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PubMed2004

The Avon Longitudinal Study of Parents and Children (ALSPAC): a resource for genetic epidemiology.

The Avon Longitudinal Study of Parents and Children (ALSPAC) has collected detailed phenotypic and environmental information from pregnancy onwards on approximately 14 000 babies born in 1991-1992. A DNA bank on over 10 000 mothers and children has been established with generic consent for (undisclosed) genetic analysis, and cell lines on both children and parents are planned. As a multigenerational population cohort unselected by disease, trait or exposure, ALSPAC is uniquely placed to explore the genetic and environmental determinants of adverse developmental responses and common disease. Added value for genetic epidemiology generally is the ability to detect distortion of the expected Mendelian 50:50 transmission of alleles to study subjects (e.g. due to differential loss of embryos of one genotype) or to test for heterosis, i.e. whether heterozygotes have a greater or lesser effect than either homozygote. Finally, phenome scans (a fixed format analysis of the associations between a genotype of interest and thousands of outcome variables from the cohort database) could be used as a screening tool to test whether certain classes of genetic variation have more impact than others on human health and development.

Cohort Studies↗
PubMed1997

Childhood antecedents of adult respiratory disease.

This review examines the relations between early childhood lower respiratory symptoms and adult respiratory disease. The problems associated with investigating potential associations between respiratory disease in children and adults are discussed. Some studies have limitations because they are retrospective and early childhood respiratory symptoms have not been accurately diagnosed. Therefore, in this review, particular attention is paid to longitudinal studies (some from birth) that have used strict diagnostic criteria for respiratory episodes. These studies provide unique insights into the risk factors for the development of childhood respiratory problems and for persistence of symptoms into adulthood. Although cross-sectional studies have indicated that early childhood respiratory disease is more frequent in adults with respiratory disease, evidence from longitudinal studies suggests that respiratory symptoms such as wheezing, are transient in the majority of infants and result from developmentally small airways. These longitudinal investigations have also indicated that persistence of symptoms into later childhood is associated with atopy. The important role of cigarette-smoke exposure as a risk factor for abnormal pulmonary development, persistence of respiratory disease and reduction in lung function is discussed. The discovery of genetic markers associated with respiratory syndromes such as asthma, should facilitate studies that investigate the childhood antecedents of adult respiratory disease. Future longitudinal studies using genetic markers, will allow relations between specific genotypes and phenotypic outcomes to be examined.

Adult↗
PubMed2006

Early learning and adaptive behaviour in toddlers with Down syndrome: evidence for an emerging behavioural phenotype?

BACKGROUND: Though the Down syndrome behavioural phenotype has been described as involving relative strengths in visuo-spatial processing and sociability, and relative weaknesses in verbal skills and motor planning, the early emergence of this phenotypic pattern of strengths and weaknesses has not yet been fully explored. METHOD: In this study, we compared the performance of eighteen 2 to 3-year-olds with Down syndrome to an MA-matched comparison group of nineteen 2 to 3-year-olds with mixed developmental disabilities, and an MA-matched comparison group of 24 children with typical development on two developmental measures: the Mullen Scales of Early Learning and the Vineland Adaptive Behaviour Scales. RESULTS: While the specificity of the Down syndrome profile was (for the most part) not yet evident, results showed that toddlers with Down syndrome in this study did show emerging areas of relative strength and weakness similar to that which has been described in older children and young adults with Down syndrome. This pattern included relatively stronger social skills, weaker expressive language, and poor motor coordination. When this pattern of strengths and weaknesses was compared to the developmental profiles of the two comparison groups, socialisation strengths differentiated the Down syndrome group from the mixed developmental disabilities group.

Adaptation, Psychological↗
PubMed1998

Individual differences in P300 amplitude: a genetic study in adolescent twins.

Using quantitative genetic research designs, we decomposed phenotypic variance in P300 parameters into genetic and environmental components. The twin method was used to carry out this decomposition. Event related potentials (ERPs) were measured during a visual oddball paradigm in a sample of 213 adolescent twin pairs. The presence of male and female same-sex and opposite-sex twins in the sample enabled us to study sex differences in the contributions of genetic and environmental effects to P300 parameters. For targets and nontargets, half of the variance in the P300 amplitude is attributable to factors shared by the family members. However, it remains unclear whether this resemblance is attributable to shared environmental or genetic influences. The same factors (genetic or shared environmental) were found to contribute to the individual differences in males and females. The contributions do, however, differ across gender. Multivariate genetic analyses investigated the covariance among various brain areas to determine whether the covariance between two or more leads is attributable to the same genetic and/or the same environmental factors. The covariance of the P300 amplitude measured at different locations was attributable both to unshared environmental and to shared factors. Again it was not possible to show that the shared factors where either genetic or shared environmental.

Adolescent↗
PubMed2006

Clinical and genetic findings in 26 Italian patients with Lafora disease.

PURPOSE: EPM2B mutations have been found in a variable proportion of patients with Lafora disease (LD). Genotype-phenotype correlations suggested that EPM2B patients show a slower course of the disease, with delayed age at death, compared with EPM2A patients. We herein report clinical and genetic findings of 26 Italian LD patients. METHODS: Disease progression was evaluated by means of a disability scale based on residual motor and cognitive functions and daily living and social abilities, at 4 years from the onset. Mutational analysis was performed by sequencing the coding regions of the EPM2A and EPM2B genes. RESULTS: Age at onset ranged from 8.5 to 18.5 years (mean, 13.7+/-2.6). The mean duration of follow-up was 7.1+/-3.9 years. Daily living activities and social interactions were preserved in five of 24 patients. The remaining patients showed moderate to extremely severe limitations of daily living and social abilities. Sixteen (72%) of 22 families showed mutations in the EPM2B gene, and five (22%), in the EPM2A gene. One family showed no mutations. A novel EPM2B mutation also was identified. CONCLUSIONS: In our series, EPM2B mutations occurred in 72% of families, thus indicating that EPM2B is the major gene for LD in the Italian population. Moreover, we found that six of 17 EPM2B patients preserved daily living activities and social interactions at 4 years from onset, suggesting a slow disease progression. Additional clinical and functional studies will clarify whether specific mutations may influence the course of the disease in LD patients.

Activities of Daily Living↗
PubMed1999

Growth retardation in Turner syndrome: aneuploidy, rather than specific gene loss, may explain growth failure.

The etiology of short stature (SST) in Turner syndrome (TS) is still a subject of speculation. A variety of hypotheses have been put forward, from SST as a result of increased intrauterine tissue pressure after fetal lymphedema to haploinsufficiency of a specific growth gene(s). These hypotheses have various statistical-auxological implications on the growth distribution in TS. Empirical research has provided no clear evidence for any of these theories, but the well known correlation between patients' and midparental height (MPH) could be established. The influence of undetected mosaic status has often been cited as a major problem in the investigation of growth in TS. However, an assessment of mosaic status (simultaneous analysis of karyotype and phenotype) and its effect on growth with inclusion of MPH has been not yet carried out for a large sample. The aim of this study was to evaluate growth and its complex relationship to mosaic status and MPH in TS. In a mixed cross-sectional and longitudinal study we retrospectively analyzed the auxological and clinical data of 447 patients with a pure loss of X-chromosomal material (n = 381 with 45,X0; n = 66 mosaics). The 447 patients were selected from a series of 609 consecutive patients with TS. To assess the effect of mosaic status on growth, we computed a bifactorial analysis of variance (phenotype, karyotype), including MPH as a covariate. In line with the mosaic hypothesis, we found a correlation between individual loss of X-chromosomal material and phenotypical expressivity. In contrast, no correlation was found with respect to growth. With respect to MPH, we found growth retardation (GR) even in those patients with "normal" height above the third percentile (-2 or more SD score). The interindividual variance of GR in TS (comparable to growth variance in the normal population) seems to be unrelated to other TS-specific factors (e.g. mosaic status or single gene loss). Instead, both interindividual variance and the global growth shift distribution are best explained by the presence of an unspecific aneuploidic effect. Furthermore, consideration of patient height in relation to MPH should lead to a better understanding of the nature of GR in TS than the commonly used, strictly qualitative definition of SST.

Adolescent↗
PubMed2002

Does education mediate the relationship between IQ and age of first birth? A behavioural genetic analysis.

This study presents a multivariate behavioural genetic analysis of the relationship between education, intelligence and age of first birth. Analyses investigated the mediational role of education in explaining the relationship between intelligence and age of first birth at both the phenotypic and behavioural genetic level. The data come from the National Longitudinal Survey of Youth (NLSY), a nationally representative survey that included genetically informative full- and half-sibling pairs (n = 1423 pairs). Respondents were aged 14 to 22 when contacted in 1979. Heritability estimates were 0.32, 0.50 and 0.06 for IQ, education and age of first birth, respectively. Shared environment estimates were 0.35, 0.23 and 0.20 respectively. Common genetic and shared environmental factors were substantial in explaining the relationship between intelligence and education, and also education and age of first birth. Education partially mediated the relationship between intelligence and age of first birth only in the phenotypic analyses. After considering the genetic and shared environmental factors that influence all three variables, evidence for mediation was less convincing. This pattern of results suggests that the apparent mediational role of education at the phenotypic level is in fact the result of underlying genetic and shared environmental influences that affect education, IQ and age of first birth in common.

Adolescent↗
PubMed2002

Evolution of phenotypic drug susceptibility and viral replication capacity during long-term virologic failure of protease inhibitor therapy in human immunodeficiency virus-infected adults.

Continued use of antiretroviral therapy despite the emergence of drug-resistant human immunodeficiency virus (HIV) has been associated with the durable maintenance of plasma HIV RNA levels below pretherapy levels. The factors that may account for this partial control of viral replication were assessed in a longitudinal observational study of 20 HIV-infected adults who remained on a stable protease inhibitor-based regimen despite ongoing viral replication (plasma HIV RNA levels consistently >500 copies/ml). Longitudinal plasma samples (n = 248) were assayed for drug susceptibility and viral replication capacity (measured by using a single-cycle recombinant-virus assay). The initial treatment-mediated decrease in plasma viremia was directly proportional to the reduction in replicative capacity (P = 0.01). Early virologic rebound was associated the emergence of a virus population exhibiting increased protease inhibitor phenotypic resistance, while replicative capacity remained low. During long-term virologic failure, plasma HIV RNA levels often remained stable or increased slowly, while phenotypic resistance continued to increase and replicative capacity decreased slowly. The emergence of primary genotypic mutations within protease (particularly V82A, I84V, and L90M) was temporally associated with increasing phenotypic resistance and decreasing replicative capacity, while the emergence of secondary mutations within protease was associated with more-gradual changes in both phenotypic resistance and replicative capacity. We conclude that HIV may be constrained in its ability to become both highly resistant and highly fit and that this may contribute to the continued partial suppression of plasma HIV RNA levels that is observed in some patients with drug-resistant viremia.

Adult↗
PubMedDate not supplied

Recent results in ataxia research.

Five families with late onset spinocerebellar ataxia (SCA) were studied. A high association was found between the disease and HLA. A stronger association results with a marker called D6S89. Clinical data of 26 patients and neuropathological study in two are reported. The clinical phenotypes of other HLA-linked SCA kindreds shows differences when comparison is made. The Authors suggest that the phenotype might appear more homogeneous if disease duration is taken into account.

Adult↗
PubMed1998

Association between apolipoprotein E epsilon4 and the rate of cognitive decline in community-dwelling elderly individuals with and without dementia.

OBJECTIVE: To determine whether the apolipoprotein E epsilon4 allele (apoE epsilon4) is associated with cognitive decline in individuals with and without dementia, we conducted a 4-year longitudinal study of subjects with a range of cognitive function. SETTING: At baseline, respondents (n=511) were randomly selected according to age and Mini-Mental State Examination score from a community-based study of dementia among noninstitutionalized persons aged 65 to 84 years. Respondents were examined at baseline and followed up in 3 annual visits. At baseline, subjects were classified as having normal cognitive function, minimal dementia, or dementia, according to criteria from the Cambridge Examination for Mental Disorders of the Elderly (CAMDEX) and the Diagnostic and Statistical Manual of Mental Disorders, Revised Third Edition. Of the 511 respondents at baseline, 405 who were examined at least 2 times are included in this analysis. MAIN OUTCOME MEASURES: Cognitive decline was determined by a slope estimating yearly change in score on the neuropsychological test, the CAMCOG (the cognitive section of the CAMDEX), and its sub-scales of memory and nonmemory functions. RESULTS: Among the subjects who had normal cognitive function at baseline, apoE epsilon4 carriers showed a significantly greater decline (P<.001) in score on the CAMCOG compared with noncarriers. Differences in decline on the memory and nonmemory subtests were also significant (P<.001). Rates of cognitive decline were not related to apoE epsilon4 status in the groups with minimal dementia and dementia. CONCLUSIONS: In our community-based sample, apoE epsilon4 was associated with the rate of cognitive decline prior to the clinically symptomatic phase of dementia. Knowing the apoE epsilon4 status of those already symptomatic for dementia may not improve knowledge about a patient's prognosis.

Aged↗
PubMed2006

Individual differences in puberty onset in girls: Bayesian estimation of heritabilities and genetic correlations.

: We report heritabilities for individual differences in female pubertal development at the age of 12. Tanner data on breast and pubic hair development in girls and data on menarche were obtained from a total of 184 pairs of monozygotic and dizygotic twins. Genetic correlations were estimated to determine to what extent the same genes are involved in different aspects of physical development in puberty. A Bayesian estimation approach was taken, using Markov-chain Monte Carlo simulation to estimate model parameters. All three phenotypes were to a significant extent heritable and showed high genetic correlations, suggesting that a common set of genes is involved in the timing of puberty in general. However, gonadarche (menarche and breast development) and adrenarche (pubic hair) are affected by different environmental factors, which does not support the three phenotypes to be regarded as indicators of a unitary physiological factor.

Bayes Theorem↗
PubMed2006

Genetic analysis of anger: genetic dominance or competitive sibling interaction.

The knowledge of the causes and development of anger is still scarce. Previous studies on the sources of variance on Type A Behavior Pattern (TABP) related measures found variable heritability estimates ranging from 0.12 to 0.68, and large differences between MZ and DZ correlations. Some authors considered dominance genetic effects, competitive sibling interaction and sex differences as possible mechanisms to explain the results, but most studies lacked power. The present study uses a large sample of more than 2,500 families, with longitudinal data from MZ and DZ pairs as well as their parents, to disentangle the sources of variance on anger. Model Fitting results showed that the sources of variance differ across sexes. For males 23% of the variance is due to additive genetic effects, and 26% to dominance genetic effects. For females 34% of the variance is due to additive genetic effects, and no dominance effects are found. There was no consistent evidence to confirm the presence of competitive sibling interaction as an alternative explanation for the low correlations in DZ males. The focus of research on the prediction of coronary heart disease (CHD) risk through psychological characteristics has recently changed from the multidimensional TABP to its emotional component: Anger. Understanding the sources of individual differences on anger can help to clarify the mechanisms that link it with CHD and its possible implications for treatment and prevention.

Adolescent↗
PubMed2005

Association between the 5HT1B receptor gene (HTR1B) and the inattentive subtype of ADHD.

BACKGROUND: Preclinical and genetic studies have implicated the 5HT1B receptor gene (HTR1B) in attention-deficit/hyperactivity disorder (ADHD). Association with a single nucleotide polymorphism (SNP; G861C) has been observed, but more extensive linkage disequilibrium analyses have not been reported. METHODS: To examine haplotype structure, we genotyped 21 SNPs in and around the gene in 12 multigenerational CEPH pedigrees. We identified a haplotype block encompassing HTR1B and performed haplotype and single-marker association analyses for the eight SNPs within or flanking this block in 229 families of ADHD probands. In light of previous studies suggesting distinct genetic influences on ADHD subtypes, we also examined association with the inattentive and combined subtypes. RESULTS: We observed nonsignificant overtransmission of the G861 allele to ADHD offspring (one-tailed p = .07). Single-marker and haplotype tests of a haplotype block encompassing HTR1B revealed no other associations with ADHD. However, this haplotype block was associated with the inattentive subtype (global p < .01). Additionally, three SNPs in this block were nominally (p < .05) associated with the inattentive subtype, although these did not remain significant after correction for multiple testing. As reported in previous studies, we found paternal overtransmission of the G861 allele to offspring with ADHD; this appeared to be largely attributable to inattentive cases. CONCLUSIONS: These analyses suggest that variation in the HTR1B gene may primarily affect the inattentive subtype of ADHD.

Adolescent↗
PubMed2005

B lymphocyte reconstitution after hematopoietic stem cell transplantation: functional immaturity and slow recovery of memory CD27+ B cells.

OBJECTIVE: Functional recovery of B lymphocytes after hematopoietic stem cell transplantation (HSCT) can take up to 2 years. HSCT recipients may obtain protective titers of pathogen-specific antibody through vaccination, but optimal timing of reimmunization remains to be defined. PATIENTS AND METHODS: In this study, we evaluated the reconstitution of B-cell number and activity in 139 children given HSCT, by B-cell subset phenotyping and in vitro immunoglobulin (Ig) production. RESULTS: Patients were longitudinally studied at 3, 6, 12, and 18 to 24 months after transplantation. At all time points, recipients displayed a significantly higher percentage of naive (IgD+CD27-) B cells and showed significantly lower production of stimulated in vitro Ig as compared to healthy controls. Moreover, during follow-up, we observed an increase in the proportion of patients who had CD27+ B subsets and who were able to mount in vitro Ig production greater than the 5th percentile. CONCLUSION: Similar to what has been described in adults, most children lack memory B cells and produce low amounts of Ig. However, the number of B cells, as well as their function, gradually recovered over time and the spread of data we observed suggests that the reimmunization schedule should be individualized for each patient. It remains to be defined in a prospective clinical study the time point at which a patient should start reimmunization. A reasonable hypothesis to be explored is the time point at which a percentage of memory B cells greater than the 5th percentile of normal controls is reached.

Adolescent↗
PubMed2006

Impact of obesity on cardiac geometry and function in a population of adolescents: the Strong Heart Study.

OBJECTIVES: The goal here was to examine left ventricular (LV) geometry and function in a large, unselected group of adolescents with different degrees of abnormal body build, and verify whether possibly higher LV mass is compensatory for increased cardiac workload. BACKGROUND: There is little information on how much the excess of body weight impacts LV geometry and function in populations of adolescents. METHODS: Anthropometric, laboratory, and Doppler echocardiographic parameters of cardiac geometry and function were obtained in 460 adolescent participants (age 14 to 20 years, 245 female participants, 27 hypertensive, 10 with diabetes) from the Strong Heart Study. Body build was classified based on 85th and 95th percentiles of body mass index (BMI)-for-age charts. RESULTS: Range of BMI was 16.3 to 56.5 kg/m2 (28.8 +/- 8.3 kg/m2); 114 participants (24.9%) fell within the 85th percentile of BMI distribution (normal weight [NW]), 113 (24.6%) fell between 85th and 95th percentile (overweight [OW]), and 223 (48.5%) fell above the 95th percentile (obese [OB]). Obese participants were older than OW and NW subjects (p < 0.01), without differences in heart rate. Both OW and OB had greater LV diameter and mass than NW (all p < 0.05). Left ventricular hypertrophy was more prevalent in the OB (33.5%) and OW (12.4%), as compared with NW participants (3.5%; p < 0.001), largely compensating increased cardiac workload. However, OB subjects had four-fold higher probability of carrying an LV mass exceeding values compensatory for their cardiac workload (p < 0.001), a feature associated with lower ejection fraction, myocardial contractility, and greater force developed by left atrium to complete LV filling (all p < 0.05). CONCLUSIONS: While in OW adolescents increased levels of LV mass are appropriate to compensate their higher hemodynamic load, in OB increase in LV mass exceeds this need and is associated with mildly reduced LV myocardial performance and increased left atrial force to contribute to LV filling.

Adaptation, Physiological↗
PubMed2002

Electroencephalographic sleep profiles in single-episode and recurrent unipolar forms of major depression: II. Comparison during remission.

BACKGROUND: Previous studies indicate that recurrent forms of depression are associated with greater biological disturbances as compared to single-episode cases. This study examines whether the observed differences in the sleep patterns during recurrent and single-episode depression persist into remission following nonpharmacologic treatment. METHODS: Two groups of patients (27 single episode [SE] and 53 recurrent unipolar [RU]) with major depression underwent sleep studies before and after nonpharmacologic treatment. Groups were equated for age, severity, and proportion of men and women. Groups were compared using multivariate analyses of covariance and/or analyses of covariance to examine six sets of sleep measures. RESULTS: The differences observed between the SE and RU groups during the index episode persisted into early remission. The findings of greater disturbances of sleep continuity, rapid eye movement sleep and diminished slow wave sleep in the RU group supports the hypothesis that recurrent depression is associated with a more severe neurophysiological substrate than clinically comparable SE cases. CONCLUSIONS: Although these observations are consistent with an illness progression model, the possibility that recurrent affective illness is associated with a more virulent, stable phenotype cannot be ruled out. Resolution of this issue requires longitudinal and family studies.

Adult↗
PubMed2001

Spreading of HIV-specific CD8+ T-cell repertoire in long-term nonprogressors and its role in the control of viral load and disease activity.

Long-term non-progressors (LTNP) represent a minority of human immunodeficiency virus (HIV) infected individuals characterized by stable or even increasing CD4+ T-cell count and by stronger immune responses against HIV than progressors. In this study, HIV-specific effector CD8+ T cells, as detected by both a sensitive ex vivo enzyme-linked immunospot (ELISPOT) assay and specific major histocompatibility complex (MHC) peptide tetramers, were at a low frequency in the peripheral blood of LTNP, and recognized a lower number of HIV peptides than their memory resting cell counterparts. Both factors may account for the lack of complete HIV clearance by LTNP, who could control the viral spread, and displayed a higher magnitude of cytotoxic T lymphocyte (CTL) responses than progressors. By combining cell purification and ELISPOT assays this study demonstrates that both effector and memory resting cells were confined to a CD8+ population with memory CD45RO+ phenotype, with the former being CD28- and the latter CD28+. Longitudinal studies highlighted a relatively stable HIV-specific effector repertoire, viremia, and CD4+ T-cell counts, which were all correlated with maintenance of nonprogressor status. In conclusion, the analysis of HIV-specific cellular responses in these individuals may help define clear correlates of protective immunity in HIV infection.

Adult↗
PubMed2002

Analysis of epidemiological studies: facts and artifacts.

Cohort studies have provided the foundation for much of our knowledge of childhood asthma. Four important lessons have been learned from these longitudinal studies: that asthma is a complex disease, encompassing many phenotypes; that it is linked to the development of the immune system and respiratory tract in the first years of life; that early life events strongly affect the development of asthma risk and that relationships between certain exposures and asthma risk are age dependent. The Tucson Children's Respiratory Study is used to exemplify these lessons and to illustrate the advantages of cohort studies in investigating a complex disease.

Animals↗