Autism And Genes – Understanding Genetics | Spectrum | Research

Ranjeet KumarReviewed by Mr. Ranjeet Kumar Sr. Audiologist, Speech Therapist & Cochlear Implant Specialist, BASLP on May 7th, 2020 written by Editorial Team

National Institute of Child Health and Human Development (NICHD) provides some great information regarding Autism and Genes or Genes related to ASD.

If you need any assistance or have a question about Autism and Genes, you can consult our HearingSol  experts with your problem, feel free to call us on +91-9327901950. We are always here to help you.

Let’s discuss these terms in detail.

Causes of Autism

Basically, researchers are still unsure about the main cause of Autism. Scientists believe that it is a result of a mixture of causes. This is so because this is a biological disorder with no two sufferers being the same.

Therefore, it is not possible to find one cause for all cases of autism spectrum disorder and it is strongly believed by Scientists that it is a Genetic condition.

According to the scientists working for the Network on the Neurobiology and Genetics of Autism (NNGA): Collaborative Programs of Excellence in Autism (CPEA), a group of scientists who are supported by the National Institute of Child Health and Human Development (NICHD) and the National Institute on Deafness and Other Communication Disorders (NIDCD), along with other NICHD, NIH, as well as non-NIH scientists are studying about involvement of Genes in Autism.

Therefore, this worldwide research program hopes to solve the mysteries related to Autism by understanding its underlying causes.

Describing Genes

Genes are defined as a small piece of hereditary material. This means that it is passed on from parents to their children i.e. half their genes from the mother and the other half from their father.

These genes are in a pattern or sequence which provides a blueprint to inform your body to build its different parts.

This Gene sequence controls your physical features i.e. height, eye and hair color, and other features of body and mind. Any change in this blueprint can cause a change in body and mind development.

Genes are located on chromosomes. There are 23 pairs of chromosomes i.e 46 in total, which are found in almost every cell of our body.

Genes and chromosomes provide all the information to the body required to “build a person”.

Reason To Study Genes

Most of the past research hints towards the link between Autism and Genes. For example:

  • If there are identical twins with Autism, both of them have condition 60 percent of the time. If there are fraternal twins with Autism, both of them have the condition only 3 to 6 percent of the time. In the case of identical twins, a single egg will split into two, sharing 100 percent of genes. In the case of fraternal twins, two different eggs are present, making them genetically different. If genes had no role to play in ASD, then the number of identical twins with Autism would not have been higher than the number of fraternal twins with the same condition. This is the condition that compelled scientists to think that genes play an important role in Autism.
  • Many family studies show that some of the autism-like symptoms such as language development delay occur more often in parents, adult brothers or sisters of people having ASD, as compared to families with no autistic members. As members of the same family have similar gene patterns, the studies suggest something about the link between gene sequences and autism. It is a spectrum disorder which means people suffering from this show a wide range of symptoms. Certain changes in gene sequences can make the condition mild, therefore a person not having autism but still showing one of its symptoms instead. A different change in that gene sequence can worsen the symptoms of autism.

Based on the above findings, it shows a strong link between Genes and Autism. But it is still not expected by the researchers to find that one gene that causes Autism.

As there is a huge difference in people’s symptoms, it is believed by scientists that the interaction of many genes with each other results in Autism.

At such a point, it seems like some children are born with a genetic susceptibility to ASD. One of the most important research questions is, “What causes some susceptible individuals to develop autism while others not?”

Autism And Chromosomes

A process called linkage analysis is used to identify “genetic hotspots” or chromosome areas having defective genes related to autism, as stated by CPEA investigators who are working with researchers from around the world.

So far the most promising lead seems to be present on chromosome 7, which also consists of genes responsible for other language disorders, and chromosome 15 having genes for other developmental disorders.

Scientists performing research at the University of California, Irvine, found that their seven-year-old autistic patient was missing a certain section of chromosome 15.

This raises a question, “Why is it such a great discovery? ” This is so because it’s among the first time that a specific genetic problem has actually being discovered in an autistic person.

After taking a close look at the chromosomes it was found that nearly 1000 pieces of the genetic sequence were missing from chromosome 15.

These missing pieces mean that some of the instruction for the building of the body or mind is missing, without which the body or mind may not be built properly.

Earlier, studies undertook a group of autistic people, some of the more general features of their genes, such as chromosome which might have problem genes, whether they had one or more copies of a chromosome.

But in this study, scientists undertook one person at a time to carefully focus on their genes.

This is a slow and complex process that allows creating a detailed catalog of all 46 chromosomes for every autistic person to find any of the blocks missing in these chromosomes.

This discovery is used by scientists to match the missing chromosome pieces to some of the genes which are thought to play an important role in autism.

If a gene is matched to any of the missing sections of the chromosome, it may be possible to uncover how gene changes the body to cause autism.

These findings will lead to treatments for correcting changes caused by some of the missing chromosome pieces.

Genetic Changes Found In Autistic Patients

Scientists performing research at the University of Rochester School of Medicine and Dentistry in Rochester, New York, found that almost 40 percent of autistic people had a change in their genetic linkage which could be a factor causing autism.

The genes pattern controls the building of body parts. An alteration in that particular pattern can change the built of your body and mind, leading to autism.

To be specific, 39 percent of autistic people considered for the study showed a change in one of the two copies of the HOXA1 gene, located on chromosome 7. Chromosomes are present in pair i.e cells have 2 copies of every gene.

The percentage of people with a change in one of their genes, but not having autism and were not even related to anyone having autism was very low i.e. only 22 percent.

Compared to this percentage of people not having autism but had a gene change, twice as many people having autism had a gene change. The HOXA1 gene plays an important role in causing autism.

Additionally, 33 percent of people not having autism, but related to someone having autism, also had a gene change. This supports the idea of the HOXA1 gene playing an important role in causing autism.

These results suggest that the genetic sequence of these families is linked to autism or similar symptoms. More study is required to find out what that link is.

According to scientists, change in the HOXA1 gene by itself doesn’t cause autism. Therefore, scientists think that the HOXA1 gene is one of the many genes that are responsible for causing autism in a person.

Autism And Gene Studies

The CPEA Network is studying other genetic mechanisms that may account for genetic defects related to autism.

Researchers of this network will share their information and methods to see if other researchers also get the same result with other autistic people or not. Several scientists getting the same result confirms the discovery.

Once confirmed, this discovery will become a stepping stone for other discoveries. Researchers of the network hope those latest findings on autism and genes are just the beginning.

Understanding both genetic and environmental causes of autism may help scientists to understand how to treat and maybe even prevent it.

While some of the scientists focus on confirming the findings reported here, others are doing their studies on different features of genes and autism.

Scientists and doctors keep looking at genes, their environment, and how they interact with each other until the mysteries of autism are solved.

Examining Y-Chromosome In Autism Spectrum Disorder

Various pieces of evidence show that Autism Spectrum Disorder also known as ASD is caused due to the rare inherited or spontaneous genetic mutations.

Such as changes in copy number and single nucleotide alterations. Genetic causes found recently, accounts for about 15% of the total cases.

Further identification of these genetic causes will help in early diagnosis and aid in the development of interventions for improved outcomes.

One of the most striking characteristics of ASD is a strong gender bias i.e. in males it is four times more likely to be on the spectrum as compared to girls.

Recent studies show that gender bias is caused by genetic mutations found only on the sex chromosome present in a person.

For example, the mutation in various genes such as PTCHD1, NLGN3 as well as NLGN4, on chromosome X is associated with the ASD phenotype.

The y chromosome is highly complex and has a repetitive DNA sequence structure, which often leads to its disregard.

This makes it more difficult to examine comprehensively by using conventional genetic technologies. Most importantly, chromosome Y contains genes that are crucial for brain development.

It also has a high frequency of spontaneous mutations. Moreover, males having abnormal XYY or XXYY karyotypes possess increased the risk of developing ASD.

According to the hypothesis, additional genetic mutations involved in ASD can be found on the Y chromosome.

Latest genome-sequencing and microarray technologies are used by investigators for the discovery of the variants of the Y chromosome in males, which associated with the condition of autism.

The specific aims of genome-sequencing and microarray technologies are to do the following:

  • Characterizing the DNA sequences as well as the structure of the whole Y chromosome. This is for providing a foundation for investigating in this poorly characterized genomic region.
  • Identifying and validating the autism-associated variants of the candidate with the help of independent technologies across large cases and control cohorts.
  • Defining the effects of mutations on the clinical outcomes of autistic individuals and their families.

These outcomes of the project promise to include the discovery of novel genetic biomarkers. These are helpful for early diagnosis and development of novel interventions for autism.

If you need any assistance or have a question about Autism and Genes, you can consult our HearingSol  experts with your problem, feel free to call us on +91-9327901950. We are always here to help you

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