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“Having at our fingertips detailed information about when and where specific gene products are expressed in the brain brings new hope for understanding how this process can go awry in schizophrenia, autism and other brain disorders,” said NIMH Director Thomas R. Insel, M.D.

Among key findings in the prefrontal cortex:Individual genetic variations are profoundly linked to expression patterns. The most similarity across individuals is detected early in development and again as we approach the end of life.Different types of related genes are expressed during prenatal development, infancy, and childhood, so that each of these stages shows a relatively distinct transcriptional identity. Three-fourths of genes reverse their direction of expression after birth, with most switching from on to off.Expression of genes involved in cell division declines prenatally and in infancy, while expression of genes important for making synapses, or connections between brain cells, increases. In contrast, genes required for neuronal projections decline after birth – likely as unused connections are pruned.By the time we reach our 50s, overall gene expression begins to increase, mirroring the sharp reversal of fetal expression changes that occur in infancy.Genetic variation in the genome as a whole showed no effect on variation in the transcriptome as a whole, despite how genetically distant individuals might be. Hence, human cortexes have a consistent molecular architecture, despite our diversity.

Among key findings:Over 90 percent of the genes expressed in the brain are differentially regulated across brain regions and/or over developmental time periods. There are also widespread differences across region and time periods in the combination of a gene’s exons that are expressed.Timing and location are far more influential in regulating gene expression than gender, ethnicity or individual variation.Among 29 modules of co-expressed genes identified, each had distinct expression patterns and represented different biological processes. Genetic variation in some of the most well-connected genes in these modules, called hub genes, has previously been linked to mental disorders, including schizophrenia and depression.Telltale similarities in expression profiles with genes previously implicated in schizophrenia and autism are providing leads to discovery of other genes potentially involved in those disorders.Sex differences in the risk for certain mental disorders may be traceable to transcriptional mechanisms. More than three-fourths of 159 genes expressed differentially between the sexes were male-biased, most prenatally. Some genes found to have such sex-biased expression had previously been associated with disorders that affect males more than females, such as schizophrenia, Williams syndrome, and autism.

The Howard Hughes Medical Institute describes how researchers using "high-throughput gene sequencing technology" were able to identify several de novo or spontaneous gene mutations in 20 children with sporadic autism spectrum disorders -- that is, their family members showed no other sign of autism.

The team identified 21 spontaneous mutations -- meaning they weren't inherited from either parent -- in the children's DNA. Eleven of these were mutations that would alter the protein encoded by the affected gene. In four of the 20 children, the researchers found mutations that were severe, some of which have been previously linked to autism, intellectual disability, and epilepsy.

one child had a mutation in the GRIN2B gene, which is crucial for neuronal signaling.

Mutations in 3 Genes Linked to Autism Spectrum Disorders : Mutations in three new genes have been linked to autism, according to new studies including one with investigators at Mount Sinai School of Medicine

The findings, in a trio of papers revealing new genetic targets in autism, are published in the April 4th online issue of the journal Nature.

The genes with mutations identified in the studies – CHD8, SNC2A, and KATNAL2 – were discovered with a new state-of-the-art genomics technology known as exome sequencing, where all protein coding regions of the genome, called the exome, are analyzed.

Researchers have known for years that when one identical twin has autism, the other is also likely to be diagnosed with it – evidence that autism likely has a genetic component.

Researchers at Kennedy Krieger Institute studied 277 pairs of twins and found that when one identical twin had the disorder, the other developed it 88 percent of the time; for fraternal twins, that figure was 31 percent.

Despite this progress in unlocking the mysteries of autism, scientists have simply confirmed that there are likely numerous genetic links to autism.

Research on the genomics of autism from the Center for Biomedical Informatics at The Childrens Hospital of Philadelphia indicated that several genes and genomic variants contribute to autism. The gene alterations are rare but when they are in play, they seem to disrupt genes that are significantly involved in brain development and nerve signaling.

According to the September 15, 2010 issue of Science Translational Medicine, males with certain DNA alterations to their X-chromosome are at high risk of having autism.

This research was performed at the Centre for Addiction and Mental Health (CAMH) and The Hospital for Sick Children (SickKids), in Toronto Canada.

genetic mutations in the SHANK2 gene, partially responsible for linking nerve cells,  and variants in the number of gene copies that were common to patients with autism and patients with mental retardation.

the same mutation can be present in an autistic patient with normal intelligence and in a mentally impaired patient

Our findings further link common genes between ASD and intellectual disability.

The study’s major finding was that children with ASD have significantly more CNVs affecting their genes than children without ASD. Children with ASD have 20 percent more CNVs in general, and 70 percent more CNVs impacting genes known to be associated with ASD or cognitive problems. Significantly, many of the genes that are affected control important functions such as cell proliferation and cell-to-cell communication.

Some of the newly discovered genetic variants are inherited, and are found in parents or siblings of children with them. Others, however, seem to have originated spontaneously in the affected child, and do not appear in other family members.

While these findings add significantly to the scientific understanding of the genetic and biological underpinnings of ASD, the immediate usefulness is limited. That’s because there are a very large number of CNVs, and each child shows a different pattern of genetic changes. Each of these changes is rare; no CNV showed up in more than one percent of the children studied.

The results show for the first time the role of the SYN1 gene in autism, in addition to epilepsy, and strengthen the hypothesis that a deregulation of the function of synapse because of this mutation is the cause of both diseases

until now, no other genetic study of humans has made this demonstration.

The different forms of autism are often genetic in origin and nearly a third of people with autism also suffer from epilepsy.

The researchers behind the study, from Imperial College London and the University of South Australia, suggest that their findings could ultimately lead to a simple urine test to determine whether or not a young child has autism.

People with autism are also known to suffer from gastrointestinal disorders and they have a different makeup of bacteria in their guts from non-autistic people.

Today's research shows that it is possible to distinguish between autistic and non-autistic children by looking at the by-products of gut bacteria and the body's metabolic processes in the children's urine. The exact biological significance of gastrointestinal disorders in the development of autism is unknown.