effect, in that expansion of the dopamine progenitor domain is severely compromised. Next, we provide evidence that microRNAs are involved in restricting dopamine progenitor allocation. Conditional loss of Dicer1 in embryonic stem cells (ESCs) results in expanded Lmx1a/b+ progenitors. In contrast, forced elevation of miR135a2 during an early window in vivo phenocopies the LMX1B conditional knockout. When En1::Cre, but not Shh::Cre or Nes::Cre, is used for recombination, the expansion of Lmx1a/b+ progenitors is selectively reduced. Bioinformatics and luciferase assay data suggests that miR135a2 targets LMX1B and many genes in the Wnt signaling pathway, including Ccnd1, Gsk3b, and Tcf7l2. Consistent with this, we demonstrate that this mutant displays reductions in the size of the LMX1B/Wnt1 domain and range of canonical Wnt signaling. We posit that microRNA modulation of the LMX1B/Wnt axis in the early midbrain/isthmus could determine midbrain size and allocation of dopamine progenitors. Since canonical Wnt activity has recently been recognized as a key ingredient for programming ESCs towards a dopaminergic fate in vitro, these studies could impact the rational design of such protocols.

  • The transcription factor, LMX1B, promotes a neuronal glutamate phenotype and suppresses a GABA one in the embryonic trigeminal brainstem complex
    Somatosensory & motor research, 2012
    Co-Authors: Chuanxi Xiang, Randy L. Johnson, Kai-hua Zhang, Mark F. Jacquin, Zhoufeng Chen
    Abstract:

    Achieving an appropriate balance between inhibitory and excitatory neuronal fate is critical for development of effective synaptic transmission. However, the molecular mechanisms dictating such phenotypic outcomes are not well understood, especially in the whisker‐to‐barrel cortex neuraxis, an oft‐used model system for revealing developmental mechanisms. In trigeminal nucleus principalis (PrV), the brainstem link in the whisker–barrel pathway, the transcription factor LMX1B marks glutamatergic cells. In PrV of LMX1B knockout mice (−/−), initial specification of glutamatergic vs. GABAergic cell fate is normal until embryonic day 14.5. Subsequently, until the day of birth, glutamatergic markers (e.g., VGLUT2) stain significantly fewer PrV neurons, whereas, GABAergic markers (Pax2 and Gad1) stain significantly more PrV cells, notably in LMX1B null PrV cells. These changes also occurred in LMX1B/Bax double−/− mice, where PrV cells are rescued from LMX1B−/− induced apoptosis; thus, effects upon excitatory/inhi...

  • Lmx1a and LMX1B Function Cooperatively to Regulate Proliferation, Specification, and Differentiation of Midbrain Dopaminergic Progenitors
    The Journal of neuroscience : the official journal of the Society for Neuroscience, 2011
    Co-Authors: Carol H. Yan, Randy L. Johnson, Martin Lévesque, Suzanne Claxton, Siew-lan Ang
    Abstract:

    LIM homeodomain transcription factors, Lmx1a and LMX1B, are required for the development of midbrain dopaminergic (mDA) neurons. LMX1B is required for the specification and maintenance of mDA neurons, primarily due to its role in isthmic organizer development that is essential for the induction of mDA neurons. Here, we conditionally deleted LMX1B in the ventral neural tube using ShhCre and found that LMX1B conditional mutant mouse embryos show no defect in the development and maintenance of mDA neurons. In addition, Dreher (Lmx1a mutant) embryos display only a moderate reduction in the number of mDA neurons, suggesting that the related family member LMX1B might compensate for Lmx1a function. We therefore generated Lmx1a and LMX1B double mutants. Severe loss of mDA neurons occurred in Lmx1a(dr/dr);Shh(Cre/+);LMX1B(f/f) double mutants due to essential roles for Lmx1a and LMX1B in regulating the proliferation and neuronal commitment of mDA progenitors through the expression of Wnt1 and Ngn2, respectively. Lmx1a and LMX1B also negatively regulate Hes1 expression and consequently cell cycle exit through activation of p27(Kip1) expression. In addition, Lmx1a and LMX1B also regulate the expression of floor plate genes such as Corin and Slit2 and specification of postmitotic mDA neurons. These defects were more severe with decreasing gene dosage of Lmx1a and LMX1B or observed only when all four copies of Lmx1a and LMX1B genes were inactivated. Together, our results demonstrate that Lmx1a and LMX1B function cooperatively to regulate proliferation, specification, and differentiation of mDA progenitors, including their floor plate-like properties.

  • LMX1B is required for murine trabecular meshwork formation and for maintenance of corneal transparency
    Developmental Dynamics, 2010
    Co-Authors: Randy L. Johnson, Pu Liu
    Abstract:

    Studies of LMX1B have shown that it is required for anterior segment formation during embryonic development and that reduction of LMX1B may contribute to elevated intraocular pressure in the adult. However, whether LMX1B is required for formation of anterior segment tissues that are associated with regulation of intraocular pressure has not been addressed due to the perinatal lethality of LMX1B null allele. Here we use conditional deletion strategies to circumvent perinatal lethality. Our results indicate that LMX1B is required in neural crest–derived periocular mesenchyme for formation of anterior segment tissues, including trabecular meshwork, a critical regulator of intraocular pressure. Furthermore, we show that LMX1B is essential to maintain proper functioning of those tissues in the adult. Taken together, our results are the first to link a specific transcription factor to trabecular meshwork formation and the first to demonstrate specific requirements for LMX1B in maintaining the integrity of adult anterior segment. Developmental Dynamics 239:2161–2171, 2010. © 2010 Wiley-Liss, Inc.

Yu-qiang Ding - One of the best experts on this subject based on the ideXlab platform.

  • Adult Raphe-Specific Deletion of LMX1B Leads to Central Serotonin Deficiency
    PloS one, 2011
    Co-Authors: Ning-ning Song, Ying Huang, Jian Bo Xiu, Jia Yin Chen, Lei Zhang, Lise Gutknecht, Klaus-peter Lesch, Yu-qiang Ding
    Abstract:

    The transcription factor LMX1B is essential for the differentiation and survival of central serotonergic (5-HTergic) neurons during embryonic development. However, the role of LMX1B in adult 5-HTergic neurons is unknown. We used an inducible Cre-LoxP system to selectively inactivate LMX1B expression in the raphe nuclei of adult mice. Pet1-CreER(T2) mice were generated and crossed with LMX1B(flox/flox) mice to obtain Pet1-CreER(T2); LMX1B(flox/flox) mice (which termed as LMX1B iCKO). After administration of tamoxifen, the level of 5-HT in the brain of LMX1B iCKO mice was reduced to 60% of that in control mice, and the expression of tryptophan hydroxylase 2 (Tph2), serotonin transporter (Sert) and vesicular monoamine transporter 2 (Vmat2) was greatly down-regulated. On the other hand, the expression of dopamine and norepinephrine as well as aromatic L-amino acid decarboxylase (Aadc) and Pet1 was unchanged. Our results reveal that LMX1B is required for the biosynthesis of 5-HT in adult mouse brain, and it may be involved in maintaining normal functions of central 5-HTergic neurons by regulating the expression of Tph2, Sert and Vmat2.

  • Manifold functions of the Nail-Patella Syndrome gene LMX1B in vertebrate development.
    Development growth & differentiation, 2009
    Co-Authors: Jin-xia Dai, Randy L. Johnson, Yu-qiang Ding
    Abstract:

    The LIM (Lin-1, Isl-1 and Mec-3)-homeodomain transcription factor 1 beta (LMX1B) is widely expressed in vertebrate embryos, and is implicated in the development of diverse structures such as limbs, kidneys, eyes and brains. LMX1B mutations in humans cause an autosomal dominant inherited disease called nail-patella syndrome (NPS), which is characterized by abnormalities of the arms and legs as well as kidney disease and glaucoma. Expression of LMX1B in the dorsal compartment of growing limb buds is critical for specification of dorsal limb cell fates and consequently dorsoventral patterning of limbs. In addition, LMX1B is involved in the differentiation of anterior eye structures, formation of the glomerular basement membrane in kidneys and development of the skeleton, especially calvarial bones. In the central nervous system, LMX1B controls the inductive activity of isthmic organizer, differentiation and maintenance of central serotonergic neurons, as well as the differentiation and migration of spinal dorsal horn neurons. Although details of the genetic programs involved in these developmental events are largely unknown, it is suggested that LMX1B plays central roles in fate determination or cell differentiation in these tissues. Sustained expression of LMX1B in the postnatal and mature mouse brain suggests that it also plays important roles in brain maturation and in the regulation of normal brain functions. This review aims to highlight recent insights into the many activities of LMX1B in vertebrates.

  • LMX1B-controlled isthmic organizer is essential for development of midbrain dopaminergic neurons.
    The Journal of neuroscience : the official journal of the Society for Neuroscience, 2008
    Co-Authors: Chao Guo, Randy L. Johnson, Hai Yan Qiu, Ming Shi, Ying Huang, Marcelo Rubinstein, Sheng-di Chen, Yu-qiang Ding
    Abstract:

    The LIM homeodomain transcription factor LMX1B has been suggested to be required for the differentiation of midbrain dopaminergic (mDA) neurons. However, whether the loss of mDA neurons in LMX1B(-/-) mice is due to its intrinsic role in the mDA lineage or to a consequence of the malformations caused by the earlier mid/hindbrain patterning defects remains to be clarified. We report here that LMX1B expression in mDA neurons is dispensable for their differentiation and maintenance, and the loss of mDA neurons in LMX1B(-/-) mice is due to the disruption of inductive activity of the isthmic organizer (IsO) in the absence of LMX1B at the mid/hindbrain boundary (MHB). We found that mDA neurons revealed by tyrosine hydroxylase (TH), Pitx3, Nurr1, and dopamine transporter were indistinguishable from wild-type controls during embryonic development as well as in adulthood in TH-Cre;LMX1B(flox/-) and Dat(Cre/+);LMX1B(flox/-) mice, in which LMX1B was selectively deleted in differentiating mDA neurons. In addition, mDA neurons were recovered in LMX1B(-/-) mice, when IsO activity was restored by Wnt1-LMX1B transgene at MHB. The restored IsO activity was evidenced by apparently normal tectum and cerebellum and recurrence of expression of Fgf8 and Wnt1 at MHB in Wnt1(LMX1B);LMX1B(-/-). Furthermore, when LMX1B was deleted in the whole brain after the formation of IsO by Nestin-Cre, mDA neurons were normal, whereas serotonergic neurons displayed defective development phenocopying what observed in LMX1B(-/-) mice. Thus, our results indicate that the inductive activity of IsO is essential, but LMX1B expression in mDA neurons is dispensable for their differentiation and maintenance.

  • Postnatal ontogeny of the transcription factor LMX1B in the mouse central nervous system.
    The Journal of comparative neurology, 2008
    Co-Authors: Jin-xia Dai, Chao Guo, Ming Shi, Yu-qiang Ding
    Abstract:

    The expression profile of Lim homeodomain transcription factor LMX1B in the mouse brain was investigated at different postnatal stages by immunohistochemistry and in situ hybridization. At postnatal day (P) 7, many LMX1B-expressing neurons were found in the posterior hypothalamic area, supramammillary nucleus, ventral premammillary nucleus, and subthalamic nucleus. In the midbrain, numerous LMX1B-expressing neurons were present in the substantia nigra pars compacta and ventral tegmental area. In the hindbrain, LMX1B-expressing neurons were primarily observed in the raphe nuclei, parabrachial nuclei, principal sensory trigeminal nucleus, nucleus of the solitary tract, and laminae I-II of the medullary dorsal horn as well as spinal dorsal horn. Although expression levels diminished as postnatal life progressed, persistent expression throughout the first year of life was observed in many of these regions. In contrast, LMX1B was present in a few brain regions (e.g., principal sensory trigeminal nucleus) only in early life with expression expiring by P60. LMX1B was observed in dopaminergic neurons in the midbrain and serotonergic neurons in the hindbrain, as determined by double labeling with specific markers. In addition, we found that LMX1B-expressing neurons are not GABAergic, and LMX1B was colocalized with Tlx3 in the parabrachial nuclei, principal sensory trigeminal nucleus, nucleus of the solitary tract. as well as the medullary and spinal dorsal horns, suggesting that LMX1B-expressing cells in these areas are excitatory neurons. Our data suggest that LMX1B is involved in the postnatal maturation of certain types of neurons and maintenance of their normal functions in the adult brain.

  • LMX1B is essential for Fgf8 and Wnt1 expression in the isthmic organizer during tectum and cerebellum development in mice.
    Development (Cambridge England), 2006
    Co-Authors: Chao Guo, Haixu Chen, Randy L. Johnson, Zhoufeng Chen, Hai Yan Qiu, Ying Huang, Sheng-di Chen, Rong Qiang Yang, Yu-qiang Ding
    Abstract:

    Secreted factors FGF8 and WNT1 are essential either for the inductive activity of the isthmus organizer or for the regionalization of the midbrain-hindbrain boundary (MHB). However, transcriptional regulation of these secreted factors during development remains to be elucidated. Here we show that the LIM homeobox gene LMX1B is expressed in the anterior embryo as early as E7.5 and its expression becomes progressively restricted to the isthmus at E9.0. Analysis of gene expression in the MHB of the mutant embryos showed that many genes were lost by E9.5. In the MHB of LMX1B(-/-) embryos, the expression of Fgf8, which normally occurs at the 4-somite stage, was completely absent, whereas Wnt1 was downregulated before the 4-somite stage. Moreover, transcription factors En1 and Pax2 were also downregulated prior to the 4-somite stage, whereas Gbx2 downregulation occurred at the 4-somite stage. By contrast, Otx2 and Pax6 expression was not affected in LMX1B(-/-) embryos. The requirement of specific LMX1B expression in the MHB was further confirmed by Wnt1-Cre-mediated region-specific conditional knockout of LMX1B. As a result of these molecular defects, the development of the tectum and cerebellum was severely impaired in LMX1B(-/-) mice. Taken together, our results indicate that LMX1B plays an essential role in the development of the tectum and cerebellum by regulating expression of Fgf8, Wnt1 and several isthmus-related transcription factors in the MHB, and is a crucial component of a cross-regulatory network required for the induction activity of the isthmic organizer in the MHB.

Kerby C. Oberg - One of the best experts on this subject based on the ideXlab platform.

  • LMX1B-targeted cis-regulatory modules involved in limb dorsalization.
    Development (Cambridge England), 2017
    Co-Authors: Endika Haro, Jennifer M. Feenstra, Charmaine U. Pira, Billy A. Watson, Luke Tegeler, Subburaman Mohan, Kerby C. Oberg
    Abstract:

    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 gene targets in the limb have been confirmed. To determine direct targets, we performed a chromatin immunoprecipitation against LMX1B in mouse limbs at embryonic day 12.5 followed by next-generation sequencing (ChIP-seq). Nearly 84% (n=617) of the LMX1B-bound genomic intervals (LBIs) identified overlap with chromatin regulatory marks indicative of potential cis-regulatory modules (PCRMs). In addition, 73 LBIs mapped to CRMs that are known to be active during limb development. We compared LMX1B-bound PCRMs with genes regulated by LMX1B and found 292 PCRMs within 1 Mb of 254 LMX1B-regulated genes. Gene ontological analysis suggests that LMX1B targets extracellular matrix production, bone/joint formation, axonal guidance, vascular development, cell proliferation and cell movement. We validated the functional activity of a PCRM associated with joint-related Gdf5 that provides a mechanism for LMX1B-mediated joint modification and a PCRM associated with LMX1B that suggests a role in autoregulation. This is the first report to describe genome-wide LMX1B binding during limb development, directly linking LMX1B to targets that accomplish limb dorsalization.

  • evidence for LMX1B self regulation during limb dorsalization
    The FASEB Journal, 2015
    Co-Authors: Conor Spady, Charmaine U. Pira, Endika Haro, Luke Tegeler, Kerby C. Oberg
    Abstract:

    The transcription factor LMX1B is integral to limb dorsalization. In the limb, LMX1B expression is restricted to dorsal mesoderm. Mice lacking functional LMX1B develop ventral-ventral limbs. Direct...

  • LMX1B-Mediated Emx2-Associated Regulatory Region Active During Limb Development
    The FASEB Journal, 2015
    Co-Authors: Emily Kim, Charmaine U. Pira, Endika Haro, Luke Tegeler, Kerby C. Oberg
    Abstract:

    LMX1B is a LIM-homeodomain transcription factor that has dorsally restricted expression in limb mesoderm and is responsible for limb dorsalization. Mice lacking functional LMX1B exhibit ventral-ven...

  • The use of human embryonic kidney (HEK 293) cells to enhance characterization of the LMX1B pathway
    The FASEB Journal, 2012
    Co-Authors: Robert Patrick Stump, Jennifer M. Feenstra, Michael A Castillo, Salvador Soriano, Kerby C. Oberg
    Abstract:

    LMX1B is a homeodomain transcription factor critical to kidney development and glomerular filtration. In humans, LMX1B haploinsufficiency causes a condition known as Nail Patella syndrome (NPS). Individuals with NPS typically have under developed nails, absent patellae, and impaired kidney function. In LMX1B knockout mice, the absence of LMX1B function disrupts glomerular filtration and abates urine production. The molecules targeted by LMX1B that regulate glomerular development and function, however, are poorly characterized. Immortalized human embryonic kidney (HEK 293) cells provide a potential tool for high-throughput identification of LMX1B targets and an in vitro system for dissecting the functional role of targets. Thus, we characterized the known LMX1B pathway in HEK 293 cells and evaluated sites of LMX1B binding. We demonstrate the expression of LMX1B and its renal targets, COLLAGEN 4 ALPHA 4 and PODICIN in HEK 293 cells by RT-PCR. Protein expression of LMX1B was verified by w...

  • Detection of genes regulated by LMX1B during limb dorsalization.
    Development growth & differentiation, 2012
    Co-Authors: Jennifer M. Feenstra, Charmaine U. Pira, Kohei Kanaya, Sarah E. Hoffman, Richard J. Eppey, Kerby C. Oberg
    Abstract:

    LMX1B is a homeodomain transcription factor that regulates dorsal identity during limb development. LMX1B knockout (KO) mice develop distal ventral-ventral limbs. Although induction of LMX1B is linked to Wnt7a expression in the dorsal limb ectoderm, the downstream targets of LMX1B that accomplish limb dorsalization are unknown. To identify genes targeted by LMX1B, we compared gene arrays from LMX1B KO and wild type mouse limbs during limb dorsalization, i.e., 11.5, 12.5, and 13.5 days post coitum. We identified 54 target genes that were differentially expressed in all three stages. Several skeletal targets, including Emx2, Matrilin1 and Matrilin4, demonstrated a loss of scapular expression in the LMX1B KO mice, supporting a role for LMX1B in scapula development. Furthermore, the relative abundance of extracellular matrix-related soft tissue targets regulated by LMX1B, such as collagens and proteoglycans, suggests a mechanism that includes changes in the extracellular matrix composition to accomplish limb dorsalization. Our study provides the most comprehensive characterization of genes regulated by LMX1B during limb development to-date and provides targets for further investigation.

Brendan Lee - One of the best experts on this subject based on the ideXlab platform.

  • LMX1B expression during joint and tendon formation: localization and evaluation of potential downstream targets.
    Gene expression patterns : GEP, 2004
    Co-Authors: Sandra D. Dreyer, Randy L. Johnson, Roy Morello, Brendan Lee, Andreas Winterpacht, Takuji Naruse, Bernhard Zabel, Kerby C. Oberg
    Abstract:

    The tetrapod limb exhibits distinct dorsoventral joint, tendon, and muscle asymmetry. The LIM-homeodomain transcription factor, LMX1B, is required to achieve the dorsal character of these structures, but the mechanism by which LMX1B orchestrates this asymmetrical development is unknown. To identify target tissues and genes regulated by LMX1B, we examined LMX1B expression during joint, tendon and muscle formation (9.5-16.5 dpc) and the expression of several genes spatially restricted to developing joints and associated tissues in normal and LMX1B knockout (KO) mice including: Gdf-5, sFrp2, sFrp3, Six1 and Six2. LMX1B was diffusely expressed in the undifferentiated dorsal mesoderm of the emerging limb bud (E9.5-E11.5). With progressive proximal to distal differentiation, LMX1B expression localized to dorsal joint-forming regions, to developing tendons and ligaments, but not to migrating myocytes (E13.5-15.5). By E16.5, mature tendon and ligament associations were evident and LMX1B expression had regressed. The expression patterns of Gdf-5 and sFrp3 at E15.5 were symmetrical along the dorsoventral axis in normal and LMX1B KO mice. sFrp2, Six1 and Six2 exhibited asymmetrical dorsoventral expression and in LMX1B KO mice, this asymmetry is lost; however, none were solely restricted to or excluded from dorsal LMX1B expressing tissues.

  • Transcriptional induction of slit diaphragm genes by LMX1B is required in podocyte differentiation
    The Journal of clinical investigation, 2002
    Co-Authors: Jeffrey H. Miner, Roy Morello, Kaya L. Andrews, Corinne Antignac, Andrey S. Shaw, Brendan Lee
    Abstract:

    LMX1B encodes a LIM-homeodomain transcription factor. Mutations in LMX1B cause nail-patella syndrome (NPS), an autosomal dominant disease with skeletal abnormalities, nail hypoplasia, and nephropathy. Expression of glomerular basement membrane (GBM) collagens is reduced in LMX1B(-/-) mice, suggesting one basis for NPS nephropathy. Here, we show that LMX1B(-/-) podocytes have reduced numbers of foot processes, are dysplastic, and lack typical slit diaphragms, indicating an arrest in development. Using antibodies to podocyte proteins important for podocyte function, we found that LMX1B(-/-) podocytes express near-normal levels of nephrin, synaptopodin, ZO-1, alpha3 integrin, and GBM laminins. However, mRNA and protein levels for CD2AP and podocin were greatly reduced, suggesting a cooperative role for these molecules in foot process and slit diaphragm formation. We identified several LMX1B binding sites in the putative regulatory regions of both CD2AP and NPHS2 (podocin) and demonstrated that LMX1B binds to these sequences in vitro and can activate transcription through them in cotransfection assays. Thus, LMX1B regulates the expression of multiple podocyte genes critical for podocyte differentiation and function. Our results indicate that reduced levels of proteins associated with foot processes and the glomerular slit diaphragm likely contribute, along with reduced levels of GBM collagens, to the nephropathy associated with NPS.

  • LMX1B transactivation and expression in nail–patella syndrome
    Human molecular genetics, 2000
    Co-Authors: Sandra D. Dreyer, Kerby C. Oberg, Roy Morello, Andreas Winterpacht, Bernhard Zabel, Michael S. German, Gregory P. Lunstrum, William A. Horton, Brendan Lee
    Abstract:

    LMX1B, a member of the LIM homeodomain protein family, is essential for the specification of dorsal limb fates at the zeugopodal and autopodal level in vertebrates. We and others have shown that a skeletal dysplasia, nail-patella syndrome (NPS), results from mutations in LMX1B. While it is a unique mesenchymal determinant of dorsal limb patterning during vertebrate development, the mechanism by which LMX1B mutations generate the NPS phenotype has not been addressed at a transcriptional level or correlated with its spatial pattern of gene expression. In this study, in situ hybridizations of LMX1B on murine limb sections reveal strong expression in dorsal mesenchymal tissues (precursors of muscle, tendons, joints and patella) and, interestingly, also in anterior structures of the limb, explaining the anterior to posterior gradient of joint and nail dysplasia observed in NPS patients. Transfection studies showed that both the LIM domain-interacting protein, LDB1, and the helix-loop-helix protein, E47/shPan1, can regulate LMX1B action. While co--transfections of E47/shPan1 with LMX1B result in a synergistic effect on reporter activity, LDB1 down-regulated LMX1B-mediated transactivation irrespective of E47/shPan1. Mutant LMX1B proteins containing human mutations affecting each of the helices or the N-terminal arm of the homeodomain abolished transactivation, while LIM B and truncation mutations retained residual activity. These mutations fail to act in a dominant-negative manner on wild-type LMX1B in mixing studies, thereby supporting haploinsufficiency as the mechanism underlying NPS pathogenesis.

  • LMX1B transactivation and expression in nail patella syndrome
    Human Molecular Genetics, 2000
    Co-Authors: Sandra D. Dreyer, Kerby C. Oberg, Roy Morello, Andreas Winterpacht, Bernhard Zabel, Michael S. German, Gregory P. Lunstrum, William A. Horton, Brendan Lee
    Abstract:

    LMX1B, a member of the LIM homeodomain protein family, is essential for the specification of dorsal limb fates at the zeugopodal and autopodal level in vertebrates. We and others have shown that a skeletal dysplasia, nail-patella syndrome (NPS), results from mutations in LMX1B. While it is a unique mesenchymal determinant of dorsal limb patterning during vertebrate development, the mechanism by which LMX1B mutations generate the NPS phenotype has not been addressed at a transcriptional level or correlated with its spatial pattern of gene expression. In this study, in situ hybridizations of LMX1B on murine limb sections reveal strong expression in dorsal mesenchymal tissues (precursors of muscle, tendons, joints and patella) and, interestingly, also in anterior structures of the limb, explaining the anterior to posterior gradient of joint and nail dysplasia observed in NPS patients. Transfection studies showed that both the LIM domain-interacting protein, LDB1, and the helix-loop-helix protein, E47/shPan1, can regulate LMX1B action. While co--transfections of E47/shPan1 with LMX1B result in a synergistic effect on reporter activity, LDB1 down-regulated LMX1B-mediated transactivation irrespective of E47/shPan1. Mutant LMX1B proteins containing human mutations affecting each of the helices or the N-terminal arm of the homeodomain abolished transactivation, while LIM B and truncation mutations retained residual activity. These mutations fail to act in a dominant-negative manner on wild-type LMX1B in mixing studies, thereby supporting haploinsufficiency as the mechanism underlying NPS pathogenesis.

  • Limb and kidney defects in LMX1B mutant mice suggest an involvement of LMX1B in human nail patella syndrome
    Nature genetics, 1998
    Co-Authors: Haixu Chen, Dmitry A. Ovchinnikov, Kerby C. Oberg, Brendan Lee, Yi Lun, Hiroki Kokubo, Carmen Pepicelli, Lin Gan, Randy L. Johnson
    Abstract:

    Dorsal-ventral limb patterning in vertebrates is thought to be controlled by the LIM-homeodomain protein LMX1B which is expressed in a spatially and temporally restricted manner along the dorsal-ventral limb axis1,2. Here we describe the phenotype resulting from targeted disruption of LMX1B. Our results demonstrate that LMX1B is essential for the specification of dorsal limb fates at both the zeugopodal and autopodal level with prominent phenotypes including an absence of nails and patellae. These features are similar to those present in a dominantly inherited human condition called nail patella syndrome3 (NPS) which also has renal involvement. Mouse LMX1B maps to a region syntenic to that of the NPS gene4, and kidneys of LMX1B mutant mice exhibit pathological changes similar to that observed in NPS (refs 5,6). Our results demonstrate an essential function for LMX1B in mouse limb and kidney development and suggest that NPS might result from mutations in the human LMX1B gene.

Motoshi Hattori - One of the best experts on this subject based on the ideXlab platform.

  • Spectrum of LMX1B mutations: from nail–patella syndrome to isolated nephropathy
    Pediatric Nephrology, 2017
    Co-Authors: Yutaka Harita, Sachiko Kitanaka, Tsuyoshi Isojima, Akira Ashida, Motoshi Hattori
    Abstract:

    Nail–patella syndrome (NPS) is an autosomal-dominant disease caused by LMX1B mutations and is characterized by dysplastic nails, absent or hypoplastic patellae, elbow dysplasia, and iliac horns. Renal involvement is the major determinant of the prognosis for NPS. Patients often present with varying degrees of proteinuria or hematuria, and can occasionally progress to chronic renal failure. Recent genetic analysis has found that some mutations in the homeodomain of LMX1B cause isolated nephropathy without nail, patellar or skeletal abnormality ( LMX1B -associated nephropathy). The classic term “nail–patella syndrome” would not represent disease conditions in these cases. This review provides an overview of NPS, and highlights the molecular genetics of NPS nephropathy and LMX1B -associated nephropathy. Our current understanding of LMX1B function in the pathogenesis of NPS and LMX1B -associated nephropathy is also presented, and its downstream regulatory networks discussed. This recent progress provides insights that help to define potential targeted therapeutic strategies for LMX1B -associated diseases.

  • Spectrum of LMX1B mutations: from nail-patella syndrome to isolated nephropathy.
    Pediatric nephrology (Berlin Germany), 2016
    Co-Authors: Yutaka Harita, Sachiko Kitanaka, Tsuyoshi Isojima, Akira Ashida, Motoshi Hattori
    Abstract:

    Nail–patella syndrome (NPS) is an autosomal-dominant disease caused by LMX1B mutations and is characterized by dysplastic nails, absent or hypoplastic patellae, elbow dysplasia, and iliac horns. Renal involvement is the major determinant of the prognosis for NPS. Patients often present with varying degrees of proteinuria or hematuria, and can occasionally progress to chronic renal failure. Recent genetic analysis has found that some mutations in the homeodomain of LMX1B cause isolated nephropathy without nail, patellar or skeletal abnormality (LMX1B-associated nephropathy). The classic term “nail–patella syndrome” would not represent disease conditions in these cases. This review provides an overview of NPS, and highlights the molecular genetics of NPS nephropathy and LMX1B-associated nephropathy. Our current understanding of LMX1B function in the pathogenesis of NPS and LMX1B-associated nephropathy is also presented, and its downstream regulatory networks discussed. This recent progress provides insights that help to define potential targeted therapeutic strategies for LMX1B-associated diseases.

  • LMX1B mutation with residual transcriptional activity as a cause of isolated glomerulopathy
    Nephrology Dialysis Transplantation, 2014
    Co-Authors: Tsuyoshi Isojima, Yutaka Harita, Takashi Igarashi, Masayuki Furuyama, Noriko Sugawara, Kiyonobu Ishizuka, Shigeru Horita, Yuko Kajiho, Kenichiro Miura, Motoshi Hattori
    Abstract:

    Background Nail-patella syndrome (NPS) is a rare autosomal-dominant disorder caused by LMX1B mutation. In patients with the renal lesions typical of NPS without skeletal or nail findings, it is described as nail-patella-like renal disease (NPLRD). However, the pathogenesis of NPLRD is largely unknown. Methods A 6-year-old girl with microscopic haematuria and mild proteinuria was diagnosed with NPLRD because of an aberrantly thickened glomerular basement membrane (GBM) and deposition of Type III collagen in the GBM observed by electron microscopy. Immunohistological analyses of podocyte protein expression were performed on biopsy tissues. Sequence analysis of LMX1B was performed, and the functional consequences of the detected mutation were analysed by luciferase reporter assay. Results When analysing molecules that are important for podocyte development, maintenance and maturation, CD2AP expression was found to be altered in the podocytes. A novel LMX1B missense mutation (R246Q) was identified. Functional analyses revealed partial but significant impairment of R246Q transcriptional activity. However, no dominant-negative effect of R246Q was detected, which suggests that NPLRD is caused by LMX1B haploinsufficiency. Conclusions This is the first report on LMX1B mutation identified in a patient with NPLRD. Residual transcriptional activity would account for normality of the nails and patella in this case. Genetic and pathological analyses of additional cases would clarify the role of LMX1B in glomerulopathy without systemic symptoms, which, together with nephropathy in NPS, can be designated as 'LMX1B nephropathy'.

  • LMX1B mutation with residual transcriptional activity as a cause of isolated glomerulopathy
    Nephrology dialysis transplantation : official publication of the European Dialysis and Transplant Association - European Renal Association, 2013
    Co-Authors: Tsuyoshi Isojima, Yutaka Harita, Takashi Igarashi, Masayuki Furuyama, Noriko Sugawara, Kiyonobu Ishizuka, Shigeru Horita, Yuko Kajiho, Kenichiro Miura, Motoshi Hattori
    Abstract:

    Nail-patella syndrome (NPS) is a rare autosomal-dominant disorder caused by LMX1B mutation. In patients with the renal lesions typical of NPS without skeletal or nail findings, it is described as nail-patella-like renal disease (NPLRD). However, the pathogenesis of NPLRD is largely unknown. A 6-year-old girl with microscopic haematuria and mild proteinuria was diagnosed with NPLRD because of an aberrantly thickened glomerular basement membrane (GBM) and deposition of Type III collagen in the GBM observed by electron microscopy. Immunohistological analyses of podocyte protein expression were performed on biopsy tissues. Sequence analysis of LMX1B was performed, and the functional consequences of the detected mutation were analysed by luciferase reporter assay. When analysing molecules that are important for podocyte development, maintenance and maturation, CD2AP expression was found to be altered in the podocytes. A novel LMX1B missense mutation (R246Q) was identified. Functional analyses revealed partial but significant impairment of R246Q transcriptional activity. However, no dominant-negative effect of R246Q was detected, which suggests that NPLRD is caused by LMX1B haploinsufficiency. This is the first report on LMX1B mutation identified in a patient with NPLRD. Residual transcriptional activity would account for normality of the nails and patella in this case. Genetic and pathological analyses of additional cases would clarify the role of LMX1B in glomerulopathy without systemic symptoms, which, together with nephropathy in NPS, can be designated as 'LMX1B nephropathy'.