Childhood Academic Performance: A Potential Marker of Genetic Liability to Autism.

Autism spectrum disorder (ASD), a heritable neurodevelopmental disorder, confers genetic liability that is often expressed among relatives through subclinical, genetically-meaningful traits, or endophenotypes. For instance, relative to controls, parents of individuals with ASD differ in language-related skills, with differences emerging in childhood. To examine ASD-related endophenotypes, this study investigated developmental academic profiles among clinically unaffected siblings of individuals with ASD (n = 29). Lower performance in language-related skills among siblings mirrored previously-reported patterns among parents, which were also associated with greater subclinical ASD-related traits in themselves and their parents, and with greater symptom severity in their sibling with ASD. Findings demonstrated specific phenotypes, derived from standardized academic testing, that may represent childhood indicators of genetic liability to ASD in first-degree relatives.

2q24 deletions: further characterization of clinical findings and their relation to the SCN cluster.

As the resolution of molecular cytogenetic methods continues to improve, it has become increasingly possible to refine genotype-phenotype correlations based upon gene involvement. We report three new patients with nonrecurrent deletions involving subbands of 2q24. These patients were referred for evaluation of developmental delay, but were found to have unique, nonoverlapping clinical features. Patient 1 presented with infantile seizures, microcephaly, and brain anomalies, along with facial dysmorphism, growth retardation, neuromuscular scoliosis, and later with developmental regression. Array comparative genomic hybridization (aCGH) detected an 8 Mb interstitial deletion encompassing the neuronal sodium channel (SCN) gene cluster. Patient 2 presented with growth retardation, congenital heart defect, and hypotonia. Patient 3 presented with developmental delay and behavioral problems. Patients 2 and 3 had no history of seizures, microcephaly, or brain anomalies and were found to have deletions of 2q24, ∼8 Mb and <500 kb respectively, centromeric to and outside the SCN cluster. It has been demonstrated that mutations and copy number variants (CNVs) affecting the SCN gene cluster result in severe, early-onset seizures. It is however, less clear whether haploinsufficiency of regions outside the SCN cluster may result in phenotypically recognizable and clinically significant features. We discuss additional dosage sensitive genes that may exist outside the SCN cluster. Our and published data indicate that 2q24 deletions not involving the SCN cluster are associated with fewer neurobehavioral problems, but may predispose to congenital malformations.

Correlation of CAG repeat length between the maternal and paternal allele of the Huntingtin gene: evidence for assortative mating.

Triplet repeats contribute to normal variation in behavioral traits and when expanded, cause brain disorders. While Huntington's Disease is known to be caused by a CAG triplet repeat in the gene Huntingtin, the effect of CAG repeats on brain function below disease threshold has not been studied. The current study shows a significant correlation between the CAG repeat length of the maternal and paternal allele in the Huntingtin gene among healthy subjects, suggesting assortative mating.

Polymorphism analysis of HOPA: a candidate gene for schizophrenia.

HOPA is a 25 kb Xq13 gene that codes for a member of the thyroid receptor co-activator protein (TRAP) family of nuclear receptor co-activators. In our prior research, polymorphisms in the opposite paired (Opa) domain of HOPA have been associated with a syndrome of aberrant behavior, most prominently psychosis, and hypothyroidism. These Opa domain polymorphisms are intriguing because subsequent research has demonstrated that changes in the Opa domain of the C. elegans orthologue of HOPA results in altered neurogenesis and release of transcriptional suppression. In an effort to determine whether other allelic polymorphisms in this gene exist and may potentially contribute to increased susceptibility to neuropsychiatric illness, we have performed single stranded conformational polymorphism (SSCP) analysis of all 45 exons and each of the two potential promoter regions of HOPA using DNA from a panel of patients with psychosis. We found a rare promoter polymorphism in an individual with schizoaffective disorder and extremely low thyroid stimulating hormone (TSH). The most common exonic polymorphism in HOPA is the previously demonstrated HOPA(12 bp) polymorphism. Transmission disequilibrium analysis of the HOPA(12 bp) polymorphism showed segregation with affected status in six of eight instances. We suggest that this evidence supports previous associations of HOPA(12 bp) with a broad range of neuropsychiatric illness and conclude that further studies of this uncommon polymorphism are merited.