Nedd9/Hef1/Cas-L mediates the effects of environmental pollutants on cell migration and plasticity.

Aryl hydrocarbon receptor (AhR), or dioxin receptor, is a transcription factor that induces adaptive metabolic pathways in response to environmental pollutants. Recently, other pathways were found to be altered by AhR and its ligands. Indeed, developmental defects elicited by AhR ligands suggest that additional cellular functions may be targeted by this receptor, including cell migration and plasticity. Here, we show that dioxin-mediated activation of Ahr induces Nedd9/Hef1/Cas-L, a member of the Cas protein family recently identified as a metastasis marker. The Hef1 gene induction is mediated by two xenobiotic responsive elements present in this gene promoter. Moreover, using RNA interference, we show that Nedd9/Hef1/Cas-L mediates the dioxin-elicited changes related to cell plasticity, including alterations of cellular adhesion and shape, cytoskeleton reorganization, and increased cell migration. Furthermore, we show that both E-cadherin repression and Jun N-terminal kinases activation by dioxin and AhR also depend on the expression of Nedd9/Hef1/Cas-L. Our study unveils, for the first time, a link between pollutants exposure and the induced expression of a metastasis marker and shows that cellular migration and plasticity markers are regulated by AhR and its toxic ligands.

Activation of the dioxin/aryl hydrocarbon receptor (AhR) modulates cell plasticity through a JNK-dependent mechanism.

Environmental chemicals such as dioxin adversely affect immune, neurological and reproductive functions and have been implicated in cancer development. However, the mechanisms responsible for dioxin toxicity are still poorly understood. Here, we show that dioxin and related pollutants trigger a marked morphological change in epithelial cells that remodel their cytoskeleton to increase interaction with extra cellular matrix while loosening cell-cell contacts. Furthermore, dioxin-treated cells show increased motility. These dioxin-mediated effects are mimicked by constitutive expression and activation of the intracellular dioxin receptor (aryl hydrocarbon receptor (AhR)). They correlate with activation of the Jun NH2-terminal kinase (JNK) and are reverted by treatment with a JNK inhibitor. Dioxin-induced effects occur 48 h post-treatment initiation, a time scale, which argues for a genomic effect of the AhR, linked to induction of target genes. This novel Ahr action on cell plasticity points to a role in cancer progression.

Differential regulation of cytochrome P450 1A1 and 1B1 by a combination of dioxin and pesticides in the breast tumor cell line MCF-7.

Dioxin and pesticides with xenoestrogenic activity are environmental contaminants that are suspected of promoting human diseases such as cancers. However, few studies have addressed the molecular consequences of a combination of these contaminants, a situation that is likely to occur in the environment. We investigated the effects of natural and xenoestrogens on basal and 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced cytochrome P450 (CYP) 1A1 and 1B1. The CYP1B1/1A1 ratio is a critical determinant of the metabolism and toxicity of estradiol in mammary cells. Here we show that in MCF-7 cells, 17beta-estradiol and alpha-endosulfan can repress whole cell ethoxyresorufin-O-deethylase activity, lowering CYP1A1 mRNA levels as well as promoter activity as assessed by transient transfection assays. These negative effects are observed at both the basal and tetrachlorodibenzo-p-dioxin-induced levels. Under the same conditions, CYP1B1 mRNA levels and promoter activity are not affected. The effects on mRNA-induced levels are also observed in another mammary cell line, T47D, but not in mammary cell lines that do not express aryl hydrocarbon receptor and estrogen receptor (ER). Moreover, the use of ER antagonists shows that these effects are ER dependent in MCF-7 cells. In human hepatoma HepG2 cells, which lack functional ER, alpha-endosulfan, but not 17beta-estradiol, displays a repressive effect on CYP1A1 through a different mechanism. These results show that xenoestrogens, by altering the ratio of CYP1B1/CYP1A1, could redirect estradiol metabolism in a more toxic pathway in the breast cell line MCF-7.

A case of mitochondrial encephalomyopathy associated with a muscle coenzyme Q10 deficiency.

We report severe coenzyme Q10 deficiency of muscle in a 4-year-old boy presenting with progressive muscle weakness, seizures, cerebellar syndrome, and a raised cerebro-spinal fluid lactate concentration. State-3 respiratory rates of muscle mitochondria with glutamate, pyruvate, palmitoylcarnitine, and succinate as respiratory substrates were markedly reduced, whereas ascorbate/N,N,N',N'-tetramethyl-p-phenylenediamine were oxidized normally. The activities of complexes I, II, III and IV of the electron transport chain were normal, but the activities of complexes I+III and II+III, both systems requiring coenzyme Q10 as an electron carrier, were dramatically decreased. These results suggested a defect in the mitochondrial coenzyme Q10 content. This was confirmed by the direct assessment of coenzyme Q10 level by high-performance liquid chromatography in patient's muscle homogenate and isolated mitochondria, revealing levels of 16% and 6% of the control values, respectively. We did not find any impairment of the respiratory chain either in a lymphoblastoid cell line or in skin cultured fibroblasts from the patient, suggesting that the coenzyme Q10 depletion was tissue-specific. This is a new case of a muscle deficiency of mitochondrial coenzyme Q in a patient suffering from an encephalomyopathy.

Biochemical and genetic studies of four patients with pyruvate dehydrogenase E1 alpha deficiency.

We report studies of four patients with pyruvate dehydrogenase complex (PDH) deficiency caused by mutations in the E1 alpha subunit. Two unrelated male patients presented with Leigh syndrome and a R263G missense mutation in exon 8. This mutation has previously been described in males with the same phenotype. The two other patients had different novel mutations: (1) an 8-bp deletion at the C-terminus (exon 11) was found in one allele of a young girl suffering from microcephaly and (2) a C88S missense mutation (exon 3) in a boy who only presented with motor neuropathy. These mutations were not found in the mothers of any of the four cases. Immunoblot analysis revealed decreased immunoreactivity for the E1 alpha and E1 beta subunits in three out of the four patients. These findings confirm that: (1) PDH deficiencies are genetically heterogeneous, (2) the R263G mutation is more frequent in male cases than are other mutations and this amino acid is a hot spot for gene mutations, (3) the last eight amino acids may be important for the conformation of the tetrameric E1-PDH enzyme, and (4) the amino acids at positions 88, 263 and 382-387 are essential for the linking of the alpha subunit with the beta subunit and for the activity of the holoenzyme.

A near homoplasmic T8993G mtDNA mutation in a patient with atypic Leigh syndrome not present in the mother's tissues.

We report an interesting case of a T8993G mutation in the muscle mtDNA of a 2-year-old girl who presented with myoclonia, developmental delay, increased lactate concentration in CSF and cerebral MRI abnormalities without retinopathy, suggesting an atypical form of Leigh syndrome. Search for mutant molecules in the blood and skin fibroblasts of the patient's healthy mother as well as in the blood of the also unaffected patient's sister was unsuccessful. This "sporadic' case of 8993 mtDNA mutation may be due either to a de novo mutation arising during oogenesis (or early embryogenesis) or to a mutation pre-existing in oocytes in a few mtDNA molecules and selected through a narrow bottleneck mechanism. Whatever the mechanism involved, this observation illustrates a complete shift of the mtDNA type in only one generation: from 0 to nearly 100% of mtDNA molecules with the T8993G mutation.

Clinical, biochemical, and molecular analysis of a maternally inherited case of Leigh syndrome (MILS) associated with the mtDNA T8993G point mutation.

We report a new case of Leigh disease (subacute necrotizing encephalomyelopathy) in a girl with mitochondrial DNA (mtDNA) mutation in the ATPase6 gene at nucleotide position 8993. Sequence analysis of mtDNA revealed a T-to-G transversion at nucleotide position 8993 in the ATPase6 gene. Southern blot restriction analysis of patient muscle mtDNA showed only a mutant pattern for the mutation 8993. Molecular analysis of seven subjects from the family showed that except for the father they all carried the 8993 mtDNA mutation in all studied tissues, with high percentages in the two symptomatic children and even in one asymptomatic boy.

Intrafamilial heterogeneous clinical presentation of the mitochondrial 3243 MELAS mutation; molecular investigations among four generations.

We have identified the A3243G heteroplasmic point mutation in mitochondrial DNA from a female patient with headache as the main clinical feature. The mitochondrial origin of her disease was only suspected because of her brother with MELAS syndrome. Morphological and biochemical studies failed to reveal mitochondrial respiratory chain dysfunction in her muscle which contained 65% of mutated mitochondrial DNA molecules. Molecular studies performed among four generations (in the blood of seven subjects) showed the variable transmission of mutated molecules and pointed out the difficulty in giving genetic counsel.

Myo-leukoencephalopathy in twins: study of 3243-myopathy, encephalopathy, lactic acidosis, and strokelike episodes mitochondrial DNA mutation.

Two dizygotic twins with myopathy and leukoencephalopathy are described. The female twin had an incomplete form of MELAS syndrome (myopathy, encephalopathy, lactic acidosis, and strokelike episodes) with severe myopathy, epileptic seizures without strokelike episodes. The male twin presented clinical features exclusively of myopathy and subclinical leukoencephalopathy. The MELAS mitochondrial DNA point mutation (MELAS-3243) was found by southern blot and polymerase chain reaction in muscle, skin fibroblasts, and blood of the female twin and was not detected in the skin fibroblasts nor in the blood of the mother, nor in any of the tissues tested in the male twin. The absence of mutation in male twin tissues raises questions about the pathogenetic significance of the mutation in this family.

Merrf family with 8344 mutation in tRNA (lys). Evidence of a mitochondrial vasculopathy in muscle biopsies.

This article reports a new MERRF family. The mother, regarded as suffering from Ramsay-Hunt Syndrome, and her three daughters, had the same clinical pattern: myoclonic epilepsy and ataxia. Two daughters were studied on morphological, biochemical and molecular genetic levels. Muscle biopsies showed ragged-red fibres and mitochondrial vasculopathy. Arterioles were strongly SDH-reactive and COX-negative. By electron microscopy, abnormal mitochondria were observed in skeletal muscle fibres, in smooth muscle fibres of intramuscular vessels and in sweat gland epithelium. The study of the respiratory chain showed complex IV and I + IV deficiency, respectively. Mitochondrial tRNA (lys) mutation at position 8344 was pointed out as previously reported in the MERRF syndrome.

E1 pyruvate dehydrogenase deficiency in a child with motor neuropathy.

We report the case of a boy who developed a motor neuropathy during infectious episodes at 18 mo and 3 y of age. When he was 7 y old, he suffered persistent weakness and areflexia; his resting lactate and pyruvate values were 3.65 mM and 398 microM, respectively (controls: 1.1 +/- 0.3 mM and 90 +/- 22 microM), and an exercise test demonstrated a lactic acidosis (13.6 mM; controls: 6.4 +/- 1.3 mM) with a high pyruvate level (537 microM; controls: 176 +/- 15 microM) and a low lactate/pyruvate ratio (24.2; controls: 35 +/- 2). The results of polarographic studies on muscle mitochondria suggested a defect in pyruvate oxidation (pyruvate 17 ng atom O/min/mg protein; controls: 115 +/- 42), whereas glutamate, palmitoylcarnitine, and succinate were good respiratory substrates. The activity of total pyruvate dehydrogenase complex (PDHC) in muscle mitochondria and in fresh mononuclear cells was markedly decreased (9.7 and 0.054 nmol 14CO2/min/mg protein, respectively; controls: 123 +/- 4.5 and 0.733 +/- 0.03, respectively). Immunochemical analysis in muscle mitochondria demonstrated an absence of the alpha and beta E1 PDHC subunits. After 2 y of treatment with 500 mg/d thiamine, the patient was clinically improved. A genetic study of the main regions of mutations (exon 10 and 11) in the X chromosome encoding for the E1 alpha subunit of PDHC did not show any mutation. These data indicate that, although genetically different, this case enters in a very rare category of patients with PDHC deficiency without cerebral dysfunction and improved by thiamine + L-carnitine therapy.

Isolation of heparin-binding growth factors from dogfish (Mustela canis) brain and retina.

We have purified two growth factors from dogfish brain and retina by using their binding affinity for heparin-Sepharose. These growth factors were eluted at 1 and 2 M NaCl similarly to those purified from bovine brain or retina. Their mitogenic activity was assayed in vitro on the same mammalian cells: bovine lens epithelial cells or human fibroblasts. All these data seem to indicate that these growth factors belong to the families of other well defined mammalian growth factors: EDGF I, brain basic FGF, AGF II, on the one hand and EDGF II, brain acidic FGF, AGF I, ECGF, on the other. Thus, these growth factors have been widely distributed during evolution and retain at least a conservative sequence to stimulate cell proliferation, in mammalian cells.