Involvement of the N-terminus of Bax in its intracellular localization and function

We have identified, using site-directed mutagenesis, a proline located at position 13 of Baxalpha (Bax) as crucial for the maintenance of its cytosolic conformation. The substitution of this proline by a valine results in a strong binding of Bax to mitochondria and to conformational changes monitored by a decreased sensitivity of Bax to mild proteolysis and the enhancement of its oligomerization state. Deletion of the C-terminus of Bax does not modify its intracellular localization. On the other hand, the pro-apoptotic activity of Bax is enhanced by a deletion of the C-terminus in the absence of the N-terminus but is decreased in its presence. These results suggest that both extremities functionally interact to control the activity but not the subcellular localization of Bax.

[Interest of the ketogenic diet in a refractory status epilepticus in adults]

INTRODUCTION

Ketogenic diets have been employed for the treatment of intractable epilepsy in children since 1921, although underlying mechanism remains unknown.

OBSERVATION

We report the case of a 54-year-old man with partial refractory status epilepticus who exhibited a favourable outcome about seven days after introduction of a ketogenic diet in association with antiepileptic drugs.

DISCUSSION

Although its efficiency was largely demonstrated in children, little is known about the impact of a ketogenic diet in adults with refractory epilepsy.

CONCLUSION

Introduction of a ketogenic diet requires a multidisciplinary approach. Its usefulness in adult intractable epilepsy and/or refractory status epilepticus merits further study into its efficacy in reducing the frequency of seizures and a possible prolonged effect.

Effect of prospectively measured pregnancy intentions on the consistency of contraceptive use among young women in Michigan

STUDY QUESTION

What is the predictive value of pregnancy intentions on contraceptive behaviours among women aged 18-19?

SUMMARY ANSWER

Women aged 18-19 have high levels of inconsistent use of contraception, which mostly occur at times when women strongly wish to avoid a pregnancy.

WHAT IS KNOWN ALREADY

Pregnancy intentions provide an indication of how well individuals achieve their reproductive goals. However, retrospective accounts of pregnancy intentions using dichotomous indicators suffer temporal instability and fail to capture the wide range of attitudes towards pregnancy.

STUDY DESIGN, SIZE, DURATION

In this study, data are drawn from a population-based survey of 992 women of ages 18-19 years in Michigan, who completed weekly journals assessing contraceptive use, pregnancy intentions and reproductive outcomes during 2.5 years of follow-up. The response rate was 86% for the baseline interview and 65% after 2.5 years of follow-up.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We examined 15 446 pairs of journal entries. We used logistic regression with random effects to assess the predictive effect of women's desire to become pregnant and to avoid a pregnancy, measured each week, on consistency of use of contraception the following week.

MAIN RESULTS AND THE ROLE OF CHANCE

Women reported inconsistent use of contraception in more than a quarter of weekly journals (28.3%). Consistent use of contraception increased from 22 to 78% as women s intentions to become pregnant decreased and increased from 23 to 78% as motivations to avoid pregnancy increased. The combination of scores of the pregnancy desire and avoidance scales shows indifferent or ambivalent pregnancy attitudes in 8.6% of weekly records. These women were more likely to report inconsistent contraceptive use compared with women who expressed anti-conception attitudes [OR = 2.8 (2.2-3.5)]. However, 23% of women who had unequivocal anti-conception feelings did not use contraception consistently, contributing to 72% of the weeks of inconsistent use in our population.

LIMITATIONS, REASONS FOR CAUTION

In this study, consistency of contraceptive use, based on the use of contraception at every act of intercourse, does not fully capture a women's risk of becoming pregnant. The 35% attrition after 2.5 years may have affected the internal validity of our results, although a reanalysis based on the first year of observation produced very similar results.

WIDER IMPLICATIONS OF THE FINDINGS

Because most instances of inconsistent use of contraception occur among women who are keen to avoid a pregnancy, our results suggest there is room for improving contraceptive behaviours by promoting use of methods which do not require user adherence.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the National Institute of Child Health and Human Development for grant #R01-HDHD050329 (P.I. Barber, University of Michigan) and grant #R24HD047879 (Center infrastructure of the Office of Population Research at Princeton University, JT and KSH). None of the authors have a competing interest.

A transmembrane domain of the sulfonylurea receptor mediates activation of ATP-sensitive K(+) channels by K(+) channel openers

ATP-sensitive K(+) (K(ATP)) channels are a complex of an ATP-binding cassette transporter, the sulfonylurea receptor (SUR), and an inward rectifier K(+) channel subunit, Kir6.2. The diverse pharmacological responsiveness of K(ATP) channels from various tissues are thought to arise from distinct SUR isoforms. Thus, when assembled with Kir6. 2, the pancreatic beta cell isoform SUR1 is activated by the hyperglycemic drug diazoxide but not by hypotensive drugs like cromakalim, whereas the cardiac muscle isoform SUR2A is activated by cromakalim and not by diazoxide. We exploited these differences between SUR1 and SUR2A to pursue a chimeric approach designed to identify the structural determinants of SUR involved in the pharmacological activation of K(ATP) channels. Wild-type and chimeric SUR were coexpressed with Kir6.2 in Xenopus oocytes, and we studied the resulting channels with the patch-clamp technique in the excised inside-out configuration. The third transmembrane domain of SUR is found to be an important determinant of the response to cromakalim, which possibly harbors at least part of its binding site. Contrary to expectations, diazoxide sensitivity could not be linked specifically to the carboxyl-terminal end (nucleotide-binding domain 2) of SUR but appeared to involve complex allosteric interactions between transmembrane and nucleotide-binding domains. In addition to providing direct evidence for the structure-function relationship governing K(ATP) channel activation by potassium channel-opening drugs, a family of drugs of the highest therapeutic interest, these findings delineate the determinants of ligand specificity within the modular ATP-binding cassette-transporter architecture of SUR.

The value of magnetic resonance imaging as a biomarker for amyotrophic lateral sclerosis: a systematic review

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is a fatal, rapidly progressive neurodegenerative disease that mainly affects the motor system. A number of potentially neuroprotective and neurorestorative disease-modifying drugs are currently in clinical development. At present, the evaluation of a drug's clinical efficacy in ALS is based on the ALS Functional Rating Scale Revised, motor tests and survival. However, these endpoints are general, variable and late-stage measures of the ALS disease process and thus require the long-term assessment of large cohorts. Hence, there is a need for more sensitive radiological biomarkers. Various sequences for magnetic resonance imaging (MRI) of the brain and spinal cord have may have value as surrogate biomarkers for use in future clinical trials. Here, we review the MRI findings in ALS, their clinical correlations, and their limitations and potential role as biomarkers.

METHODS

The PubMed database was screened to identify studies using MRI in ALS. We included general MRI studies with a control group and an ALS group and longitudinal studies even if a control group was lacking.

RESULTS

A total of 116 studies were analysed with MRI data and clinical correlations. The most disease-sensitive MRI patterns are in motor regions but the brain is more broadly affected.

CONCLUSION

Despite the existing MRI biomarkers, there is a need for large cohorts with long term MRI and clinical follow-up. MRI assessment could be improved by standardized MRI protocols with multicentre studies.

Paradoxical response of VEGF expression to hypoxia in CSF of patients with ALS

Vascular endothelial growth factor (VEGF) is implicated in motor neurone degeneration. In normal individuals, hypoxia is known to induce an overexpression of VEGF, as measured in CSF. We show that patients with ALS do not manifest this VEGF overexpression in the presence of hypoxia. Although VEGF gene expression is mainly stimulated by hypoxia, we have measured lower VEGF levels in cerebrospinal fluid (CSF) from hypoxaemic patients with amyotrophic lateral sclerosis (ALS) than in CSF from normoxaemic patients with ALS. In contrast, hypoxaemic neurological controls displayed higher levels than normoxaemic neurological controls. There was a negative correlation between VEGF levels and the severity of hypoxaemia in patients with ALS, suggesting deregulation of VEGF in ALS.

The insulin-like growth factor axis in cell cycle progression

Emerging evidence suggests that members of the Insulin-like Growth Factors (IGFs) family, including IGF-I, IGF-II, the IGF-I receptor (IGF-IR), and the IGF-binding proteins (IGFBPs) play a central role in the development and progression of cancer. Cancer cells exhibit an increased and deregulated proliferative activity. Abnormalities in many positive and negative modulators of the cell cycle are also frequent in many cancer types. Recent advances in the understanding of cell-cycle control mechanisms have been applied to outline the molecular mechanism through which IGFs regulate cell cycle progression. In this review, we will provide a brief overview of the role of the IGF system as a regulator of some components of the cell cycle.

Externally provoked freezing of gait in open runways in advanced Parkinson's disease results from motor and mental collapse

Freezing of gait (FOG) in Parkinson's disease (PD) is defined as a sudden inability to maintain effective stepping movements. However, its pathophysiology remains unclear. The objectives are: (1) To assess the contribution of both spatial (walking speed, stride length) and temporal parameters (cadence, stride time) and their coefficients of variation to the genesis of FOG in PD. (2) To evaluate whether and how externally imposed modifications of self-determined gait would elicit FOG. We included ten patients with advanced PD, and with daily off drug FOG episodes. We focused on walking in an open runway. For each subject, we manipulated gait by externally imposing four changes in walking speed and four changes in cadence. FOG episodes, often with a long duration of more than 5-s, were observed mostly under conditions with a high imposed cadence. The steps that immediately preceded these episodes were mainly characterized by an increase in cadence and an increase in stride length variability. The results also underscore that FOG can be elicited in a laboratory setting when patients are placed under considerable strain, at least in advanced stages of PD. Patients were unable to adequately negotiate the extreme imposed cadence condition, and this resulted in frequent FOG episodes, even while walking in an open runway. Placing advanced PD patients into extreme imposed conditions leads to a motor wise and mental collapse response, culminating in FOG. Future work should establish the relevance of these findings for the more common forms of FOG, including brief episodes during turning or gait initiation.

VKORC1 mutations detected in patients resistant to vitamin K antagonists are not all associated with a resistant VKOR activity

BACKGROUND

The VKORC1 gene codes for the VKORC1 enzyme, which is responsible for the reduction of vitamin K epoxide into vitamin K. VKORC1 enzyme is the target of vitamin K antagonists (VKA). Twenty-eight rare single mutations in the VKORC1 coding sequence have been reported from resistant patients receiving unusually high doses of VKA to achieve therapeutic anticoagulation.

OBJECTIVES

It has been suggested that these mutations are responsible for the resistant phenotype, while biochemical consequences of these mutations on the VKORC1 enzyme have not yet been evaluated. Therefore, the aim of this study was to investigate the causality of the VKORC1 mutations in the resistance phenotype.

METHODS

Wild-type VKORC1 and its spontaneous mutants were expressed in Pichia pastoris and susceptibility to VKA was assessed by the in vitro determination of kinetic and inhibition constants.

RESULTS AND CONCLUSIONS

The in vitro analysis revealed that six mutations only (A26P, A41S, V54L, H68Y, I123N and Y139H) were associated with increase in K(i) , suggesting their involvement in the resistance phenotype observed in patients. A41S and H68Y led to selective resistance, respectively, to indane-1,3-dione and 4-hydroxycoumarine derivatives. The other mutations did not increase the K(i). Furthermore, 10 mutations (S52L, S52W, W59L, W59R, V66M, V66G, G71A, N77S, N77T and L128R) led to an almost complete loss of activity. These results suggest the existence of other resistance mechanisms.

Intestinal absorption of macromolecules during viral enteritis: an experimental study on rotavirus-infected conventional and germ-free mice

Epithelial transport and degradation of horseradish peroxidase (HRP), a macromolecular tracer, was studied in conventional and germ-free suckling mice following an experimental infection with rotavirus. Conventional and germ-free mice developed diarrhea from days 2 to 8 postinfection (pi), with growth failure. In mucosal homogenates, infectious virus detected by immunofluorescence on MA 104 cells was present from day 2 through day 8 pi in germ-free mice, but persisted longer (day 13 pi) in conventional mice. Only mild histological lesions were observed during diarrhea, but obvious macrovacuolation of epithelial cells and increased cellular density occurred during the convalescence period (days 9 to 13 pi). Intact and degraded HRP fluxes from mucosa to serosa were measured in vitro on segments of jejunum mounted in Ussing chambers. Both groups of mice developed increased HRP permeability during the experimental period, but at different times after inoculation: during the diarrheal period (days 2 and 3 pi) conventional mouse epithelium absorbed five times more HRP than noninfected controls and during the convalescence period (days 9 to 13 pi) HRP absorption in germ-free mice rose 10-fold as compared to its level before infection. In both cases, this increase in HRP permeability was entirely due to an increase in intact HRP absorption, probably via a transcellular route, and occurred without any alteration in degraded HRP transport. These results indicate that in mice, rotavirus infection causes a transient rise in gut permeability to undegraded proteins. The intestinal microflora seems to affect the timing, magnitude, and duration of this increased permeability.

Fulminant type 1 diabetes in Caucasians: A report of three cases

CONTEXT

Fulminant type 1 diabetes is a new clinical entity in which the process of beta-cell destruction, and the subsequent progression of hyperglycaemia and ketoacidosis, are extremely rapid. Until now, this subtype of type 1 diabetes has only been reported in the Asian population, especially Japanese and Koreans.

CASES

We report here on three cases of fulminant type 1 diabetes in Caucasian French women. Both the clinical and biological characteristics of these patients are similar to those reported in Japanese studies. Notably, all patients experienced severe ketoacidosis (pH<7.1) that occurred abruptly after the onset of hyperglycaemic symptoms (<6 days), with near-normal HbA(1c) values at diagnosis (5.6, 6.4 and 6.8%). Patients were treated in the intensive care unit with basal-bolus insulin therapy with no remission of their diabetes; pancreatic islet-related autoantibodies were all negative. Fasting C-peptide levels were undetectable, suggesting complete destruction of pancreatic beta-cells. HLA phenotyping of these Caucasian patients did not find the specific HLA haplotype (DRB1*0405-DQB1*0401) previously found to be linked to fulminant type 1 diabetes in Japanese patients.

CONCLUSION

These are the first cases of fulminant type 1 diabetes reported in Caucasians. These cases reveal new perspectives as regards the worldwide distribution of this intriguing clinical entity.

Iron deposits in post-mortem brains of patients with neurodegenerative and cerebrovascular diseases: a semi-quantitative 7.0 T magnetic resonance imaging study

BACKGROUND AND PURPOSE

Accumulation of iron (Fe) is often detected in brains of people suffering from neurodegenerative diseases. However, no studies have compared the Fe load between these disease entities. The present study investigates by T2*-weighted gradient-echo 7.0 T magnetic resonance imaging (MRI) the Fe content in post-mortem brains with different neurodegenerative and cerebrovascular diseases.

METHODS

One hundred and fifty-two post-mortem brains, composed of 46 with Alzheimer's disease (AD), 37 with frontotemporal lobar degeneration (FTLD), 11 with amyotrophic lateral sclerosis, 13 with Lewy body disease, 14 with progressive supranuclear palsy, 16 with vascular dementia (VaD) and 15 controls without a brain disease, were examined. The Fe load was determined semi-quantitatively on T2*-weighted MRI serial brain sections in the claustrum, caudate nucleus, putamen, globus pallidus, thalamus, subthalamic nucleus, hippocampus, mamillary body, lateral geniculate body, red nucleus, substantia nigra and dentate nucleus. The disease diagnosis was made on subsequent neuropathological examination.

RESULTS

The Fe load was significantly increased in the claustrum, caudate nucleus and putamen of FTLD brains and to a lesser degree in the globus pallidus, thalamus and subthalamic nucleus. In the other neurodegenerative diseases no Fe accumulation was observed, except for a mild increase in the caudate nucleus of AD brains. In VaD brains no Fe increase was detected.

CONCLUSIONS

Only FTLD displays a significant Fe load, suggesting that impaired Fe homeostasis plays an important role in the pathogenesis of this heterogeneous disease entity.

The integrin very late antigen-4 is expressed in human smooth muscle cell. Involvement of alpha 4 and vascular cell adhesion molecule-1 during smooth muscle cell differentiation

Vascular cell adhesion molecule-1 (VCAM-1) and its counterreceptor, the integrin very late antigen-4 (VLA-4), have recently been identified in smooth muscle cells during intimal thickening in humans and in newly forming vessels during ontogeny in mice, respectively. We examined the coexpression of VCAM-1 and the alpha 4 integrin subunit in human smooth muscle cells. The expression of VCAM-1 and alpha 4 subunit were studied during development of the aorta. In the 10-week-old human fetal aorta, VCAM-1 and alpha 4 were strongly expressed in smooth muscle cells. Their expression was dramatically reduced within the 24th week of gestation and disappeared in the adult aortic media. However, smooth muscle cells from intimal atherosclerotic thickening of adult aorta reexpressed both VCAM-1 and alpha 4. In a culture model mimicking smooth muscle differentiation, VCAM-1 mRNA and protein and alpha 4 integrin protein were coexpressed with smooth muscle-specific variants of cytoskeletal and contractile proteins, smooth muscle myosin heavy chain, caldesmon heavy chain, and desmin. Treatment with antibodies against VCAM-1 or alpha 4 integrin subunit interfered with the mRNA induction of smooth muscle-specific markers of differentiation. These results in vitro, associated with the transitory expression of VCAM-1 and VLA-4 during vascular ontogeny and the atherosclerosis process, point to a possible role of VCAM-1 and VLA-4 in the induction of smooth muscle differentiation.

Cloning and expression in Escherichia coli of a dog thyroid cDNA encoding a novel inositol 1,4,5-trisphosphate 5-phosphatase

In brain and many other tissues, type I inositol 1,4,5-trisphosphate (InsP3) 5-phosphatase is the major isoenzyme hydrolysing the calcium-mobilizing second messenger InsP3. This protein has been purified to apparent homogeneity from a crude soluble fraction of bovine brain, yielding a single major protein band with a molecular mass of 43 kDa after SDS/PAGE. This material was used to determine internal microsequences. A partial DNA sequence has been amplified by PCR by using degenerate primers deduced from two protein sequences (FKAKKYKKV and DENYKSQE). A cDNA clone (BVCT) was isolated by screening a dog thyroid cDNA library. The encoded protein of 412 amino acids has a calculated molecular mass of 47,681 Da. Peptide sequences generated from the bovine brain enzyme were found to be 96% conserved compared with the dog thyroid protein. When clone BVCT was expressed in Escherichia coli, the recombinant protein was shown to hydrolyse both InsP3 and inositol 1,3,4,5-tetrakisphosphate, with apparent Km values of 28 and 3 microM respectively. Enzyme activity was inhibited by EDTA and 2,3-bisphosphoglycerate, both inhibitors of native InsP3 5-phosphatase, but not by EGTA and LiCl, as previously shown for the bovine brain enzyme. Our data show the cloning of type I InsP3 5-phosphatase which, interestingly, does not share any significant sequence identity with the previously cloned type III isoenzyme.

Monocyte/macrophage recruitment and expression of endothelial adhesion proteins in human atherosclerotic lesions

Since mononuclear cells are recruited in atherosclerotic lesions, the expression of adhesion proteins by the arterial endothelium may play a major role in atherogenesis. The relationships between ICAM-1, E-selectin, and VCAM-1 expression on the arterial endothelium and the presence and degree of maturation of intimal macrophages in human atherosclerotic lesions was investigated. By quantitative double immunostaining with a pan-macrophage-specific monoclonal antibody, HAM-56, and a recently developed monoclonal antibody that is specific for mature macrophages, 3MA-B38, arterial sections were classified as (I) normal, (II) thickened without macrophage infiltration, (III) atherosclerotic with recent macrophage infiltration or (IV) atherosclerotic with infiltration of mature differentiated macrophages. A marked increase in the expression of ICAM-1, E-selectin, and VCAM-1 was observed on endothelial cells adjacent to recently recruited macrophages. Endothelial cells overlying differentiated macrophages exhibited a lower but significant increase in VCAM-1 expression, with no difference in ICAM-1 and E-selectin expression with respect to that observed in endothelium of normal arteries. These findings indicate that the endothelium covering the human arterial wall exhibits different states of activation as reflected by the expression of adhesion proteins, and that intimal monocyte/macrophage recruitment appears to depend on the level of expression of adhesion proteins.

Endothelin ET(A) receptor blockade prevents the progression of renal failure and hypertension in uraemic rats

BACKGROUND

Elevated plasma and urine endothelin-1 (ET-1) levels have been reported in renal failure and may be involved in renal disease progression. We investigated whether these changes are related to increased vascular and renal ET-1 production in the pole resection remnant kidney model of chronic renal failure in the rat.

METHODS

Uraemic Wistar rats were prepared by surgical renal mass 5/6 ablation and compared with sham-operated controls (protocol 1). Immunoreactive-ET-1 (ir-ET-1) concentration was measured by radioimmunoassay after sample extraction and purification. To investigate the functional role of ET-1 during the progression of chronic renal failure, uraemic rats (protocol 2) were treated with either the vehicle or the ET-1 type A (ET(A)) receptor antagonist LU135252 (LU).

RESULTS

Systolic blood pressure and serum creatinine, as well as urinary volume and proteinuria, were significantly higher, whereas creatinine clearance was reduced in uraemic rats compared with sham-operated controls. As expected, plasma and urine ir-ET-1 concentrations were increased in uraemic rats (P<0.01) and were related to the increased ir-ET-1 levels in blood vessels and glomeruli (P<0.001). Positive correlation was found between plasma, thoracic aorta and mesenteric arterial bed ir-ET-1 levels and systolic blood pressure, as well as blood vessel hypertrophy. In addition, increased urinary ir-ET-1 excretion correlated with the rise in serum creatinine and proteinuria. In protocol 2, a 3-week treatment period with LU was initiated once uraemia and hypertension were established. In untreated uraemic rats, systolic blood pressure increased further (P<0.05), but this was not the case in LU-treated uraemic rats. At the end of treatment, serum creatinine and proteinuria were significantly lower (P<0.05) and creatinine clearance was higher (P<0.01) in LU-treated rats compared with uraemic-untreated animals. While plasma ir-ET-1 concentration was similar in the two groups, ir-ET-1 concentration in thoracic aorta, mesenteric arterial bed, renal cortex and urine was significantly lower in LU-treated animals (P<0.01). In addition, heart, thoracic aorta and mesenteric arterial wet weight to body weight ratios were also significantly reduced in LU-treated uraemic rats (P<0.05).

CONCLUSIONS

Elevated plasma ET-1 concentration and urinary ET-1 excretion in rats with renal mass ablation are related to enhanced ET-1 production in vascular and renal tissues, thus suggesting an important role for ET-1 in the aggravation of hypertension and vascular hypertrophy as well as in the progression of renal insufficiency. These pathophysiological effects are prevented by treatment with selective ET(A) receptor blockade.

Expression pattern of mouse sFRP-1 and mWnt-8 gene during heart morphogenesis

The Wnt genes encode a large family of secreted proteins that play a key role in embryonic development and tissue differentiation in many species (Rijsewijk et al., 1987; Nusse and Varmus, 1992). Genetic and biochemical studies have suggested that the frizzled proteins are cell surface receptors for Wnts (Vinson et al., 1989; Chan et al. , 1992; Bhanot et al., 1996; Wang et al., 1996). In parallel, a number of secreted frizzled-like proteins with a conserved N-terminal frizzled motif have been identified (Finch et al., 1997; Melkonyan et al., 1997; Rattner et al., 1997). One of these proteins, FrzA, the bovine counterpart of the murine sFRP-1 (93% identity) is involved in vascular cell growth control, binds Wg in vitro and antagonizes Xwnt-8 and hWnt-2 signaling in Xenopus embryos (Xu et al. , 1998; Duplàa et al., 1999). In this study, we report that sFRP-1 is expressed in the heart and in the visceral yolk sac during mouse development, and that sFRP-1 and mWnt-8 display overlapping expression patterns during heart morphogenesis. From 8.5 to 12.5 d.p. c., sFRP-1 is expressed in cardiomyocytes together with mWnt-8 but neither in the pericardium nor in the endocardium; at 17.5 d.p.c., they are no longer present in the heart. In mouse adult tissues, while sFRP-1 is highly detected in the aortic endothelium and media and in cardiomyocytes, mWnt-8 is not detected in these areas. Immunoprecipitation experiments demonstrates that FrzA binds to mWnt-8 in cell culture experiments.

Identification and cloning of a secreted protein related to the cysteine-rich domain of frizzled. Evidence for a role in endothelial cell growth control

We report the isolation of a cDNA, FrzA (frizzled in aorta; GenBank accession No. U85945), from bovine aortic endothelium. It is the bovine counterpart of the mouse sFRP1, which encodes for a secreted protein that is homologous to the cysteine-rich domain of frizzled. Members of the frizzled family of genes have been shown to be required for tissue polarity and to act as receptors for Wnt. The predicted protein product of this gene includes the cysteine-rich extracellular domain, but not the 7 putative transmembrane domains that are highly conserved among members of the frizzled family. Visualization of FrzA mRNA and protein revealed that it was widely distributed among adult tissues. FrzA is expressed by highly differentiated or polarized cells, eg, neurons, cardiocytes, or various epithelia. Analysis of its expression in endothelium revealed that FrzA mRNA levels were high in endothelial cells scraped from freshly obtained bovine aortas, decreased when cells were placed in culture and began to proliferate, but increased at confluence. Transient transfection assays and an assay using addition of purified protein indicate that FrzA reduces the proliferation of endothelial cells. These data demonstrate the existence of a secreted protein homologous to the extracellular domain of the fz receptor, which we speculate plays a role in controlling cell growth and differentiation, possibly by regulating accessibility to Wnt family members.

mtDNA haplogroup J: a contributing factor of optic neuritis

Optic neuritis frequently occurs in multiple sclerosis (MS), and shares several similarities with the optic neuritis of Leber's hereditary optic neuropathy (LHON), which is mainly due to maternally transmitted mitochondrial DNA (mtDNA) mutations. Our report shows for the first time that a mitochondrial DNA background could influence the clinical expression of MS. One European mtDNA haplogroup was found only in MS patients with optic neuritis but not in MS patients without visual symptoms. Therefore, we hypothesize that mtDNA haplogroup J might constitute a risk factor for optic neuritis occurrence when it is coincidentally associated with MS, but not be a risk factor for developing MS per se as suggested previously.

Nitrate-induced CLE35 signaling peptides inhibit nodulation through the SUNN receptor and miR2111 repression

Legume plants form nitrogen (N)-fixing symbiotic nodules when mineral N is limiting in soils. As N fixation is energetically costly compared to mineral N acquisition, these N sources, and in particular nitrate, inhibit nodule formation and N fixation. Here, in the model legume Medicago truncatula, we characterized a CLAVATA3-like (CLE) signaling peptide, MtCLE35, the expression of which is upregulated locally by high-N environments and relies on the Nodule Inception-Like Protein (NLP) MtNLP1. MtCLE35 inhibits nodule formation by affecting rhizobial infections, depending on the Super Numeric Nodules (MtSUNN) receptor. In addition, high N or the ectopic expression of MtCLE35 represses the expression and accumulation of the miR2111 shoot-to-root systemic effector, thus inhibiting its positive effect on nodulation. Conversely, ectopic expression of miR2111 or downregulation of MtCLE35 by RNA interference increased miR2111 accumulation independently of the N environment, and thus partially bypasses the nodulation inhibitory action of nitrate. Overall, these results demonstrate that the MtNLP1-dependent, N-induced MtCLE35 signaling peptide acts through the MtSUNN receptor and the miR2111 systemic effector to inhibit nodulation.