Annotation: behavioural phenotypes: a window onto the biology of behaviour

Using Alternative Definitions of Controls to Increase Statistical Power in GWAS

Genome-wide association studies (GWAS) are often underpowered due to small effect sizes of common single nucleotide polymorphisms (SNPs) on phenotypes and extreme multiple testing thresholds. The most common approach for increasing statistical power is to increase sample size. We propose an alternative strategy of redefining case-control outcomes into ordinal case-subthreshold-asymptomatic variables. While maintaining the clinical case threshold, we subdivide controls into two groups: individuals who are symptomatic but do not meet the clinical criteria for diagnosis (subthreshold) and individuals who are effectively asymptomatic. We conducted a simulation study to examine the impact of effect size, minor allele frequency, population prevalence, and the prevalence of the subthreshold group on statistical power to detect genetic associations in three scenarios: a standard case-control, an ordinal, and a case-asymptomatic control analysis. Our results suggest the ordinal model consistently provides the greatest statistical power while the case-control model the least. Power in the case-asymptomatic control model reflects the case-control or ordinal model depending on the population prevalence and size of the subthreshold category. We then analyzed a major depression phenotype from the UK Biobank to corroborate our simulation results. Overall, the ordinal model improves statistical power in GWAS consistent with increasing the sample size by approximately 10%.

Using Alternative Definitions of Controls to Increase Statistical Power in GWAS

Genome-wide association studies (GWAS) are underpowered due to small effect sizes of single nucleotide polymorphisms (SNPs) on phenotypes and extreme multiple testing thresholds. The most common approach for increasing statistical power is to increase sample size. We propose an alternative strategy of redefining case-control outcomes into ordinal case-subthreshold-asymptomatic variables. While maintaining the clinical case threshold, we subdivide controls into two groups: individuals who are symptomatic but do not meet the clinical criteria for diagnosis (subthreshold) and individuals who are effectively asymptomatic. We conducted a simulation study to examine the impact of effect size, minor allele frequency, population prevalence, and the prevalence of the subthreshold group on statistical power to detect genetic associations in three scenarios: a standard case-control, an ordinal, and a case-asymptomatic control analysis. Our results suggest the ordinal model consistently provides the most statistical power while the case-control model the least. Power in the case-asymptomatic control model reflects the case-control or ordinal model depending on the population prevalence and size of the subthreshold category. We then analyzed a major depression phenotype from the UK Biobank to corroborate our simulation results. Overall, the ordinal model improves statistical power in GWAS consistent with increasing the sample size by approximately 10%.

The behavioral phenotype of Rubinstein-Taybi syndrome: A scoping review of the literature

Rubinstein-Taybi syndrome (RTS) is a rare genetic syndrome associated with growth delay, phenotypic facial characteristics, microcephaly, developmental delay, broad thumbs, and big toes. Most research on RTS has focused on the genotype and physical phenotype; however, several studies have described behavioral, cognitive, social, and emotional characteristics, elucidating the behavioral phenotype of RTS. The reporting of this review was informed by PRISMA guidelines. A systematic search of CINAHL, Medline, and PsychINFO was carried out in March 2021 to identify group studies describing behavioral, cognitive, emotional, psychiatric, and social characteristics in RTS. The studies were quality appraised. Characteristics reported include repetitive behavior, behaviors that challenge, intellectual disability, mental health difficulties, autism characteristics, and heightened sociability. Findings were largely consistent across studies, indicating that many characteristics are likely to form part of the behavioral phenotype of RTS. However, methodological limitations, such as a lack of appropriate comparison groups and inconsistency in measurement weaken these conclusions. There is a need for multi-disciplinary studies, combining genetic and psychological measurement expertise within single research studies. Recommendations are made for future research studies in RTS.

Behavioural and psychological features of PTEN mutations: a systematic review of the literature and meta-analysis of the prevalence of autism spectrum disorder characteristics

BACKGROUND

Phosphatase and tensin homologue (PTEN) is a cancer suppressor gene. Constitutional mutations affecting this gene are associated with several conditions, collectively termed PTEN hamartoma tumour syndromes (PHTS). In addition to hamartomas, PTEN aberrations have been associated with a range of non-tumoural phenotypes such as macrocephaly, and research indicates possibly increased rates of developmental delay and autism spectrum disorder (ASD) for people with germline mutations affecting PTEN.

METHOD

A systematic review of literature reporting behavioural and psychological variables for people with constitutional PTEN mutations/PHTS was conducted using four databases. Following in-depth screening, 25 articles met the inclusion criteria and were used in the review. Fourteen papers reported the proportion of people with PTEN mutations/PTHS meeting criteria for or having characteristics of ASD and were thus used in a pooled prevalence meta-analysis.

RESULTS

Meta-analysis using a random effects model estimated pooled prevalence of ASD characteristics at 25% (95% CI 16-33%), although this should be interpreted cautiously due to possible biases in existing literature. Intellectual disability and developmental delay (global, motor and speech and language) were also reported frequently. Emotional difficulties and impaired cognitive functioning in specific domains were noted but assessed/reported less frequently. Methods of assessment of psychological/behavioural factors varied widely (with retrospective examination of medical records common).

CONCLUSIONS

Existing research suggests approximately 25% of people with constitutional PTEN mutations may meet criteria for or have characteristics of ASD. Studies have also begun to establish a range of possible cognitive impairments in affected individuals, especially when ASD is also reported. However, further large-scale studies are needed to elucidate psychological/behavioural corollaries of this mutation, and how they may relate to physiological/physical characteristics.

Cognitive performance change of pediatric patients after conducting frontal transcortical approach to treat lateral ventricular tumor

OBJECTIVE

Applying frontal transcortical approach to treat lateral ventricular tumor is one of the most common neurosurgical manipulations. The frontal transcortical approach generally passes through the middle frontal gyrus in which there is no major function involved in the traditional sense. However, current researches have suggested that the prefrontal cortex (PFC) plays a central role in the whole network of the brain cognitive frame. In addition, cognitive function is crucial in growing and developmental stages and essential for the educational achievement, especially for children. Based on this, the authors in this study analyzed cognitive performance change of pediatric patients who had accepted frontal transcortical operation in 1-year follow-up and discussed the possibility of higher cognitive functions of the damaged region.

PATIENTS AND METHODS

In this single-center study, 15 pediatric patients (median age at surgery, 9.21 years old; range, 6.42-14.17 years old) who had been treated with frontal transcortical approach for lateral ventricular tumors were selected as research objects. The cognitive function assessment was conducting by adopting the revised Wechsler Intelligence Scale for Children-fourth edition (WISC-IV). In addition, the resting-state functional magnetic resonance imaging (resting-state fMRI) and diffusion tensor imaging (DTI) were carried out to measure the level of co-activation and to explore the functional connectivity between the brain regions at the preoperative period and 1-year follow-up after surgery.

RESULTS

GTR was achieved in all patients, and all patients were in good condition after surgery. Compared to the preoperative indices of WISC-IV, patients generally had a lower level of indices of the WISC-IV after surgery, for example, the total IQ was declined to M = 83.60, SD = 9.500 from M = 95.33, SD = 13.844 within 1 year convalescence. The data of perceptual reasoning (t = - 2.392, p = 0.016), processing speed (t = - 2.121, p = 0.033), and total IQ (t = -2.638, p = 0.008) before and after surgery showed statistically significance. Furthermore, decreased functional connectivity and disconnected neural fasciculus were revealed by the size of activation regions in the resting-state fMRI and the reconstruction of three-dimensional images of white matter tracts in the DTI pre- and post-operative.

CONCLUSION

The PFC was not regarded as a major functional area in the past, but the researches at present have shown that the interactions between PFC and other posterior brain regions serve as the basis of the higher cognitive functions. According to imaging manifestations and WISC-IV tasks in this paper, we found that the PFC injury caused by the frontal transcortical approach led to damaged brain structure and impaired the performance of cognitive function. On this basis, we detected that the perceptual reasoning and processing speed maybe have more extensive connections with the middle frontal gyrus.

Abnormal Sleep Patterns Associated with Autism

Statements have recurrently been made about the high rate of sleep problems reported in children with autism, particularly difficulty initiating and maintaining sleep at appropriate times of the night and day. Autism itself is frequently associated with the presence of learning disability and a variety of other medical conditions. These often coexisting factors are themselves associated with sleep abnormalities and therefore caution is needed when attempting to assess the relationship between autism and sleep abnormalities. Detailed consideration of the various possible causes of sleep problems is required to reach meaningful diagnostic and treatment decisions. The present account reviews the published work on sleep disturbance and autism, highlighting theoretical and practical issues which need further attention. Methods of assessing and treating sleep disorders are also discussed, with special consideration of factors related to autism which may affect the choice of method.

Behavioural phenotypes of the mucopolysaccharide disorders: a systematic literature review of cognitive, motor, social, linguistic and behavioural presentation in the MPS disorders

BACKGROUND

The mucopolysaccharide disorders (MPS) are a group of recessively inherited metabolic disorders resulting in progressive physical and cognitive decline.

MATERIALS AND METHODS

MEDLINE, PsycINFO and Embase databases were searched, alongside manual screening, to identify relevant literature. Papers were included in the review if they were published in a peer reviewed journal and conducted empirical research into cognitive, motor, social or linguistic development or behaviour in one or more MPS disorders.

RESULTS

Twenty-five papers were reviewed. Two papers used methodology of a sufficiently high standard to demonstrate a behavioural phenotype; both found sleep disturbance to be part of the phenotype of MPS III. Fearfulness and sleep disturbance were frequently observed in people with MPS I and II. Cognitive and motor impairment and decline, and challenging behaviour were highly prevalent in the severe form of MPS II. Cognitive decline and severe behavioural problems relating to aggression, hyperactivity, orality, unusual affect and temper tantrums were seen in MPS III.

CONCLUSIONS

Sleep disturbance is part of the behavioural phenotype of MPS III, and challenging behaviour is highly prevalent in MPS II and MPS III, therefore the efficacy of behavioural interventions for these populations should be investigated. Further research into the behaviour and adaptive skills of children with MPS III and MPS IV is required.

Behavioural phenotypes: An emerging specialist role for nurses

The idea that behaviour can be influenced by genetics is not new and developments in the field of behavioural genetics suggest this is an area of increasing relevance to healthcare professionals who support people who have learning disabilities associated with genetic disorders. This paper considers both the evidence for behavioural phenotypes and the possible roles healthcare professionals have when supporting affected individuals and their families. The paper argues that nurses in all areas of health care need to have a foundation of skill and knowledge of behavioural phenotypes to ensure effective care is provided for individuals and their families. In addition, the paper proposes that a specialist nursing role is essential in providing direct support to clients and their families as well as in providing a consultancy and educational role to the health and social care professionals who support these families.

Analysis of quantitative trait loci that influence animal behavior

Behavioral differences between inbred strains of mice and rats have a genetic basis that can now be dissected using quantitative trait locus (QTL) analysis. Over the last 10 years, a large number of genetic loci that influence behavior have been mapped. In this article I review what that information has revealed about the genetic architecture of behavior. I show that most behaviors are influenced by QTL of small effect, each contributing to less than 10% of the variance of a behavioral trait. The small effect of each QTL on behavioral variation suggests that the mutational spectrum is different from that which results in Mendelian disorders. Regions of DNA should be appropriately prioritized to find the molecular variants, for instance by looking at sequences that control the level of gene expression rather than variants in coding regions. While the number of allelic loci that can contribute to a trait is large, this is not necessarily the case: the analysis of selected strains shows that a remarkably small number of QTL can explain the bulk of the genetic variation in behavior. I conclude by arguing that genetic mapping has more to offer than a starting point for positional cloning projects. With advances in multivariate analyses, mapping can also test hypotheses about the psychological processes that give rise to behavioral variation.

The Rett Syndrome Behaviour Questionnaire (RSBQ): refining the behavioural phenotype of Rett syndrome

BACKGROUND

Although physical features, including loss of hand skills, deceleration of head growth, spasticity and scoliosis, are cardinal features of Rett syndrome (RS), a number of behavioural features are also associated with the disorder, including hand stereotypies, hyperventilation and breath holding. No study has tested the specificity of these behavioural features to individuals with RS, compared to individuals with severe to profound mental retardation (SMR).

METHOD

A novel checklist of characteristic RS behavioural and emotional features, the Rett Syndrome Behaviour Questionnaire (RSBQ), was developed to test the type and specificity of behavioural features of RS against those found in girls with SMR.

RESULTS

After controlling for the effects of RS-related physical disabilities, the RSBQ discriminated between the groups. Some aspects of the behaviours found to be specific to RS are included in the necessary or supportive RS diagnostic criteria, notably hand behaviours and breathing problems. Additional behavioural features were also more frequently reported in the RS than the SMR group, including mood fluctuations and signs of fear/anxiety, inconsolable crying and screaming at night, and repetitive mouth and tongue movements and grimacing.

CONCLUSIONS

Full validation of the scale requires confirmation of its discriminatory power and reliability with independent samples of individuals with RS and SMR. Further delineation of the specific profile of behaviours seen in RS may help in identification of the function of the MECP2 gene and in improved differential diagnosis and management of individuals with RS.

Behaviour problems in adult women with Rett syndrome

BACKGROUND

Despite considerable interest in the genetic, physical and neurological aspects of Rett syndrome (RS), there have been few studies of associated behavioural and emotional features. Furthermore, few case studies or surveys have included adult women with RS. The main aim of the present study was to compare behaviour problems in a sample of women with RS against data from normative samples.

METHODS

The primary carers of 50 women with RS completed the community version of the Aberrant Behavior Checklist.

RESULTS

Women with RS were rated as having lower levels of irritability, hyperactivity and inappropriate speech behaviours than normative samples of adults with intellectual disability.

CONCLUSIONS

A number of factors may affect the presentation of behaviour problems in women with RS (e.g. cognitive impairments or physical disabilities). Therefore, more research is needed in order to generate information about the behavioural phenotype of RS. The implications of the present data for future research are also discussed.

Different approaches to relating genotype to phenotype in developmental disorders

In this article, we discuss the complex problem of relating genotype to phenotype and challenge the simple mapping of genes to higher level cognitive modules. We examine various methods that have been used to investigate this relation including quantitative genetics, molecular genetics, animal models, and in-depth psychological and computational studies of developmental disorders. Both single gene and multiple gene disorders indicate that the relationship between genotype and phenotype is very indirect and that, rather than identifying mere snapshots of developmental outcomes, the process of ontogenetic development itself must be taken into account.

Future directions for neurobehavioral studies of environmental neurotoxicants

Three proposals for enriching neurobehavioral toxicology studies are discussed. First, while IQ has proven useful as a primary endpoint, such apical measures are limited: they obscure important individual differences, tend to reflect the product rather than the process of learning, sample a limited range of intelligent behaviors, and are insensitive to critical outcomes such as learning disabilities. In terms of societal disease burden, behavioral and psychiatric morbidities might be even more important than cognitive morbidities. Such endpoints warrant careful attention. Second, the models of child development can be enriched, increasing our ability both to control for confounding bias and to evaluate potential modification of neurotoxicant effects by contextual factors. While the use of the Home Observation for Measurement of the Environment (HOME scale) and other measures of family-level proximal factors was an important advance, recent sociological work demonstrates the importance of broader conceptualizations of the ecology of child development (e.g. neighborhood and community characteristics). Third, much effort has been expended in attempts to identify the behavioral signature associated with exposure to a particular neurotoxicant. Given the limited success in identifying behavioral phenotypes even for well-characterized genetic disorders (e.g. Fragile-X, Williams, Velocardiofacial syndromes), the prospects seem grim for identifying specific and relatively invariant patterns in the expression of neurotoxicant effects across diverse dosing regimens and biological and cultural settings. In part this results from the likely influence of complex, but largely unknown, patterns of effect modification on the expressions of toxicity. Efforts to define the nature of these contingencies might be more productive than continued efforts to identify behavioral phenotypes.

De novo inverted duplication 9p21pter involving telomeric repeated sequences

We report on clinical and cytogenetic findings in a boy with partial 9p duplication, dup(9)(p21pter). Clinical manifestations included facial and hand anomalies and mental retardation. Fluorescence in situ hybridization (FISH) and comparative genomic hybridization (CGH) were used to characterize further and confirm the conventional banding data. Investigation by FISH using whole chromosome 9 paint probe showed that the additional material was derived from chromosome 9. Using CGH, a region of gain was found in the chromosome segment 9p21pter. YACs and telomeric probes confirmed the duplicated region. Using the all-human telomeric sequences probe, intrachromosomal telomeric signal was noted on the short arm of the abnormal chromosome 9. Mechanism of formation of the duplication, including intrachromosomal telomeric sequences, is discussed.