Tuesday, June 21, 2022

Is There A Gene For Autism

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Some Mutations Tied To Autism May Be Passed Down From Fathers

Real Questions – Is there a specific gene that causes autism?

The findings go against previous studies that suggest mutations are inherited from mothers

Some children with autism carry rare mutations in DNA segments that flank genes and control their expressionand they tend to inherit these mutations from their unaffected fathers, according to a study published today in Science1.

The finding is unexpected because most studies implicate mutations inherited from mothers in autism risk. For this reason, some experts are skeptical of the results.

The study is the largest yet to explore how mutations outside of genes contribute to autism: It is based on an analysis of 9,274 whole genomes. And it focuses on structural variantsdeletions or duplications in DNAin these noncoding regions. Once dismissed as junk DNA, some of these regions are now known to control the expression of genes.

These are the types of variants which, before, if you did clinical genetic testing, you would ignore, says lead investigator Jonathan Sebat, chief of the Beyster Center for Genomics and Neuropyschiatric Diseases at the University of California, San Diego.

The variants overall account for only a small proportion of individuals with autism, however: an estimated 0.39 to 1.13 percent.

Is There Genetic Testing For Autism

By Andréas RB Deolinda, BA, BSc

Genetic studies are evolving every day and now play a key part in identifying which genes could be the reason behind disorders and disabilities. Genetic testing is being used more and more in the medical community, but is there a form of genetic testing for autism spectrum disorder ?

This article should answer this big question while also taking a closer look at genetic testing in general and highlighting some of the controversies.

Yes The Behavioral Diagnosis Is Strengthened By The Genetic Diagnosis When Combined They Form A More Effective Way To Treat Autism Especially Since There Are Many Possible Permutations Of The Condition

The diagnosis is simply a description of the condition that can be important for a number of reasons, but it does not answer the why that is the root cause of autism in that particular individual.

Genetic testing provides a new level of information that can be used to help more clearly define how to best monitor, treat and react to the various challenges of autism. Genetic testing provides a critical roadmap on how to treat someone going forward.

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Definition And Evolution Of Asd

Autism is a developmental neuropsychiatric syndrome with onset before the age of three. The fundamental conceptualization of the disorder is based on the initial observation of Kanner in 1943 , where he described 11 children with autism, mostly boys with a combination of severe social and variable language dysfunction and the presence of repetitive restrictive behaviors. Kanner made numerous interesting observations based on these case studies, including the identification of large head size in about half of the subjects and postulated a biological, genetic basis for the disorder. However, until the 1980s autism was not considered a distinct disorder in the manuals of psychiatric diagnosis, nor was it considered by most to be biologically based.

Epigenetic Dysregulation In Autism

Researchers Reveal Connection Between BPA Exposure and ...

Although most of the epigenetic modifications described above are underpinned by genetic mechanisms, the evidence of the contribution of epigenetic dysregulation in autism raises the issue of the role of epigenetic modifications by environmental factors. An example is assisted conception. Indeed, while it was shown that in vitro fertilization and ovulation induction can result in abnormal methylation and dysregulation of imprinted genes, epidemiologic studies on the use of assisted reproductive technology and the risk of autism found conflicting results.

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Find Other Parents Who Will Understand And Support You

It always has been invaluable to have other parents who are going through the same thing as you are, to call them up and say I cant believe this is happening to me today. Because to the rest of the community, the things that happen to us, theyre really not the norm.Ruth Singer Strunck, the mom of two young adults with autism

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An Early Arrival An Early Diagnosis

Cindy Yeagers twins, a boy and girl, arrived early, as twins often do. She credits a friend, an occupational therapist, with pushing her to enroll them in Marylands program for infants and toddlers with developmental delays. A teacher in that program noticed that her son, Aaron, flapped his hands, a behavior often seen in autism.

That led to appointments with a child psychiatrist, who diagnosed both with autism. Mrs. Yeager got the news on the same day. She took it in stride. It wasnt a shock because we knew something was wrong, she said. And it offered hope: When you get the correct diagnosis, you get the correct services. Now their teachers knew what to do.

Fraternal twins are more likely to both have autism than siblings who are not twins. Scientists theorize that may because they share the same prenatal environment. Identical twins, who have the same genes, have the highest rate of both having autism 88 percent among all siblings.6

Although both Yeager twins received autism therapies and early intervention services, they travelled different paths, as siblings with ASD often do.

Hayley began talking at age 4, and entered a regular kindergarten class at 5, with a special education plan. Aaron did not develop speech, and he enrolled in an intensive program at a different school. For the Yeagers, that meant attending special education meetings and getting to know teachers and therapists at separate schools.

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The Heritability Of Autism: From Early To Modern Twin And Family Studies

Although Kanner is reported to have viewed autism as an innate disorder , a strong psycho-analytic tradition led to the growing belief that refrigerator mothers might be to blame. The first twin study of autism conducted by Folstein and Rutter was ground-breaking because it clearly showed a predominantly genetic contribution to autism. The most recent meta-analysis of all published twin studies of autism/autism spectrum disorder conducted by Tick and colleagues also yielded a large heritability estimate of 6491% and no significant shared environmental contribution. These authors demonstrated that if the estimated prevalence rate of autism is incorrectly specified for the study population , this essentially results in an increased non identical twin correlation but does not affect identical twin correlations, thereby resulting in a reduced heritability estimate and a stronger shared environmental contribution. Thus the shared environmental contribution observed in two outlying studies appeared to be explained by the assumption of prevalence and an overinclusion of concordant DZ twins. The study by Tick and colleagues is also important in showing that if the autism broad phenotype is clinically recognised, then that ought to be taken into account by assessing different thresholds when fitting statistical models.

High Levels Of Fetal Testosterone

Genetic Testing for Autism

It has long been noted that the prevalence of Autism seems to be stronger in boys than in girls. It does not mean that girls are excluded from Autism, but instead that higher numbers of boys are diagnosed than girls. Science has indeed confirmed that the trait is male-typical, although not exclusive. The study says that high levels of testosterone in the amniotic fluid may be related to certain variables of brain function, like cognition and behavior. The information was compiled from routine amniocentesis. These findings confirm a previous hypothesis that Autism could be related to the male sex hormone. The theory states that children with extreme male brain, babies exposed to too much testosterone, show a reduced capacity to empathize and a stronger urge to systemize. Researchers say that this test was too small to be conclusive and that a much larger study is necessary to confirm the link between over productions of testosterone in the amniotic fluid and Autism.

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In Autism It Depends On Which Parent Passes On The Genetic Abnormality

Date:
Duke University Medical Center
Summary:
While it has been known that genetic abnormalities are implicated in susceptibility to autism, new research by Duke University Medical Center researchers has added another variable the particular parent who contributes the defective gene can determine whether or not the child acquires autism.

PHILADELPHIA While it has been known that genetic abnormalities are implicated in susceptibility to autism, new research by Duke University Medical Center researchers has added another variable the particular parent who contributes the defective gene can determine whether or not the child acquires autism.

The researchers point out that autism is an extremely complex disease with a wide spectrum of behavioral manifestations and it is likely that other genes or environmental factors are involved. However, their sophisticated genetic analysis has for the first time suggested that a phenomenon known as genetic imprinting is at work in autism and that it appears to be an important factor in the disorder.

Genetic imprinting is a process by which a genes expression is governed solely by which parent donates the gene copy, rather than by the classic laws of Mendelian genetics, in which genes are either dominant or recessive. Imprinted genes typically become inactivated, or turned off, during the development of egg or sperm cells, or shortly after fertilization.

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Asd Risk Genes Overlap With Other Diseases

Large-scale sequencing studies of major psychiatric diseases have revealed extensive overlap in risk loci, challenging the classification of these conditions as distinctive disorders. In 2013, the Cross-Disorder Group of the Psychiatric Genomics Consortium conducted a massive study with 33,332 cases and 27,888 controls in order to identify pathogenic variants shared between ASD, schizophrenia, bipolar disorder, ADHD, and major depressive disorder . In addition to establishing varying degrees of pair-wise crossover, they found loci that reached genome-wide significance for all five disorders near the following genes: inter-alpha-trypsin inhibitor heavy chain 3 , arsenite methyltransferase , calcium voltage-gated channel subunit alpha1 C , and CACNB2. Glessner et al. have also conducted a large-scale meta-analysis of structural variants across the same diseases and correlated structural variants in the loci of dedicator of cytokinesis 8 and KN motif and ankyrin repeat domains 1 with all five conditions. Schork et al. recently hypothesized that abnormal gene regulation in radial glia and interneurons during mid-gestation is a mechanism of shared risk, after using GWAS to identify susceptibility loci in genes including phosphodiesterase 1A , protein phosphatase 1 regulatory inhibitor subunit 1C , RHOA, immunoglobulin superfamily member 11 , and sortilin related VPS10 domain containing receptor 3 .

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Several Biological Pathways Identified

Individuals with ASD vary in language ability, ranging from absent speech to fluent language, and in cognitive development, ranging from profound intellectual disability to above-average intellectual functioning. Individuals may also show associated medical comorbidities including epilepsy and minor physical anomalies, as well as psychiatric comorbidities, thus showing a wide clinical heterogeneity. The clinical heterogeneity of autism has long been a hindrance to understanding the pathophysiological mechanisms involved. However, although many questions remain and new questions are being raised, the last several years of investigation have brought important pieces to the autism puzzle. Indeed, the identification of specific alleles contributing to ASD has shed light on pathogenic mechanisms.

Going back to an individual approach, already used in mental retardation, the search for rare mutations or chromosomal rearrangements was then used, allowing new hypotheses about the mechanisms involved in autism. While the existence of many genetic syndromes associated with autism first led to considering the existence of genetic heterogeneity mirroring the clinical variability, genetic studies in idiopathic autism confirmed the existence of different defects in common pathways. The results suggest that autism may be caused by a multitude of genetic alterations that ultimately affect only limited biological pathways of brain development and plasticity.

Genetic Testing For Autism

Diverse Autism Mutations Lead to Different Disease ...

This Got Questions? answer is by geneticist Dean Hartley, Autism Speaks Senior Director of Discovery and Translational Science.

We recommend anyone with an autism diagnosis get genetic testing. Unfortunately, less than half of people with autism do.

Current genetic testing will not give answers to everyone, but without testing we will not be able to give information to some individuals or families that could explain the possible cause of autism and possible future medical conditions.

When you are ready to have genetic testing, we suggest you start with the provider who diagnosed you or your child with autism. That person should be able to refer you to a neurodevelopmental pediatrician, a medical geneticist, or a clinic that specializes in autism or developmental disorders and has experience in genetic testing. We do not recommend directly seeking a company to do genetic testing. A medical specialist or genetic counselor is best qualified to help you understand beforehand what the test will or will not provide and the interpretation of your results.

Once you see this specialist, you will likely be offered the current standard of genetic testing, called microarray testing. Of those who do, 3 to 10 percent will find a genetic variation that likely accounts for a persons autism. One reason for these small percentages is the limitations of microarray technology it only covers a small amount of our 6 billion letters of our DNA that we get from our parents.

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Prenatal Testing Or Elimination Of Autism

Perhaps these studies should be investigated along with researchers quest for more accurate prenatal testing for autism. Because the dwindling numbers of those born with Down syndrome may be the fate of kids on the spectrum if testing asks parents to choose who should live.

And then? What will the next prenatal test set out to detect? Developmental disorders, neurodiversity, or any mutant gene that may cause variation from a cognitive standard determined by science? A dystopian future with a distinct eugenics twist seems scary and a little too realistic.

References:

Bai, D., Yip, B., Windham, G. C., Sourander, A., Francis, R., Yoffe, R., Glasson, E., Mahjani, B., Suominen, A., Leonard, H., Gissler, M., Buxbaum, J. D., Wong, K., Schendel, D., Kodesh, A., Breshnahan, M., Levine, S. Z., Parner, E. T., Hansen, S. N., Hultman, C., Sandin, S. . Association of Genetic and Environmental Factors With Autism in a 5-Country Cohort. JAMA psychiatry, 76, 10351043.

Chen, W. J., Zhao, S., Huang, T. Y., Kwok, O. M., & Chen, L. S. . Autism Spectrum Disorders: Prenatal Genetic Testing and Abortion Decision-Making among Taiwanese

Mothers of Affected Children. International journal of environmental research and public health, 17, 476. .

Dawson, G., & Zanolli, K. . Early intervention and brain plasticity in autism. , 251, 266297.

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Genetic Bases Of Autism

Several psychiatric diseases have strong evidences of genetic involvement in their origin, and among them are schizophrenia, bipolar disturbance and autism. In 1977, a study with mono and dizygotic twins described for the first time the genetic predisposition of autism .

Nowadays, population studies suggest that the model that better describes DASs is multifactorial with a concordance of 60-92% in monozygotic twins and 0-10% in dizygotic twins . Differences found in studies between monozygotic twins support the multifactorial model, demonstrating the importance of environmental factors.

Several studies were performed to clarify genetic factors associated with the disease. Autism symptoms that suggest a strong genetic component are convulsions, mental deficiency, neurons and synapse decrease in amygdala, hippocampus and cerebellum, increased size of encephalon, and increased level of circulating serotonin. Even studies with monozygotic twins show a significant concordance, as opposed to dizygotic twins. Non-twin siblings present a risk of developing autism ranging from 0-30%, and this risk is much higher than in the general population .

The comparison of the mentioned populational groups, as well as the difference between men and women, shows epistatic effects that involve an interaction between several genes, suggesting the role of environmental factors .

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Indirect Evidence Suggesting A Contribution Of Environmental Factors

Prevalence

Prevalence studies of autism spectrum disorders conducted in recent years have been the source of an important debate because of a steady and highly significant increase of estimates of the total prevalence of pervasive developmental disorders. Indeed, while the prevalence was estimated at 6 per 1000 in a population of school children in 2005, recent studies have gone so far as to estimate the prevalence to be one child in 38.The last prevalence estimates in the United States, released by the Centers for Disease Control recently, reached 1 in 88 child in 2008, while their previous estimate was one in 110 in 2006. However, most of the studies are not comparable in method or in the populations studied. One hypothesis is that this increase is the result of enlargement of diagnostic criteria, and the growing importance of screening for ASDs. The results of an epidemiological study from England, based on a national sample from 2007, support this hypothesis. Indeed the authors found a rate of about 1% in adults across the entire age range, without a significant reduction in the older part of the sample, as one would expect if the prevalence had increased in recent years. However, another study suggested that diagnostic substitution, especially for the most severe cases, and better ascertainment, especially for children at the less severe end of the spectrum, explain only a part of the linear increase observed in the California registry.

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Early Detection Early Intervention

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It is comforting to believe that ASD prenatal testing is mostly about helping scientists discover more about genetic variations linked to autism, and identifying autism at the earliest opportunity to allow parents to plan ahead. The argument is convincing when you consider studies examining the effect of early autism intervention, especially with regards to brain plasticity . In this study, the authors concluded that early intervention enhancing social attention, should lead to alterations in brain activity.

A prenatal test detecting autism in a fetus could provide parents with enough time to shift expectations, appeal for all the support theyll need, and prepare themselves emotionally and financially. But preparing for a life of care will also bring up the inevitable question for some parents of whether it would be easier not to embark on the journey at all.

Looking at a study about the estimation of people with Down syndrome in Europe, a reduction of 27% was estimated, meaning approximately 417 000 people with Down Syndrome were living in Europebut without elective abortions there may have been an estimated 572 000.

Another review tells us that between 71 and 100% of women decide to terminate a pregnancy with fetal Down syndrome. In countries like Denmark and Iceland the statistics are close to 100%.

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