Novel mutations in Myoclonin1/EFHC1 in sporadic and familial juvenile myoclonic epilepsy

BACKGROUND

Juvenile myoclonic epilepsy (JME) accounts for 3 to 12% of all epilepsies. In 2004, the GENESS Consortium demonstrated four missense mutations in Myoclonin1/EFHC1 of chromosome 6p12.1 segregating in 20% of Hispanic families with JME.

OBJECTIVE

To examine what percentage of consecutive JME clinic cases have mutations in Myoclonin1/EFHC1.

METHODS

We screened 44 consecutive patients from Mexico and Honduras and 67 patients from Japan using heteroduplex analysis and direct sequencing.

RESULTS

We found five novel mutations in transcripts A and B of Myoclonin1/EFHC1. Two novel heterozygous missense mutations (c.755C>A and c.1523C>G) in transcript A occurred in both a singleton from Mexico and another singleton from Japan. A deletion/frameshift (C.789del.AV264fsx280) in transcript B was present in a mother and daughter from Mexico. A nonsense mutation (c.829C>T) in transcript B segregated in four clinically and seven epileptiform-EEG affected members of a large Honduran family. The same nonsense mutation (c.829C>T) occurred as a de novo mutation in a sporadic case. Finally, we found a three-base deletion (-364--362del.GAT) in the promoter region in a family from Japan.

CONCLUSION

Nine percent of consecutive juvenile myoclonic epilepsy cases from Mexico and Honduras clinics and 3% of clinic patients from Japan carry mutations in Myoclonin1/EFCH1. These results represent the highest number and percentage of mutations found for a juvenile myoclonic epilepsy causing gene of any population group.

Molecular and genomic characterization of human DLEC, a novel member of the C-type lectin receptor gene family preferentially expressed on monocyte-derived dendritic cells

We have identified a novel gene encoding a protein designated DLEC (dendritic cell lectin), which is a type II membrane glycoprotein of 213 amino acids and belongs to the human calcium-dependent (C-type) lectin family. The cytoplasmic tail of DLEC lacks consensus signaling motifs and its extracellular region shows a single carbohydrate recognition domain (CRD), closest in homology to the dendritic cell immunoreceptor (DCIR) CRD. The DLEC gene has been localized linked to DCIR on the telomeric region of the NK gene complex. RT-PCR and Northern blot analyses show that DLEC mRNA is preferentially expressed in monocyte-derived dendritic cells.

The hepatitis B virus X protein (HBx) induces a migratory phenotype in a CD44-dependent manner: possible role of HBx in invasion and metastasis

The hepatitis B virus X protein (HBx) of the hepatitis B virus (HBV) has been involved in the development of hepatocellular carcinoma (HCC). However, its possible contribution to the metastatic spreading of liver tumors has not been explored so far. We report here the ability of HBx to enhance cell motility, both alone and in synergy with growth factors, and to induce a migratory phenotype in transformed cells. HBx altered the cellular morphology by inducing the formation of pseudopodial protrusions and cytoskeletal rearrangements, which was accompanied by the polarization of cell-surface adhesion molecules, including the hyaluronan (HA) receptor, CD44. Furthermore, HBx induced the redistribution to the pseudopodial tips of F-actin-binding proteins of the ezrin/radixin/moesin (ERM) family in a Rho- and Rac-dependent manner and increased the association of CD44 with moesin. The migration of HBx-bearing cells in response to HA and growth factors was impaired by a blocking anti-CD44 monoclonal antibody (mAb), suggesting that the HBx-induced cell motility is partially mediated by CD44. Interestingly, HBx-bearing cells showed increased HA-interaction efficiency as assessed under laminar flow conditions, which was the result, at least in part, of an enhanced binding affinity of CD44. HBx may therefore contribute to the acquisition of metastatic properties by modifying the migratory behavior of transformed hepatocytes and by increasing their ability to bind HA in the outer margin of the tumors or in secondary target organs.

Memory B lymphocytes from secondary lymphoid organs interact with E-selectin through a novel glycoprotein ligand

Recirculation of B lymphocytes through the secondary lymphoid organs is key for recognition and response to foreign antigen. B lymphocytes within secondary lymphoid organs comprise a heterogeneous population of cells at distinct differentiation stages. To ascribe a particular adhesive behavior to discrete B-cell subsets within secondary lymphoid organs, we investigated their functional interaction with endothelial selectins under flow. We describe herein the characterization of a subset of human tonsillar B cells that interact with E-selectin but not P-selectin. E-selectin-interacting B cells had a phenotype of non-germinal center (CD10(-), CD38(-), CD44(+)), memory (IgD-) cells. Furthermore, FucT-VII was expressed selectively in CD44(+) E-selectin-adherent B lymphocytes. B-cell rolling on E-selectin required sialic acid but was independent of previously described selectin ligands. A novel glycoprotein ligand of 240 kDa carrying N-linked glycans was isolated from B-cell membranes by an E-selectin immunoadhesin. Binding of this protein was strictly Ca2+ dependent, was inhibited by a cell adhesion-blocking mAb against E-selectin, and required the presence of sialic acid but not N-linked carbohydrates. Our results enable us to assign to resident memory B lymphocytes a novel adhesion function, the rolling on E-selectin, that provides insights on the adhesion pathways involved in homing of memory B cells to tertiary sites.

The chemokine SDF-1alpha triggers a chemotactic response and induces cell polarization in human B lymphocytes

We studied the expression and possible functional role of chemokine receptors CXCR3, CXCR4 and CCR5 in normal human B lymphocytes. B cells from both peripheral blood and tonsils expressed high levels of CXCR4 but not the other chemokine receptors tested. CXCR4 ligand, stromal cell-derived factor (SDF)-1alpha, elicited a potent chemotactic response and induced a polarized motile phenotype in B cells, resulting in redistribution of the adhesion molecule ICAM-3 to a posterior appendage of the cell, termed uropod, and of CXCR4 receptor to the leading edge of migrating B cells. Time-lapse videomicroscopy studies revealed that SDF-1alpha-treated cells recruited additional bystander B cells through the uropod. SDF-1alpha induced levels of cellular recruitment comparable to those elicited by polarization-inducing anti-ICAM-3 monoclonal antibody, in an LFA-1/ICAM-1, -3-dependent fashion. Moreover, this chemokine increased intracellular Ca2+ levels in B lymphocytes, and induced a rapid CXCR4 receptor down-regulation on the cell surface membrane. These results provide new insight into the important biological role of SDF-1alpha in physiological processes in which B cells participate, and suggest a key role for chemokines in normal B cell trafficking and recirculation.

Expression of the leukocyte early activation antigen CD69 is regulated by the transcription factor AP-1

The leukocyte Ag CD69, one of the earliest cell surface activation Ags, is up-regulated at the transcriptional level by proinflammatory stimuli involving the NF-kappaB/Rel family of transcription factors. However, promoter fragments lacking a critical kappaB motif respond to other stimuli such as phorbol esters and triggering Abs against TCR/CD3. Since the 5' promoter flanking region of the CD69 gene contains several putative binding sequences for transcription factor activating protein-1 (AP-1), we explored its role in the inducible expression of CD69. Stimuli that induce AP-1, but not NF-kappaB, such as pyrrolidine dithiocarbamate, augmented the cell surface expression of CD69 as well as its mRNA levels, and the promoter activity of the CD69 gene. This up-regulation is accompanied by an increased binding of jun and fos family members to a consensus AP-1 binding site of the proximal (-16) CD69 promoter region, which seems to be functionally responsive to different activation signals and is trans activated by c-jun expression vectors. Furthermore, cotransfection of a dominant negative version of c-jun, but not IkappaB, abolished the inducible transcriptional activity of the CD69 promoter. In conclusion, the inducible expression of the CD69 gene by mitogenic signals is regulated by the transcription factor AP-1.

Expression of the leukocyte early activation antigen CD69 is regulated by the transcription factor AP-1

The leukocyte Ag CD69, one of the earliest cell surface activation Ags, is up-regulated at the transcriptional level by proinflammatory stimuli involving the NF-kappaB/Rel family of transcription factors. However, promoter fragments lacking a critical kappaB motif respond to other stimuli such as phorbol esters and triggering Abs against TCR/CD3. Since the 5' promoter flanking region of the CD69 gene contains several putative binding sequences for transcription factor activating protein-1 (AP-1), we explored its role in the inducible expression of CD69. Stimuli that induce AP-1, but not NF-kappaB, such as pyrrolidine dithiocarbamate, augmented the cell surface expression of CD69 as well as its mRNA levels, and the promoter activity of the CD69 gene. This up-regulation is accompanied by an increased binding of jun and fos family members to a consensus AP-1 binding site of the proximal (-16) CD69 promoter region, which seems to be functionally responsive to different activation signals and is trans activated by c-jun expression vectors. Furthermore, cotransfection of a dominant negative version of c-jun, but not IkappaB, abolished the inducible transcriptional activity of the CD69 promoter. In conclusion, the inducible expression of the CD69 gene by mitogenic signals is regulated by the transcription factor AP-1.

Reduced intracellular oxidative metabolism promotes firm adhesion of human polymorphonuclear leukocytes to vascular endothelium under flow conditions

The interaction of polymorphonuclear leukocytes (PMN) with the vascular endothelium and their subsequent extravasation to the tissues is a key step during different physiological and pathological processes. In certain of these pathologies the oxygen tension becomes very low, leading to reduced cellular oxidative status. To evaluate the effect of lowering the intracellular redox status in the interaction of PMN with the endothelium, exposure to hypoxic conditions as well as treatment with different antioxidant agents was carried out. PMN exposure to hypoxia enhanced beta2 integrin-dependent adhesion to intercellular adhesion molecule-1-coated surfaces, concomitant with a decrease in the intracellular redox status of the cell. As occurs with hypoxia, treatment with antioxidants produced a decrease in the oxidation state of PMN. These agents enhanced adhesion of PMN to human umbilical vein endothelial cells stimulated with tumor necrosis factor-alpha (TNF-alpha), and this effect was also mediated by beta2 integrins LFA-1 and Mac-1. Adhesion studies under defined laminar flow conditions showed that the antioxidant treatment induced an enhanced adhesion mediated by beta2 integrins with a decrease in the fraction of PMN rolling on TNF-alpha-activated endothelial cells. The up-regulated PMN adhesion was correlated to an increase in the expression and activation of integrin Mac-1, without loss of L-selectin surface expression. Altogether, these results demonstrate that a reduction in the intracellular oxidative state produces an enhanced beta2 integrin-dependent adhesion of PMN to stimulated endothelial cells under conditions of flow.

ICAMs redistributed by chemokines to cellular uropods as a mechanism for recruitment of T lymphocytes

The recruitment of leukocytes from the bloodstream is a key step in the inflammatory reaction, and chemokines are among the main regulators of this process. During lymphocyte-endothelial interaction, chemokines induce the polarization of T lymphocytes, with the formation of a cytoplasmic projection (uropod) and redistribution of several adhesion molecules (ICAM-1,-3, CD43, CD44) to this structure. Although it has been reported that these cytokines regulate the adhesive state of integrins in leukocytes, their precise mechanisms of chemoattraction remain to be elucidated. We have herein studied the functional role of the lymphocyte uropod. Confocal microscopy studies clearly showed that cell uropods project away from the cell bodies of adhered lymphocytes and that polarized T cells contact other T cells through the uropod structure. Time-lapse videomicroscopy studies revealed that uropod-bearing T cells were able, through this cellular projection, to contact, capture, and transport additional bystander T cells. Quantitative analysis revealed that the induction of uropods results in a 5-10-fold increase in cell recruitment. Uropod-mediated cell recruitment seems to have physiological relevance, since it was promoted by both CD45R0+ peripheral blood memory T cells as well as by in vivo activated lymphocytes. Additional studies showed that the cell recruitment mediated by uropods was abrogated with antibodies to ICAM-1, -3, and LFA-1, whereas mAb to CD43, CD44, CD45, and L-selectin did not have a significant effect, thus indicating that the interaction of LFA-1 with ICAM-1 and -3 appears to be responsible for this process. To determine whether the increment in cell recruitment mediated by uropod may affect the transendothelial migration of T cells, we carried out chemotaxis assays through confluent monolayers of endothelial cells specialized in lymphocyte extravasation. An enhancement of T cell migration was observed under conditions of uropod formation, and this increase was prevented by incubation with either blocking anti-ICAM-3 mAbs or drugs that impair uropod formation. These data indicate that the cell interactions mediated by cell uropods represent a cooperative mechanism in lymphocyte recruitment, which may act as an amplification system in the inflammatory response.

Effect of anticysticercal treatment on the prognosis of epilepsy in neurocysticercosis: a pilot trial

Epilepsy secondary to active or inactive neurocysticercosis (NCC) is a major public health problem in Latin American countries. In an open-label pilot trial, we evaluated and followed (mean = 13 months) 16 patients with epilepsy resulting from active NCC which was treated with anticisticercal (ACC) drugs. These patients were aged 12-68 years with confirmed active NCC and seizures not controlled by adequate antiepileptic drug (AED) therapy. Patients were treated with albendazole or praziquantel (ALB and PZQ, ACC drugs) and AED monotherapy. The number of NCC cysts was markedly reduced by ACC therapy. Thirteen patients remained seizure-free and 2 had only one seizure during follow-up. Our data suggest a positive effect of ACC treatment on the prognosis of epilepsy caused by active NCC, but a prospective, double-blind, controlled study with long-term follow-up must be performed to determine whether ACC therapy improves long-term seizure control.