Group items tagged

“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 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.

1. Autism Is a 'Spectrum' Disorder

it is possible to be bright, verbal, and autistic as well as mentally retarded, non-verbal and autistic.

2. Asperger Syndrome is a High Functioning Form of 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.

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.