Wednesday, November 29, 2023

What Gene Causes Autism

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Autism And Gene Studies

Genetic causes of autism: neuroscience at Scripps Research, Florida

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.

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Getting An Autism Diagnosis

Autism is diagnosed by a medical professional, often a pediatrician or specialist.

According to the Diagnostic and Statistical Manual of Mental Disorders , an autistic person must have both social and behavioral patterns that meet the criteria for autism spectrum disorder.

Someone might receive an autism diagnosis at 18 months or younger, but its more common to get diagnosed around 2 years old.

Still, some people dont get a diagnosis until much older or until adulthood.

When diagnosing ASD, clinicians may look for patterns in communication like:

  • difficulty with back-and-forth conversation
  • differences in nonverbal communication like facial expressions or body language
  • difficulty adjusting behavior to different social settings

A doctor may also look at these behavioral patterns when screening for autism:

  • specific movements, actions, or gestures
  • strong attachment to routine
  • specific, strong interests
  • differences in sensory processing

Many autistic people see autism as an identity, not as a condition to be treated. But if youre experiencing challenges related to being autistic, there are many ways to find support, depending on your needs.

If youre a parent of an autistic child, you can get some tips for how to support your child here. And if youre an autistic adult, you can learn more about strategies, support, and therapies here.

Why Is It Important To Know If You Have A Family Health History Of Autism Spectrum Disorder

Having a family health history of ASD makes you more likely to have a child with ASD, or to have ASD yourself. If you have a child with ASD, you are more likely to have another child with ASD, especially if you have a daughter with ASD or more than one child with ASD. Your other family members would also be more likely to have a child with ASD.

If you are pregnant or planning a pregnancy, tell your doctor if you or your partner have a family health history of ASD. This information can help your doctor determine how likely you are to have a child with ASD.

When collecting family health history information,

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Biological Risk Factors For Autism

Recent studies have also found that random or spontaneous gene mutations can lead to a higher risk of autism. Spontaneous gene mutations are not passed down from the parents but instead occur randomly in the egg or sperm during fertilization.

As the fertilized egg divides itself, the mutation can continue to occur in each cell. What happens with these mutations? Research is ongoing, but it appears that the mutation can affect single genes or entire strands of DNA.

When a full strand of DNA is affected, multiple genes may be duplicated or deleted. Studies have recently found that people with autism have more duplicated genes than people without autism.

As with genetic risk factors, the spontaneously mutated genes do not seem to cause autism, but it appears that they can increase the risk factor.

Researchers Have Identified New Gene Variants That Influence Your Risk Of Adhd And Autism

Autism spectrum disorder (Part 2)

In the group of neurodevelopmental disorders, ADHD and autism have a number of things in common: They are two of the most frequent child psychiatric diagnoses both are highly heritable and, although the fundamental symptoms vary, autism and ADHD have a large overlap in their underlying genetic origins.

Professor Anders Børglum has headed a study that provides new insight into the biological basis for developing both autism and ADHD, or just one of the diagnoses. Credit: Lars Kruse, Aarhus University

Researchers have now discovered five gene variants that are unique to only one of the two diagnoses, as well as seven genetic variants that are shared by both ADHD and autism.

We have succeeded in identifying both shared genetic risk variants and genetic variants that differentiate the two developmental disorders, says Professor Anders Børglum of the Department of Biomedicine at Aarhus University and iPSYCH, Denmarks largest research project within psychiatry, which is behind the study.

That means that we are beginning to understand both the biological processes that are behind the development of both diagnoses, and as something completely new also the processes that push the developmental disorder specifically in the direction of either autism or ADHD.

What happens in the brain?

Altered diagnostic guidelines

A few years ago due to an official diagnosis hierarchy it was not in principle possible to diagnose ADHD in a person who had autism, he says.

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What Causes Autism Spectrum Disorder

Although the cause of ASD is known in some people and not known in others, genetics, biology, and environment are all important factors. Having older parents, a difficult birth, or infections during pregnancy are all examples of factors that might increase the risk for having ASD. Beyond these factors, certain people are at higher risk than others. For example, ASD is four times more common in males than females. People with certain genetic disorders, such as fragile X syndrome, tuberous sclerosis, and Down syndrome, are more likely to have ASD.

Fly Rearing And Stocks

Drosophila strains were raised on standard cornmeal media and, unless noted, were maintained at room temperature on a 12h light:12h dark light:dark cycle. Young flies were defined as those < 10 days old and old flies as > 30 days old . We used wild type Canton-S and white1118 flies as control genotypes, as appropriate. trp1 and trpG4 are null trp alleles and were kindly provided by Craig Montell , as were UAS-trp, and a trp transgenic rescue line . UAS-RNAi lines for trp were obtained from the Vienna Drosophila RNAi Center, Vienna, Austria and the Bloomington Drosophila Stock Center at Indiana University, Bloomington, USA . Preliminary tests showed that the results obtained using the VDRC UAS-trp RNAi line were more severe and similar to those obtained with the trp null alleles. For this reason, all results reported here used RNAi line 105280 from VDRC. The elav-GAL4 driver , flies bearing a chromosomal deletion that uncovers trp ED1109 stock BL8945) and reporter UAS-mCD8::GFP , were obtained from the Bloomington Drosophila Stock Center. For hyperforin treatments we placed adult flies on apple juice-agar media containing 10µM hyperforin for 96h prior to testing.

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Is Autism Inherited From Mother Or Father

In almost 50% of the cases where theres only one child in the family with autism, the cause appears to be spontaneous mutations.

Spontaneous mutations are genetic mutations that are absent in the parents and siblings of affected children.

Image: Spontaneous mutations

Researchers have long noted that parents of autistic children display some of the traits seen in their children in a much more muted manner.

A 2020 study examined the role of familial relationships in explaining similarities in behaviors across family members.

The study found a relationship between parents and children’s behavioral traits and maternal polygenic scores and broad autism behavior traits in children.

This means that traits in children with autism may take after the mother’s subtle autism-like behaviors.

For example, if a mother has issues communicating in a social setting, then her autistic child may have communication difficulties themselves.

On the other hand, a large study based on the analysis of 9,275 whole genomes suggests that some mutations tied to autism may be passed down from fathers.

The study focused on flanking gene regions, where mutations are rarely observed.

The researchers reported that such rare variants are inherited from fathers twice as much compared to mothers.

The protective effect

Studies have revealed that a type of mutation called the copy number variation seen in autism was three times more common in girls than boys.

Can Autism Be Inherited From A Parent

Autism Environment Vs. Genetic Causes

A study of autism prevalence in five countries discovered that 80 percent of risk is determined by inherited genes rather than environmental factors or random mutations.

Study: Girls Need More Extreme Genetic Mutations To Develop Neurodevelopmental Disorders

A study involving nearly 1.1 million people in the UK Biobank discovered that boys are three times more likely than girls to be diagnosed with autism spectrum disorder and that boys with more severe cases are even more at risk. According to study author Dr. Simon Baron-Cohen, a researcher on autism at Cambridge University, the increased risk of ASD in boys may be due to a higher prevalence of extreme genetic mutations. According to the study, there is a gender bias in how neurodevelopmental disorders are diagnosed, and more research is needed to determine why boys are more likely than girls to develop these disorders. Boys are more likely to be diagnosed with neuro developmental disorders like autism than girls because girls must undergo more extreme genetic mutations in order to develop them, according to a study published today in the American Journal of Human Genetics.

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Study Points Toward Treatment And Diagnosis

While scientists now understand ASD better as a result of this study, this kind of research also points toward better ways to help children with ASD.

The greatest benefit of studies of this type is helping researchers, families, and interventionists better understand how genetic factors actually function in the developing brain and body of the individual, said Warner, so that treatments can be developed to ameliorate or completely block the disruptive changes that lead to disorders such as ASD.

But Zwaigenbaum cautions that the results of the study will not lead to clinical benefits right away.

Theres a lot of translational work that would still need to happen in order to assess whether the findings from this study will directly inform assessment, diagnosis, or treatment, he said.

Still, he said the results provide direction for future research into potential biological treatments, as well as genetic tests that could allow earlier diagnosis of ASD.

Warner said there are medications currently approved for use in children with ASD, but they address symptoms like agitation or anxiety, rather than the core social or behavioral deficits of ASD.

Early diagnosis is another goal of ASD research, because the sooner children are identified and appropriately assessed, the sooner families can receive needed supports, said Warner.

But ASD is a complex condition, so genetic diagnosis isnt always straightforward.

Clinical Implications And Future Perspectives

When autism was first described, it was hypothesized to be an environmentally caused disease. Decades of research have since revealed that autism is a highly heterogeneous and extremely complex genetic condition. Even though great progress had been made in identifying hundreds of risk genes, very little is known about the different types of modifiers that may exacerbate or ameliorate disease severity. Such modifiers could include epigenetics, sex-linked modifiers, CNVs, double-hit mutations, or environmental factors .

Figure 1. Genetic modifiers in autism spectrum disorder. Autism is estimated to be 4080% heritable. However, both genetic and non-genetic factors modulate the penetrance of risk genes, resulting in a highly heterogeneous disease phenotype for similar pathogenic variants. Examples of genetic modulators include CNV, epigenetics, and double-hit mutations. Examples of non-genetic modifiers include environmental exposures and sex-linked modifiers.

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About The Center For Autism And Neurodevelopment At Northwestern

The centers mission is to spur interdisciplinary research collaborations aimed at understanding the biological bases of autism and related neurodevelopmental disorders and to facilitate the translation of this knowledge into new treatments.

Autism is a highly prevalent neurodevelopmental disorder. According to the Centers for Disease Control and Prevention, one in 68 children are identified as having Autism Spectrum Disorder.

Over the past few years, many genetic causes of autism and related disorders have been found, which could provide insight into its neurobiological bases, Penzes said. The next major challenge is to understand the function of these genes in shaping the development of brain circuits and how their improper function may derail neurodevelopment. These genes and neurodevelopmental processes could serve as targets for new drugs aimed at treating autism and related disorders.

Other Northwestern authors are Sehyoun Yoon, PhD, Euan Parnell, PhD, and Marc Forrest, PhD.

The research was supported by grant R01MH107182 from the National Institute of Mental Health of the National Institutes of Health.

Discovery Points Toward New Treatment Approach

Immune Response and Inflammation in Autism Spectrum Disorder

As described in a study in the journal Neuron, Northwestern Medicine scientists have discovered why a specific genetic mutation causes intellectual disability and autism spectrum disorder in children.

We have solved an important piece of the puzzle in understanding how this mutation causes intellectual disabilities and mental illness, said lead author Peter Penzes, PhD, director of the new Center for Autism and Neurodevelopment and the Ruth and Evelyn Dunbar Professor of Psychiatry and Behavioral Sciences and of Physiology.

The Northwestern scientists discovered that genetic mutations in human patients in a gene called Usp9x result in the brain growing fewer synapses. Thats because Usp9x protects another protein called ankyrin-G, whose role is to grow and stabilize synapses. The developing brain needs to build lots of synapses between neurons so cells can communicate while the brain grows, and to learn.

But when Usp9x is mutated, it cant stabilize the synapse-enhancing ankyrin-G. Thus, the would-be enhancer protein degrades and destabilizes, resulting in fewer synapses in the brain, scientists found. Individuals with this mutation have developmental delay, difficulty learning, increased anxiety and hyperactivity.

In addition to ankyrin-G, Usp9x also protects several other important synapse-enhancing proteins, which when mutated also cause intellectual disability and autism. Usp9x is a master-stabilizer of many key proteins essential for brain development and learning.

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Direct Evidence For The Contribution Of Environmental Factors

There has been much discussion about the initial suggestion that MMR vaccine.79 However there is now a scientific consensus that the evidence favors rejection of a causal relationship between thimerosal-containing vaccines and autism, based on multiple epidemiologic studies which did not support a link between thimerosal-containing vaccines and ASD . However, other environmental factors are likely to contribute to a significant proportion of ASD risk.

Prenatal and perinatal factors

In another meta-analysis focusing on the perinatal and neonatal period,83 the same authors identified several potential risk factors, the main being fetal presentation, umbilieal-cord complications, fetal distress, birth injury or trauma, multiple birth, maternal hemorrhage, summer birth, low birth weight, small for gestational age, low 5minute Apgar score, meconium aspiration, neonatal anemia, ABO or Rh incompatibility, and hyperbilirubinemia. Feeding difficulties and congenital malformation that are also mentioned should rather be considered as symptoms of an underlying cause of autism. The identification of summer birth as a risk factor is consistent with the results of a recent study showing that maternal infection in the first trimester increases autism risk.84

Socioeconomic status

Drugs and toxic exposure

If My Older Child Is Diagnosed With Asd What Are The Chances Any Other Children Would Have Autism

Parents may take genetic tests to determine if their defective gene was passed on and led to their child developing autism. Research conducted at Duke University Medical Center found that this happens through a process called genetic imprinting.

Genetic imprinting goes against the typical laws of Mendelian genetics where genes are either recessive or dominant. In genetic imprinting, genes become turned off shortly after fertilization, or during the development of egg or sperm cells.

Imprinting affects a genes development, and through testing, genetic specialists can trace the pattern of inheritance of a disorder between parent and child.

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Scientists Discover How A Gene Mutation Causes Autism

Though previous research has associated numerous different gene mutations with autism, exactly how these mutations contribute to the development of the condition has been unclear. Now, a new study published in the journal Cell has uncovered the workings behind one autism-related gene mutation.

Conducted by researchers from the University of North Carolina School of Medicine in Chapel Hill, the study reveals how mutations in a gene called UBE3A drive it to become hyperactive, leading to abnormal brain development and autism.

In individuals with autism, duplication of the 15q chromosome region referred to as Dup15q syndrome is one of the most common genetic abnormalities. It was previously believed that too much UBE3A is the cause.

Study leader Mark Zylka, associate professor of cell biology and physiology, and his team explain that in normal brain development, the UBE3A gene can be turned on or off via the attachment of a phosphate molecule, which acts as a regulatory switch.

However, the researchers found that mutations in UBE3A destroy the regulatory switch which they identified as protein kinase A meaning the gene cannot be turned off, causing it to become hyperactive. This hyperactivity, according to the team, causes autism.

Zylka and colleagues reached their findings by sequencing the genes of human cell lines from children with autism and their parents.

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