Remote assessment of ADHD in children and adolescents: recommendations from the European ADHD Guidelines Group following the clinical experience during the COVID-19 pandemic.

The COVID-19 pandemic led ADHD services to modify the clinical practice to reduce in-person contact as much as possible to minimise viral spread. This had far-reaching effects on day-to-day clinical practice as remote assessments were widely adopted. Despite the attenuation of the acute threat from COVID, many clinical services are retaining some remote practices. The lack of clear evidence-based guidance about the most appropriate way to conduct remote assessments meant that these changes were typically implemented in a localised, ad hoc, and un-coordinated way. Here, the European ADHD Guidelines Group (EAGG) discusses the strengths and weaknesses of remote assessment methods of children and adolescents with ADHD in a narrative review based on available data and expert opinions to highlight key recommendations for future studies and clinical practice. We conclude that going forward, despite remote working in clinical services functioning adequately during the pandemic, all required components of ADHD assessment should still be completed following national/international guidelines; however, the process may need adaptation. Social restrictions, including changes in education provision, can either mask or exacerbate features associated with ADHD and therefore assessment should carefully chart symptom profile and impairment prior to, as well as during an ongoing pandemic. While remote assessments are valuable in allowing clinical services to continue despite restrictions and may have benefits for routine care in the post-pandemic world, particular attention must be paid to those who may be at high risk but not be able to use/access remote technologies and prioritize these groups for conventional face-to-face assessments.

Women's quality of life and mental health in the first year after birth: Associated factors and effects of antenatal preventive measures among mothers in the ELFE cohort.

BACKGROUND: During the perinatal period, women's perceived quality of life (QOL) may be altered due to physiological, psychological, and bodily changes, as well as changes in family functioning. OBJECTIVES: to explore in a sample of women from the general population, the associations between physical and mental QOL at 1 year post-partum and i) pregnancy social support, demographic, socioeconomic, medical and child health-related factors, paternal and maternal psychological characteristics at 2 months and 1 year post-partum, ii) antenatal preventive measures (early prenatal interview/antenatal classes). METHODS: We used data from the "French Longitudinal Study since Childhood" (ELFE), a representative cohort of children and their parents followed from birth to adulthood. Data were collected from mothers in the maternity ward, at 2 months and 1-year post-partum. QOL was assessed using the SF12 physical (PCS-12) and mental (MCS-12) subscales. RESULTS: Women with both low PCS-12 and MCS-12 scores were more likely to have high maternal age and to experience psychological difficulties during pregnancy. They also had more frequent PNDS, quarrels with insults within the couple, low sleep time at 2 months postpartum, and more frequently received psychological, social and child caregiver support, and were more often housewives or students at 1-year post-partum. Others factors are specific for low PCS-12 or MCS-12. There was no association with antenatal preventive measure and QOL at 1-year post-partum. CONCLUSION: Factors influencing maternal QOL are multiple and multidimensional and can mostly be identified during the ante or early postnatal period. A graduated and coordinated preventive and curative pathway would improve women's health. An ecosystemic approach to pregnancy and the perinatal period could help preventing the negative effects of environment on mothers and thus infants during the "1000-day period".

Impact of an enhanced screening program on the detection of non-AIDS neoplasias in patients with human immunodeficiency virus infection.

BACKGROUND: The incidence of non-AIDS defining cancer (NADC) is higher in people living with HIV (PLWH) than in the general population, and it is already one of the leading causes of death in the HIV-infected population. It is estimated that the situation will be aggravated by the progressive aging of PLWH. Early diagnosis through intensive cancer screening may improve the ability for therapeutic interventions and could be critical in reducing mortality, but it might also increase expenditure and harms associated with adverse events. The aim of this study is to evaluate an enhanced screening program for early diagnosis of cancer in PLWH compared to standard practice. The specific objectives are (1) to compare the frequency of cancer diagnosed at an early stage, (2) to analyze safety of the enhanced program: adverse events and unnecessary interventions, (3) to analyze the cost-utility of the program, and (4) to estimate the overall and site-specific incidence of NADC in PLWH. METHODS: We will conduct a multicenter, non-blinded, randomized, controlled trial, comparing two parallel arms: conventional vs enhanced screening. Data will be recorded in an electronic data collection notebook. Conventional intervention group will follow the standard of care screening in the participating centers, according to the European AIDS Clinical Society recommendations, and the enhanced intervention group will follow an expanded screening aimed to early detection of lung, liver, anal, cervical, breast, prostate, colorectal, and skin cancer. The trial will be conducted within the framework of the Spanish AIDS Research Network Cohort (CoRIS). DISCUSSION: The trial will evaluate the efficacy, safety, and efficiency of an enhanced screening program for the early diagnosis of cancer in HIV patients compared to standard of care practice. The information provided will be relevant since there are currently no studies on expanded cancer screening strategies in patients with HIV, and available data estimating cost effectiveness or cost-utility of such as programs are scarce. An enhanced program for NADC screening in patients with HIV could lead to early diagnosis and improve the prognosis of these patients, with an acceptable rate of unnecessary interventions, but it is critical to demonstrate that the benefits clearly outweigh the harms, before the strategy could be implemented. TRIAL REGISTRATION: ClinicalTrials.gov NCT04735445. Registered on 25 June 2019.

Liver stiffness change with HCV cure in HIV-infected patients on non-nucleoside analogues.

BACKGROUND: Liver stiffness (LS) at sustained viral response (SVR) is strongly associated with a lower incidence of subsequent hepatic events. HIV NNRTIs may have a beneficial impact on fibrogenesis. OBJECTIVES: Our aim was to analyse the influence of NNRTI-based therapy on the change in LS from starting direct-acting antiviral (DAA) therapy to achieving SVR in HIV/HCV-coinfected patients. METHODS: Three hundred and thirteen HIV/HCV-coinfected patients who fulfilled the following criteria were included: (i) had achieved SVR with an IFN-free, DAA-including regimen; (ii) LS ≥9.5 kPa before therapy; (iii) LS measurement available at SVR; (iv) seronegative for HBsAg; and (v) ART containing 2 NRTIs plus either 1 NNRTI or 1 integrase inhibitor (INI) or 1-2 NRTIs plus 1 PI. LS changes were assessed. RESULTS: Seventy-four patients received NNRTI-based combinations [53 (71.6%) rilpivirine and 16 (21.6%) efavirenz] and 239 patients received other regimens. At baseline, the median (IQR) LS was 16.7 kPa (11.8-25.6) in the NNRTI group and 17.3 kPa (11.9-27.4) in the non-NNRTI group (P = 0.278). The median (IQR) percentage of LS decrease from baseline to SVR was 35.2% (18.2%-52.3%) for NNRTI-based therapy and 29.5% (10%-45.9%) for PI- or INI-based therapy (P = 0.018). In multivariate analysis, adjusted for sex, age, HCV genotype, NRTI backbone and propensity score for HIV therapy, NNRTI-based regimen use was associated with a higher LS decrease [ß = 11.088 (95% CI = 1.67-20.51); P = 0.021]. CONCLUSIONS: Treatment with NNRTI plus 2 NRTI combinations is associated with a higher LS decline than other ART combinations in HIV/HCV-coinfected patients receiving DAA-based therapy.

[Observation and comparison of social abilities in Attention-Deficit/Hyperactivity Disorder and Autism Spectrum Disorder children]. / Étude des altérations des habilités sociales chez des enfants ayant un Trouble Déficit de l'Attention/Hyperactivité : comparatif avec des sujets contrôles et des sujets présentant un Trouble du Spectre de l'Autisme.

OBJECTIVES: Different studies centered on social relationship issues among ADHD children struggled to provide a unicist explanation between primary social cognition process alteration on the one hand and a mere symptomatic outcome of the disorder triad on the other. Some authors support the idea of a potential "social phenotype" shared at a different intensity by Attention Deficit/Hyperactivity Disorder (ADHD) and Autism Spectrum Disorder (ASD). The point of the study is to characterize this possible social disability in a French ADHD population and compare it to control subjects and subjects with Autism Spectrum Disorder (ASD). METHODS: Three groups, composed of 319 subjects aged 6 to 12 years, were recruited in Bordeaux: 88 untreated ADHD subjects, 24 ASD subjects and 207 control subjects. The main measure was the social skill disruption through the rating of the Social Responsiveness Scale (SRS). The ADHD-RS-IV, WFIRS-P and CBCL scales were also used. RESULTS: Asignificant alteration in social abilities in ADHD children in comparison with controls was noted, with an average raw total SRS score intermediary between the control group and the ASD group (respectively 65.31±20.99, 37.15±16.37 and 95 75±30.83, P<0.05). When the 5 sub-scores of the SRS were taken into account, if the ASD subjects showed the highest average scores, the alteration pattern appeared qualitatively similar between the ADHD and TSA groups, with also an intermediate dispersion for the ADHD group between the control group and the group with ASD. Finally, more severe impairment of social skills in children with ADHD was associated with increased severity of the disorder (on ADHD-RS-IV scale cotation), higher daily functional impact (WFIRS-P scale), and more frequent behavioral issues (according to CBCL). CONCLUSIONS: Our results suggest the presence of social disturbances in ADHD and characterize a symptomatic profile qualitatively similar to that of ASD, but of less intensity. Overall results promote a need for a systematic dimensional assessment of social disability in ADHD.

Facial emotion recognition in children with or without Attention Deficit/Hyperactivity Disorder: Impact of comorbidity.

OBJECTIVES: This study sought to assess facial emotion recognition deficit in children with Attention Deficit/Hyperactivity Disorder (ADHD) and to test the hypothesis that it is increased by comorbid features. METHOD: Forty children diagnosed with ADHD were compared with 40 typically developing children, all aged from 7 to 11years old, on a computerized facial emotion recognition task (based on the Pictures of Facial Affect). Data from parents' ratings of ADHD and comorbid symptoms (on the Conners' Revised Parent Rating Scale) were also collected. RESULTS: Children with ADHD had significantly fewer correct answer scores than typically developing controls on the emotional task while they performed similarly on the control task. Recognition of sadness was especially impaired in children with ADHD. While ADHD symptoms were slightly related to facial emotion recognition deficit, oppositional symptoms were related to a decrease in the number of correct answers on sadness and surprise recognition. CONCLUSION: Facial emotion recognition deficit in children with ADHD might be related to an impaired emotional process during childhood. Moreover, Oppositional Defiant Disorder seems to be a risk factor for difficulties in emotion recognition especially in children with ADHD.

Stress, attention deficit hyperactivity disorder (ADHD) symptoms and tobacco smoking: The i-Share study.

BACKGROUND: The contribution of mental health to the risk of smoking is increasingly acknowledged but still insufficiently studied during the key period of student life. In particular, the simultaneous action of stress and Attention Deficit Hyperactivity Disorder (ADHD) symptoms on the risk of smoking remains poorly understood. AIMS: To assess the effects of stress and ADHD symptoms on tobacco smoking. METHOD: Multivariate modeling was conducted on the French i-Share study (n=8110, median age 20.3 years, 74.8% females, 32.9% regular/occasional smokers) to evaluate the associations between stress, ADHD symptoms and tobacco smoking, adjusting for potential family/socio-demographic confounders. RESULTS: Students with high levels of stress were more likely to smoke>10 cigarettes/day (adjusted odds ratio (aOR): 1.48, 95% CI: 1.12-1.96) than those with low levels of stress. Students with high levels of ADHD symptoms were more likely to smoke>10 cigarettes/day (aOR: 2.08, 95% CI: 1.58-2.75) than those with low levels of ADHD symptoms. CONCLUSIONS: Stress and ADHD contribute independently to the risk of smoking. Interventions targeting each condition are likely to reduce the burden of tobacco use in students.

Maternal tobacco smoking in pregnancy and children's socio-emotional development at age 5: The EDEN mother-child birth cohort study.

BACKGROUND: There is debate as to whether maternal tobacco use in pregnancy is related to offspring behaviour later on. We tested this association examining multiple aspects of children's behaviour at age 5 and accounting for parental smoking outside of pregnancy, as well as child and family characteristics. METHODS: Data come from a prospective community based birth cohort study (EDEN; n=1113 families in France followed since pregnancy in 2003-2005 until the child's 5th birthday). Maternal tobacco use in pregnancy was self-reported. Children's socio-emotional development (emotional symptoms, conduct problems, symptoms of hyperactivity/inattention, peer relationship problems, prosocial behaviour) was assessed by mothers using the Strengths and Difficulties Questionnaire (SDQ) at age 5 years. Logistic regression analyses controlled for Inverse Probability Weights (IPW) of maternal tobacco use calculated based on study center, children's characteristics (sex, premature birth, low birth weight, breastfeeding), maternal characteristics (age at the child's birth, psychological difficulties and alcohol use in pregnancy, post-pregnancy depression, and smoking), paternal smoking in and post-pregnancy, parental educational attainment, family income, parental separation, and maternal negative life events. RESULTS: Maternal smoking in pregnancy only predicted children's high symptoms of hyperactivity/inattention (sex and study center-adjusted ORs: maternal smoking in the 1st trimester: 1.95, 95%CI: 1.13-3.38; maternal smoking throughout pregnancy: OR=2.11, 95%CI: 1.36-3.27). In IPW-controlled regression models, only children of mothers who smoked throughout pregnancy had significantly elevated levels of hyperactivity/inattention (OR=2.20, 95%CI: 1.21-4.00). CONCLUSIONS: Maternal tobacco smoking in pregnancy may contribute directly or through epigenetic mechanisms to children's symptoms of hyperactivity/inattention.

Predictors of persistent maternal depression trajectories in early childhood: results from the EDEN mother-child cohort study in France.

BACKGROUND: Maternal depression in the pre- and postpartum period may set women on a course of chronic depressive symptoms. Little is known about predictors of persistently elevated depressive symptoms in mothers from pregnancy onwards. The aims of this study are to determine maternal depression trajectories from pregnancy to the child's fifth birthday and identify associated risk factors. METHOD: Mothers (N = 1807) from the EDEN mother-child birth cohort study based in France (2003-2011) were followed from 24-28 weeks of pregnancy to their child's fifth birthday. Maternal depression trajectories were determined with a semi-parametric group-based modelling strategy. Sociodemographic, psychosocial and psychiatric predictors were explored for their association with trajectory class membership. RESULTS: Five trajectories of maternal symptoms of depression from pregnancy onwards were identified: no symptoms (60.2%); persistent intermediate-level depressive symptoms (25.2%); persistent high depressive symptoms (5.0%); high symptoms in pregnancy only (4.7%); high symptoms in the child's preschool period only (4.9%). Socio-demographic predictors associated with persistent depression were non-French origin; psychosocial predictors were childhood adversities, life events during pregnancy and work overinvestment; psychiatric predictors were previous mental health problems, psychological help, and high anxiety during pregnancy. CONCLUSIONS: Persistent depression in mothers of young children is associated to several risk factors present prior to or during pregnancy, notably anxiety. These characteristics precede depression trajectories and offer a possible entry point to enhance mother's mental health and reduce its burden on children.

Childhood trajectories of inattention, hyperactivity and oppositional behaviors and prediction of substance abuse/dependence: a 15-year longitudinal population-based study.

Numerous prospective studies have shown that children diagnosed with attention deficit/hyperactivity disorder (ADHD) are at higher risk of long-term substance abuse/dependence. However, there are three important limits to these studies: (a) most did not differentiate the role of hyperactivity and inattention; (b) most did not control for associated behavioral problems; and (c) most did not consider females. Our aim was to clarify the unique and interactive contributions of childhood inattention and hyperactivity symptoms to early adulthood substance abuse/dependence. Behavioral problems of 1803 participants (814 males) in a population-based longitudinal study were assessed yearly between 6 and 12 years by mothers and teachers. The prevalence of substance abuse/dependence at age 21 years was 30.7% for nicotine, 13.4% for alcohol, 9.1% for cannabis and 2.0% for cocaine. The significant predictors of nicotine dependence were inattention (odds ratio (OR): 2.25; 95% confidence interval (CI): 1.63-3.11) and opposition (OR: 1.65; 95%: 1.20-2.28). Only opposition contributed to the prediction of cannabis dependence (OR: 2.33; 95% CI: 1.40-3.87) and cocaine dependence (OR: 2.97; 95% CI: 1.06-8.57). The best behavioral predictor of alcohol abuse/dependence (opposition) was only marginally significant (OR: 1.38; 95% CI: 0.98-1.95). Frequent oppositional behaviors during elementary school were clearly the most pervasive predictors of substance abuse/dependence in early adulthood. The association of childhood ADHD with substance abuse/dependence is largely attributable to its association with opposition problems during childhood. However, inattention remained an important predictor of nicotine dependence, in line with genetic and molecular commonalities between the two phenotypes suggested in the literature.

[Aggregation of social deficits and psychiatric disorders in parents of children with autism: toward a temperamental link?]. / Agrégation de déficits sociaux et de troubles psychopathologiques chez les parents de personnes avec autisme : vers une implication du tempérament ?

BACKGROUND: Autism is a group of neurodevelopmental disorders with heterogeneous phenotypic expression. Twin and family-based studies have demonstrated the importance of genetic factors in the etiology of these disorders. The pioneering work of Folstein and Rutter (1977), showing concordance - 82 % in non affected monozygotic twins and 10 % in non affected dizygotic twins - for cognitive deficits (mostly affecting language), has directed work towards family-based studies aiming at demonstrating the existence of a "broad autism phenotype" (BAP), corresponding to the extension of the "autistic" phenotype in the relatives of affected children (Bailey et al., 1998). This notion of a broad phenotype makes it possible to take into account abnormalities in one or more of the three domains of the syndrome: communication, socialization and restrained and obsessive interest in a succession of subjects, with qualitatively similar but quantitatively smaller difficulties observed in the relatives. LITERATURE FINDINGS: We review here previous studies investigating the broad phenotype in the relatives of children with autism. We focus specifically on the hypothesis of a link between the aggregation of social deficits and of psychopathological problems, such problems being more frequently observed in these families than in families with other types of handicap (Abbeduto et al., 2004). Although the difficulties observed in these families may be partly explained by the stress of having to raise a heavily disabled child, genetic susceptibility factors may play a role in the occurrence of these problems in the families of autistic children. Constantino and Todd (2003) support the hypothesis that a single factor is transmitted in families - social reciprocity - and may be responsible for the overall dysfunction in the various domains of the syndrome in affected individuals. However, this susceptibility factor may be linked to other deficits observed in certain psychiatric disorders (e.g., attention deficit in ADHD), consistent with the hypothesis that there is a link between the broad phenotype and psychopathological problems. CONCLUSION: This paper reviews this issue in the two domains of study described and presents a hypothesis to account for the possible link between the presence of the broad phenotype - or more specifically, of social deficits - and the more frequent occurrence of psychological problems in the families of autistic individuals. The notion of temperament (Garon et al., 2009) is proposed and considered to present essential characteristics that might account for this relationship: indeed, temperament is associated with notions of IQ, psychopathology and social function and could potentially be used as a predictive variable in affected individuals. Finally, the link between temperament and psychopathology in the relatives of affected individuals may be reflected in the presence of cognitive peculiarities more specifically linked to socioemotional dysfunction (Losh and Piven, 2007).

Disruptive symptoms in childhood and adolescence and early initiation of tobacco and cannabis use: the Gazel Youth study.

PURPOSE: To examine the link between symptoms of hyperactivity-inattention and conduct disorder in childhood, and the initiation of tobacco and cannabis use, controlling for other behavioral symptoms, temperament and environmental risk factors. METHOD: The sample (N=1107 participants, aged 4 to 18 years at baseline) was recruited from the population-based longitudinal Gazel Youth study with a follow-up assessment 8 years later. Psychopathology, temperament, environmental variables, and initiation of tobacco and cannabis use were self-reported. Event time analyses were performed to assess the effects of childhood disruptive symptoms on age at first use of tobacco and cannabis. RESULTS: Proportional hazard models revealed that participants with high levels of childhood symptoms of both hyperactivity-inattention and conduct disorder were at highest risk of early tobacco initiation (in males: hazard ratio [HR]=2.05; confidence interval [CI]: 1.24-3.38; in females: HR=2.01; CI: 1.31-3.09), and, in males, of early cannabis initiation (HR=1.95; CI: 1.04-3.64). Temperament, through activity in both males and females and negative emotionality in females, was also associated to early substance use initiation. CONCLUSIONS: Children who simultaneously have high levels of symptoms of hyperactivity-inattention and conduct disorder are at increased risk for early substance initiation. These associations may guide childhood health professionals to consider the liability for early substance initiation in high-risk groups.

Severe anaphylaxis to bee venom immunotherapy: efficacy of pretreatment and concurrent treatment with omalizumab.

Immunotherapy is an established mode of treatment for Hymenoptera venom anaphylaxis, although adverse reactions may occur. We report the case of a 33-year-old woman, the wife of a beekeeper, who experienced a systemic allergic reaction following a bee sting. Initial specific immunotherapy had to be stopped due to anaphylaxis (multiple immediate cardiovascular reactions). We looked for an alternative treatment option, and repeated immunotherapy accompanied by the anti-immunoglobulin (Ig) E monoclonal antibody omalizumab. Our new protocol was well tolerated. After 1 year of therapy, the patient was stung by a bee and developed only a slight local reaction, which resolved spontaneously. This result confirmed the success of our specific immunotherapy. We compared our results with those of 6 similar cases in the literature. AntiIgE has provided a treatment option for patients with severe IgE-mediated allergic disease that is difficult to treat. This case suggests that omalizumab may be able to prevent anaphylaxis during immunotherapy.

Childhood and adolescent hyperactivity-inattention symptoms and academic achievement 8 years later: the GAZEL Youth study.

BACKGROUND: Children with attention deficit/hyperactivity disorder (ADHD) are at risk of negative academic outcomes. However, relatively few studies in this area have been based on long-term longitudinal designs and community-based settings. This study examined the link between childhood hyperactivity-inattention symptoms (HI-s) and subsequent academic achievement in a community setting, controlling for other behavioural symptoms, socio-economic status (SES) and environmental factors at baseline. METHOD: The sample consisted of 1264 subjects (aged 12 to 26 years at follow-up) recruited from the longitudinal GAZEL Youth study. Psychopathology, environmental variables and academic outcomes were measured through self-reports. Multivariate modelling was performed to evaluate the effects of childhood HI-s and other risk factors on academic achievement 8 years later. RESULTS: HI-s independently predicted grade retention [adjusted odds ratio (OR) 3.58, 95% confidence interval (CI) 2.38-5.39], failure to graduate from secondary school (adjusted OR 2.41, 95% CI 1.43-4.05), obtaining a lower-level diploma (adjusted OR 3.00, 95% CI 1.84-4.89), and lower academic performance. These results remained significant even after accounting for school difficulties at baseline. Negative academic outcomes were also significantly associated with childhood symptoms of conduct disorder (CD), even after accounting for adjustment variables. CONCLUSIONS: This longitudinal survey replicates, in a general population-based setting, the finding of a link between HI-s and negative academic outcomes.

Hyperactivity-inattention symptoms in childhood and suicidal behaviors in adolescence: the Youth Gazel Cohort.

OBJECTIVE: Although a link has been suggested between attention deficit/hyperactivity disorder (ADHD) and completed suicide, little is known about the association with suicidal behaviors in community settings. This study addresses the relationship between childhood hyperactivity-inattention symptoms (HI-s) and subsequent suicidal behaviors. METHOD: Nine hundred sixteen subjects aged 7-18 were recruited from the general population and surveyed in 1991 and 1999. Parent and adolescent self-reports provided psychopathology and suicidal behavior pattern measures. Multivariate modeling was used to evaluate the effects of childhood HI-s and other risk factors on adolescent suicidal behaviors. RESULTS: In males, HI-s independently accounted for the risk of lifetime suicide plans/attempts (OR=3.25, P = 0.02) and adolescent 12-month prevalence rates of suicide plans/attempts (OR=5.46, P = 0.03). In females, HI-s did not independently heighten the likelihood of suicidal behaviors. CONCLUSION: This survey suggests a possible specific link between HI-s and suicide plans/attempts in males.

Attentive mechanisms in visual search.

Selective attention can be employed to a restricted region in space or to specific objects. Many properties of this attentional window or spotlight are not well understood. In the present study, we examined the question whether the putative shape of the attentional spotlight can be determined by endogenous cueing within a visual search paradigm. Participants searched for a target among distractors, which were arranged within a vertical or horizontal rectangle. The shape of this rectangle was cued endogenously in a valid or invalid way. Response times (RTs) to correct identification of target orientation were recorded. In Experiment 1, the difference between valid and invalid RTs demonstrated that cueing resulted in elongated attentional areas. This was true only for a group of experienced psychophysical participants, whereas a group of inexperienced participants were not able to use cueing in this way. In Experiment 2, the line motion illusion was used to examine the spatial properties of the attended area. The results confirmed for both experienced and inexperienced participants that attention was confined to the cued elongated area only. We present converging evidence for an attentional spotlight whose shape can be adjusted flexibly by appropriate endogenous cueing.

The HCL gene of Medicago truncatula controls Rhizobium-induced root hair curling.

The symbiotic infection of the model legume Medicago truncatula by Sinorhizobium meliloti involves marked root hair curling, a stage where entrapment of the microsymbiont occurs in a chamber from which infection thread formation is initiated within the root hair. We have genetically dissected these early symbiotic interactions using both plant and rhizobial mutants and have identified a M. truncatula gene, HCL, which controls root hair curling. S. meliloti Nod factors, which are required for the infection process, induced wild-type epidermal nodulin gene expression and root hair deformation in hcl mutants, while Nod factor induction of cortical cell division foci was reduced compared to wild-type plants. Studies of the position of nuclei and of the microtubule cytoskeleton network of hcl mutants revealed that root hair, as well as cortical cells, were activated in response to S. meliloti. However, the asymmetric microtubule network that is typical of curled root hairs, did not form in the mutants, and activated cortical cells did not become polarised and did not exhibit the microtubular cytoplasmic bridges characteristic of the pre-infection threads induced by rhizobia in M. truncatula. These data suggest that hcl mutations alter the formation of signalling centres that normally provide positional information for the reorganisation of the microtubular cytoskeleton in epidermal and cortical cells.

Genetic analysis of calcium spiking responses in nodulation mutants of Medicago truncatula.

The symbiotic interaction between Medicago truncatula and Sinorhizobium meliloti results in the formation of nitrogen-fixing nodules on the roots of the host plant. The early stages of nodule formation are induced by bacteria via lipochitooligosaccharide signals known as Nod factors (NFs). These NFs are structurally specific for bacterium-host pairs and are sufficient to cause a range of early responses involved in the host developmental program. Early events in the signal transduction of NFs are not well defined. We have previously reported that Medicago sativa root hairs exposed to NF display sharp oscillations of cytoplasmic calcium ion concentration (calcium spiking). To assess the possible role of calcium spiking in the nodulation response, we analyzed M. truncatula mutants in five complementation groups. Each of the plant mutants is completely Nod- and is blocked at early stages of the symbiosis. We defined two genes, DMI1 and DMI2, required in common for early steps of infection and nodulation and for calcium spiking. Another mutant, altered in the DMI3 gene, has a similar mutant phenotype to dmi1 and dmi2 mutants but displays normal calcium spiking. The calcium behavior thus implies that the DMI3 gene acts either downstream of calcium spiking or downstream of a common branch point for the calcium response and the later nodulation responses. Two additional mutants, altered in the NSP and HCL genes, which show root hair branching in response to NF, are normal for calcium spiking. This system provides an opportunity to use genetics to study ligand-stimulated calcium spiking as a signal transduction event.