Why Genetics are Suspected to be Linked to Autism

Did you know that individuals who have siblings with autism or related pervasive developmental disorders have a greater chance of having the disorder as well? Studies also show that identical twins are more likely to share autistic traits than fraternal twins. These are major indicators that there may be a genetic cause for autistic disorder.

Current research says that there may be other factors that contribute to the autism including gene abnormality and gene mutation. The combination of gene mutations might help to explain why there is such a wide spectrum of abilities in individual who have autism or related pervasive developmental disorders. Some cases of autism are quite severe while others are very mild. If the problems are caused by a combination of different genetic abnormalities then we can expect the disorder to manifest itself in a number of ways.

Researchers are targeting certain chromosomal regions in order to pinpoint the specific genes that may have a direct link to autistic disorder. As of right now there is no conclusive evidence that all pervasive developmental disorders are caused by genetic mutations.

Genes and Choromosomes

Genes play an important role in the basic makeup of cell structure that they also factor into our heredity. Everything from eye color to certain behavioral traits can be traced back to the genetic composition within the cells. This includes behaviors associated with autism. Researchers search chromosomes to find the defective genes.

When researchers suggest that a possible problem exists on chromosome 2, the problem would actually lie in a gene (or in genes) on that chromosome. Chromosomes are used to locate the genes in the cells. We can consider a chromosome to be a country and genes to be cities within that country.

Targeting Genes as Sources for Autism

There are specific genes found on five different chromosomes that are thought by some researchers to have a direct link to autism. The chromosomal regions are: chromosome 2, 3, 7 and 15 as well as the X chromosome. Let's break down the different regions:

• Chromosome 2 and 7 seem to be linked in some studies of autistic disorder according to a 2001 article from the Nation Institutes of Health, . Chromosome 7 is associated with language development and it seems to be a factor in some studies but not in others. Chromosome 2 is the second larges chromosome in the human genome. Researches are interested in the interrelation of genes on these two chromosomal regions as a possible cause for autistic disorder.
• Chromosome 3 contains genes that are associated with early brain development as well as brain messaging. Dysfunction in these genes may cause mixed messages in the brain cells and improper early brain development.
• Duplications of chromosome 15 may be associated with a lack of language skills, seizures and anxiety according to an article by Hugh McIntosh.
  
• The X chromosome is directly linked to Rett's disorder. This developmental disorder fall within that autism spectrum. Rett's syndrome is more common in females because the condition is fatal in males. Chromosome X is also linked to the chemical messages passed in the central nervous system. Genes located on this chromosome make proteins called neuroligins. These proteins work with the centarl nervous system to help cells chemically communicate with each other.
  

Some of the suspect genes are classified as positional candidate genes while others are considered functional candidate genes.

Rett's Disorder and Chromosome X

Rhett's disorder was discovered back in 1999 and is credited to researchers form the Baylor College of Medicine. Rhett's disorder has profound symptoms. The child develops normally then progressively loses previously mastered skills between the ages of five months and two years.

Previously, researchers assumed that Rett's syndrome affected females and not males. However, newer findings show that the condition is found in both sexes. The male babies who have Rett's syndrome die before or shortly after birth.

The cases of Rett's disorder are very rare even in females. The child experiences significant loss of language and motor skills and begins to exhibit stereotyped repetitive movements commonly associated with autism.

Clear signs of Rett's disorder include significant loss of previously mastered skills after seemingly normal development. Language development is severely affected by Rett's disorder and the child replaces deliberate, useful hand movements with repetitive movements associated with autism. The child's head growth slows between five and 48 months of age and she may be prone to have seizures.

Medications are commonly used in the treatment of this rare pervasive developmental disorder. Common medications include antidepressants, beta blockers, anti psychotic medications and medications that block opiates in the brain.

Interventions for Rhett's disorder include behavioral and social interventions commonly used in the treatment of autism. A neuropsychiatric doctor or neurologist will often be assigned to these severe cases.

Parents of children with Rett's disorder can find support and information through The International Rett Syndrome Association.

Chromosome X and Autistic Disorders

The Exploring Autism website recognizes that many researchers suspect that this particular chromosome is linked to autism and other pervasive developmental disorders aside from Rett's syndrome.

Since more males than females have autism in general, researchers automatically suspect the X chromosome because males have only one while females have two. If there is a defect on one X chromosome in females the other will compensate for it. Males do not have such compensation so the defect will manifest itself developmentally and physically.

Positional and Functional Candidate Genes

Candidate genes are suspected to be directly linked to autism and related pervasive developmental disorders. The researchers work toward either ruling out the candidate gene or finding the specific link between the gene and autism.

According th the website Exploring Autism, candidate genes can be separated into two major groups: positional and functional.

• Positional candidate genes are suspect because they are located in a certain area of a chromosome that is thought to be linked to autistic disorder.
• Functional candidate genes are suspect because researchers have made other discoveries that trace back to the specific function of those genes. If a certain gene makes a chemical that is either lacking or in excess in cases of autism then that gene is considered a functional candidate gene.
  
  

Books About Autism and Genetics

Two books really stand out when it comes to autism and genetic research. The first is The Research Basis for Autism Intervention by Eric Schopler, Nurit Yirmiya, Cory Shulman and Lee Marcus. This book is a collaborative effort to bridge the gap between research and clinical practice in the field of autism. This publication helps individuals who work in the field as well as families make connections between genetic and therapeutic interventions.

When families and therapists understand the link between the autistic child's specific needs they are better equipped to develop useful interventions. Understanding the deficits that the genetic problems cause is a great starting point for developing a plan.

For example, we know that children with autism have a dysfunction with "mirror" neurons in the brain. It is important to develop interventions that help the child compensate for the shortcomings like non-verbal imitation and emotion drills.

Autism, Brain and Environment written by Richard Lathe is a great resource that taps into the possibility of environmental factors in combination with genetically compromised immune systems. The text links environmental elements to a genetic predisposition to autistic traits.

A person may have a weakness in his genetic makeup that may not manifest itself until he is exposed to certain environmental elements. For example, many attribute some cases of autism to the MMR vaccines that contained the preservative thimerisol. However, not all children who received the vaccines developed autism.

There is a possibility that some autistic children have a neurological allergic reaction to the vaccines because of an underlying genetic weakness. The genetic weakness is comparable to an allergy to peanuts. One person can eat them but another person might have serious medical problems if he does.

The two books help us look at autism in a new light. Therapeutic approaches need to address the challenges the child has because of the genetic abnormality. Researchers might want to consider a combination of environmental as well as genetic factors in the possible causes of autism.

NAAR and Genetic Research Funding

NAAR is the National Alliance for Autism Research. This organization merged with Autism Speaks (WHEN) and raises money every year for autism research. One of the approaches that NAAR takes to raising funds for the study of autistic disorders is through annual fundraisers.

Various cities across the United States and Canada participate in Walk FAR (For Autism Research) fundraisers. The focus of the research conducted through NAAR funding is biomedical and genetic.

The National Alliance for Autism Research also receives funding through the private sector as well as corporations. The programs available through NAAR include the Autism Tissue Program and research organizations like TGen.

TGen

TGen is an institute dedicated to genetic research as well as the search for the causes of pervasive developmental disorders. This organization was established in 2002 and its expansive research embraces other neurological disorder and illness like cancer in its efforts.

TGen uses transitional genomics in its research. It involves diagnosis, prognostics and therapies for various illnesses and disorders. Transitional genomics is a cutting edge approach to genetic research developed through the Human Genome Project.

Website Resources for Autism Genetic Research

On-line resources for genetic research and autism include but are not limited to, the following:

Exploring Autism is the central hub of genetic research and autism. This comprehensive website offers the latest finding as well as the fundamentals of genetics as related to autism. The complex information is delivered in layman's terms and is quite accessible to the novice. There is a plethora of information including a time line that charts the history of autism, environmental factors as well as family stories.

The National Institute for Child Health and Development offers a wonderful resource for anyone who wants to learn more about autism research and genetics. this website houses over 1,000 articles on the subject of autism and related pervasive developmental disorders.

There are many other on-line resources for genetics and autism including Autism Link. This comprehensive website offers a plethora of links and information as well as a magnificent discussion forum.