Lisa S. Freund

Neurodevelopmental effects of the FMR-1 full mutation in humans

Brain dysfunction is the most important sequelae of the fragile X (FMR-1) mutation, the most common heritable cause of developmental disability. Using magnetic resonance imaging (MRI) and quantitative morphometry, we have compared the neuroanatomy of 51 individuals with an FMR-1 mutation with matched controls and showed that subjects with an FMR-1 mutation have increased volume of the caudate nucleus and, in males, the lateral ventricle. Both caudate and lateral ventricular volumes are correlated with IQ. Caudate volume is also correlated with the methylation status of the FMR-1 gene. Neuroanatom-ical differences between two monozygotic twins with an FMR-1 mutation who are discordant for mental retardation are localized to the cerebellum, lateral ventricles and subcortical nuclei. These findings suggest that the FMR-1 mutation causing the fragile X syndrome leads to observable changes in neuroanatomy that may be relevant to the neurodevelopmental disability and behavioural problems observed in affected individuals.

Neuroanatomy of fragile X syndrome The temporal lobe

Fragile X syndrome, an X-linked genetic disorder caused by a mutation in the FMR-1 gene, is associated with a particular profile of abnormalities of behavior, learning, language, and memory, suggesting temporal lobe dysfunction. We undertook a quantitative neuroimaging study investigating the neuroanatomy of the temporal lobe in individuals with the fragile X mutation. The temporal lobe neuroanatomy of 15 young fragile X subjects was quantified and compared with that of 26 age- and IQ-matched control subjects. Analyses showed the right and left hippocampal volumes to be significantly larger in the fragile X group compared with the control group. Subjects with the fragile X mutation showed an age-related increase in volume of the hippocampus and an age-related decrease in volume of the superior temporal gyrus. Along with the findings of previous imaging studies of fragile X subjects, the results of the present investigation are consistent with studies showing a nonrandom distribution of expression of the FMR-1 gene in the developing brain, with increased expression in the cerebellum, hippocampus, and specific cortical regions. The results also suggest involvement of temporal lobe regions in the behavioral and cognitive abnormalities associated with fragile X syndrome.

Autistic Behaviors Among Girls with Fragile X Syndrome

Reports of autistic behaviors were examined for 30 school-age girls with fragile X (fraX) and 31 age- and IQ-matched controls through a structured interview administered to each girls parent(s). IQ scores were obtained for each participant; anxiety, neuroanatomical, and molecular-genetic data were derived for girls with fraX. Girls with fraX had significantly more autistic behaviors than controls. These behaviors were qualitatively similar to those reported for boys with fraX, but were not correlated with IQ. Anxiety in girls with fraX was positively correlated with abnormal social and communication behaviors; posterior cerebellar vermis area was negatively correlated with measures of communication and stereotypic/restricted behaviors. Severity of stereotypic/restricted behaviors was negatively correlated with the prevalence of active non-fraX chromosomes. Thus anxiety and posterior cerebellar area measures had distinct associations with subsets of autistic behaviors; these associations may have important implications for understanding the neurobiology of autism.

Social Functioning among Girls with Fragile X or Turner Syndrome and Their Sisters.

Social behaviors among two genetically homogeneous groups—girls with fragile X (fraX) or Turner syndrome (TS)—were examined to address the role of family environment versus biological determinants of social dysfunction in girls with these disorders. Using a sibling pair design, girls with fraX or TS were compared with their own sisters on measures of IQ and social functioning. The 8 girls with fraX and the 9 girls with TS had lower FSIQ scores and higher ratings of social and attention problems relative to their own sisters. Girls with fraX also had higher ratings of withdrawn behaviors, relative to their own sisters. The unaffected sisters were not rated as demonstrating any difficulties in these areas, relative to controls. Correlations between problem ratings and FSIQ were not statistically significant. Although these preliminary findings do not indicate a lack of familial impact on social development in girls with either disorder, the results provide preliminary evidence that social dysfunction reported for girls with fraX or TS cannot be attributed solely, nor primarily, to global aspects of the family environment.

Early behavior signs of psychiatric phenotypes in fragile X syndrome.

Whether preschool males with fragile X syndrome can be distinguished from those with idiopathic developmental delay in the four problem behavior areas associated with the fragile X phenotypes was examined. Males with fragile X (n = 41) and age- and IQ-matched controls (n = 16) were rated by their mothers on the Dimensions of Temperament Scale-Revised, the Child Behavior Checklist, and the Aberrant Behavior Checklist--Community. The fragile X group showed deficits in motor skills, increased initial avoidance, decreased social withdrawal, deficits in attention, increased hyperactivity, and positive mood. They were distinguished from controls on all of these variables except hyperactivity and attention. When maternal characteristics were controlled for, the fragile X group showed a significantly higher level of generalized activity level than did controls.

Cortisol and social stressors in children with fragile X: a pilot study.

Evidence of neuroendocrine dysfunction, behavioral features of social anxiety and avoidance, and neuroanatomical abnormalities suggest that abnormal hypothalamic-pituitary-adrenal (HPA) function may be a component of the fragile X (fra X) syndrome. In this preliminary study, salivary cortisol levels of males (n = 8, mean age = 13.5 yr) and females (n = 7, mean age = 13.9 yr) with the fra X full mutation were studied for 3 days. Day 1 was an experimental day, during which subjects experienced a Social Stressor task midmorning. Days 2 and 3 were routine days, during which the subjects were engaged in their typical activities. Saliva samples were collected before breakfast, lunch, dinner, and bedtime. On the experimental day, the prelunch sample collection occurred 30 and 90 minutes after the Social Stressor task. Compared with childrens norms, the combined group of males and females with fra X had significantly higher cortisol levels in the prelunch and the prebedtime samples for the routine days. Comparisons between the two fra X groups for the experimental day revealed similar diurnal patterns for cortisol level. However, compared with females with fra X, males with fra X had significantly higher cortisol levels at two points during the day: 30 minutes after the social stressor and at bedtime. These preliminary data suggest that individuals with fra X have abnormal HPA function. Understanding the relations among HPA dysfunction, abnormalities in brain structure and/or function, and maladaptive behavior and cognition in fra X could inform the design of early interventions using pharmacological or environmental measures designed to normalize neuroendocrine function.

The Children's Affective Lability Scale: A psychometric evaluation of reliability

The Childrens Affective Lability Scale (CALS) is a 20-item parent report measure developed to assess affect regulation in children aged 6-16. It was normed with school children in regular education classrooms and with children hospitalized in a psychiatric facility. Internal-consistency reliability, split-half reliability, and two-week test-retest reliability were excellent. Staff interrater reliability in the psychiatric sample was acceptable. Higher CALS scores were observed in an in-patient psychiatric sample than in either an out-patient or a normative sample. A principal components factor analysis yielded two components for the normative sample.

Trajectories and profiles of adaptive behavior in males with fragile X syndrome : Multicenter studies

We conducted two multicenter studies on adaptive trajectories and profiles in males with fragile X syndrome. Study 1 longitudinally assessed 29 males ages 1–20 years using ageequivalent scores from the Vineland Adaptive Behavior Scales. Fragile X boys ages 1–10 years showed significant gains in adaptive skills from first to second testing; males ages 11–20 years were stable in their adaptive development. Study 2 cross-sectionally examined 132 males ages 1–20 years. Significant age-related gains were found in boys ages 1–10, particularly in preschool children. Subjects ages 11–20 showed increased variability and nonsignificant relations between age and adaptive skills. Preliminary findings from 26 young adults with fragile X syndrome ages 21–40 years showed stable age-equivalent adaptive scores during these years. Relative strengths in daily living skills and weaknesses in communication were only evident among older subjects. Significant relations were found between adaptive behavior standard scores and IQ; these two scores also showed age-related declines that likely parallel one another. Findings are related to adaptive features in other genetic syndromes, and to directions for future adaptive behavior research.

Rating Problem Behaviors in Outpatients with Mental Retardation: Use of the Aberrant Behavior Checklist.

Parent and teacher ratings of behavior problems of an outpatient sample of 110 children, adolescents, and young adults with IQs ranging from severe mental retardation to borderline were obtained using a modified version of the Aberrant Behavior Checklist (ABC). Using factor analytic techniques, the five-factor structure of the parent data corresponded extremely well with the five factors originally obtained from staff ratings of mentally retarded inpatients (i.e., Irritability, Withdrawal, Hyperactivity, Stereotypies, and Inappropriate Speech). Factor content was virtually identical between the parent and original ABC data with differences involving only one or two items per scale. The teacher data also revealed a factor structure that corresponded to the same five factors as the parent and original data. Although the teacher and parent factors showed a high degree of similarity, the teacher data suggested that the Stereotypies and Inappropriate Speech factors of the parent and original analyses were not the same constructs for teacher respondents. Age was related to the withdrawal factor for parent data; level of intellectual functioning was the only subject characteristic related to factor scale scores in both parent and teacher data. Test-retest reliabilities were adequate to excellent for all factors for both parent and teacher data. Parent-teacher cross-informant reliabilities were adequate for at least four of the factors. The results of the report indicate that the ABC is a useful, reliable instrument for assessing maladaptive behaviors in young, developmentally disabled outpatients.

Cognitive, behavioral, and neuroanatomical assessment of two unrelated male children expressing FRAXE

Standardized cognitive, behavioral, and neuroanatomical data are presented on 2 unrelated boys with the FRAXE (FMR2) GCC expansion mutation. In the context of normal IQ, both boys had a history of developmental delay, including significant problems with communication, attention, and overactivity. Additionally, one child was diagnosed with autistic disorder. Data from these 2 cases are compared to analogous information from previous reports about individuals with the FRAXE or FRAXA (FMR1) mutation. These comparisons support the idea that FRAXE is associated with nonspecific developmental delay and possibly high-functioning autism.