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Yukio Kato - One of the best experts on this subject based on the ideXlab platform.
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Pituitary homeodomain transcription factors HESX1 and PROP1 form a heterodimer on the inverted TAAT motif.
Molecular and cellular endocrinology, 2009Co-Authors: Yukio Kato, Fuyuko Kimoto, Takao Susa, Michie Nakayama, Akio Ishikawa, Takako KatoAbstract:The development and differentiation of the pituitary gland progress through spatial and temporal expressions of many transcription factors. Transcription factor HESX1, which begins to be expressed in the Rathke's pouch at the early stage of pituitary development, acts as a transcription repressor. Another transcription factor, PROP1, which is a pituitary-specific factor and important for the determination of the differentiation of pituitary hormone-producing cells, appears later than HESX1 and is assumed to block the action of HESX1. Both factors are members of the homeodomain family, and the amino acid residue at the 50th position of the homeodomain is glutamine (Gln-50). We recently observed that both factors share the same target sequence through different binding profiles. Hence, using random oligonucleotides and an electrophoretic mobility-shift assay, we have examined the DNA-binding preference of HESX1 by a determination of its binding sequence. HESX1 binds as a monomer to a TAATT motif but not to a TAAT motif. In the presence of PROP1, HESX1 develops to bind to an inverted TAAT motif by forming a heterodimer. Thus, the formation of a heterodimer between HESX1 and PROP1 provides a condition in which, in the early pituitary primordium, HESX1 alters its repressive role to an active one by forming a heterodimer with newly appearing PROP1 so that PROP1 finally replaces HESX1 to advance to the middle stage of pituitary development.
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homeodomain transcription factor HESX1 rpx occupies prop 1 activation sites in porcine follicle stimulating hormone fsh β subunit promoter
Biochemical and Biophysical Research Communications, 2007Co-Authors: Takao Susa, Yukio Kato, Fuyuko Kimoto, Michie Nakayama, Takako Kato, Kousuke KitaharaAbstract:Abstract Homeodomain repressor factor HESX1/Rpx plays a crucial role in the formation of Rathke’s pouch at the start of pituitary organogenesis and represses the Prop-1-dependent expression of Pit-1 gene, which promotes the differentiation of Pit-1-dependent hormone producing cells. Recently, we discovered a novel function of Prop-1 by which it activates the porcine follicle stimulating hormone β subunit (FSHβ) gene through Fd2 region (−852/−746). The present study aimed to determine whether HESX1 exerts its role in the Prop-1-dependent activation of FSHβ gene. Transient transfection assay for the porcine FSHβ promoter −985/+10, electrophoretic mobility shift assay (EMSA) and DNase I footprinting analysis for Fd2 region were carried out. Transfection assay in GH3 cells demonstrated that expression of HESX1 alone does not change the promoter activity but the coexpression with Prop-1 represses the Prop-1-dependent activation of FSHβ promoter. Similar results were obtained for the mutant reporter vector deleting the region −745/−104 indicating that Fd2 region is a target site of HESX1 as well as Prop-1. EMSA and DNase I footprinting analysis using recombinant HESX1 and Prop-1 protein demonstrated that HESX1 and Prop-1 certainly bind to the AT-rich regions in a different manner. These results suggest that HESX1 blocks the advanced expression of FSHβ gene in the early stage of pituitary development, and Prop-1 thereafter appears and activates this gene.
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Homeodomain transcription factor HESX1/Rpx occupies Prop-1 activation sites in porcine follicle stimulating hormone (FSH) β subunit promoter
Biochemical and biophysical research communications, 2007Co-Authors: Takao Susa, Fuyuko Kimoto, Michie Nakayama, Takako Kato, Kousuke Kitahara, Yukio KatoAbstract:Abstract Homeodomain repressor factor HESX1/Rpx plays a crucial role in the formation of Rathke’s pouch at the start of pituitary organogenesis and represses the Prop-1-dependent expression of Pit-1 gene, which promotes the differentiation of Pit-1-dependent hormone producing cells. Recently, we discovered a novel function of Prop-1 by which it activates the porcine follicle stimulating hormone β subunit (FSHβ) gene through Fd2 region (−852/−746). The present study aimed to determine whether HESX1 exerts its role in the Prop-1-dependent activation of FSHβ gene. Transient transfection assay for the porcine FSHβ promoter −985/+10, electrophoretic mobility shift assay (EMSA) and DNase I footprinting analysis for Fd2 region were carried out. Transfection assay in GH3 cells demonstrated that expression of HESX1 alone does not change the promoter activity but the coexpression with Prop-1 represses the Prop-1-dependent activation of FSHβ promoter. Similar results were obtained for the mutant reporter vector deleting the region −745/−104 indicating that Fd2 region is a target site of HESX1 as well as Prop-1. EMSA and DNase I footprinting analysis using recombinant HESX1 and Prop-1 protein demonstrated that HESX1 and Prop-1 certainly bind to the AT-rich regions in a different manner. These results suggest that HESX1 blocks the advanced expression of FSHβ gene in the early stage of pituitary development, and Prop-1 thereafter appears and activates this gene.
Juan Pedro Martinez-barbera - One of the best experts on this subject based on the ideXlab platform.
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HESX1- and TCF3-mediated repression of Wnt/β-catenin targets is required for normal development of the anterior forebrain.
Development (Cambridge England), 2011Co-Authors: Cynthia L. Andoniadou, Carles Gaston-massuet, Massimo Signore, Rodrigo M. Young, Stephen W. Wilson, Elaine Fuchs, Juan Pedro Martinez-barberaAbstract:The Wnt/β-catenin pathway plays an essential role during regionalisation of the vertebrate neural plate and its inhibition in the most anterior neural ectoderm is required for normal forebrain development. HESX1 is a conserved vertebrate-specific transcription factor that is required for forebrain development in Xenopus, mice and humans. Mouse embryos deficient for HESX1 exhibit a variable degree of forebrain defects, but the molecular mechanisms underlying these defects are not fully understood. Here, we show that injection of a HESX1 morpholino into a ‘sensitised’ zygotic headless (tcf3) mutant background leads to severe forebrain and eye defects, suggesting an interaction between HESX1 and the Wnt pathway during zebrafish forebrain development. Consistent with a requirement for Wnt signalling repression, we highlight a synergistic gene dosage-dependent interaction between HESX1 and Tcf3, a transcriptional repressor of Wnt target genes, to maintain anterior forebrain identity during mouse embryogenesis. In addition, we reveal that Tcf3 is essential within the neural ectoderm to maintain anterior character and that its interaction with HESX1 ensures the repression of Wnt targets in the developing forebrain. By employing a conditional loss-of-function approach in mouse, we demonstrate that deletion of β-catenin, and concomitant reduction of Wnt signalling in the developing anterior forebrain of HESX1-deficient embryos, leads to a significant rescue of the forebrain defects. Finally, transcriptional profiling of anterior forebrain precursors from mouse embryos expressing eGFP from the HESX1 locus provides molecular evidence supporting a novel function of HESX1 in mediating repression of Wnt/β-catenin target activation in the developing forebrain.
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Analysis of mouse models carrying the I26T and R160C substitutions in the transcriptional repressor HESX1 as models for septo-optic dysplasia and hypopituitarism.
Disease models & mechanisms, 2008Co-Authors: Ezat Sajedi, Carles Gaston-massuet, Cynthia L. Andoniadou, Massimo Signore, Mehul T. Dattani, Daniel Kelberman, Sandra C. P. De Castro, Heather C. Etchevers, Dianne Gerrelli, Juan Pedro Martinez-barberaAbstract:A homozygous substitution of the highly conserved isoleucine at position 26 by threonine (I26T) in the transcriptional repressor HESX1 has been associated with anterior pituitary hypoplasia in a human patient, with no forebrain or eye defects. Two individuals carrying a homozygous substitution of the conserved arginine at position 160 by cysteine (R160C) manifest septo-optic dysplasia (SOD), a condition characterised by pituitary abnormalities associated with midline telencephalic structure defects and optic nerve hypoplasia. We have generated two knock-in mouse models containing either the I26T or R160C substitution in the genomic locus. HESX1(I26T/I26T) embryos show pituitary defects comparable with HESX1(-/-) mouse mutants, with frequent occurrence of ocular abnormalities, although the telencephalon develops normally. HESX1(R160C/R160C) mutants display forebrain and pituitary defects that are identical to those observed in HESX1(-/-) null mice. We also show that the expression pattern of HESX1 during early human development is very similar to that described in the mouse, suggesting that the function of HESX1 is conserved between the two species. Together, these results suggest that the I26T mutation yields a hypomorphic allele, whereas R160C produces a null allele and, consequently, a more severe phenotype in both mice and humans.
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DNMT1 interacts with the developmental transcriptional repressor HESX1.
Biochimica et biophysica acta, 2007Co-Authors: Ezat Sajedi, Carles Gaston-massuet, Cynthia L. Andoniadou, Massimo Signore, Paul J. Hurd, Mehul T. Dattani, Juan Pedro Martinez-barberaAbstract:HESX1 is a highly conserved homeobox gene present in vertebrates, but absent from invertebrates. Gene targeting experiments in mice have shown that this transcriptional repressor is required for normal forebrain and pituitary development. In humans, mutations in HESX1 impairing either its repressing activity or DNA binding properties lead to a comparable phenotype to that observed in HESX1 deficient mice. In an attempt to gain insights into the molecular function of HESX1, we have performed a yeast two-hybrid screen and identified DNA methyltransferase 1 (DNMT1) as a HESX1 binding protein. We show that Dnmt1 is co-expressed with HESX1 within the anterior forebrain and in the developing Rathke's pouch. Mapping of the interacting regions indicates that the entire HESX1 protein is required to establish binding to a portion of the N-terminus of DNMT1 and its catalytic domain in the C-terminus. The HESX1–DNMT1 complexes can be immunoprecipitated in cells and co-localise in the nucleus. These results establish a link between HESX1 and DNMT1 and suggest a novel mechanism for the repressing properties of HESX1.
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Lack of the murine homeobox gene HESX1 leads to a posterior transformation of the anterior forebrain.
Development (Cambridge England), 2007Co-Authors: Cynthia L. Andoniadou, Ezat Sajedi, Carles Gaston-massuet, Massimo Signore, Mehul T. Dattani, Daniel Kelberman, Alan J. Burns, Nobue Itasaki, Juan Pedro Martinez-barberaAbstract:The homeobox gene HESX1 is an essential repressor that is required within the anterior neural plate for normal forebrain development in mouse and humans. Combining genetic cell labelling and marker analyses, we demonstrate that the absence of HESX1 leads to a posterior transformation of the anterior forebrain (AFB) during mouse development. Our data suggest that the mechanism underlying this transformation is the ectopic activation of Wnt/-catenin signalling within the HESX1 expression domain in the AFB. When ectopically expressed in the developing mouse embryo, HESX1 alone cannot alter the normal fate of posterior neural tissue. However, conditional expression of HESX1 within the AFB can rescue the forebrain defects observed in the HESX1 mutants. The results presented here provide new insights into the function of HESX1 in forebrain formation.
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The Homeobox Gene HESX1 Is Required in the Anterior Neural Ectoderm for Normal Forebrain Formation
Developmental biology, 2000Co-Authors: Juan Pedro Martinez-barbera, Tristan A Rodriguez, Rosa S. P. BeddingtonAbstract:Abstract The homeobox gene HESX1 is expressed in the anterior visceral endoderm (AVE), anterior axial mesendoderm (AME), and anterior neural ectoderm (ANE) during early mouse embryogenesis. Previous studies have shown that HESX1 is essential for normal murine forebrain development. HESX1 homozygous mutants showed variable forebrain truncations ranging from mild to severe lack of forebrain tissue. Here, we have investigated the requirement of HESX1 in the AVE, AME, and ANE using chimeric and in situ hybridization analyses to understand better the nature of the forebrain defects. Chimeric embryos composed predominantly of HESX1 +/+ cells developing within HESX1 −/− visceral endoderm showed no evident forebrain abnormalities. In contrast, injection of HESX1 −/− ES cells into wild-type blastocysts gave rise to chimeras with forebrain defects similar to those observed in the HESX1 −/− mutants. RNA in situ hybridization analysis showed that the AVE and AME markers Cerrl, Lim1, and Shh were normally expressed in 6.5- and 7.5-dpc HESX1 −/− mutants. Expression of the ANE markers Six3 and Rax/Rx was also unperturbed in the HESX1 −/− mutants from late gastrula to late headfold stages. However, transcripts for both genes were markedly reduced by the early somite stage, about 24 h after HESX1 is first expressed in the ANE. Therefore, HESX1 seems to be required autonomously in the ANE for normal forebrain formation.
Mehul T. Dattani - One of the best experts on this subject based on the ideXlab platform.
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HESX1 mutations in patients with congenital hypopituitarism: variable phenotypes with the same genotype
Clinical endocrinology, 2016Co-Authors: Qing Fang, Mehul T. Dattani, Berenice B. Mendonca, Ivo J. P. Arnhold, Anna Flavia Figueredo Benedetti, Louise C. Gregory, Abdollah Sadeghi-nejad, Sally A. CamperAbstract:SummaryIntroduction Mutations in the transcription factor HESX1 can cause isolated growth hormone deficiency (IGHD) or combined pituitary hormone deficiency (CPHD) with or without septo-optic dysplasia (SOD). So far there is no clear genotype–phenotype correlation. Patients and Results We report four different recessive loss-of-function mutations in three unrelated families with CPHD and no midline defects or SOD. A homozygous p.R160C mutation was found by Sanger sequencing in two siblings from a consanguineous family. These patients presented with ACTH, TSH and GH deficiencies, severe anterior pituitary hypoplasia (APH) or pituitary aplasia (PA) and normal posterior pituitary. The p.R160C mutation was previously reported in a case with SOD, CPHD and ectopic posterior pituitary (EPP). Using exome sequencing, a homozygous p.I26T mutation was found in a Brazilian patient born to consanguineous parents. This patient had evolving CPHD, normal ACTH, APH and normal posterior pituitary (NPP). A previously reported patient homozygous for p.I26T had evolving CPHD and EPP. Finally, we identified compound heterozygous mutations in HESX1, p.[R159W];[R160H], in a patient with PA and CPHD. We showed that both of these mutations abrogate the ability of HESX1 to repress PROP1-mediated transcriptional activation. A patient homozygous for p.R160H was previously reported in a patient with CPHD, EPP, APH. Conclusion These three examples demonstrate that HESX1 mutations cause variable clinical features in patients, which suggests an influence of modifier genes or environmental factors on the phenotype.
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Analysis of mouse models carrying the I26T and R160C substitutions in the transcriptional repressor HESX1 as models for septo-optic dysplasia and hypopituitarism.
Disease models & mechanisms, 2008Co-Authors: Ezat Sajedi, Carles Gaston-massuet, Cynthia L. Andoniadou, Massimo Signore, Mehul T. Dattani, Daniel Kelberman, Sandra C. P. De Castro, Heather C. Etchevers, Dianne Gerrelli, Juan Pedro Martinez-barberaAbstract:A homozygous substitution of the highly conserved isoleucine at position 26 by threonine (I26T) in the transcriptional repressor HESX1 has been associated with anterior pituitary hypoplasia in a human patient, with no forebrain or eye defects. Two individuals carrying a homozygous substitution of the conserved arginine at position 160 by cysteine (R160C) manifest septo-optic dysplasia (SOD), a condition characterised by pituitary abnormalities associated with midline telencephalic structure defects and optic nerve hypoplasia. We have generated two knock-in mouse models containing either the I26T or R160C substitution in the genomic locus. HESX1(I26T/I26T) embryos show pituitary defects comparable with HESX1(-/-) mouse mutants, with frequent occurrence of ocular abnormalities, although the telencephalon develops normally. HESX1(R160C/R160C) mutants display forebrain and pituitary defects that are identical to those observed in HESX1(-/-) null mice. We also show that the expression pattern of HESX1 during early human development is very similar to that described in the mouse, suggesting that the function of HESX1 is conserved between the two species. Together, these results suggest that the I26T mutation yields a hypomorphic allele, whereas R160C produces a null allele and, consequently, a more severe phenotype in both mice and humans.
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DNMT1 interacts with the developmental transcriptional repressor HESX1.
Biochimica et biophysica acta, 2007Co-Authors: Ezat Sajedi, Carles Gaston-massuet, Cynthia L. Andoniadou, Massimo Signore, Paul J. Hurd, Mehul T. Dattani, Juan Pedro Martinez-barberaAbstract:HESX1 is a highly conserved homeobox gene present in vertebrates, but absent from invertebrates. Gene targeting experiments in mice have shown that this transcriptional repressor is required for normal forebrain and pituitary development. In humans, mutations in HESX1 impairing either its repressing activity or DNA binding properties lead to a comparable phenotype to that observed in HESX1 deficient mice. In an attempt to gain insights into the molecular function of HESX1, we have performed a yeast two-hybrid screen and identified DNA methyltransferase 1 (DNMT1) as a HESX1 binding protein. We show that Dnmt1 is co-expressed with HESX1 within the anterior forebrain and in the developing Rathke's pouch. Mapping of the interacting regions indicates that the entire HESX1 protein is required to establish binding to a portion of the N-terminus of DNMT1 and its catalytic domain in the C-terminus. The HESX1–DNMT1 complexes can be immunoprecipitated in cells and co-localise in the nucleus. These results establish a link between HESX1 and DNMT1 and suggest a novel mechanism for the repressing properties of HESX1.
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Lack of the murine homeobox gene HESX1 leads to a posterior transformation of the anterior forebrain.
Development (Cambridge England), 2007Co-Authors: Cynthia L. Andoniadou, Ezat Sajedi, Carles Gaston-massuet, Massimo Signore, Mehul T. Dattani, Daniel Kelberman, Alan J. Burns, Nobue Itasaki, Juan Pedro Martinez-barberaAbstract:The homeobox gene HESX1 is an essential repressor that is required within the anterior neural plate for normal forebrain development in mouse and humans. Combining genetic cell labelling and marker analyses, we demonstrate that the absence of HESX1 leads to a posterior transformation of the anterior forebrain (AFB) during mouse development. Our data suggest that the mechanism underlying this transformation is the ectopic activation of Wnt/-catenin signalling within the HESX1 expression domain in the AFB. When ectopically expressed in the developing mouse embryo, HESX1 alone cannot alter the normal fate of posterior neural tissue. However, conditional expression of HESX1 within the AFB can rescue the forebrain defects observed in the HESX1 mutants. The results presented here provide new insights into the function of HESX1 in forebrain formation.
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A homozygous mutation in HESX1 is associated with evolving hypopituitarism due to impaired repressor-corepressor interaction.
The Journal of clinical investigation, 2003Co-Authors: Luciani R. Carvalho, Stefano Stifani, Joshua M Brickman, Kathryn S. Woods, Berenice B. Mendonca, Nathalie Marcal, Andrea L. Zamparini, Ivo J. P. Arnhold, Mehul T. DattaniAbstract:The paired-like homeobox gene expressed in embryonic stem cells HESX1/HESX1 encodes a developmental repressor and is expressed in early development in a region fated to form the forebrain, with subsequent localization to Rathke's pouch, the primordium of the anterior pituitary gland. Mutations within the gene have been associated with septo-optic dysplasia, a constellation of phenotypes including eye, forebrain, and pituitary abnormalities, or milder degrees of hypopituitarism. We identified a novel homozygous nonconservative missense mutation (I26T) in the critical Engrailed homology repressor domain (eh1) of HESX1, the first, to our knowledge, to be described in humans, in a girl with evolving combined pituitary hormone deficiency born to consanguineous parents. Neuroimaging revealed a thin pituitary stalk with anterior pituitary hypoplasia and an ectopic posterior pituitary, but no midline or optic nerve abnormalities. This I26T mutation did not affect the DNA-binding ability of HESX1 but led to an impaired ability to recruit the mammalian Groucho homolog/Transducin-like enhancer of split-1 (Gro/TLE1), a crucial corepressor for HESX1, thereby leading to partial loss of repression. Thus, the novel pituitary phenotype highlighted here appears to be a specific consequence of the inability of HESX1 to recruit Groucho-related corepressors, suggesting that other molecular mechanisms govern HESX1 function in the forebrain.
Cynthia L. Andoniadou - One of the best experts on this subject based on the ideXlab platform.
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HESX1 and tcf3 mediated repression of wnt β catenin targets is required for normal development of the anterior forebrain
Development, 2011Co-Authors: Cynthia L. Andoniadou, Massimo Signore, Rodrigo M. Young, Stephen W. Wilson, Elaine Fuchs, Carles Gastonmassuet, Juan Pedro MartinezbarberaAbstract:The Wnt/β-catenin pathway plays an essential role during regionalisation of the vertebrate neural plate and its inhibition in the most anterior neural ectoderm is required for normal forebrain development. HESX1 is a conserved vertebrate-specific transcription factor that is required for forebrain development in Xenopus, mice and humans. Mouse embryos deficient for HESX1 exhibit a variable degree of forebrain defects, but the molecular mechanisms underlying these defects are not fully understood. Here, we show that injection of a HESX1 morpholino into a ‘sensitised’ zygotic headless (tcf3) mutant background leads to severe forebrain and eye defects, suggesting an interaction between HESX1 and the Wnt pathway during zebrafish forebrain development. Consistent with a requirement for Wnt signalling repression, we highlight a synergistic gene dosage-dependent interaction between HESX1 and Tcf3, a transcriptional repressor of Wnt target genes, to maintain anterior forebrain identity during mouse embryogenesis. In addition, we reveal that Tcf3 is essential within the neural ectoderm to maintain anterior character and that its interaction with HESX1 ensures the repression of Wnt targets in the developing forebrain. By employing a conditional loss-of-function approach in mouse, we demonstrate that deletion of β-catenin, and concomitant reduction of Wnt signalling in the developing anterior forebrain of HESX1-deficient embryos, leads to a significant rescue of the forebrain defects. Finally, transcriptional profiling of anterior forebrain precursors from mouse embryos expressing eGFP from the HESX1 locus provides molecular evidence supporting a novel function of HESX1 in mediating repression of Wnt/β-catenin target activation in the developing forebrain.
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HESX1- and TCF3-mediated repression of Wnt/β-catenin targets is required for normal development of the anterior forebrain.
Development (Cambridge England), 2011Co-Authors: Cynthia L. Andoniadou, Carles Gaston-massuet, Massimo Signore, Rodrigo M. Young, Stephen W. Wilson, Elaine Fuchs, Juan Pedro Martinez-barberaAbstract:The Wnt/β-catenin pathway plays an essential role during regionalisation of the vertebrate neural plate and its inhibition in the most anterior neural ectoderm is required for normal forebrain development. HESX1 is a conserved vertebrate-specific transcription factor that is required for forebrain development in Xenopus, mice and humans. Mouse embryos deficient for HESX1 exhibit a variable degree of forebrain defects, but the molecular mechanisms underlying these defects are not fully understood. Here, we show that injection of a HESX1 morpholino into a ‘sensitised’ zygotic headless (tcf3) mutant background leads to severe forebrain and eye defects, suggesting an interaction between HESX1 and the Wnt pathway during zebrafish forebrain development. Consistent with a requirement for Wnt signalling repression, we highlight a synergistic gene dosage-dependent interaction between HESX1 and Tcf3, a transcriptional repressor of Wnt target genes, to maintain anterior forebrain identity during mouse embryogenesis. In addition, we reveal that Tcf3 is essential within the neural ectoderm to maintain anterior character and that its interaction with HESX1 ensures the repression of Wnt targets in the developing forebrain. By employing a conditional loss-of-function approach in mouse, we demonstrate that deletion of β-catenin, and concomitant reduction of Wnt signalling in the developing anterior forebrain of HESX1-deficient embryos, leads to a significant rescue of the forebrain defects. Finally, transcriptional profiling of anterior forebrain precursors from mouse embryos expressing eGFP from the HESX1 locus provides molecular evidence supporting a novel function of HESX1 in mediating repression of Wnt/β-catenin target activation in the developing forebrain.
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Analysis of mouse models carrying the I26T and R160C substitutions in the transcriptional repressor HESX1 as models for septo-optic dysplasia and hypopituitarism.
Disease models & mechanisms, 2008Co-Authors: Ezat Sajedi, Carles Gaston-massuet, Cynthia L. Andoniadou, Massimo Signore, Mehul T. Dattani, Daniel Kelberman, Sandra C. P. De Castro, Heather C. Etchevers, Dianne Gerrelli, Juan Pedro Martinez-barberaAbstract:A homozygous substitution of the highly conserved isoleucine at position 26 by threonine (I26T) in the transcriptional repressor HESX1 has been associated with anterior pituitary hypoplasia in a human patient, with no forebrain or eye defects. Two individuals carrying a homozygous substitution of the conserved arginine at position 160 by cysteine (R160C) manifest septo-optic dysplasia (SOD), a condition characterised by pituitary abnormalities associated with midline telencephalic structure defects and optic nerve hypoplasia. We have generated two knock-in mouse models containing either the I26T or R160C substitution in the genomic locus. HESX1(I26T/I26T) embryos show pituitary defects comparable with HESX1(-/-) mouse mutants, with frequent occurrence of ocular abnormalities, although the telencephalon develops normally. HESX1(R160C/R160C) mutants display forebrain and pituitary defects that are identical to those observed in HESX1(-/-) null mice. We also show that the expression pattern of HESX1 during early human development is very similar to that described in the mouse, suggesting that the function of HESX1 is conserved between the two species. Together, these results suggest that the I26T mutation yields a hypomorphic allele, whereas R160C produces a null allele and, consequently, a more severe phenotype in both mice and humans.
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DNMT1 interacts with the developmental transcriptional repressor HESX1.
Biochimica et biophysica acta, 2007Co-Authors: Ezat Sajedi, Carles Gaston-massuet, Cynthia L. Andoniadou, Massimo Signore, Paul J. Hurd, Mehul T. Dattani, Juan Pedro Martinez-barberaAbstract:HESX1 is a highly conserved homeobox gene present in vertebrates, but absent from invertebrates. Gene targeting experiments in mice have shown that this transcriptional repressor is required for normal forebrain and pituitary development. In humans, mutations in HESX1 impairing either its repressing activity or DNA binding properties lead to a comparable phenotype to that observed in HESX1 deficient mice. In an attempt to gain insights into the molecular function of HESX1, we have performed a yeast two-hybrid screen and identified DNA methyltransferase 1 (DNMT1) as a HESX1 binding protein. We show that Dnmt1 is co-expressed with HESX1 within the anterior forebrain and in the developing Rathke's pouch. Mapping of the interacting regions indicates that the entire HESX1 protein is required to establish binding to a portion of the N-terminus of DNMT1 and its catalytic domain in the C-terminus. The HESX1–DNMT1 complexes can be immunoprecipitated in cells and co-localise in the nucleus. These results establish a link between HESX1 and DNMT1 and suggest a novel mechanism for the repressing properties of HESX1.
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Lack of the murine homeobox gene HESX1 leads to a posterior transformation of the anterior forebrain.
Development (Cambridge England), 2007Co-Authors: Cynthia L. Andoniadou, Ezat Sajedi, Carles Gaston-massuet, Massimo Signore, Mehul T. Dattani, Daniel Kelberman, Alan J. Burns, Nobue Itasaki, Juan Pedro Martinez-barberaAbstract:The homeobox gene HESX1 is an essential repressor that is required within the anterior neural plate for normal forebrain development in mouse and humans. Combining genetic cell labelling and marker analyses, we demonstrate that the absence of HESX1 leads to a posterior transformation of the anterior forebrain (AFB) during mouse development. Our data suggest that the mechanism underlying this transformation is the ectopic activation of Wnt/-catenin signalling within the HESX1 expression domain in the AFB. When ectopically expressed in the developing mouse embryo, HESX1 alone cannot alter the normal fate of posterior neural tissue. However, conditional expression of HESX1 within the AFB can rescue the forebrain defects observed in the HESX1 mutants. The results presented here provide new insights into the function of HESX1 in forebrain formation.
Takao Susa - One of the best experts on this subject based on the ideXlab platform.
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Pituitary homeodomain transcription factors HESX1 and PROP1 form a heterodimer on the inverted TAAT motif.
Molecular and cellular endocrinology, 2009Co-Authors: Yukio Kato, Fuyuko Kimoto, Takao Susa, Michie Nakayama, Akio Ishikawa, Takako KatoAbstract:The development and differentiation of the pituitary gland progress through spatial and temporal expressions of many transcription factors. Transcription factor HESX1, which begins to be expressed in the Rathke's pouch at the early stage of pituitary development, acts as a transcription repressor. Another transcription factor, PROP1, which is a pituitary-specific factor and important for the determination of the differentiation of pituitary hormone-producing cells, appears later than HESX1 and is assumed to block the action of HESX1. Both factors are members of the homeodomain family, and the amino acid residue at the 50th position of the homeodomain is glutamine (Gln-50). We recently observed that both factors share the same target sequence through different binding profiles. Hence, using random oligonucleotides and an electrophoretic mobility-shift assay, we have examined the DNA-binding preference of HESX1 by a determination of its binding sequence. HESX1 binds as a monomer to a TAATT motif but not to a TAAT motif. In the presence of PROP1, HESX1 develops to bind to an inverted TAAT motif by forming a heterodimer. Thus, the formation of a heterodimer between HESX1 and PROP1 provides a condition in which, in the early pituitary primordium, HESX1 alters its repressive role to an active one by forming a heterodimer with newly appearing PROP1 so that PROP1 finally replaces HESX1 to advance to the middle stage of pituitary development.
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homeodomain transcription factor HESX1 rpx occupies prop 1 activation sites in porcine follicle stimulating hormone fsh β subunit promoter
Biochemical and Biophysical Research Communications, 2007Co-Authors: Takao Susa, Yukio Kato, Fuyuko Kimoto, Michie Nakayama, Takako Kato, Kousuke KitaharaAbstract:Abstract Homeodomain repressor factor HESX1/Rpx plays a crucial role in the formation of Rathke’s pouch at the start of pituitary organogenesis and represses the Prop-1-dependent expression of Pit-1 gene, which promotes the differentiation of Pit-1-dependent hormone producing cells. Recently, we discovered a novel function of Prop-1 by which it activates the porcine follicle stimulating hormone β subunit (FSHβ) gene through Fd2 region (−852/−746). The present study aimed to determine whether HESX1 exerts its role in the Prop-1-dependent activation of FSHβ gene. Transient transfection assay for the porcine FSHβ promoter −985/+10, electrophoretic mobility shift assay (EMSA) and DNase I footprinting analysis for Fd2 region were carried out. Transfection assay in GH3 cells demonstrated that expression of HESX1 alone does not change the promoter activity but the coexpression with Prop-1 represses the Prop-1-dependent activation of FSHβ promoter. Similar results were obtained for the mutant reporter vector deleting the region −745/−104 indicating that Fd2 region is a target site of HESX1 as well as Prop-1. EMSA and DNase I footprinting analysis using recombinant HESX1 and Prop-1 protein demonstrated that HESX1 and Prop-1 certainly bind to the AT-rich regions in a different manner. These results suggest that HESX1 blocks the advanced expression of FSHβ gene in the early stage of pituitary development, and Prop-1 thereafter appears and activates this gene.
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Homeodomain transcription factor HESX1/Rpx occupies Prop-1 activation sites in porcine follicle stimulating hormone (FSH) β subunit promoter
Biochemical and biophysical research communications, 2007Co-Authors: Takao Susa, Fuyuko Kimoto, Michie Nakayama, Takako Kato, Kousuke Kitahara, Yukio KatoAbstract:Abstract Homeodomain repressor factor HESX1/Rpx plays a crucial role in the formation of Rathke’s pouch at the start of pituitary organogenesis and represses the Prop-1-dependent expression of Pit-1 gene, which promotes the differentiation of Pit-1-dependent hormone producing cells. Recently, we discovered a novel function of Prop-1 by which it activates the porcine follicle stimulating hormone β subunit (FSHβ) gene through Fd2 region (−852/−746). The present study aimed to determine whether HESX1 exerts its role in the Prop-1-dependent activation of FSHβ gene. Transient transfection assay for the porcine FSHβ promoter −985/+10, electrophoretic mobility shift assay (EMSA) and DNase I footprinting analysis for Fd2 region were carried out. Transfection assay in GH3 cells demonstrated that expression of HESX1 alone does not change the promoter activity but the coexpression with Prop-1 represses the Prop-1-dependent activation of FSHβ promoter. Similar results were obtained for the mutant reporter vector deleting the region −745/−104 indicating that Fd2 region is a target site of HESX1 as well as Prop-1. EMSA and DNase I footprinting analysis using recombinant HESX1 and Prop-1 protein demonstrated that HESX1 and Prop-1 certainly bind to the AT-rich regions in a different manner. These results suggest that HESX1 blocks the advanced expression of FSHβ gene in the early stage of pituitary development, and Prop-1 thereafter appears and activates this gene.