Zebrafish Lmx1b.1 and Lmx1b.2 are required for maintenance of the isthmic organizer

O'Hara, F. Patrick; E, Beck; Barr, Lauren K.; Wong, Lily; Kessler, Daniel S.; Riddle, Robert D.

doi:10.1242/dev.01898

Cited by 46 publications

(62 citation statements)

References 63 publications

(42 reference statements)

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“…High homology (84% identity and 89% similarity) of LMX1B with zebrafish lmx1b.1 30 is in agreement with sufficient binding of LMX1B to the zebrafish enhancer. Although repeated attempts with different methods and conditions were made, we could not detect a tertiary band that indicates cobinding of two proteins to the probe at the same time by a conventional EMSA in vitro.…”

Section: Identification Of a Podocyte-specific Enhancer By Analysis Osupporting

confidence: 64%

Lmx1b and FoxC Combinatorially Regulate Podocin Expression in Podocytes

Ebarasi

Zhao

et al. 2014

Journal of the American Society of Nephrology

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Podocin is a key protein of the kidney podocyte slit diaphragm protein complex, an important part of the glomerular filtration barrier. Mutations in the human podocin gene NPHS2 cause familial or sporadic forms of renal disease owing to the disruption of filtration barrier integrity. The exclusive expression of NPHS2 in podocytes reflects its unique function and raises interesting questions about its transcriptional regulation. Here, we further define a 2.5-kb zebrafish nphs2 promoter fragment previously described and identify a 49-bp podocyte-specific transcriptional enhancer using Tol2-mediated G 0 transgenesis in zebrafish. Within this enhancer, we identified a cis-acting element composed of two adjacent DNA-binding sites (FLAT-E and forkhead) bound by transcription factors Lmx1b and FoxC. In zebrafish, double knockdown of Lmx1b and FoxC orthologs using morpholino doses that caused no or minimal phenotypic changes upon individual knockdown completely disrupted podocyte development in 40% of injected embryos. Cooverexpression of the two genes potently induced endogenous nphs2 expression in zebrafish podocytes. We found that the NPHS2 promoter also contains a cis-acting Lmx1b-FoxC motif that binds LMX1B and FoxC2. Furthermore, a genome-wide search identified several genes that carry the Lmx1b-FoxC motif in their promoter regions. Among these candidates, motif-driven podocyte enhancer activity of CCNC and MEIS2 was functionally analyzed in vivo. Our results show that podocyte expression of some genes is combinatorially regulated by two transcription factors interacting synergistically with a common enhancer. This finding provides insights into transcriptional mechanisms required for normal and pathologic podocyte functions. Normal glomerular filtration function depends on structural integrity of the filtration barrier. Glomerular podocytes play a key role in establishing and maintaining this unique filtration barrier structure. Mature podocytes are characterized by cell cycle arrest, foot process formation, and the presence of the slit diaphragm, 1 which bridges the gaps between the interdigitating foot processes of neighboring podocytes and functions as a size-selective filtration barrier. 2,3 For their differentiation, as well as for the maintenance of their complex architecture, podocytes require the expression of several specific genes in a correct spatial and temporal fashion. This notion is supported by the identification of many mutations in podocyte-expressed genes as the underlying cause of inherited renal diseases. 4 Moreover, recent studies from genetically modified mice

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Section: Identification Of a Podocyte-specific Enhancer By Analysis Osupporting

confidence: 64%

Lmx1b and FoxC Combinatorially Regulate Podocin Expression in Podocytes

Ebarasi

Zhao

et al. 2014

Journal of the American Society of Nephrology

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“…The relationship between LIM-homeobox transcription factors and Wnt signaling has been reported in the developmental processes of several organisms (Riddle et al, 1995;Adams et al, 2000;Matsunaga et al, 2002;O'Hara et al, 2005). Furthermore, -catenin is involved in Isl1 expression in cardiac progenitors in the mouse embryo Kwon et al, 2009 (E)Relative gene expression levels during regeneration measured by qPCR in the posterior blastema after Djislet RNAi (upper panels), and in whole regenerants after -ray irradiation (lower panels).…”

Section: Islet Functions In the Wnt-expressing Cells Of Planarianmentioning

confidence: 99%

A LIM-homeobox gene is required for differentiation of Wnt-expressing cells at the posterior end of the planarian body

Hayashi¹,

Motoishi²,

Yazawa

et al. 2011

Development

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SUMMARYPlanarians have high regenerative ability, which is dependent on pluripotent adult somatic stem cells called neoblasts. Recently, canonical Wnt/-catenin signaling was shown to be required for posterior specification, and Hedgehog signaling was shown to control anterior-posterior polarity via activation of the Djwnt1/P-1 gene at the posterior end of planarians. Thus, various signaling molecules play an important role in planarian stem cell regulation. However, the molecular mechanisms directly involved in stem cell differentiation have remained unclear. Here, we demonstrate that one of the planarian LIM-homeobox genes, Djislet, is required for the differentiation of Djwnt1/P-1-expressing cells from stem cells at the posterior end. RNA interference (RNAi)-treated planarians of Djislet [Djislet(RNAi)] show a tail-less phenotype. Thus, we speculated that Djislet might be involved in activation of the Wnt signaling pathway in the posterior blastema. When we carefully examined the expression pattern of Djwnt1/P-1 by quantitative real-time PCR during posterior regeneration, we found two phases of Djwnt1/P-1 expression: the first phase was detected in the differentiated cells in the old tissue in the early stage of regeneration and then a second phase was observed in the cells derived from stem cells in the posterior blastema. Interestingly, Djislet is expressed in stem cell-derived DjPiwiA-and Djwnt1/P-1-expressing cells, and Djislet(RNAi) only perturbed the second phase. Thus, we propose that Djislet might act to trigger the differentiation of cells expressing Djwnt1/P-1 from stem cells.

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“…Its activity is regulated by an interdependent network of nuclear factors and signaling proteins, which includes the transcription factors En1/En2, Pax2/ Pax5,Lmx1b,Hes1/Hes3,iro1/iro7, and members of the Fgf and Wnt families of secreted proteins (Bally-Cuif et al, 1992;Rowitch and McMahon, 1995;Araki and Nakamura, 1999;Shamim et al, 1999;Adams et al, 2000;Hirata et al, 2001;Itoh et al, 2002;Matsunaga et al, 2002;O'Hara et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

A Role for Receptor Protein Tyrosine Phosphatase in Midbrain Development

Badde

Schulte

2008

Journal of Neuroscience

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The mid-hindbrain boundary (MHB) harbors an important organizing center for the adjacent brain regions. Here, we present evidence that the receptor protein tyrosine phosphatase (RPTP) is part of the complex molecular network that maintains and shapes the MHB region. RPTP is expressed in a tight band of cells in the caudal midbrain, anterior to the transverse ring of Wnt1 expression. Forced expression of RPTP across the mid-hindbrain region repressed expression of Wnt1, whereas RNA interference-mediated knock-down of RPTP resulted in expansion and distortion of the Wnt1 domain. When ectopically expressed in the mesencephalon, RPTP specifically inhibited the induction of Wnt1 expression after subsequent stimulation with Fgf8. Reduced Wnt1 expression after RPTP transfection correlated with a decrease in Ras-mitogen-activated protein kinase activity at the MHB. We further show that in the embryonic midbrain, RPTP can bind to ␤-catenin, a central component of the canonical Wnt signaling pathway. Overexpression of RPTP suppressed the activity of a ␤-catenin responsive promoter in the midbrain and reduced progenitor cell proliferation. Cotransfection of Wnt1 or of a stabilized form of ␤-catenin together with RPTP partially rescued the RPTP-mediated proliferation defect. Together, these data suggest that RPTP may play a dual role in the control of midbrain development: as a negative modulator of Fgf8-induced Wnt1 expression at the MHB, which may help to confine the Wnt1 domain to it characteristic tight ring at the MHB; and as an inhibitor of canonical Wnt signaling through interaction with and presumably sequestration of ␤-catenin.

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Zebrafish Lmx1b.1 and Lmx1b.2 are required for maintenance of the isthmic organizer

Cited by 46 publications

References 63 publications

Lmx1b and FoxC Combinatorially Regulate Podocin Expression in Podocytes

Lmx1b and FoxC Combinatorially Regulate Podocin Expression in Podocytes

A LIM-homeobox gene is required for differentiation of Wnt-expressing cells at the posterior end of the planarian body

A Role for Receptor Protein Tyrosine Phosphatase in Midbrain Development

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