[SAMHD1 acts at stalled replication forks to prevent interferon induction]. / SAMHD1 agit sur les fourches de réplication bloquées pour empêcher l'induction d'interféron.

DNA replication is an extremely complex process, involving thousands of replication forks progressing along chromosomes. These forks are frequently slowed down or stopped by various obstacles, such as secondary DNA structures, chromatin-acting proteins or a lack of nucleotides. This slowing down, known as replicative stress, plays a central role in tumour development. Complex processes, which are not yet fully understood, are set up to respond to this stress. Certain nucleases, such as MRE11 and DNA2, degrade the neo-replicated DNA at the level of blocked forks, allowing the replication to restart. The interferon pathway is a defense mechanism against pathogens that detects the presence of foreign nucleic acids in the cytoplasm and activates the innate immune response. DNA fragments resulting from genomic DNA metabolism (repair, retrotransposition) can diffuse into the cytoplasm and activate this pathway. A pathological manifestation of this process is the Aicardi-Goutières syndrome, a rare disease characterized by chronic inflammation leading to neurodegenerative and developmental problems. In this encephalopathy, it has been suggested that DNA replication may generate cytosolic DNA fragments, but the mechanisms involved have not been characterized. SAMHD1 is frequently mutated in the Aicardi-Goutières syndrome as well as in some cancers, but its role in the etiology of these diseases was largely unknown. We show that cytosolic DNA accumulates in SAMHD1-deficient cells, particularly in the presence of replicative stress, activating the interferon response. SAMHD1 is important for DNA replication under normal conditions and for the processing of stopped forks, independent of its dNTPase activity. In addition, SAMHD1 stimulates the exonuclease activity of MRE11 in vitro. When SAMHD1 is absent, degradation of neosynthesized DNA is inhibited, which prevents activation of the replication checkpoint and leads to failure to restart the replication forks. Resection of the replication forks is performed by an alternative mechanism which releases DNA fragments into the cytosol, activating the interferon response. The results obtained show, for the first time, a direct link between the response to replication stress and the production of interferons. These results have important implications for our understanding of the Aicardi-Goutières syndrome and cancers related to SAMHD1. For example, we have shown that MRE11 and RECQ1 are responsible for the production of DNA fragments that trigger the inflammatory response in cells deficient for SAMHD1. We can therefore imagine that blocking the activity of these enzymes could decrease the production of DNA fragments and, ultimately, the activation of innate immunity in these cells. In addition, the interferon pathway plays an essential role in the therapeutic efficacy of irradiation and certain chemotherapeutic agents such as oxaliplatin. Modulating this response could therefore be of much wider interest in anti-tumour therapy.

La réplication de l'ADN est un processus extrêmement complexe, impliquant des milliers de fourches de réplication progressant le long des chromosomes. Ces fourches sont fréquemment ralenties ou arrêtées par différents obstacles, tels que des structures secondaires de l'ADN, des protéines agissant sur la chromatine ou encore un manque de nucléotides. Ce ralentissement, qualifié de stress réplicatif, joue un rôle central dans le développement tumoral. Des processus complexes, qui ne sont pas encore totalement connus, sont mis en place pour répondre à ce stress. Certaines nucléases, comme MRE11 et DNA2, dégradent l'ADN néorépliqué au niveau des fourches bloquées, ce qui permet le redémarrage des réplisomes. La voie interféron est un mécanisme de défense contre les agents pathogènes qui détecte la présence d'acides nucléiques étrangers dans le cytoplasme et active la réponse immunitaire innée. Des fragments d'ADN issus du métabolisme de l'ADN génomique (réparation, rétrotransposition) peuvent diffuser dans le cytoplasme et activer cette voie. Une manifestation pathologique de ce processus est le syndrome d'Aicardi-Goutières, une maladie rare caractérisée par une inflammation chronique générant des problèmes neurodégénératifs et développementaux. Dans le cadre de cette encéphalopathie, il a été suggéré que la réplication de l'ADN pouvait générer des fragments d'ADN cytosoliques, mais les mécanismes impliqués n'avaient pas été caractérisés. SAMHD1 est fréquemment muté dans le syndrome d'Aicardi-Goutières ainsi que dans certains cancers, mais son rôle dans l'étiologie de ces maladies était jusqu'à présent largement inconnu. Nous montrons que de l'ADN cytosolique s'accumule dans les cellules déficientes pour SAMHD1, particulièrement en présence de stress réplicatif, activant la réponse interféron. Par ailleurs, SAMHD1 est important pour la réplication de l'ADN en conditions normales et pour le processing des fourches arrêtées, indépendamment de son activité dNTPase. De plus, SAMHD1 stimule l'activité exonucléase de MRE11 in vitro. Lorsque SAMHD1 est absent, la dégradation de l'ADN néosynthétisé est inhibée, ce qui empêche l'activation du checkpoint de réplication et entraine un défaut de redémarrage des fourches de réplication. De plus, la résection des fourches de réplication est réalisée par un mécanisme alternatif qui libère des fragments d'ADN dans le cytosol, activant la réponse interféron. Les résultats obtenus montrent, pour la première fois, un lien direct entre la réponse au stress réplicatif et la production d'interférons. Ces résultats ont des conséquences importantes dans notre compréhension du syndrome d'Aicardi Goutières et des cancers liés à SAMHD1. Par exemple, nous avons démontré que MRE11 et RECQ1 sont responsables de la production des fragments d'ADN qui déclenchent la réponse inflammatoire dans les cellules déficientes pour SAMHD1. Nous pouvons donc imaginer que bloquer l'activité de ces enzymes pourrait diminuer la production des fragments d'ADN et, in fine, l'activation de l'immunité innée dans ces cellules. Par ailleurs, la voie interférons joue un rôle essentiel dans l'efficacité thérapeutique de l'irradiation et de certains agents chimiothérapiques comme l'oxaliplatine. Moduler cette réponse pourrait donc avoir un intérêt beaucoup plus large en thérapie anti-tumorale.

Early occupational therapy programme increases hand grip strength at 3 months: results from a randomised, blind, controlled study in early rheumatoid arthritis.

AIM: The goal of occupational therapy (OT) is to facilitate adjustments to lifestyle and to prevent function loss. This study evaluated the effects of an early OT programme in early rheumatoid arthritis (RA). METHODS: We conducted a randomised, blind, controlled trial enrolling 60 patients with early RA, divided into 2 groups. At baseline, group 1 received the full information programme and group 2 received no information. In an extension phase, patients in group 2 received the full information programme at 3 months and were assessed at 6 months. The main outcomes were grip strength of hands (as objective assessment) and Health Assessment Questionnaire (HAQ) score (as subjective assessment). RESULTS: At 3 months, grip strength of the dominant and non-dominant hands increased more in group 1 than in group 2 (p = 0.021 and 0.047 respectively). HAQ score decreased more in group 1 than in group 2 (p<0.001). In the extension phase, changes in grip strength and HAQ score in group 2 were similar to those seen in group 1 between baseline and 3 months. CONCLUSIONS: This study comparing two schedules of OT programme showed that an early extended information programme improved hand function in patients with early RA.

Two mutations in the HSN2 gene explain the high prevalence of HSAN2 in French Canadians.

BACKGROUND: Hereditary sensory and autonomic neuropathy type 2 (HSAN2; MIM 201300) is a rare recessive neuropathy typically diagnosed in the first decade. The 1973 study of a French Canadian family led to the definition of HSAN2. OBJECTIVES: To demonstrate that the apparent higher prevalence of HSAN2 in Quebec is due to the presence of two HSN2 mutations and that carriers of different mutations appear to have a similar phenotype. METHODS: Through attending physicians, the authors recruited French Canadian patients with HSAN2. Exclusion of linkage to the known HSAN loci and linkage to the HSAN2 was performed using standard methods. Sequencing of the HSN2 gene was used to uncover the causal mutations. RESULTS: A large cluster of HSAN2 patients comprising 16 affected individuals belonging to 13 families was identified. The mode of inheritance is clearly autosomal recessive. All patients originated from southern Quebec, and 75% are from the Lanaudière region. Whereas linkage to the HSAN1, 3, and 4 loci was excluded, linkage to the 12p13.33 HSAN2 locus was confirmed. Sequencing of the HSN2 gene uncovered two French Canadian mutations and a novel nonsense mutation in a patient of Lebanese origin, all predicted to lead to truncations of the HSN2 protein. The comparison of clinical variables between patients with different genotypes does not suggest any difference in phenotype. CONCLUSIONS: Two founder mutations are responsible for the apparently higher prevalence of HSAN2 in French Canadians. Genotype-phenotype correlation does not suggest any significant clinical variability.

Sudden infant death syndrome (SIDS) in a family with myophosphorylase deficiency.

A previously healthy girl died suddenly and unexpectedly at three months of age in her sleep and an autopsy failed to reveal an adequate cause of death. As the father was known to have myophosphorylase (PPL) deficiency (McArdle's disease), we performed molecular genetic analysis of the PPL gene in autopsy muscle of the proposita. The girl was homozygous for the nonsense mutation at codon 49 most commonly associated with typical McArdle's disease. This report suggests that among children presenting as Sudden Infant Death Syndrome (SIDS) there may be cases associated with myophosphorylase deficiency.

Two large Spanish pedigrees with nonsyndromic sensorineural deafness and the mtDNA mutation at nt 1555 in the 12s rRNA gene: evidence of heteroplasmy.

We describe two unrelated Spanish families with isolated sensorineural hearing loss. In both pedigrees, the deafness was transmitted maternally, which suggested a mitochondrial, DNA (mtDNA) defect. Within the same pedigree, some relatives showed aminoglycoside-induced deafness, whereas others were not exposed to aminoglycosides before the onset of hearing loss. Molecular genetic analysis in both families showed the A-to-G transition at nt 1555 (A1555G) in the mitochondrial 12S rRNA gene. In one pedigree, the mutation was homoplasmic; in the other, it was heteroplasmic. To assess the frequency of this mutation, we screened 42 patients of various ethnic backgrounds with isolated sensorineural hearing loss; none harbored the A1555G mutation. This is the first report of heteroplasmy in a family with isolated sensorineural deafness associated with the A1555G mutation.

[A case of VIP and somatostatin-secreting phaeochromocytoma (author's transl)]. / Phéochromocytome sécrétant du vaso-active intestinal peptide et de la somatostatine. Une observation.

A man with watery diarrhoea was found to have adrenal tumour. Pre-operative examinations located the tumour in the right adrenal gland and revealed that it secreted an excess of vasoactive intestinal peptide (VIP). All symptoms disappeared after excision of the phaeochromocytoma; they have not recurred after a 3 years' follow-up period. Histological examination of the tumour confirmed that it was the site of a triple hormonal secretion (VIP somatostatin and catecholamines).

[Study of vigilance after ingestion of zopiclone in comparison with nitrazepam and placebo (author's transl)]. / Etude de la vigilance après prise de zopiclone en comparaison avec nitrazépam et placebo. Méthodologie de l'étude : questionnaires d'auto-évaluation et tests psychométriques.

Increasing importance is being given to the residual effects of hypnotics on the day following absorption; with zopiclone, a new hypnotic, we have studied vigilance 9, 12 and 15 hours after a single evening dose of 10 mg, on a double-blind basis in comparison with 10 mg of nitrazepam and a placebo. The assessment of vigilance is based on responses to self-rating questionnaires and psychometric tests. Twenty-one healthy subjects forming a homogeneous group as regards age, I.Q., and vigilance were included in this study. Each subject received the three products in random distributed order, with an interval of three months between each trial. The results of these tests reveal modifications which, particularly 9 hours after administration, reflect a modification in vigilance, appearing to be more marked with nitrazepam than with zopiclone. Thus, from the point of view of the residual effects of hypnotics on vigilance, it is possible to position the products tested in the following order: placebo -- zopiclone -- nitrazepam.

[Clinical and developmental aspects of hepatoma]. / Les aspects cliniques et évolutifs de l'hépatome

We have reported here 38 cases of hepatoma observed over a period of 3 1/2 years in a Paris hospital, and recall the main circumstances of discovery of this primary tumour of the liver. Clinically, hepatomegaly with a hard, painful border, increasing rapidly in volume in a patient with a past history of alcoholism and with a poor general condition, remains the best sign. More often, decompensated cirrhosis is the only sign and may lead to the wrong diagnosis, until alphafoetoprotein estimation and laparoscopy are carried out. Unfortunately, the almost constant presence of cirrhosis, usually diffuse, and the pluricentric character of the hepatoma, make any attempt at removal immpossible. Treatment consists simply of the administration of analgesics whilst awaiting a fatal issue within 3 to 4 months. We believe that it is useful to have constantly in mind this terminal complication of cirrhosis as, at present, among the direct or associated causes of death from cirrhosis, hepatomas seem to account for about 20%.