Tuberous sclerosis: the next step

Gene expression profiling of lymphoblastoid cell lines from monozygotic twins discordant in severity of autism reveals differential regulation of neurologically relevant genes

Background

The autism spectrum encompasses a set of complex multigenic developmental disorders that severely impact the development of language, non-verbal communication, and social skills, and are associated with odd, stereotyped, repetitive behavior and restricted interests. To date, diagnosis of these neurologically based disorders relies predominantly upon behavioral observations often prompted by delayed speech or aberrant behavior, and there are no known genes that can serve as definitive biomarkers for the disorders.

Results

Here we demonstrate, for the first time, that lymphoblastoid cell lines from monozygotic twins discordant with respect to severity of autism and/or language impairment exhibit differential gene expression patterns on DNA microarrays. Furthermore, we show that genes important to the development, structure, and/or function of the nervous system are among the most differentially expressed genes, and that many of these genes map closely in silico to chromosomal regions containing previously reported autism candidate genes or quantitative trait loci.

Conclusion

Our results provide evidence that novel candidate genes for autism may be differentially expressed in lymphoid cell lines from individuals with autism spectrum disorders. This finding further suggests the possibility of developing a molecular screen for autism based on expressed biomarkers in peripheral blood lymphocytes, an easily accessible tissue. In addition, gene networks are identified that may play a role in the pathophysiology of autism.

Characterizing Magnetoencephalographic Spike Sources in Children with Tuberous Sclerosis Complex

PURPOSE

Tuberous sclerosis complex (TSC) often causes medically intractable seizures. Magnetoencephalography (MEG) localizes epileptiform discharges. To evaluate the use of MEG spike sources (MEGSSs) for localizing epileptic zones in TSC patients, we characterized MEGSSs and correlated them to EEG and magnetic resonance imaging (MRI) results.

METHODS

We analyzed data from seven children who underwent prolonged video-EEG, MEG, and MRI. We classified MEGSSs as clusters (six or more spike sources, <or=1 cm between sources) and scatters (fewer than six spike sources regardless of distance between sources; sources with >1 cm between sources regardless of number of sources).

RESULTS

A single, unilateral cluster with additional scatters occurred in two patients; these predominantly lateralized dipoles correlated to prominent tubers on MRI and ictal/interictal EEG zones. Bilateral clusters with scatters existed in two patients; cluster locations partly overlapped multiple prominent tubers. These patients also had bilateral or diffuse interictal discharges, bilateral or generalized seizures, and changing seizure types and EEG findings. Only bilateral scatters occurred in three patients; scatters partly overlapped EEG interictal/ictal-onset regions; one patient had coexisting generalized seizures. In one patient with equally bilateral scatters, scatters overlapped a prominent tuber and interictal/ictal-onset zones in the right frontal region.

CONCLUSIONS

MEG contributes to information from EEG and MRI for localizing epileptogenic zones in children with TSC. A single cluster with scatters in a unilateral hemisphere predicts a primary epileptogenic zone or hemisphere; bilateral or multiple clusters indicate bilateral primary or potential epileptogenic zones; and bilateral scatters without clusters may indicate epileptogenic zones that are hidden within extensive areas of scattered MEGSSs.

Tuberous sclerosis complex and neurofibromatosis type 1: the two most common neurocutaneous diseases

TSC and NF1 are the most common of the neurocutaneous diseases, and both are autosomal dominant with a high spontaneous mutation rate. For diagnosis, two features are necessary for each disease. Skin findings for each are especially helpful for diagnosis, as is neuroimaging in TSC. For NF1, neuroimaging is not yet reliable for diagnosis. In children, brain symptoms cause most of the morbidity in TSC, and nerve sheath and nervous system tumors as well as learning disabilities cause major morbidity in NF1. Renal disease becomes a serious problem for adults with TSC. The TSC1, TSC2, and NF1 genes function as tumor suppressor genes and have other functions that are being investigated. Blood tests for diagnosis have a high false-negative rate. Therapies for TSC and for NF1 are both medical and surgical.

Tuberous sclerosis complex and neurofibromatosis type 1: the two most common neurocutaneous diseases

TSC and NF1 are the most common of the neurocutaneous diseases, and both are autosomal dominant with a high spontaneous mutation rate. For diagnosis, two features are necessary for each disease. Skin findings for each are especially helpful for diagnosis, as is neuroimaging in TSC. For NF1, neuroimaging is not yet reliable for diagnosis. In children, brain symptoms cause most of the morbidity in TSC, and nerve sheath and nervous system tumors as well as learning disabilities cause major morbidity in NF1. Renal disease becomes a serious problem for adults with TSC. The TSC1, TSC2, and NF1 genes function as tumor suppressor genes and have other functions that are being investigated. Blood tests for diagnosis have a high false-negative rate. Therapies for TSC and for NF1 are both medical and surgical.

Clinical spectrum of cortical dysplasia in childhood: diagnosis and treatment issues

Disorders of cortical development form a spectrum of lesions produced by insults to the developing neocortex. These conditions typically first manifest in childhood with epilepsy, developmental delay, and focal neurologic signs. Although the clinical and electrophysiologic findings are often nonspecific, high-resolution magnetic resonance imaging facilitates diagnosis during life, and assists in delineating specific clinical syndromes. While many patients are dysmorphic and severely affected by mental retardation and epilepsy, some have normal or near-normal cognitive function and no seizures. Molecular studies of dysplastic cortex are providing new insights into the basic mechanisms of brain function and development, while pathologic analysis of tissue removed at surgery is helping to define epileptic circuitry. Treatment of the epilepsy associated with cortical dysplasia is often frustrating, but surgical approaches based on accurately defining epileptogenic regions are proving increasingly successful. Genetic diagnosis is important for accurate counseling of families.