Publications by authors named "Jonas von Hofsten"

20 Publications

  • Page 1 of 1

Absence of Desmin in Myofibers of the Zebrafish Extraocular Muscles.

Transl Vis Sci Technol 2020 09 1;9(10). Epub 2020 Sep 1.

Department of Integrative Medical Biology, Umeå University, Umeå, Sweden.

Purpose: To study the medial rectus (MR) muscle of zebrafish ( ) with respect to the pattern of distribution of desmin and its correlation to distinct types of myofibers and motor endplates.

Methods: The MRs of zebrafish were examined using confocal microscopy in whole-mount longitudinal specimens and in cross sections processed for immunohistochemistry with antibodies against desmin, myosin heavy chain isoforms, and innervation markers. Desmin patterns were correlated to major myofiber type and type of innervation. A total of 1382 myofibers in nine MR muscles were analyzed.

Results: Four distinct desmin immunolabeling patterns were found in the zebrafish MRs. Approximately a third of all slow myofibers lacked desmin, representing 8.5% of the total myofiber population. The adult zebrafish MR muscle displayed en grappe, en plaque, and multiterminal en plaque neuromuscular junctions (NMJs) with intricate patterns of desmin immunolabeling.

Conclusions: The MRs of zebrafish showed important similarities with the human extraocular muscles with regard to the pattern of desmin distribution and presence of the major types of NMJs and can be regarded as an adequate model to further study the role of desmin and the implications of heterogeneity in cytoskeletal protein composition.

Translational Relevance: The establishment of a zebrafish model to study the cytoskeleton in muscles that are particularly resistant to muscle disease opens new avenues to understand human myopathies and muscle dystrophies and may provide clues to new therapies.
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http://dx.doi.org/10.1167/tvst.9.10.1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7476663PMC
September 2020

dNTP production is essential for normal postnatal murine heart development.

J Biol Chem 2019 11 12;294(44):15889-15897. Epub 2019 Jul 12.

Department of Medical Biochemistry and Biophysics, Umeå University, 901 87 Umeå, Sweden

The building blocks of DNA, dNTPs, can be produced or can be salvaged from deoxyribonucleosides. However, to what extent the absence of dNTP production can be compensated for by the salvage pathway is unknown. Here, we eliminated dNTP synthesis in the mouse heart and skeletal muscle by inactivating ribonucleotide reductase (RNR), a key enzyme for the production of dNTPs, at embryonic day 13. All other tissues had normal dNTP synthesis and theoretically could supply heart and skeletal muscle with deoxyribonucleosides needed for dNTP production by salvage. We observed that the dNTP and NTP pools in WT postnatal hearts are unexpectedly asymmetric, with unusually high dGTP and GTP levels compared with those in whole mouse embryos or murine cell cultures. We found that RNR inactivation in heart led to strongly decreased dGTP and increased dCTP, dTTP, and dATP pools; aberrant DNA replication; defective expression of muscle-specific proteins; progressive heart abnormalities; disturbance of the cardiac conduction system; and lethality between the second and fourth weeks after birth. We conclude that dNTP salvage cannot substitute for dNTP synthesis in the heart and that cardiomyocytes and myocytes initiate DNA replication despite an inadequate dNTP supply. We discuss the possible reasons for the observed asymmetry in dNTP and NTP pools in WT hearts.
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http://dx.doi.org/10.1074/jbc.RA119.009492DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6827297PMC
November 2019

The zebrafish HGF receptor met controls migration of myogenic progenitor cells in appendicular development.

PLoS One 2019 9;14(7):e0219259. Epub 2019 Jul 9.

Department of Integrative Medical Biology, Umeå University, Umeå, Sweden.

The hepatocyte growth factor receptor C-met plays an important role in cellular migration, which is crucial for many developmental processes as well as for cancer cell metastasis. C-met has been linked to the development of mammalian appendicular muscle, which are derived from migrating muscle progenitor cells (MMPs) from within the somite. Mammalian limbs are homologous to the teleost pectoral and pelvic fins. In this study we used Crispr/Cas9 to mutate the zebrafish met gene and found that the MMP derived musculature of the paired appendages was severely affected. The mutation resulted in a reduced muscle fibre number, in particular in the pectoral abductor, and in a disturbed pectoral fin function. Other MMP derived muscles, such as the sternohyoid muscle and posterior hypaxial muscle were also affected in met mutants. This indicates that the role of met in MMP function and appendicular myogenesis is conserved within vertebrates.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0219259PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6615617PMC
February 2020

TRAF6 function as a novel co-regulator of Wnt3a target genes in prostate cancer.

EBioMedicine 2019 Jul 28;45:192-207. Epub 2019 Jun 28.

Medical Biosciences, Umeå University, Umeå, Sweden. Electronic address:

Background: Tumour necrosis factor receptor associated factor 6 (TRAF6) promotes inflammation in response to various cytokines. Aberrant Wnt3a signals promotes cancer progression through accumulation of β-Catenin. Here we investigated a potential role for TRAF6 in Wnt signaling.

Methods: TRAF6 expression was silenced by siRNA in human prostate cancer (PC3U) and human colorectal SW480 cells and by CRISPR/Cas9 in zebrafish. Several biochemical methods and analyses of mutant phenotype in zebrafish were used to analyse the function of TRAF6 in Wnt signaling.

Findings: Wnt3a-treatment promoted binding of TRAF6 to the Wnt co-receptors LRP5/LRP6 in PC3U and LNCaP cells in vitro. TRAF6 positively regulated mRNA expression of β-Catenin and subsequent activation of Wnt target genes in PC3U cells. Wnt3a-induced invasion of PC3U and SW480 cells were significantly reduced when TRAF6 was silenced by siRNA. Database analysis revealed a correlation between TRAF6 mRNA and Wnt target genes in patients with prostate cancer, and high expression of LRP5, TRAF6 and c-Myc correlated with poor prognosis. By using CRISPR/Cas9 to silence TRAF6 in zebrafish, we confirm TRAF6 as a key molecule in Wnt3a signaling for expression of Wnt target genes.

Interpretation: We identify TRAF6 as an important component in Wnt3a signaling to promote activation of Wnt target genes, a finding important for understanding mechanisms driving prostate cancer progression. FUND: KAW 2012.0090, CAN 2017/544, Swedish Medical Research Council (2016-02513), Prostatacancerförbundet, Konung Gustaf V:s Frimurarestiftelse and Cancerforskningsfonden Norrland. The funders did not play a role in manuscript design, data collection, data analysis, interpretation nor writing of the manuscript.
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http://dx.doi.org/10.1016/j.ebiom.2019.06.046DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6642315PMC
July 2019

Flagella-mediated secretion of a novel cytotoxin affecting both vertebrate and invertebrate hosts.

Commun Biol 2018 7;1:59. Epub 2018 Jun 7.

Department of Molecular Biology and The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, SE-90187, Umeå, Sweden.

Using as an infection host model for predator interactions, we discovered a bacterial cytotoxin, MakA, whose function as a virulence factor relies on secretion via the flagellum channel in a proton motive force-dependent manner. The MakA protein is expressed from the polycistronic (otility-ssociated lling factor) operon. Bacteria expressing induced dramatic changes in intestinal morphology leading to a defecation defect, starvation and death in . The Mak proteins also promoted colonization of the zebrafish gut causing lethal infection. A structural model of purified MakA at 1.9 Å resolution indicated similarities to members of a superfamily of bacterial toxins with unknown biological roles. Our findings reveal an unrecognized role for flagella in cytotoxin export that may contribute both to environmental spread of the bacteria by promoting survival and proliferation in encounters with predators, and to pathophysiological effects during infections.
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http://dx.doi.org/10.1038/s42003-018-0065-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6123715PMC
June 2018

Pax7 is required for establishment of the xanthophore lineage in zebrafish embryos.

Mol Biol Cell 2016 06 6;27(11):1853-62. Epub 2016 Apr 6.

Umeå Centre for Molecular Medicine, Umeå University, 90187 Umeå, Sweden Department for Integrative Medical Biology, Umeå University, 90187 Umeå, Sweden

The pigment pattern of many animal species is a result of the arrangement of different types of pigment-producing chromatophores. The zebrafish has three different types of chromatophores: black melanophores, yellow xanthophores, and shimmering iridophores arranged in a characteristic pattern of golden and blue horizontal stripes. In the zebrafish embryo, chromatophores derive from the neural crest cells. Using pax7a and pax7b zebrafish mutants, we identified a previously unknown requirement for Pax7 in xanthophore lineage formation. The absence of Pax7 results in a severe reduction of xanthophore precursor cells and a complete depletion of differentiated xanthophores in embryos as well as in adult zebrafish. In contrast, the melanophore lineage is increased in pax7a/pax7b double-mutant embryos and larvae, whereas juvenile and adult pax7a/pax7b double-mutant zebrafish display a severe decrease in melanophores and a pigment pattern disorganization indicative of a xanthophore- deficient phenotype. In summary, we propose a novel role for Pax7 in the early specification of chromatophore precursor cells.
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http://dx.doi.org/10.1091/mbc.E15-12-0821DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4884075PMC
June 2016

Differential regulation of myosin heavy chains defines new muscle domains in zebrafish.

Mol Biol Cell 2014 Apr 12;25(8):1384-95. Epub 2014 Feb 12.

Umeå Centre for Molecular Medicine, Umeå University, SE-901 87 Umeå, Sweden.

Numerous muscle lineages are formed during myogenesis within both slow- and fast-specific cell groups. In this study, we show that six fast muscle-specific myosin heavy chain genes have unique expression patterns in the zebrafish embryo. The expression of tail-specific myosin heavy chain (fmyhc2.1) requires wnt signaling and is essential for fast muscle organization within the tail. Retinoic acid treatment results in reduced wnt signaling, which leads to loss of the fmyhc2.1 domain. Retinoic acid treatment also results in a shift of muscle identity within two trunk domains defined by expression of fmyhc1.2 and fmyhc1.3 in favor of the anteriormost myosin isoform, fmyhc1.2. In summary, we identify new muscle domains along the anteroposterior axis in the zebrafish that are defined by individual nonoverlapping, differentially regulated expression of myosin heavy chain isoforms.
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http://dx.doi.org/10.1091/mbc.E13-08-0486DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3983002PMC
April 2014

Differential regulation of the rainbow trout (Oncorhynchus mykiss) MT-A gene by nuclear factor interleukin-6 and activator protein-1.

BMC Mol Biol 2013 Dec 17;14:28. Epub 2013 Dec 17.

Örebro Life Science Center, School of Science and Technology, Örebro University, Örebro SE-701 82, Sweden.

Background: Previously we have identified a distal region of the rainbow trout (Oncorhynchus mykiss) metallothionein-A (rtMT-A) enhancer region, being essential for free radical activation of the rtMT-A gene. The distal promoter region included four activator protein 1 (AP1) cis-acting elements and a single nuclear factor interleukin-6 (NF-IL6) element. In the present study we used the rainbow trout hepatoma (RTH-149) cell line to further examine the involvement of NF-IL6 and AP1 in rtMT-A gene expression following exposure to oxidative stress and tumour promotion.

Results: Using enhancer deletion studies we observed strong paraquat (PQ)-induced rtMT-A activation via NF-IL6 while the AP1 cis-elements showed a weak but significant activation. In contrast to mammals the metal responsive elements were not activated by oxidative stress. Electrophoretic mobility shift assay (EMSA) mutation analysis revealed that the two most proximal AP1 elements, AP11,2, exhibited strong binding to the AP1 consensus sequence, while the more distal AP1 elements, AP13,4 were ineffective. Phorbol-12-myristate-13-acetate (PMA), a known tumor promoter, resulted in a robust induction of rtMT-A via the AP1 elements alone. To determine the conservation of regulatory functions we transfected human Hep G2 cells with the rtMT-A enhancer constructs and were able to demonstrate that the cis-elements were functionally conserved. The importance of NF-IL6 in regulation of teleost MT is supported by the conservation of these elements in MT genes from different teleosts. In addition, PMA and PQ injection of rainbow trout resulted in increased hepatic rtMT-A mRNA levels.

Conclusions: These studies suggest that AP1 primarily is involved in PMA regulation of the rtMT-A gene while NF-IL6 is involved in free radical regulation. Taken together this study demonstrates the functionality of the NF-IL6 and AP-1 elements and suggests an involvement of MT in protection during pathological processes such as inflammation and cancer.
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http://dx.doi.org/10.1186/1471-2199-14-28DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3867414PMC
December 2013

Six1 regulates proliferation of Pax7-positive muscle progenitors in zebrafish.

J Cell Sci 2013 Apr 26;126(Pt 8):1868-80. Epub 2013 Feb 26.

Umeå Center for Molecular Medicine, UCMM, Umeå University, 901 87 Umeå, Sweden.

In the embryonic zebrafish, skeletal muscle fibres are formed from muscle progenitors in the paraxial mesoderm. The embryonic myotome is mostly constituted of fast-twitch-specific fibres, which are formed from a fast-specific progenitor cell pool. The most lateral fraction of the fast domain in the myotome of zebrafish embryos derives from the Pax7-positive dermomyotome-like cells. In this study, we show that two genes, belonging to the sine oculus class 1 (six1) genes (six1a and six1b), are both essential for the regulation of Pax7(+) cell proliferation and, consequently, in their differentiation during the establishment of the zebrafish dermomyotome. In both six1a and six1b morphant embryos, Pax7(+) cells are initially formed but fail to proliferate, as detected by reduced levels of the proliferation marker phosphohistone3 and reduced brdU incorporation. In congruence, overexpression of six1a or six1b leads to increased Pax7(+) cell number and reduced or alternatively delayed fibre cell differentiation. Bone morphogenetic protein signalling has previously been suggested to inhibit differentiation of Pax7(+) cells in the dermomyotome. Here we show that the remaining Pax7(+) cells in six1a and six1b morphant embryos also have significantly reduced pSmad1/5/8 levels and propose that this leads to a reduced proliferative activity, which may result in a premature differentiation of Pax7(+) cells in the zebrafish dermomyotome. In summary, we show a mechanism for Six1a and Six1b in establishing the Pax7(+) cell derived part of the fast muscle and suggest new important roles for Six1 in the regulation of the Pax7(+) muscle cell population through pSmad1/5/8 signalling.
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http://dx.doi.org/10.1242/jcs.119917DOI Listing
April 2013

A balance of BMP and notch activity regulates neurogenesis and olfactory nerve formation.

PLoS One 2011 Feb 23;6(2):e17379. Epub 2011 Feb 23.

Umeå Center for Molecular Medicine, Umeå University, Umeå, Sweden.

Although the function of the adult olfactory system has been thoroughly studied, the molecular mechanisms regulating the initial formation of the olfactory nerve, the first cranial nerve, remain poorly defined. Here, we provide evidence that both modulated Notch and bone morphogenetic protein (BMP) signaling affect the generation of neurons in the olfactory epithelium and reduce the number of migratory neurons, so called epithelioid cells. We show that this reduction of epithelial and migratory neurons is followed by a subsequent failure or complete absence of olfactory nerve formation. These data provide new insights into the early generation of neurons in the olfactory epithelium and the initial formation of the olfactory nerve tract. Our results present a novel mechanism in which BMP signals negatively affect Notch activity in a dominant manner in the olfactory epithelium, thereby regulating neurogenesis and explain why a balance of BMP and Notch activity is critical for the generation of neurons and proper development of the olfactory nerve.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0017379PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3044177PMC
February 2011

Opposing Fgf and Bmp activities regulate the specification of olfactory sensory and respiratory epithelial cell fates.

Development 2010 May 14;137(10):1601-11. Epub 2010 Apr 14.

Umeå Center for Molecular Medicine, Building 6M, 4th Floor, Umeå University, Umeå, Sweden.

The olfactory sensory epithelium and the respiratory epithelium are derived from the olfactory placode. However, the molecular mechanisms regulating the differential specification of the sensory and the respiratory epithelium have remained undefined. To address this issue, we first identified Msx1/2 and Id3 as markers for respiratory epithelial cells by performing quail chick transplantation studies. Next, we established chick explant and intact chick embryo assays of sensory/respiratory epithelial cell differentiation and analyzed two mice mutants deleted of Bmpr1a;Bmpr1b or Fgfr1;Fgfr2 in the olfactory placode. In this study, we provide evidence that in both chick and mouse, Bmp signals promote respiratory epithelial character, whereas Fgf signals are required for the generation of sensory epithelial cells. Moreover, olfactory placodal cells can switch between sensory and respiratory epithelial cell fates in response to Fgf and Bmp activity, respectively. Our results provide evidence that Fgf activity suppresses and restricts the ability of Bmp signals to induce respiratory cell fate in the nasal epithelium. In addition, we show that in both chick and mouse the lack of Bmp or Fgf activity results in disturbed placodal invagination; however, the fate of cells in the remaining olfactory epithelium is independent of morphological movements related to invagination. In summary, we present a conserved mechanism in amniotes in which Bmp and Fgf signals act in an opposing manner to regulate the respiratory versus sensory epithelial cell fate decision.
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http://dx.doi.org/10.1242/dev.051219DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2860246PMC
May 2010

Prdm1- and Sox6-mediated transcriptional repression specifies muscle fibre type in the zebrafish embryo.

EMBO Rep 2008 Jul 6;9(7):683-9. Epub 2008 Jun 6.

MRC Centre for Developmental and Biomedical Genetics, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK.

The zebrafish u-boot (ubo) gene encodes the transcription factor Prdm1, which is essential for the specification of the primary slow-twitch muscle fibres that derive from adaxial cells. Here, we show that Prdm1 functions by acting as a transcriptional repressor and that slow-twitch-specific muscle gene expression is activated by Prdm1-mediated repression of the transcriptional repressor Sox6. Genes encoding fast-specific isoforms of sarcomeric proteins are ectopically expressed in the adaxial cells of ubo(tp39) mutant embryos. By using chromatin immunoprecipitation, we show that these are direct targets of Prdm1. Thus, Prdm1 promotes slow-twitch fibre differentiation by acting as a global repressor of fast-fibre-specific genes, as well as by abrogating the repression of slow-fibre-specific genes.
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http://dx.doi.org/10.1038/embor.2008.73DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2424280PMC
July 2008

P53 mediated regulation of metallothionein transcription in breast cancer cells.

J Cell Biochem 2007 Dec;102(6):1571-83

Department of Pathology, University of Western Ontario, London, Ontario N6A 5C1, Canada.

Recent studies have shown that only breast cancer epithelial cells with intact p53 can induce metallothionein (MT) synthesis after exposure to metals. In this study, the potential role of p53 on regulation of MT was investigated. Results demonstrate that zinc and copper increased metal response elements (MREs) activity and MTF-1 expression in p53 positive MN1 and parental MCF7 cells. However, inactivation of p53 by treatment with pifithrin-alpha or the presence of inactive p53 inhibited MRE-dependent reporter gene expression in response to metals. MTF-1 levels remained unchanged after treatment with zinc in cells with nonfunctional p53. The introduction of wild-type p53 in MDD2 cells, containing nonfunctional p53, enhanced the ability of zinc to increase MRE-dependent reporter gene expression. The cellular level of p21Cip1/WAF1 was increased in MDD2 cells after p53 transfection, confirming the presence of active p53. The treatment of MN1 and parental MCF7 with trichostatin A led to a sixfold increase in the MRE activity in response to zinc. On the contrary, MRE activity remained unaltered in MDD2 cells with inactive p53. The above results demonstrate that activation of p53 is an important factor in metal regulation of MT.
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http://dx.doi.org/10.1002/jcb.21381DOI Listing
December 2007

Molecular characterization and expression pattern of zona pellucida proteins in gilthead seabream (Sparus aurata).

Biol Reprod 2006 Nov 19;75(5):717-25. Epub 2006 Jul 19.

Orebro Life Science Center, Department of Natural Science, Orebro University, SE-70182 Orebro, Sweden.

The developing oocyte is surrounded by an acellular envelope that is composed of 2-4 isoforms of zona pellucida (ZP) proteins. The ZP proteins comprise the ZP1, ZP2, ZP3, and ZPX isoforms. While ZP1 (ZPB) and ZP3 (ZPC) are present in all species, ZP2 (ZPA) is not found in teleost fish and ZPX is not found in mammals. In the present study, we identify and characterize the ZP1, ZP3 and ZPX isoforms of gilthead seabream. Furthermore, by analyzing the conserved domains, which include the external hydrophobic patch and the internal hydrophobic patch, we show that ZP2 and ZPX are closely related isoforms. ZP proteins are synthesized in either the liver or ovary of most teleosts. Only in rainbow trout has it been shown that zp3 has dual transcription sites. In gilthead seabream, all four mRNA isoforms are transcribed in both the liver and ovary, with zp1a, zp1b, and zp3 being highly expressed in the liver, and zpx being primarily expressed in the ovary. However, determination of the ZP proteins in plasma showed high levels of ZP1b, ZP3, and ZPX, with low or non-detectable levels of ZP1a. In similarity to other teleost ZPs, the hepatic transcription of all four ZP isoforms is under estrogenic control. Previously, we have shown that cortisol can potentiate estrogen-induced ZP synthesis in salmonids, and now we show that this is not the case in the gilthead seabream. The present study shows for the first time the endocrine regulation of a teleost ZPX isoform, and demonstrates the dual-organ transcriptional activities of all the ZP proteins in one species.
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http://dx.doi.org/10.1095/biolreprod.106.050757DOI Listing
November 2006

Zebrafish sex determination and differentiation: involvement of FTZ-F1 genes.

Reprod Biol Endocrinol 2005 Nov 10;3:63. Epub 2005 Nov 10.

Department of Molecular Biology, Umeå University, Umeå, Sweden.

Sex determination is the process deciding the sex of a developing embryo. This is usually determined genetically; however it is a delicate process, which in many cases can be influenced by environmental factors. The mechanisms controlling zebrafish sex determination and differentiation are not known. To date no sex linked genes have been identified in zebrafish and no sex chromosomes have been identified. However, a number of genes, as presented here, have been linked to the process of sex determination or differentiation in zebrafish. The zebrafish FTZ-F1 genes are of central interest as they are involved in regulating interrenal development and thereby steroid biosynthesis, as well as that they show expression patterns congruent with reproductive tissue differentiation and function. Zebrafish can be sex reversed by exposure to estrogens, suggesting that the estrogen levels are crucial during sex differentiation. The Cyp19 gene product aromatase converts testosterone into 17 beta-estradiol, and when inhibited leads to male to female sex reversal. FTZ-F1 genes are strongly linked to steroid biosynthesis and the regulatory region of Cyp19 contains binding sites for FTZ-F1 genes, further linking FTZ-F1 to this process. The role of FTZ-F1 and other candidates for zebrafish sex determination and differentiation is in focus of this review.
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http://dx.doi.org/10.1186/1477-7827-3-63DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1298332PMC
November 2005

Molecular cloning and characterization of a nuclear androgen receptor activated by 11-ketotestosterone.

Reprod Biol Endocrinol 2005 Aug 17;3:37. Epub 2005 Aug 17.

Department of Natural Science, Unit of Molecular Biology, Orebro University, SE-701 82 Orebro, Sweden.

Although 11-ketotestosterone is a potent androgen and induces male secondary sex characteristics in many teleosts, androgen receptors with high binding affinity for 11-ketotestosterone or preferential activation by 11-ketotestosterone have not been identified. So, the mechanism by which 11-ketotestosterone exhibits such high potency remains unclear. Recently we cloned the cDNA of an 11-ketotestosterone regulated protein, spiggin, from three-spined stickleback renal tissue. As spiggin is the only identified gene product regulated by 11-ketotestosterone, the stickleback kidney is ideal for determination of the mechanism of 11-ketotestosterone gene regulation. A single androgen receptor gene with two splicing variants, belonging to the androgen receptor-beta subfamily was cloned from stickleback kidney. A high affinity, saturable, single class of androgen specific binding sites, with the characteristics of an androgen receptor, was identified in renal cytosolic and nuclear fractions. Measurement of ligand binding moieties in the cytosolic and nuclear fractions as well as to the recombinant receptor revealed lower affinity for 11-ketotestosterone than for dihydrotestosterone. Treatment with different androgens did not up-regulate androgen receptor mRNA level or increase receptor abundance, suggesting that auto-regulation is not involved in differential ligand activation. However, comparison of the trans-activation potential of the stickleback androgen receptor with the human androgen receptor, in both human HepG2 cells and zebrafish ZFL cells, revealed preferential activation by 11-ketotestosterone of the stickleback receptor, but not of the human receptor. These findings demonstrate the presence of a receptor preferentially activated by 11-ketotestosterone in the three-spined stickleback, so far the only one known in any animal.
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http://dx.doi.org/10.1186/1477-7827-3-37DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1192819PMC
August 2005

Visualisation of zebrafish infection by GFP-labelled Vibrio anguillarum.

Microb Pathog 2004 Jul;37(1):41-6

Department of Molecular Biology, Umeå University, S-901 87 Umeå, Sweden.

Vibrio anguillarum is an invasive pathogen of fish causing a septicaemia called vibriosis. In this work, transparent zebrafish were immersed in water containing green fluorescent protein labelled V. anguillarum. The infection was visualised at the whole fish and single bacterium levels using microscopy. The gastrointestinal tract was the first site where the pathogen was detected. This enteric localisation occurred independently of the flagellum or motility. On the other hand, chemotactic motility was essential for association of the pathogen with the fish surface. In conclusion, the zebrafish infection model provides evidence that the intestine and skin represent sites of infection by V. anguillarum and suggests a host site where chemotaxis may function in virulence.
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http://dx.doi.org/10.1016/j.micpath.2004.03.001DOI Listing
July 2004

Fushi tarazu factor-1 mRNA and protein is expressed in steroidogenic and cholesterol metabolising tissues during different life stages in Arctic char (Salvelinus alpinus).

Gen Comp Endocrinol 2003 Jun;132(1):96-102

Department of Molecular Biology, Umeå University, SE-901 87 Umeå, Sweden.

Fushi tarazu factor-1 (FTZ-F1) genes belong to the nuclear receptor family 5A (NR5A). The distribution pattern of NR5A genes in teleosts suggests that they control functions separate to, or in addition to, those of other vertebrates. In mammals NR5A1 genes, including steroidogenic factor-1 (SF-1), are primarily involved in steroidogenesis. NR5A2 contain the alpha-fetoprotein transcription factor (FTF) genes, which protect mammalian embryos against maternal estrogens, and are involved in cholesterol transfer and metabolism. In this study we have analysed the expression of two Arctic char FTZ-F1 forms belonging to the NR5A2 group. The expression starts during early development and the transcripts are present in embryonic liver/pancreas and gonadal regions. The genes are up-regulated during embryogenesis as the embryo develops towards hatch, as shown by increased mRNA and protein levels. In adult Arctic char the FTZ-F1 forms are primarily located to tissues involved in steroidogenesis as well as cholesterol metabolism. Thus, a division of NR5A into SF-1 (NR5A1) and FTF (NR5A2) specific functions does not appear to have occurred in teleosts.
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http://dx.doi.org/10.1016/s0016-6480(03)00034-0DOI Listing
June 2003

Expression and regulation of fushi tarazu factor-1 and steroidogenic genes during reproduction in Arctic char (Salvelinus alpinus).

Biol Reprod 2002 Oct;67(4):1297-304

Department of Molecular Biology, Umeå University, Sweden.

Teleost fushi tarazu factor-1 (FTZ-F1) is a potential regulator of steroidogenesis. The present study shows sex-specific regulation of Arctic char fushi tarazu factor-1 (acFF1) and steroidogenic genes during reproductive maturation and in response to hormone treatment. A link between gonadal expression of acFF1, steroidogenic acute regulatory protein (StAR), and cytochrome P450-11A (CYP11A), was observed in the reproductive maturation process, as elevated acFF1 mRNA and protein levels preceded increased StAR and CYP11A transcription. Sex-specific differences were observed as estrogen treatment resulted in down-regulated levels of acFF1 mRNA in testis and male head kidney, whereas no significant effect was observed in females. 11-Ketotestosterone (11-KT) down-regulated CYP11A and 3beta-hydroxysteroid dehydrogenase (3betaHSD) in head kidney and up-regulated CYP11A in testis. StAR remained unaffected by hormone treatment. This suggests that acFF1 is controlled by 17beta-estradiol, whereas the effects on CYP11A and 3betaHSD are mediated by 11-KT. Coexpression of acFF1, StAR, and CYP11A was observed in head kidney, in addition to gonads, indicating correlation between these steroidogenic genes. StAR and acFF1 were also coexpressed in liver, suggesting a potential role in cholesterol metabolism. Although these results indicate conserved steroidogenic functions for FTZ-F1 among vertebrates, they also raise the question of additional roles for FTZ-F1 in teleosts.
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http://dx.doi.org/10.1095/biolreprod67.4.1297DOI Listing
October 2002
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