Epigenetics And The Environment
Autism susceptibility is currently estimated to be 4080% genetic. Environmental factors likely acting through epigenetic regulation as the major mechanism presumably compromise the remainder of the risk. Hundreds of potential environmental factors have been suggested to contribute to risk, such as increased parental age , maternal complications or infections during pregnancy, or prenatal exposure to anticonvulsants . In-depth reviews of these findings can be found elsewhere . In this review, we will only discuss the epigenetic modifying effects of valproic acid an anticonvulsant as one example of the widespread modifications that an environmental factor can induce. Valproic acid has been hypothesized to modify gene expression through histone deacetylase inhibition activity and is sometimes used to induce an autistic phenotype in animal models . Examples of its far-reaching effects include apoptotic cell death in the neocortex, decreased proliferation in the ganglionic eminence, increased homeobox A1 expression, abnormal serotonergic differentiation via Achaete-Scute family BHLH transcription factor 1 silencing, disrupted serotonin homeostasis in the amygdala, dendritic spine loss, reduced prefrontal dopaminergic activity, and disruption of the glutamatergic/GABAergic balance .
Genetic Studies On Autism
Following extensive research on autism and genetic links, several genes have been found to potentially be connected to ASD. Rylaarsdam, et al. highlights various findings from genetic studies these are highlighted below:
At the genesis of genome studies, genetic studies on heredity have been conducted through twin studies, namely monozygotic twins and dizygotic twins. Monozygotic twins are derived from one fertilized egg that has split into two and dizygotic twins are derived from two separate eggs released at the same time fertilized by two separate sperm. It has been found that monozygotic twins are more likely to share a diagnosis than dizygotic twins, therefore suggesting a genetic influence.
Thanks to the growth of genetic research, genomic studies have increased with findings citing that the etiology of autism spectrum disorder is both multigenic and heterogeneous.
Large scale genetic studies have been conducted on patients with ASD as well as their families. Through these studies, several risk genes have been identified. Of these, two broad classes of proteins have been found to be related, namely: synapse formation and transcriptional regulation and chromatin-remodeling pathways. In addition, several studies have found a variety of changes in chromosome structure and number in some samples of autistic children.
Lets break down the two classes and why autism risk genes are found to be related with these classes:
What Is The Treatment For Autism
There is currently no cure for autism. However, autism can be managed and shaped at a young age, even as early as pre-school. Early intensive therapy can have a positive effect on development later in life.
Treatment of autism involves medical and behavioral therapies to help children with conversational language and social interactions. Treatment also involves helping children decrease their repetitive, self-stimulatory behaviors, tantrums and self-injurious behavior.
Medications can help treat specific symptoms such as aggressive or self-injurious behavior, inattention, poor sleep and repetitive behaviors. However, no medications are autism specific and medications should be used in conjunction with a family-centered, behavioral and educational program.
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The Characteristics Of Autism Spectrum Disorders
1.What are the characteristics of Autism Spectrum Disorders ?As described in the textbook, there is a broad range of characteristics associated with Autism Spectrum Disorders . One of the first characteristics noted with ASD is language deficits, or using language in odd ways. As stated in the textbook, Children with classic autism may be nonverbal. Alternatively, they may have significant language difficulties, so that their language may consist primarily of echolalia or delayed
Is Autism A Chromosomal Disorder
According to El-Baz, et al. clinical genetic studies have conducted research on the genetic causes of autism and found autism genes in 5% with high resolution chromosomal abnormality, 5% with fragile x syndrome, 5% with Rett syndrome, 10% with other genetic syndromes and 10% with structural genomic deletions or duplications
From a genetic standpoint, the chromosomal abnormality found in autism explains why theres such a high number of varieties in the phenotypic expression of autism. Therefore, autism is considered to be polygenic is influenced by more than one gene) and multifactorial .
While it is believed that some genes on the X chromosome contribute to the development of autism, studies point to the fact there are genes across the human genome capable of epigenetic modulation that are found to be involved in the susceptibility of autism. Epigenetic changes are those which do not change your DNA sequence, but the manner in which that sequence is read.
There are genes that are involved in regulating the occurrence of an epigenetic change. If theres any mutation in these genes, it can lead to other risk genes related to disorders such as autism. According to Rylaarsdam, et al. there are two key genes that increase an individuals susceptibility or predisposition to autism if mutated, namely: MeCP2 and UBE3A.
- UBE3A lies in the chromosomal region 15q11-13, which is commonly duplicated in autism according to Rylaarsdam, et al.
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The Treatment Of Speech And Communication Disorders
ntroductionHave you ever been seen by a therapist due to an injury or simply for recovery? Therapy is defined as treatment projected to heal a certain disorder. Within this field, there are various types of therapy. For example, speech, physical, and occupational therapy. Speech therapy includes the treatment of speech and communication disorders. While physical therapy focuses on the use of exercises and equipment to help patients regain or improve their physical abilities, occupational therapy
Association And Candidate Gene Studies
Association methods are considerably more powerful than linkage methods at a given locus, allowing genes of weaker effect to be detected, but the polymorphisms tested must be much closer to the susceptibility variant. For this reason, tests of genetic association have generally been used to study candidate genes in disease. Family-based association testing has become the gold standard in avoiding population stratification bias. More recently, methods that properly control for potential population differences have been developed for casecontrol studies., As genotyping throughput increases and costs decrease, genome-wide association studies of large samples will soon offer the potential to detect genes of small effect without requiring hypotheses about pathophysiology or chromosomal location. Coupling this approach with layered analysis of multiple samples may allow investigators to efficiently avoid both types I and II error. Population isolates with extensive linkage disequilibrium may also be very helpful for genome-wide association mapping.
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Who Should Have Fragile X Testing
Any male or female with intellectual disabilities, developmental delay, speech and language delay, autism or learning disabilities of unknown cause.
Any female with infertility, elevated FSH levels, premature ovarian failure, primary ovarian insufficiency, or irregular menses. Learn more.
Any male or female over 50 with features of FXTAS, including intention tremors, ataxia, memory loss, cognitive decline, or personality change, especially in combination with a positive family history of Fragile X.
Any preconception or pregnant female who expresses interest in or requests Fragile X carrier testing.
What Research Is Being Done
The mission of the National Institute of Neurological Disorders and Stroke is to seek fundamental knowledge about the brain and nervous system and to use that knowledge to reduce the burden of neurological disease. The NINDS is a component of the National Institutes of Health , the leading supporter of biomedical research in the world. NINDS and several other NIH Institutes and Centers support research on autism spectrum disorder.
Nearly 20 years ago the NIH formed the Autism Coordinating Committee to enhance the quality, pace, and coordination of efforts at the NIH to find a cure for autism. The NIH/ACC has been instrumental in promoting research to understand and advance ASD. The NIH/ACC also participates in the broader Federal Interagency Autism Coordinating Committee , composed of representatives from various U.S. Department of Health and Human Services agencies, the Department of Education, and other governmental organizations, as well as public members, including individuals with ASD and representatives of patient advocacy organizations. One responsibility of the IACC is to develop a strategic plan for ASD research, which guides research programs supported by NIH and other participating organizations.
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The Path To Diagnosis: Autism Screenings School And Specialists
Parents and caregivers will notice their childs symptoms at different times. Some parents will notice symptoms before the childs first birthday and can receive a reliable, valid, and stable diagnosis by age two, but most children are not diagnosed with ASD until after four years. The Autism Science Foundation has curated a list of common early signs of an ASD in infants and children that are usually indicators that your child may need to be evaluated.
As early as six to 18 months you might notice that your baby fixates on objects or does not respond to peopleOlder babies and toddlers may fail to respond to their names, avoid eye contact, lack joint attention , or engage in repetitive movements such as rocking or arm flapping. They may play with toys in unusual ways, like lining them up or focusing on parts of toys rather than the whole.
Screenings for autism are typically done at 18 and 24-month check-ups, but if you notice signs of autism in your child sooner, do not hesitate to contact your childs pediatrician. Developmental screenings are available at 9, 18, 24, and 30 months of age, but screenings specific to your concerns and your childs needs can be conducted at any time.
Genes Involved In Autism
In addition to clinically identifying known genetic disorders which may predispose to the development of autism, intense efforts have been directed to identifying genes that specifically cause or increase the risk of developing autism. The methods used include both large genome-wide association studies and investigation of candidate genes. The Genetic Association Database provides online access to human genetic association studies performed on autism and other complex disorders. Authoritative reviews of the current status of candidate genes and loci are available. SFARIGENE is a new web-based searchable list of candidate genes associated with ASD. The candidate genes are richly annotated for their relevance to autism, along with an in-depth, up-to-date view of their molecular function extracted from the current scientific literature.
that lists known and putative autism genes is unquestionably incomplete, as new candidate genes are being reported at an unprecedented rate. The genes are organized by pathogenesis to highlight the progress made in the functional assessment of autism candidate genes and pathways. Some genes are included because of their compelling initial descriptions that still await confirmation.
Table 2 Known and putative autism genes
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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 .
A Research Study On Autistic Spectrum Disorder
of ASD dates back to the year 1908 when the word autism was first used to describe a subset of withdrawn schizophrenic patients. The word autism was then used again in 1943 when American child psychiatrist Leo Kanner, M.D., published a paper called Autistic Disturbance of Affective Contact describing eleven socially isolated children who displayed the same desire for sameness and aloneness describing their condition as early infantile autism . A year later German scientist named
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Types Of Support To Help People With Asd
ASD is a lifelong disorder. You cannot change the fact that a person has ASD. But support can significantly improve the ability of that person to be successful in all areas of their life. This support is referred to as intervention.
Intensive intervention and therapy can help a person
- learn new skills
- change some behaviours that interfere with their functioning.
Intervening as early as possible helps most people, so diagnosis in young children is important.
There are many programs and supports available for people diagnosed with ASD. Interventions for ASD can include:
- occupational therapy
- training for parents, families and caregivers
- behavioural therapy, like applied behaviour analysis
- education and school planning in the form of an individual education plan
Autism Chromosome: A Look At Genome Studies On Autism
The study of genes has led to the discovery that some genes contribute to deficits in communication, social cognition, and behavior. Individuals diagnosed with autism experience a variety of related symptoms, as such, a growing number of studies have been conducted from physiological studies to genetic studies. These seek to determine the cause of autism in an effort to improve the lifestyle of children with autism by targeting the biological cause of their symptoms.
The core features of autism spectrum disorder include persistent deficits in social communication and social interaction and restricted, repetitive patterns of behavior or interests. Other symptoms include intellectual disability, some experience developmental delay, delayed brain development, pervasive developmental symptoms etc. Due to all these anomalies, autism is generally considered a developmental disorder.
The core features of autism spectrum disorder include persistent deficits in social communication and social interaction and restricted, repetitive patterns of behavior or interests.
According to Rylaarsdam, et al. , other conditions that occur with autism include motor abnormalities, epilepsy, intellectual disability, sleep disorders, and gastrointestinal problems.
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A Complex & Evolving Relationship
The relationship between FXS and autism is complex and constantly evolving, and despite the frequency and severity of autism in FXS, there are still important gaps in knowledge due to limited research, samples, and surveys.
For further reading on the relationship between autism and Fragile X syndrome, see Fragile X Syndrome Related Concerns on the CDC website, and related consensus documents and articles below.
How Is Asd Diagnosed
ASD symptoms can vary greatly from person to person depending on the severity of the disorder. Symptoms may even go unrecognized for young children who have mild ASD or less debilitating handicaps.
Autism spectrum disorder is diagnosed by clinicians based on symptoms, signs, and testing according to the Diagnostic and Statistical Manual of Mental Disorders-V, a guide created by the American Psychiatric Association used to diagnose mental disorders. Children should be screened for developmental delays during periodic checkups and specifically for autism at 18- and 24-month well-child visits.
Very early indicators that require evaluation by an expert include:
- no babbling or pointing by age 1
- no single words by age 16 months or two-word phrases by age 2
- no response to name
- excessive lining up of toys or objects
- no smiling or social responsiveness
Later indicators include:
- impaired ability to make friends with peers
- impaired ability to initiate or sustain a conversation with others
- absence or impairment of imaginative and social play
- repetitive or unusual use of language
- abnormally intense or focused interest
- preoccupation with certain objects or subjects
- inflexible adherence to specific routines or rituals
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Is There Such A Thing As An Autism Gene
Of course, therein nor really such as thing called autism gene. There are several conditions associated with autism spectrum disorder that stem from mutations in a single gene, including fragile X and Rett syndromes. But less than 1% of non-syndromic cases of autism stem from mutations in any single gene.
So far, at least, there is no such thing as an autism gene, meaning that no gene is consistently mutated in every person with autism. There also does not seem to be any gene that causes autism every time it is mutated. Still, the list of genes implicated in autism is growing. Many of these genes are important for communication between neurons or control the expression of other genes.
What Are The Symptoms Of Autism
Autism usually develops before 3 years of age and affects each individual differently and to varying degrees. It ranges in severity from relatively mild social and communicative impairments to a severe disability requiring lifelong parental, school and societal support.
The hallmark symptom of autism is impaired social interaction. Children with autism may fail to respond to their name and often avoid eye contact with other people. They have difficulty interpreting what others are thinking or feeling because they don’t understand social cues provided by tone of voice or facial expressions and they don’t watch other people’s faces to pick up on these cues.
Many children with autism engage in repetitive movements such as rocking, spinning, twirling or jumping, or in self-abusive behavior such as hand biting or head-banging.
Of children being diagnosed now with an autism spectrum disorder, about half will have intellectual disabilities defined by nonverbal IQ testing, and 25 percent will also develop seizures. Though most children show signs of autism in the first year of life, about 30 percent will seem fine and then regress in both their language and social interactions at around 18 months of age.
About 30 percent of children with autism have physical signs of some alteration in early development such as physical features that differ from their parents , small head size or structural brain malformations.
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