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Valdivia LE, Lamb DB, Horner W, Wierzbicki C, Tafessu A, Williams AM, Gestri G, Krasnow AM, Vleeshouwer-Neumann TS, Givens M, Young RM, Lawrence LM, Stickney HL, Hawkins TA, Schwarz QP, Cavodeassi F, Wilson SW, Cerveny KL. Antagonism between Gdf6a and retinoic acid pathways controls timing of retinal neurogenesis and growth of the eye in zebrafish. Development 2016; 143:1087-98. [PMID: 26893342 PMCID: PMC4852494 DOI: 10.1242/dev.130922] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Accepted: 02/08/2016] [Indexed: 12/27/2022]
Abstract
Maintaining neurogenesis in growing tissues requires a tight balance between progenitor cell proliferation and differentiation. In the zebrafish retina, neuronal differentiation proceeds in two stages with embryonic retinal progenitor cells (RPCs) of the central retina accounting for the first rounds of differentiation, and stem cells from the ciliary marginal zone (CMZ) being responsible for late neurogenesis and growth of the eye. In this study, we analyse two mutants with small eyes that display defects during both early and late phases of retinal neurogenesis. These mutants carry lesions in gdf6a, a gene encoding a BMP family member previously implicated in dorsoventral patterning of the eye. We show that gdf6a mutant eyes exhibit expanded retinoic acid (RA) signalling and demonstrate that exogenous activation of this pathway in wild-type eyes inhibits retinal growth, generating small eyes with a reduced CMZ and fewer proliferating progenitors, similar to gdf6a mutants. We provide evidence that RA regulates the timing of RPC differentiation by promoting cell cycle exit. Furthermore, reducing RA signalling in gdf6a mutants re-establishes appropriate timing of embryonic retinal neurogenesis and restores putative stem and progenitor cell populations in the CMZ. Together, our results support a model in which dorsally expressed gdf6a limits RA pathway activity to control the transition from proliferation to differentiation in the growing eye. Summary: In the vertebrate eye, dorsally expressed Gdf6a limits RA pathway activity to control the transition from proliferation to differentiation, thereby regulating eye size.
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Affiliation(s)
- Leonardo E Valdivia
- Department of Cell and Developmental Biology, UCL, Gower Street, London WC1E 6BT, UK
| | - Dayna B Lamb
- Department of Biology, Reed College, 3203 SE Woodstock Boulevard, Portland, OR 97202, USA
| | - Wilson Horner
- Department of Biology, Reed College, 3203 SE Woodstock Boulevard, Portland, OR 97202, USA
| | - Claudia Wierzbicki
- Department of Cell and Developmental Biology, UCL, Gower Street, London WC1E 6BT, UK
| | - Amanuel Tafessu
- Department of Biology, Reed College, 3203 SE Woodstock Boulevard, Portland, OR 97202, USA
| | - Audrey M Williams
- Department of Biology, Reed College, 3203 SE Woodstock Boulevard, Portland, OR 97202, USA
| | - Gaia Gestri
- Department of Cell and Developmental Biology, UCL, Gower Street, London WC1E 6BT, UK
| | - Anna M Krasnow
- Department of Cell and Developmental Biology, UCL, Gower Street, London WC1E 6BT, UK
| | | | - McKenzie Givens
- Department of Biology, Reed College, 3203 SE Woodstock Boulevard, Portland, OR 97202, USA
| | - Rodrigo M Young
- Department of Cell and Developmental Biology, UCL, Gower Street, London WC1E 6BT, UK
| | - Lisa M Lawrence
- Department of Cell and Developmental Biology, UCL, Gower Street, London WC1E 6BT, UK
| | - Heather L Stickney
- Department of Cell and Developmental Biology, UCL, Gower Street, London WC1E 6BT, UK
| | - Thomas A Hawkins
- Department of Cell and Developmental Biology, UCL, Gower Street, London WC1E 6BT, UK
| | - Quenten P Schwarz
- Department of Cell and Developmental Biology, UCL, Gower Street, London WC1E 6BT, UK
| | - Florencia Cavodeassi
- Department of Cell and Developmental Biology, UCL, Gower Street, London WC1E 6BT, UK
| | - Stephen W Wilson
- Department of Cell and Developmental Biology, UCL, Gower Street, London WC1E 6BT, UK
| | - Kara L Cerveny
- Department of Cell and Developmental Biology, UCL, Gower Street, London WC1E 6BT, UK Department of Biology, Reed College, 3203 SE Woodstock Boulevard, Portland, OR 97202, USA
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Kolesnikoff N, Attema JL, Roslan S, Bert AG, Schwarz QP, Gregory PA, Goodall GJ. Specificity protein 1 (Sp1) maintains basal epithelial expression of the miR-200 family: implications for epithelial-mesenchymal transition. J Biol Chem 2014; 289:11194-11205. [PMID: 24627491 DOI: 10.1074/jbc.m113.529172] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Epithelial-mesenchymal transition (EMT) is required for the specification of tissues during embryonic development and is recapitulated during the metastatic progression of tumors. The miR-200 family plays a critical role in enforcing the epithelial state with their expression lost in cells undergoing EMT. EMT can be mediated by activation of the ZEB1 and ZEB2 (ZEB) transcription factors, which repress miR-200 expression via a self-reinforcing double negative feedback loop to promote the mesenchymal state. However, it remains unclear what factors drive and maintain epithelial-specific expression of miR-200 in the absence of EMT-inducing factors. Here, we show that the transcription factor Specificity Protein 1 (Sp1) binds to the miR-200b∼200a∼429 proximal promoter and activates miR-200 expression in epithelial cells. In mesenchymal cells, Sp1 expression is maintained, but its ability to activate the miR-200 promoter is perturbed by ZEB-mediated repression. Reduction of Sp1 expression caused changes in EMT-associated markers in epithelial cells. Furthermore, we observed co-expression of Sp1 and miR-200 during mouse embryonic development wherein miR-200 expression was only lost in regions with high ZEB expression. Together, these findings indicate that miR-200 family members require Sp1 to drive basal expression and to maintain an epithelial state.
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Affiliation(s)
- Natasha Kolesnikoff
- Centre for Cancer Biology, University of South Australia and SA Pathology, Adelaide, South Australia 5000, Australia
| | - Joanne L Attema
- Centre for Cancer Biology, University of South Australia and SA Pathology, Adelaide, South Australia 5000, Australia,; Discipline of Medicine, The University of Adelaide, Adelaide, South Australia 5005, Australia, and
| | - Suraya Roslan
- Centre for Cancer Biology, University of South Australia and SA Pathology, Adelaide, South Australia 5000, Australia
| | - Andrew G Bert
- Centre for Cancer Biology, University of South Australia and SA Pathology, Adelaide, South Australia 5000, Australia
| | - Quenten P Schwarz
- Centre for Cancer Biology, University of South Australia and SA Pathology, Adelaide, South Australia 5000, Australia
| | - Philip A Gregory
- Centre for Cancer Biology, University of South Australia and SA Pathology, Adelaide, South Australia 5000, Australia,; Discipline of Medicine, The University of Adelaide, Adelaide, South Australia 5005, Australia, and.
| | - Gregory J Goodall
- Centre for Cancer Biology, University of South Australia and SA Pathology, Adelaide, South Australia 5000, Australia,; Discipline of Medicine, The University of Adelaide, Adelaide, South Australia 5005, Australia, and; School of Molecular and Biomedical Science, The University of Adelaide, Adelaide, South Australia 5005, Australia.
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Cheah PS, Ramshaw HS, Thomas PQ, Toyo-Oka K, Xu X, Martin S, Coyle P, Guthridge MA, Stomski F, van den Buuse M, Wynshaw-Boris A, Lopez AF, Schwarz QP. Neurodevelopmental and neuropsychiatric behaviour defects arise from 14-3-3ζ deficiency. Mol Psychiatry 2012; 17:451-66. [PMID: 22124272 DOI: 10.1038/mp.2011.158] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Complex neuropsychiatric disorders are believed to arise from multiple synergistic deficiencies within connected biological networks controlling neuronal migration, axonal pathfinding and synapse formation. Here, we show that deletion of 14-3-3ζ causes neurodevelopmental anomalies similar to those seen in neuropsychiatric disorders such as schizophrenia, autism spectrum disorder and bipolar disorder. 14-3-3ζ-deficient mice displayed striking behavioural and cognitive deficiencies including a reduced capacity to learn and remember, hyperactivity and disrupted sensorimotor gating. These deficits are accompanied by subtle developmental abnormalities of the hippocampus that are underpinned by aberrant neuronal migration. Significantly, 14-3-3ζ-deficient mice exhibited abnormal mossy fibre navigation and glutamatergic synapse formation. The molecular basis of these defects involves the schizophrenia risk factor, DISC1, which interacts isoform specifically with 14-3-3ζ. Our data provide the first evidence of a direct role for 14-3-3ζ deficiency in the aetiology of neurodevelopmental disorders and identifies 14-3-3ζ as a central risk factor in the schizophrenia protein interaction network.
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Affiliation(s)
- P S Cheah
- Department of Human Immunology, Centre for Cancer Biology, SA Pathology, Adelaide, South Australia, Australia
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Drenckhahn JD, Schwarz QP, Gray S, Laskowski A, Kiriazis H, Ming Z, Harvey RP, Du XJ, Thorburn DR, Cox TC. Compensatory growth of healthy cardiac cells in the presence of diseased cells restores tissue homeostasis during heart development. Dev Cell 2008; 15:521-33. [PMID: 18854137 DOI: 10.1016/j.devcel.2008.09.005] [Citation(s) in RCA: 146] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2007] [Revised: 08/18/2008] [Accepted: 09/17/2008] [Indexed: 11/18/2022]
Abstract
Energy generation by mitochondrial respiration is an absolute requirement for cardiac function. Here, we used a heart-specific conditional knockout approach to inactivate the X-linked gene encoding Holocytochrome c synthase (Hccs), an enzyme responsible for activation of respiratory cytochromes c and c1. Heterozygous knockout female mice were thus mosaic for Hccs function due to random X chromosome inactivation. In contrast to midgestational lethality of Hccs knockout males, heterozygous females appeared normal after birth. Analyses of heterozygous embryos revealed the expected 50:50 ratio of Hccs deficient to normal cardiac cells at midgestation; however, diseased tissue contributed progressively less over time and by birth represented only 10% of cardiac tissue volume. This change is accounted for by increased proliferation of remaining healthy cardiac cells resulting in a fully functional heart. These data reveal an impressive regenerative capacity of the fetal heart that can compensate for an effective loss of 50% of cardiac tissue.
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Affiliation(s)
- Jörg-Detlef Drenckhahn
- Department of Anatomy & Developmental Biology, Monash University, Wellington Road, Clayton VIC 3800, Melbourne, Australia
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Secker GA, Shortt AJ, Sampson E, Schwarz QP, Schultz GS, Daniels JT. TGFbeta stimulated re-epithelialisation is regulated by CTGF and Ras/MEK/ERK signalling. Exp Cell Res 2007; 314:131-42. [PMID: 17915216 DOI: 10.1016/j.yexcr.2007.09.001] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2007] [Revised: 08/31/2007] [Accepted: 09/04/2007] [Indexed: 12/13/2022]
Abstract
The complex mechanisms by which transforming growth factor beta (TGFbeta) regulate re-epithelialisation following injury of stratified epithelia are not fully understood. TGFbeta signals via binding to distinct receptors activating downstream effectors, including Smads which initiate transcription of target genes. However, studies have shown that TGFbeta can also signal independently of Smads through MAPK pathways, demonstrating the diversity of TGFbeta signalling. Connective tissue growth factor (CTGF) is strongly induced by and acts downstream of TGFbeta causing pathophysiology in tissues by inducing matrix deposition, conversion of fibroblasts into contractile myofibroblasts (e.g. dermis and corneal stroma) and stimulation of epithelial-to-mesenchymal transition (e.g. kidney and lung) all of which are known to cause fibrosis. However, a role for CTGF in epithelial cell function which does not involve direct contribution to fibrosis has not been demonstrated. We show for the first time that synthesis of CTGF in cultures of human corneal epithelial cells is induced by TGFbeta through the Ras/MEK/ERK MAPK signalling pathway and that this is required for re-epithelialisation to occur through cell migration. These data reveal a novel function for CTGF in the regulation of epithelial tissue repair beyond its established role in fibrosis, and further highlight the complexity of TGFbeta regulation of epithelial cell function.
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Affiliation(s)
- Genevieve A Secker
- Department of Pathology, Cells for Sight Transplantation and Research Programme, UCL Institute of Ophthalmology, 11-43 Bath Street, London, EC1V 9EL, UK
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Cox TC, Sadlon TJ, Schwarz QP, Matthews CS, Wise PD, Cox LL, Bottomley SS, May BK. The major splice variant of human 5-aminolevulinate synthase-2 contributes significantly to erythroid heme biosynthesis. Int J Biochem Cell Biol 2004; 36:281-95. [PMID: 14643893 DOI: 10.1016/s1357-2725(03)00246-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The initial step of the heme biosynthetic pathway in erythroid cells is catalyzed by an erythroid-specific isoform of 5-aminolevulinate synthase-2 (ALAS2). Previously, an alternatively spliced mRNA isoform of ALAS2 was identified although the functional significance of the encoded protein was unknown. We sought to characterize the contribution of this ALAS2 isoform to overall erythroid heme biosynthesis. Here, we report the identification of three novel ALAS2 mRNA splice isoforms in addition to the previously described isoform lacking exon 4-derived sequence. Quantitation of these mRNAs using ribonuclease protection experiments revealed that the isoform without exon 4-derived sequence represents approximately 35-45% of total ALAS2 mRNA while the newly identified transcripts together represent approximately 15%. Despite the significant amounts of these three new transcripts, their features indicate that they are unlikely to substantially contribute to overall mitochondrial ALAS2 activity. In contrast, in vitro studies show that the major splice variant (lacking exon 4-encoded sequence) produces a functional enzyme, albeit with slightly reduced activity and with affinity for the ATP-specific, beta subunit of succinyl CoA synthase, comparable to that of mature ALAS2. It was also established that the first 49 amino acids of the ALAS2 pre-protein are necessary and sufficient for translocation across the mitochondrial inner membrane and that this process is not affected by the absence of exon 4-encoded sequence. We conclude that the major splice isoform of ALAS2 is functional in vivo and could significantly contribute to erythroid heme biosynthesis and hemoglobin formation.
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Affiliation(s)
- Timothy C Cox
- School of Molecular and Biomedical Science, University of Adelaide, SA 5005, Adelaide, Australia.
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Abstract
We have shown by indirect immunofluorescence and enhanced green fluorescent protein fusions that a mammalian sequence exhibiting similar levels of homology to the two yeast heme lyases Cyc3p (holocytochrome c synthase; HCCS) and Cyt2p (holocytochrome c1 synthase; HCC1S) is also targeted to mitochondria. The human protein was able to complement the yeast Cyc3p (but not Cyt2p) deficiency, which indicates that it specifically activates apocytochrome c. Consistent with a respiratory role, expression of the mammalian gene was detected in all tissues, with the highest levels found in heart. Notably, the human gene HCCS is the only known gene located within the critical region for the deletion-defined disorder microphthalmia with linear skin defects (MLS). We believe the spectrum of clinical features seen in females with MLS and the paucity of male patients are consistent with significant involvement of HCCS. Toward clarification of a role for HCCS in disease, we have extensively characterized the X-linked mouse Hccs genomic locus, showing conservation in gene size and arrangement despite its location in a region that has undergone significant evolutionary rearrangement.
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Affiliation(s)
- Quenten P Schwarz
- Department of Molecular Biosciences and Centre for the Molecular Genetics of Development, University of Adelaide, North Terrace, Adelaide, South Australia, Australia 5005
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