Gender

Changes in Autism Spectrum Disorder Prevalance in 4 Areas in the United States

Source: 
Diability and Health Journal, Rice et al
Date Published: 
July 2010
Year Published: 
2010

Study sought to describe autism spectrum disorder (ASD) population characteristics and changes in identified prevalence across 3 time periods.  Children with a potential ASD were identified through records abstraction at multiple sources with clinician review based on Diagnostic and Statistical Manual (DSM-IV-TR) criteria. Multisite, population-based data from the Autism and Developmental Disabilities Monitoring (ADDM) Network were analyzed from areas of Arizona (AZ), Georgia (GA), Maryland (MD), and South Carolina (SC). Participants were 8-year-old children (born in 1992, 1994, or 1996) in 2000, 2002, or 2004 (and children born in 1988 residing in metropolitan Atlanta in 1996) who had been evaluated for a variety of developmental concerns at education and/or health sources.  There was a trend toward increase in identified ASD prevalence among 8-year-old children who met the surveillance case definition in 3 of the 4 study sites from 2000 to 2004. Some of the observed increases are due to improved ascertainment; however, a true increase in ASD symptoms cannot be ruled out. These data confirm that the prevalence of ASDs is undergoing significant change in some areas of the United States and that ASDs continue to be of urgent public health concern.

UT Southwestern researchers uncover fragile X syndrome gene's role

Source: 
EurekAlert
Date Published: 
May 7, 2010
Abstract: 

Researchers at UT Southwestern Medical Center have discovered how the genetic mutation that causes Fragile X syndrome, the most common form of inherited mental retardation, interferes with the "pruning" of nerve connections in the brain. They found Fragile X is caused by a mutation in a single gene, Fmr1, on the X chromosome. The gene codes for a protein called FMRP, which plays a role in learning and memory but whose full function is unknown. The protein's role in pruning nerve connections had been unclear.

Longitude Magnetic Resonance Imaging Study of Cortical Development Through Early Childhood in Autism

Source: 
Journal of Neuroscience, Courchesne et al
Date Published: 
March 2010
Year Published: 
2010

The first longitudinal study of brain growth in toddlers at the time symptoms of autism are becoming clinically apparent using structural MRI scans at multiple time points beginning at 1.5 years up to 5 years of age. They collected 193 scans on 41 toddlers who received a confirmed diagnosis of autistic disorder at approximately 48 months of age and 44 typically developing controls. By 2.5 years of age, both cerebral gray and white matter were significantly enlarged in toddlers with autistic disorder, with the most severe enlargement occurring in frontal, temporal, and cingulate cortices. In the longitudinal analyses, which they accounted for age and gender effect, we found that all regions (cerebral gray, cerebral white, frontal gray, temporal gray, cingulate gray, and parietal gray) except occipital gray developed at an abnormal growth rate in toddlers with autistic disorder that was mainly characterized by a quadratic age effect. Females with autistic disorder displayed a more pronounced abnormal growth profile in more brain regions than males with the disorder. Given that overgrowth clearly begins before 2 years of age, future longitudinal studies would benefit from inclusion of even younger populations as well as further characterization of genetic and other biomarkers to determine the underlying neuropathological processes causing the onset of autistic symptoms.

How the Autistic Brain Distinguishes Oneself from Others

Source: 
Science Daily
Date Published: 
December 14, 2009
Abstract: 

Scientists at the University of Cambridge have discovered that the brains of individuals with autism are less active when engaged in self-reflective thought. The study published in the journal Brain provides new evidence for the neural correlates of self-awareness and a new window into understanding social difficulties in autism spectrum conditions.

High-density SNP association study of the 17q21 chromosomal region linked to autism identifies CACNA1G as a novel candidate gene

Source: 
Molecular Psychiatry, Strom, Stone, Bosch, Merriman, Cantor, Geschwind, and Nelson
Date Published: 
May 2009
Year Published: 
2009

(From a UCLA press release) UCLA scientists have discovered a variant of a gene called CACNA1G that may increase a child's risk of developing autism, particularly in boys. "We found that a common form of the gene occurs more frequently in the DNA of families that have two or more sons affected by autism, but no affected daughters," explained Dr. Stanley Nelson, professor of human genetics at the David Geffen School of Medicine at UCLA. The researchers traced the genetic markers to CACNA1G, which helps move calcium between the cells. They discovered that the gene has a common variant that appears in the DNA of nearly 40 percent of the population. "This alternate form of CACNA1G consistently increased the correlation to autism spectrum disorder, suggesting that inheriting the gene may heighten a child's risk of developing autism," observed Nelson. How the gene contributes to higher autism risk remains unclear, but Nelson emphasized that it cannot be considered a risk factor on its own. "This variant is a single piece of the puzzle," he said. "We need a larger sample size to identify all of the genes involved in autism and to solve the whole puzzle of this disease." The UCLA team's next step will be to sequence the gene in people who possess the altered variant in order to identify the exact change that increases autism risk. These subtle variations offer potential markers for the real mutation causing greater susceptibility to the disease.

Neuropsychological performance 10 years after immunization in infancy with thimerosal-containing vaccines

Source: 
Pediatrics, Tozzi AE, Bisiacchi P, Tarantino V, De Mei B, D'Elia L, Chariotti F, Salmaso S.
Date Published: 
January 2009
Year Published: 
2009

Thimerosal, a mercury compound used as a preservative in vaccines administered during infancy, has been suspected to affect neuropsychological development. We compared the neuropsychological performance, 10 years after vaccination, of 2 groups of children exposed randomly to different amounts of thimerosal through immunization. Children who were enrolled in an efficacy trial of pertussis vaccines in 1992–1993 were contacted in 2003. Two groups of children were identified, according to thimerosal content in vaccines assigned randomly in the first year of life (cumulative ethylmercury intake of 62.5 or 137.5 µg), and were compared with respect to neuropsychological outcomes. Eleven standardized neuropsychological tests, for a total of 24 outcomes, were administered to children during school hours. Mean scores of neuropsychological tests in the domains of memory and learning, attention, executive functions, visuospatial functions, language, and motor skills were compared according to thimerosal exposure and gender. Nearly 70% of the invited subjects participated in the neuropsychological assessment (N = 1403). Among the 24 neuropsychological outcomes that were evaluated, only 2 were significantly associated with thimerosal exposure. Girls with higher thimerosal intake had lower mean scores in the finger-tapping test with the dominant hand and in the Boston Naming Test. Given the large number of statistical comparisons performed, the few associations found between thimerosal exposure and neuropsychological development might be attributable to chance. The associations found, although statistically significant, were based on small differences in mean test scores, and their clinical relevance remains to be determined.

Linkage, Association, and Gene Expression Analyses Identify CNTNAP2 as an Autism-Susceptibility Gene

Source: 
American Journal of Human Genetics, Alarcon, Abrahams, et al.
Date Published: 
January 2008
Year Published: 
2008

Autism is a genetically complex neurodevelopmental syndrome in which language deficits are a core feature. We describe results from two complimentary approaches used to identify risk variants on chromosome 7 that likely contribute to the etiology of autism. A two-stage association study tested 2758 SNPs across a 10 Mb 7q35 language-related autism QTL in AGRE (Autism Genetic Resource Exchange) trios and found significant association with Contactin Associated Protein-Like 2 (CNTNAP2), a strong a priori candidate. Male-only containing families were identified as primarily responsible for this association signal, consistent with the strong male affection bias in ASD and other language-based disorders. Gene-expression analyses in developing human brain further identified CNTNAP2 as enriched in circuits important for language development. Together, these results provide convergent evidence for involvement of CNTNAP2, a Neurexin family member, in autism, and demonstrate a connection between genetic risk for autism and specific brain structures.

A Common Genetic variant in the neurexin superfamily member CNTNAP2 increases Familial Risk of Autism

Source: 
American Journal of Human Genetics, Arking, Cutler, et al
Date Published: 
December 2008
Year Published: 
2008

Autism is a childhood neuropsychiatric disorder that, despite exhibiting high heritability, has largely eluded efforts to identify specific genetic variants underlying its etiology. We performed a two-stage genetic study in which genome-wide linkage and family-based association mapping was followed up by association and replication studies in an independent sample. We identified a common polymorphism in contactin-associated protein-like 2 (CNTNAP2), a member of the neurexin superfamily, that is significantly associated with autism susceptibility. Importantly, the genetic variant displays a parent-of-origin and gender effect recapitulating the inheritance of autism.

Mortality and Causes of Death in Autism Spectrum Disorders: An Update

Source: 
Autism, Mouridsen, Bronnum-Hansen, et al
Date Published: 
2008

This study compared mortality among Danish citizens with autism spectrum disorders (ASDs) with that of the general population. A clinical cohort of 341 Danish individuals with variants of ASD, previously followed over the period 1960-93, now on average 43 years of age, were updated with respect to mortality and causes of death. Standardized mortality ratios (SMRs) were calculated for various times after diagnosis. In all, 26 persons with ASD had died, whereas the expected number of deaths was 13.5. Thus the mortality risk among those with ASD was nearly twice that of the general population. The SMR was particularly high in females. The excess mortality risk has remained unchanged since our first study in 1993. Eight of the 26 deaths were associated with epilepsy and four died from epilepsy. Future staff education should focus on better managing of the complex relationships between ASD and physical illness to prevent avoidable deaths.