BBA - Molecular Basis of Disease (v.1762, #3)
Editorial Board (ii).
Involvement of Kupffer cells in lipopolysaccharide-induced rapid accumulation of platelets in the liver and the ensuing anaphylaxis-like shock in mice by Kouji Yamaguchi; Zhiqian Yu; Hiroyuki Kumamoto; Yumiko Sugawara; Hiroshi Kawamura; Haruhiko Takada; Takashi Yokochi; Shunji Sugawara; Yasuo Endo (269-275).
Intravenous injection of Klebsiella O3 lipopolysaccharide (LPS) into BALB/c mice induces an anaphylaxis-like shock within minutes. Using 5-hydroxytryptamine as a marker for platelets, we previously suggested that a rapid platelet accumulation in the liver and lung precedes the shock, and that a complement-dependent platelet-degradation is involved in the shock. Here, we examined (i) the effect of platelet-depletion (using an anti-platelet monoclonal antibody) on the shock and (ii) the contribution of macrophages to the platelet-accumulation in those organs. LPS-induced platelet-accumulations in the liver and lung were confirmed by immunostaining. In platelet-depleted mice, the shock was largely prevented. The number of F4/80-positive macrophages was much greater in liver than in lung, and the hepatic macrophages were largely lost in mice given clodronate-encapsulated liposomes. In mice treated with such liposomes, both the LPS-induced accumulation of platelets in the liver (but not in the lung) and the shock were largely prevented, and repopulation of hepatic macrophages restored these LPS-induced responses. These results suggest that (i) platelets are indeed involved in the shock, (ii) Kupffer cells mediate the hepatic platelet accumulation, and (iii) preventing this hepatic accumulation can largely prevent rapid shock being induced by LPS (at the dose used here).
Keywords: Platelet; Lipopolysaccharide; Liver; Lung; Shock; Macrophage;
In vivo contribution of Class III alcohol dehydrogenase (ADH3) to alcohol metabolism through activation by cytoplasmic solution hydrophobicity by Takeshi Haseba; Gregg Duester; Akio Shimizu; Isao Yamamoto; Kouji Kameyama; Youkichi Ohno (276-283).
Alcohol metabolism in vivo cannot be explained solely by the action of the classical alcohol dehydrogenase, Class I ADH (ADH1). Over the past three decades, attempts to identify the metabolizing enzymes responsible for the ADH1-independent pathway have focused on the microsomal ethanol oxidizing system (MEOS) and catalase, but have failed to clarify their roles in systemic alcohol metabolism. In this study, we used Adh3-null mutant mice to demonstrate that Class III ADH (ADH3), a ubiquitous enzyme of ancient origin, contributes to alcohol metabolism in vivo dose-dependently resulting in a diminution of acute alcohol intoxication. Although the ethanol oxidation activity of ADH3 in vitro is low due to its very high K m, it was found to exhibit a markedly enhanced catalytic efficiency (k cat/K m) toward ethanol when the solution hydrophobicity of the reaction medium was increased with a hydrophobic substance. Confocal laser scanning microscopy with Nile red as a hydrophobic probe revealed a cytoplasmic solution of mouse liver cells to be much more hydrophobic than the buffer solution used for in vitro experiments. So, the in vivo contribution of high-K m ADH3 to alcohol metabolism is likely to involve activation in a hydrophobic solution. Thus, the present study demonstrated that ADH3 plays an important role in systemic ethanol metabolism at higher levels of blood ethanol through activation by cytoplasmic solution hydrophobicity.
Keywords: Alcohol metabolism; Class III ADH; Class I ADH; Knockout mouse; Activation by solution hydrophobicity; Acute alcohol intoxication;
Molecular chaperone α-crystallin prevents detrimental effects of neuroinflammation by J.G. Masilamoni; E.P. Jesudason; B'joe Baben; Charles E. Jebaraj; S. Dhandayuthapani; R. Jayakumar (284-293).
Silver nitrate administration stimulates immune activation, inflammation and deterioration in cell function. It is well established that hippocampal and cortical tissue are susceptible to degeneration in responses to insult such as oxidative stress or infection. This study was designed to investigate the prophylactic effect of α-crystallin, a major chaperone lens protein comprising of α-A and α-B subunits in inflammation induced mice. Mice were divided into three groups (n = 6 in each), control, inflammation and α-crystallin treated. Our result shows that α-crystallin pretreatment effectively diminished systemic inflammation induced glial fibrillary acidic protein (GFAP) and nuclear factor kappa B (NFκB) expression in the mice neocortex, reversed elevated intracellular calcium levels, acetylcholine esterase activity and depletion of glucose. Furthermore it also significantly prevented nitric oxide (P < 0.05) and lipid peroxide production in the plasma, liver, neocortex and hippocampus of the inflammation-induced mice. In order to demonstrate the direct • OH and nitric oxide radical scavenging ability of α-crystallin, an In vitro experiment using primary astrocyte culture subjected to lipopolysaccharide (LPS), a well-known inflammatory stimuli were also carried out. This study reiterates that α-crystallin therapy may serve as a potent pharmacological agent in neuroinflammation.
Keywords: α-Crystallin; Neuroinflammation; Nitric oxide; Lipid peroxide; Glial fibrillary acidic protein; Nuclear factor kappa-B; Calcium; Acetylcholine; Lipopolysaccharide;
Changes in functioning of rat submandibular salivary gland under streptozotocin-induced diabetes are associated with alterations of Ca2+ signaling and Ca2+ transporting pumps by N.V. Fedirko; I.A. Kruglikov; O.V. Kopach; J.A. Vats; P.G. Kostyuk; N.V. Voitenko (294-303).
Xerostomia and pathological thirst are troublesome complications of diabetes mellitus associated with impaired functioning of salivary glands; however, their cellular mechanisms are not yet determined. Isolated acinar cells were loaded with Ca2+ indicators fura-2/AM for measuring cytosolic Ca2+ concentration ([Ca2+]i) or mag-fura-2/AM—inside the endoplasmic reticulum (ER). We found a dramatic decrease in pilocarpine-stimulated saliva flow, protein content and amylase activity in rats after 6 weeks of diabetes vs. healthy animals. This was accompanied with rise in resting [Ca2+]i and increased potency of acetylcholine (ACh) and carbachol (CCh) but not norepinephrine (NE) to induce [Ca2+]i transients in acinar cells from diabetic animals. However, [Ca2+]i transients mediated by Ca2+ release from ER stores (induced by application of either ACh, CCh, NE, or ionomycin in Ca2+-free extracellular medium) were decreased under diabetes. Application of inositol-1,4,5-trisphosphate led to smaller Ca2+ release from ER under the diabetes. Both plasmalemma and ER Ca2+-ATPases activity was reduced and the latter showed the increased affinity to ATP under the diabetes. We conclude that the diabetes caused impairment of salivary cells functions that, on the cellular level, associates with Ca2+ overload, increased Ca2+-mobilizing ability of muscarinic but not adrenergic receptors, decreased Ca2+-ATPases activity and ER Ca2+ content.
Keywords: Salivary gland; Streptozotocin-induced diabetes; Calcium signaling; Ca2(+)-transporting ATPase; Endoplasmic reticulum; Muscarinic receptor; Adrenergic receptor;
A study of the nuclear trafficking of the splicing factor protein PRPF31 linked to autosomal dominant retinitis pigmentosa (ADRP) by Susan E. Wilkie; Keith J. Morris; Shomi S. Bhattacharya; Martin J. Warren; David M. Hunt (304-311).
In this study the mechanism of nuclear importation of the splicing factor PRPF31 is examined and the impact of two disease-linked mutations, A194E and A216P, assessed. Using pull-down assays with GST-tagged importin proteins, we demonstrate that His-tagged PRPF31 interacts with importin β1 for translocation to the nucleus, with no requirement for importin α1. The A194E and A216P mutations have no affect on this interaction. Fluorescence recovery after photobleaching (FRAP) was used to estimate the rate of movement of EGFP-tagged PRPF31 into the nuclei of live cells. The kinetics indicated a two-component recovery process; a fast component with τ ∼ 6 s and a slow component with τ ∼ 80 s. The mutations affected neither component. We conclude that the two mutations have no negative effect on interaction with the nuclear importation machinery. Reduced mutant protein solubility resulting in an insufficiency of splicing activity in cells with a very high metabolic demand remains the most likely explanation for the disease pathology in ADRP patients.
Keywords: PRPF31; Retinitis pigmentosa; Nuclear transport; FRAP;
A yeast-based model of α-synucleinopathy identifies compounds with therapeutic potential by Gerard Griffioen; Hein Duhamel; Nele Van Damme; Klaartje Pellens; Piotr Zabrocki; Christophe Pannecouque; Fred van Leuven; Joris Winderickx; Stefaan Wera (312-318).
We have developed a yeast-based model recapitulating neurotoxicity of α-synuclein fibrilization. This model recognized metal ions, known risk factors of α-synucleinopathy, as stimulators of α-synuclein aggregation and cytotoxicity. Elimination of Yca1 caspase activity augmented both cytotoxicity and inclusion body formation, suggesting the involvement of apoptotic pathway components in toxic α-synuclein amyloidogenesis. Deletion of hydrophobic amino acids at positions 66–74 in α-synuclein reduced its cytotoxicity but, remarkably, did not lower the levels of insoluble α-synuclein, indicating that noxious α-synuclein species are different from insoluble aggregates. A compound screen aimed at finding molecules with therapeutic potential identified flavonoids with strong activity to restrain α-synuclein toxicity. Subsequent structure–activity analysis elucidated that these acted by virtue of anti-oxidant and metal-chelating activities. In conclusion, this yeast-cell model as presented allows not only fundamental studies related to mechanisms of α-synuclein-instigated cellular degeneration, but is also a valid high-throughput identification tool for novel neuroprotective agents.
Keywords: α-synuclein; Parkinson's disease; Phenotype-based model; Protein-aggregation; Yeast;
A search for genes modulated by interleukin-6 alone or with interleukin-1β in HepG2 cells using differential display analysis by Paulina Węgrzyn; Jolanta Jura; Tomasz Kupiec; Wojciech Piekoszewski; Benedykt Władyka; Adrian Zarębski; Aleksander Koj (319-328).
Interleukin-1 and interleukin-6 are principal cytokines involved in regulation of expression of acute-phase proteins. In the joint action of both cytokines IL-1 can suppress or enhance the IL-6-dependent induction of gene expression. Here, we report changes in the transcriptome profile of HepG2 cells exposed to IL-6 alone, or IL-1 and IL-6. Cytokine-responsive genes were identified by differential display analysis. Validation of observed changes in the transcript level was carried out using the slot blot method. Out of 88 cDNA species modulated by IL-6, only 38 represent different known genes whereas 18 clones match genomic clones in NCBI data with hypothetical cDNA sequences (the remaining 32 clones showed no homology with the database or represented several clones of the same gene). In the experiments with HepG2 cells prestimulated for 3 h with IL-1 and then stimulated with IL-6, 43 cDNA fragments were amplified. Twenty-three of them represent known genes while 10 clones have inserts matching hypothetical cDNA sequences in NCBI data. The identified transcripts modulated by IL-6 or both cytokines in HepG2 cells code for intracellular proteins of various function. The largest groups represent genes engaged in metabolism, protein synthesis and signaling pathways. Among all genes identified as differentially regulated under stimulation by IL-6, or IL-1/IL-6, six were detected in both types of stimulation. None of the typical genes coding for plasma acute phase proteins was identified in our experiments. This indicates that differential display cannot be used to characterize the profile of a given transcriptome. On the other hand, it is a useful technique for detection of new genes responding to IL-6 alone or IL-6 in combination with IL-1.
Keywords: Acute phase response; Human hepatoma HepG2; Inflammatory cytokine; Differential display;
Effect of the [CCTG]n repeat expansion on ZNF9 expression in myotonic dystrophy type II (DM2) by Annalisa Botta; Sara Caldarola; Laura Vallo; Emanuela Bonifazi; Doriana Fruci; Francesca Gullotta; Roberto Massa; Giuseppe Novelli; Fabrizio Loreni (329-334).
Myotonic dystrophy is caused by two different mutations: a (CTG)n expansion in 3′ UTR region of the DMPK gene (DM1) and a (CCTG)n expansion in intron 1 of the ZNF9 gene (DM2). The most accredited mechanism for DM pathogenesis is an RNA gain-of-function. Other findings suggest a contributory role of DMPK-insufficiency in DM1. To address the issue of ZNF9 role in DM2, we have analyzed the effects of (CCTG)n expansion on ZNF9 expression in lymphoblastoid cell lines (n = 4) from DM2 patients. We did not observe any significant alteration in ZNF9 mRNA and protein levels, as shown by QRT-PCR and Western blot analyses. Additional RT-PCR experiments demonstrated that ZNF9 pre-mRNA splicing pattern, which includes two isoforms, is unmodified in DM2 cells. Our results indicate that the (CCTG)n expansion in the ZNF9 intron does not appear to have a direct consequence on the expression of the gene itself.
Keywords: Myotonic dystrophy; DM2; CCTG expansion; ZNF9 expression; Splicing isoform;
Female hyper IgM syndrome type 1 with a chromosomal translocation disrupting CD40LG by Kohsuke Imai; Mitsunobu Shimadzu; Takeo Kubota; Tomohiro Morio; Takeshi Matsunaga; Young-Dong Park; Akira Yoshioka; Shigeaki Nonoyama (335-340).
Hyper-IgM syndrome type 1 (HIGM1) is a primary immunodeficiency characterized by recurrent bacterial and opportunistic infections, associated with normal or high serum level of IgM and decreased serum levels of IgG, IgA and IgE due to the defect of class switch recombination. CD40LG, located in Xq26, has been reported to be mutated in male HIGM1 patients. Here, we report the second case of a female HIGM1 with the defect of CD40 ligand (CD40L) expression and of soluble serum CD40L. Clinical course and HIGM phenotype was indistinguishable from that of male HIGM1 including severe neutropenia. High-resolution chromosome banding revealed that this patient's karyotype is 46, X, t(X;14)(q26.3;q13.1), and FISH analysis demonstrated that the break point of the chromosomal translocation is within CD40LG. Using four chimeric cDNA clones obtained by 3′ RACE method, the break point was identified within the intron 4 of CD40LG on X chromosome and non-coding region of chromosome 14. We also found an extremely skewed X-chromosome inactivation pattern by methylation-specific PCR. Thus, the reciprocal translocation caused the disruption of CD40LG, resulting in defective CD40L expression in the female patient with an extremely skewed X-inactivation pattern in T cells leading to the HIGM1 phenotype.
Keywords: Primary Immunodeficiency; B lymphocyte; T lymphocyte; CD40 ligand; Balanced translocation; X-inactivation;
Alterations in intestinal fatty acid metabolism in inflammatory bowel disease by Susanne Heimerl; Christoph Moehle; Alexandra Zahn; Alfred Boettcher; Wolfgang Stremmel; Thomas Langmann; Gerd Schmitz (341-350).
Inflammatory bowel disease (IBD) constitutes a severe intestinal disorder in developed countries with increasing incidence worldwide. Upcoming evidence indicates an important role of intestinal epithelial barrier function in the development of IBD. Fatty acids exert nutritional and protective effects on enterocytes, serve as activators of transcription and constitute precursors of inflammatory mediators. The aim of this study was to investigate differential regulation of genes involved in fatty acid uptake and endogenous fatty acid biosynthesis in IBD. Mucosal biopsy specimens from non-affected regions of the intestine were subjected to DNA microarray analysis. Gene array analysis revealed a variety of genes involved in fatty acid uptake and synthesis to be differentially expressed in ileum and colon of selected IBD patients. To verify these results, real-time RT-PCR was performed for selected regulated candidate genes in larger IBD sample numbers. In single biopsy analysis long chain acyl-CoA synthetase (ACSL) 1 and 4 were upregulated in IBD (P < 0.05), while a significant decrease in fatty acid synthase expression was found in ileum and colon of ulcerative colitis patients (P < 0.001). Expression of the transcription factor liver X receptor (LXR) which was previously shown to induce fatty acid synthase gene expression was not altered on mRNA level in IBD. However, in cell culture experiments using the human intestinal cell line LS174T induction of fatty acid synthase by the LXR ligand T0901317 was inhibited by TNFα. Moreover, these experiments indicated a decrease of LXR protein levels by TNFα treatment. These data suggest that the decrease of fatty acid synthase expression in ulcerative colitis patients could be at least partially due to a loss of LXR expression and function in the presence of pro-inflammatory cytokines. Observed alterations in expression of genes of fatty acid metabolism may contribute to the pathophysiology of ulcerative colitis.
Keywords: Fatty acid transport; Fatty acid synthase; Inflammatory bowel disease; Cytokine; Liver X receptor;
Cysteine cathepsins in human silicotic bronchoalveolar lavage fluids by Céline Perdereau; Emmanuel Godat; Marie-Christine Maurel; Eric Hazouard; Elisabeth Diot; Gilles Lalmanach (351-356).
Mature, active cysteine cathepsins (CPs) were identified in human inflammatory bronchoalveolar lavage fluid (BALF) supernatants from patients suffering from silicosis by both western blot and surface plasmon resonance analyses. BALFs are not a reservoir of activatable proforms, since no autocatalytic maturation at acidic pH occurs. Cathepsin H is the most profuse among studied CPs (median value: 36.5 nM), while cathepsins B and L are the two most abundant thiol-dependent endoproteases. The overall concentration of active cathepsins B, H, K, L, and S is ∼10-fold lower than their concentration in BALF supernatants from patients suffering from inflammatory acute lung injuries (962 ± 347 nM).The cathepsins (approximately 70 nM)/cystatin-like inhibitors (approximately 9 nM) ratio is unbalanced in favor of enzymes (∼8-fold). This presence of uncontrolled CPs suggests that they may contribute, in addition to matrix metalloproteases, to the lung tissue breakdown/remodeling occurring during silicosis, although their exact contribution to interstitial inflammation remains to be evaluated.
Keywords: Activity-based probe; Bronchoalveolar lavage; Cathepsin; Cysteine protease; Protease inhibitor; Silicosis;
A new type of anti-ganglioside antibodies present in neurological patients by Pablo H.H. Lopez; Romina Comín; Andres M. Villa; Mariana Di Egidio; Roberto D. Saizar; Roberto E.P. Sica; Gustavo A. Nores (357-361).
High titers of anti-GA1 antibodies have been associated with neurological syndromes. In most cases, these antibodies cross-react with the structurally related glycolipids GM1 and GD1b, although specific anti-GA1 antibodies have also been reported. The role of specific anti-GA1 antibodies is uncertain since the presence of GA1 in the human nervous system has not been clarified. A rabbit was immunized with GD1a and its sera were screened for antibody reactivity by standard immunoassay methods (HPTLC-immunostaining and ELISA). Anti-GD1a antibodies were not detected but, unexpectedly, anti-GA1 IgG-antibodies were found. Antibody binding to GA1 was inhibited by soluble GA1 but also by GD1a. These results indicate that the rabbit produced antibodies that recognize epitopes present on the glycolipids, that are absent or not exposed on solid phase adsorbed GD1a. We investigated the presence of these unusual anti-ganglioside antibodies in normal and neurological patient sera. Approximately, 10% of normal human sera contained low titer of specific anti-GA1 IgG-antibodies but none of them recognized soluble GD1a. High titers of IgG-antibodies reacting only with GA1 were detected in 12 patient sera out of 325 analyzed. Of these, 6 sera showed binding that was inhibited by soluble GD1a and four of them also by GM1. This new type of anti-ganglioside antibodies should be considered important elements for understanding of the pathogenesis of these diseases as well as their diagnosis.
Keywords: Ganglioside; Anti-GD1a antibody; Anti-GM1 antibody; Anti-GA1 antibody; Neuropathy; Motor syndrome;
Pathological pattern of Mdx mice diaphragm correlates with gradual expression of the short utrophin isoform Up71 by Karim Hnia; Sylvie Tuffery-Giraud; Marianne Vermaelen; Gerald Hugon; Delphine Chazalette; Ahmed Masmoudi; François Rivier; Dominique Mornet (362-372).
Utrophin gene is transcribed in a large mRNA of 13 kb that codes for a protein of 395 kDa. It shows amino acid identity with dystrophin of up to 73% and is widely expressed in muscle and non-muscle tissues. Up71 is a short utrophin product of the utrophin gene with the same cysteine-rich and C-terminal domains as full-length utrophin (Up395). Using RT-PCR, Western blots analysis, we demonstrated that Up71 is overexpressed in the mdx diaphragm, the most pathological muscle in dystrophin-deficient mdx mice, compared to wild-type C57BL/10 or other mdx skeletal muscles. Subsequently, we demonstrated that this isoform displayed an increased expression level up to 12 months, whereas full-length utrophin (Up395) decreased. In addition, β-dystroglycan, the transmembrane glycoprotein that anchors the cytoplasmic C-terminal domain of utrophin, showed similar increase expression in mdx diaphragm, as opposed to other components of the dystrophin-associated protein complex (DAPC) such as α-dystrobrevin1 and α-sarcoglycan. We demonstrated that Up71 and β-dystroglycan were progressively accumulated along the extrasynaptic region of regenerating clusters in mdx diaphragm. Our data provide novel functional insights into the pathological role of the Up71 isoform in dystrophinopathies.
Keywords: Utrophin isoform; Beta-dystroglycan; Muscle; Mdx; Sarcolemma; DMD;
Combination therapy using minocycline and coenzyme Q10 in R6/2 transgenic Huntington's disease mice by Edward C. Stack; Karen M. Smith; Hoon Ryu; Kerry Cormier; Minghua Chen; Sean W. Hagerty; Steven J. Del Signore; Merit E. Cudkowicz; Robert M. Friedlander; Robert J. Ferrante (373-380).
Huntington's disease (HD) is a fatal neurodegenerative disorder of genetic origin with no known therapeutic intervention that can slow or halt disease progression. Transgenic murine models of HD have significantly improved the ability to assess potential therapeutic strategies. The R6/2 murine model of HD, which recapitulates many aspects of human HD, has been used extensively in pre-clinical HD therapeutic treatment trials. Of several potential therapeutic candidates, both minocycline and coenzyme Q10 (CoQ10) have been demonstrated to provide significant improvement in the R6/2 mouse. Given the specific cellular targets of each compound, and the broad array of abnormalities thought to underlie HD, we sought to assess the effects of combined minocycline and CoQ10 treatment in the R6/2 mouse. Combined minocycline and CoQ10 therapy provided an enhanced beneficial effect, ameliorating behavioral and neuropathological alterations in the R6/2 mouse. Minocycline and CoQ10 treatment significantly extended survival and improved rotarod performance to a greater degree than either minocycline or CoQ10 alone. In addition, combined minocycline and CoQ10 treatment attenuated gross brain atrophy, striatal neuron atrophy, and huntingtin aggregation in the R6/2 mice relative to individual treatment. These data suggest that combined minocycline and CoQ10 treatment may offer therapeutic benefit to patients suffering from HD.
Keywords: Huntington's disease; Therapy; R6/2 mice; Coenzyme Q10; Minocycline;
The plasma membrane Ca2+-ATPase protein from red blood cells is not modified in preeclampsia by Néstor J. Oviedo; Gustavo Benaim; Vincenza Cervino; Teresa Proverbio; Fulgencio Proverbio; Reinaldo Marín (381-385).
Plasma membrane Ca2+-ATPase activity diminishes by about 50% in red blood cells during preeclampsia. We investigated whether the number of Ca2+-ATPase molecules is modified in red cell membranes from preeclamptic pregnant women by measuring the specific phosphorylated intermediate of this enzyme. Also, we isolated the Ca2+-ATPase protein from both normotensive and preeclamptic pregnant women and estimated its molecular weight, and its cross-reactions with specific polyclonal and monoclonal (5F10) antibodies against it. We measured the Ca2+-ATPase activity in a purified state and the effect of known modulators of this ATPase. It was found that the phosphorylated intermediate associated with PMCA is similar for red cell ghosts from normotensive and preeclamptic women, suggesting a similar number of ATPase molecules in these membranes. The molecular weight of the Ca2+-ATPase is around 140 kDa for both normotensive and preeclamptic membranes, and its cross-reactions with specific antibodies is similar, suggesting that the protein structure remains intact in preeclampsia. Calmodulin, ethanol, or both calmodulin plus ethanol, stimulated the Ca2+-ATPase activity to the same extent for both normotensive and preeclamptic preparations. Our results showed that the reduced Ca2+-ATPase activity of the red cell membranes from preeclamptic women is not associated with a defective enzyme, but rather with a high level of lipid peroxidation.
Keywords: Preeclampsia; Ca2+-ATPase; Human red blood cell; Lipid peroxidation;
Defining the heterochromatin localization and repression domains of SALL1 by Christian Netzer; Stefan K. Bohlander; Markus Hinzke; Ying Chen; Jürgen Kohlhase (386-391).
SALL1 has been identified as one of four human homologues of the Drosophila region-specific homeotic gene spalt (sal), encoding zinc finger proteins of characteristic structure. Mutations of SALL1 on chromosome 16q12.1 cause Townes–Brocks syndrome (TBS, OMIM 107480). We have shown previously that SALL1 acts as a strong transcriptional repressor in mammalian cells when fused to a heterologous DNA-binding domain. Here, we report that SALL1 contains two repression domains, one located at the extreme N-terminus of the protein and the other in the central region. SALL1 fragments with the central repression domain exhibited a punctate nuclear distribution pattern at pericentromeric heterochromatin foci in murine NIH-3T3 cells, suggesting an association between repression and heterochromatin localization. The implications of these findings for the pathogenesis of Townes–Brocks syndrome are discussed.
Keywords: SALL1; Townes–Brocks syndrome; Transcriptional repression; Repression domain; Heterochromatin;