Genetics of Autism Spectrum Disorder

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Questions and Answers

What is the percentage chance that a sibling of a child with ASD will also have ASD?

5% (correct)

60%

Approximately 5%

10-30%

What is the approximate percentage of cases of ASD that can be explained by a single genetic mutation?

Approximately 5% (correct)

60%

10-30%

Which chromosome has a strong evidence for loci associated with ASD?

Chromosome 1

Chromosome 10

Chromosome 20

Chromosome 7 (correct)

What is the name of the transcription factor located on chromosome 7 that has been linked to ASD?

EN2 (A) Signup and view all the answers

Which of the following is NOT a functional family of genes identified by the Autism Genome Project with de novo mutations?

Neurotransmitter synthesis (B) Signup and view all the answers

How do genetic factors contribute to the development of ASD?

They interact with environmental factors to trigger the disorder. (B) Signup and view all the answers

What is the role of the postsynaptic density in relation to ASD?

It is critical for the functioning of excitatory synapses. (B) Signup and view all the answers

Which of the following statements is TRUE about de novo mutations in ASD?

They are not present in family members. (A), They are more likely to be found in females with ASD. (B) Signup and view all the answers

What is a common intellectual characteristic of individuals with Williams Syndrome?

Very low IQ around 55 (A) Signup and view all the answers

Which of the following traits is NOT associated with Williams Syndrome?

High spatial reasoning skills (C) Signup and view all the answers

What specific genetic alteration is primarily related to Williams Syndrome?

Deletion in chromosome 7 (A) Signup and view all the answers

What anatomical feature associated with Williams Syndrome may explain poor spatial abilities?

Underdeveloped parietal cortex (D) Signup and view all the answers

Which factor is commonly used as a diagnostic test for Williams Syndrome?

Blood test for elastin (A) Signup and view all the answers

Individuals with Williams Syndrome are known for their emotional characteristics. Which of the following correctly describes them?

Experiencing high emotionality and overreactions (B) Signup and view all the answers

What type of subject are individuals with Williams Syndrome often preoccupied with?

A single subject or activity (C) Signup and view all the answers

Which of the following brain structures remains normal in individuals with Williams Syndrome, potentially explaining their strong language abilities?

Frontal cortex (D) Signup and view all the answers

What is a key difference between Autism Spectrum Disorder and Williams Syndrome regarding intellectual disability?

Autism Spectrum Disorder may involve an intellectual disability while Williams Syndrome always does. (B) Signup and view all the answers

Which of the following describes the social behavior typically associated with Autism Spectrum Disorder?

Typically socially avoidant. (A) Signup and view all the answers

What cognitive ability is typically observed in individuals with Autism Spectrum Disorder?

Excellent spatial abilities. (D) Signup and view all the answers

Which gene-related characteristic is unique to Williams Syndrome?

Gene(s) on chromosome 7. (D) Signup and view all the answers

How does the sociability of individuals with Williams Syndrome differ from that of individuals with Autism Spectrum Disorder?

Williams Syndrome individuals exhibit high sociability. (B) Signup and view all the answers

Which emotional characteristic is commonly shared by individuals with both Autism Spectrum Disorder and Williams Syndrome?

Emotional reactivity. (A) Signup and view all the answers

Which condition often leads to a preoccupation with a single subject or activity?

Both Autism Spectrum Disorder and Williams Syndrome. (A) Signup and view all the answers

What has the case of Genie highlighted about human development?

Experience plays a crucial role in overall development. (A) Signup and view all the answers

What is the name of the Canadian doctor who prevented thalidomide from being prescribed to pregnant women in the US?

Frances Kelsey (C) Signup and view all the answers

Which of the following is NOT a characteristic of the neurological phenotype of ASD?

Enhanced activation of the fusiform face area (D) Signup and view all the answers

What is a key characteristic of brain growth in individuals with ASD during the ages of 6-14 months?

Rapid and large brain overgrowth leading to increased brain size (A) Signup and view all the answers

What is the primary characteristic of brain connectivity in individuals with ASD?

Enhanced long-range connectivity (C) Signup and view all the answers

Which of the following statements is TRUE about oxytocin and ASD?

Oxytocin administration has demonstrated potential benefits in improving some social skills and behaviors in individuals with ASD. (B) Signup and view all the answers

How does thalidomide impact brain development?

Thalidomide can lead to cognitive and behavioral issues, including ASD, later in life. (A) Signup and view all the answers

What does the "mirror neuron system" refer to?

A network of brain regions that helps us understand the intentions and actions of others. (D) Signup and view all the answers

Which brain region is associated with face recognition and is often found to have reduced activation in individuals with ASD?

Fusiform face area (B) Signup and view all the answers

What is the current prevalence of autism spectrum disorder (ASD) in the United States?

1 in 68 births (B) Signup and view all the answers

Which of the following is NOT a frequent non-diagnostic co-symptom of Autism Spectrum Disorder?

Many suffer from anxiety disorders (D) Signup and view all the answers

What is the significance of the 'rote memory,' 'musical and artistic abilities,' and 'the ability to solve jigsaw puzzles' in individuals with autism spectrum disorder?

These abilities are often preserved even in individuals with severe intellectual disability and autism. (B) Signup and view all the answers

Which of the following is NOT a possible reason for the increase in ASD prevalence?

Increased use of vaccines (D) Signup and view all the answers

What does the acronym 'DSM' stand for in the context of the text?

Diagnostic Statistical Manual of Mental Disorders (A) Signup and view all the answers

Which of the following is a key symptom of autism spectrum disorder, as outlined in the DSM-5?

Reduced capacity for social interaction and communication (D) Signup and view all the answers

What is a potential reason for the shift between DSM-III, DSM-IV, and DSM-V potentially contributing to the increase in ASD diagnoses?

The DSM-V makes the diagnosis less strict, potentially leading to more diagnoses. (A) Signup and view all the answers

What is Williams syndrome?

A rare genetic disorder characterized by distinct facial features, cognitive and developmental delays, and a strong social disposition. (A) Signup and view all the answers

Study Notes

Atypical Neurodevelopment

Atypical neurodevelopment refers to conditions where brain development deviates from typical patterns.
Examples include Autism Spectrum Disorder (ASD) and Williams Syndrome.

Autism Spectrum Disorder (ASD)

Incidence: Occurs in approximately 1 in 68 births. (note: debate exists on the accuracy of this figure).
Diagnostic criteria (in DSM-5):
- Reduced capacity for social interaction and communication.
- Restricted and repetitive patterns of behavior, interests, or activities.
Co-occurring symptoms (often, not for diagnosis):
- 75% are males.
- Many experience intellectual or learning disabilities.
- Many suffer from epilepsy.

Autism Prevalence

Prevalence has increased substantially (over 600%) over the past two decades.
Recent research shows that changes in diagnostic practices may account for at least 25% of this increase.

Percentage of Autistic Quebec Children Attending Schools (1990-2000)

The percentage of autistic Quebec children attending school rose slightly between 1990 and 2000.
This data illustrates a clear trend, albeit a modest one on the graphic.

Prevalence of ASD in Canada (2019)

Prevalence rates for ASD in Canada were measured across different age groups (1-4, 5-11, 12-17, and all ages) in 2019.
Rates are shown for males, females and both sexes across the same age groups; with male to female ratios provided for each.

Reasons for Increased Prevalence of ASD

Possible factors that contribute to increasing prevalence of ASD:
- Environmental factors.
- Improved early identification and diagnosis.
- Increased awareness.

Prevalence of ASD, Intellectual Disability over Time (200-2010)

Data shows the number of enrolled students with autism and intellectual disability from 2000 to 2010.

Percentage of Persons with Autism (2003)

Shows a breakdown (by category) of the various groups of people with autism in a particular location.

Mean of All States: Total 3-5 year old population (various groups) (1995 - 2013)

The mean of all states for Total 3-5 year old population by various groups (e.g., white, black, Hispanic, and Asian) from 1995-2013 shows an increase in individuals with ASD in this age group, across these particular demographics during this time frame.

Evaluations (2012-2016 vs 2016-2020)

Shows the number of evaluations by time period, before and after the Covid-19 pandemic.

Total Prevalent Cases (1990-2020)

Includes a graphic displaying total prevalent cases, classified by gender in millions.
A related graph shows the M/F ratio, both in terms of numbers and prevalence rates.
Provides a detailed historical view of prevalence of ASD over time.

MMR Coverage and Prevalence (1987-1998)

Shows the rate for various grades for a certain percentage and prevalence.

Why an Increase in ASD Prevalence?

Potential factors influencing the increase in autism prevalence:
- Environmental factors (possibly, but not just vaccines)
- Improved early identification and diagnosis (DSM-III to DSM-V changed diagnostic criteria)
- Increased awareness

Autism Re-Definition (DSM-IV vs DSM-V)

DSM-IV and DSM-V provide distinct core symptom domains for autism.
DSM-5 incorporates associated features alongside core domains.

Features of Autism Spectrum Disorder

Highly heterogeneous disorder.
Functions may be impaired, normal, or improved.
Even individuals with severe intellectual disabilities may demonstrate preserved abilities (e.g., rote memory, musical/artistic abilities).

Savants Associated With ASD

Autistic savants (about 10-30% of those with ASD).
Savants are individuals with an intellectual disability who display spectacular cognitive and artistic aptitudes.

Neurobiological Bases of Autism Spectrum Disorder

Genetic factors influence ASD, often interacting with environmental factors in causing autism.

Results from the Autism Genome Project

Chromosomes 7, 17, 2, 5, 11, 15, 16, and X often exhibit links to ASD.
Several genes associated with ASD, including serotonin transporter, transcription factor EN2, glutamate action-related genes, and Neurexin 1.
Mutations occur in a functional network among diverse genes and other factors.

Many Genes Active During ASD Development

During early to mid-development, many genes show higher activity levels in those with ASD.
Most mutations are de novo and absent from family members.

Functional Families of Genes In ASD and De Novo Mutations

159 genes linked to ASD have de novo mutations that fall into specific clusters and functional categories, such as:
- Chromatin/DNA modification/regulation
- Postsynaptic density
- Neuronal signaling/cytoskeleton
- Ion channels activity

Environmental Factors and ASD

Thalidomide (a morning sickness medicine).
- It is a known environmental factor related to the development of ASD.

ASD Neurological Phenotype

Problems with facial recognition, prosopagnosia (difficulty recognizing faces).
Reduced activation of the mirror neuron system (difficulties understanding others' actions/emotions).
Abnormalities in regions like the amygdala and fusiform face area.

Brain Growth Phases in ASD

Slight prenatal underdevelopment.
Rapid and large brain overgrowth (6-14 months), which may predict the severity of ASD.
Overall slower brain growth rates between ages 1-5.
By adolescence, brain sizes usually do not differ from typical healthy brains.

ASD and Local Brain Connectivity

High-severity ASD features lower density of local connections compared to typical development.
All ASD children have higher connectivity density than typically developing brains.
Connectivity density often relates to severity of symptoms in those with ASD.

ASD Hyperconnectivity

ASD is characterized by both short-range and long-range hyperconnectivity.
In typical brains there is an balance between inhibition and excitation mechanisms, which are disbalanced in those with ASD.

Oxytocin and ASD

Children with ASD often have lower levels of plasma oxytocin.
Some cases have shown a mutated form of the oxytocin peptide.
Studies using oxytocin administration have shown improvements in aspects of social functioning in children with autism (emotion recognition, social interaction, etc.) but not for all core symptoms.

Williams Syndrome

Occurs in about 1 in 7500 people.
Features include:
- Intellectual disability, with often much lower IQ scores.
- Amazing language abilities.
- Poor spatial abilities
- Sociable and empathetic.
- High interest in single topics.
- Proficient in learning musical instruments.

Diagnostic Indicators of Williams Syndrome

"Elfin" facial features.
Severe spatial cognition impairments.
Many health concerns, (usually cardiovascular).
Emotional immaturity (overreactions).

Spatial vs. Language Abilities

A contrasting example for highlighting the relative strengths and weaknesses for people with Williams Syndrome versus typical development is providing drawings that people with are presented with, and asks for a description for the content of the drawing
Differences across language fluency and abilities can be demonstrated in the context of these descriptions.

Genetic Causes of Williams Syndrome

Considered a genetic disorder.
The correlation of cardiac abnormalities helped to isolate the major genetic factor associated with Williams syndrome.
Deletion on chromosome 7.
Deletion involves at least 26 genes, including elastin (a protein associated with elasticity in tissues and organs).
Around 95% of individuals with Williams Syndrome exhibit this unique deletion.

Anatomical Anomalies in Williams Syndrome

Smaller occipital and parietal cortices which may correlate with spatial impairments.
Normal frontal and temporal cortices, associated with potentially improved speech abilities.
Changes in the limbic system, possibly correlating with high emotionality.

Comparing ASD and Williams Syndrome Neurobiology

Comparison of ASD and Williams Syndrome highlights distinctions in:
- Genetic causes (ASD: multiple genes, often de novo; WS: single gene deletion).
- Sociability (ASD: often avoidant; WS: often highly sociable).
- Spatial cognitive abilities (ASD: often strong; WS: often weak).
- Other characteristics (e.g., musical talents, emotional reactivity).

Genes and Environment: Case of "Genie"

"Genie's" (a real person) case highlights the crucial role of experience in development, but emphasizes that stories of children with limited experience are insufficient for fully understanding the impact of experience

Image References

A collection of citations for the image sources used.

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Description

This quiz explores the genetic aspects of Autism Spectrum Disorder (ASD), examining familial connections, specific mutations, and associated genetic factors. Questions also cover related syndromes like Williams Syndrome, and their genetic characteristics. Test your knowledge on the complex interplay between genes and ASD development.