Genetics of Autism
Spectrum Disorder
Abstract:
In this paper I briefly will summarize current research articles and journals
of authors in reference to the genetics of autism spectrum disorder.
Outline of how paper should be constructed:
I.
Introduction
II.
Background on Autism Spectrum Disorder
III.
Genetics of Autism Spectrum Disorder
IIII.
Neuroscience of Autism Spectrum Disorder
V.
Summary of Autism Spectrum Disorder
Autism
Spectrum Disorder (ASD) is a cluster of developmental disorders whose characteristics
include adverse and pervasive impairments in social interaction and
communication as they emanate from the brain (Sanchack & Thomas, 2016). The
disorders include Asperger syndrome (AS), childhood disintegrative disorder,
pervasive developmental disorder and Autistic Disorder (Barna, 2017). There are the specific
set of symptoms that tend to display in an individual with any of these
disorders. Among these symptoms are Impaired social and communication
interactions, restricted set of thinking and interests, and finally repetitive
movements and behavior. The reason behind the occurrence of these symptoms in
people with ASD cannot yet be explained, but most of them usually appear at the
age of three in an individual (Rodger,
2014).
Background on Autism Spectrum Disorder
Autism is
a term that was introduced in the psychiatric literature by a Swiss
psychiatrist by the name Eugen Bleuler in 1911. The term was coined from the word
autos Greek for self. The word describes the extreme antisocial and
self-obsessive behavior observed in children. Ever since, efforts have been
made to recount the existence of the disorder historically through observation
of the symptoms. There have been reports of features of autism from as early as
the mid-1700s (Barna,
2017). However, it was not until 1943 when Leo Kanner from John Hopkins
Hospital published the first ever case study of autism referring to it as a
medical condition. In 1944 Hans Asperger, a scientist from Australia described
a disorder which had similar symptoms with autism, however milder. The disorder
was referred to as Asperger’s syndrome. More work continued to be done on
observing and recording various aspects of autism. Bernard Rimland in 1964, published
his work on autism in a book he called Infantile Autism: The Syndrome and Its
Implications. In this manuscript, Rimland argues that autism emanates from the
brain and not just a physiological condition. The main feature of the disorder
being inability to develop normal relationships with people and repetitive
behavior, Donald Baer, Todd Risley and Montrose Wolf in 1968 published a paper
on a behavioral therapy that would focus on minimizing repetitive behavior in
children and developing social skills (Lubetsky, Handen & McGonigle, 2017).
More
modern work has been published on the disorder among them being that of
Professor Uta Frith. In two of her works as late as 1991, Frith has made a
significant contribution in recording historical autism-like characteristics
observed in Europe. Among these were two cases, that of France and the other
from Scotland both of which took place in the eighteenth-century. From the case
of the man from Scotland, the story goes that the man appeared in court in
regards to his mental ability to contract a marriage. In Frith’s observation of
this case, the man displayed that would be today classified as similar to
autism which included, abnormal gazing, echolalia, poor social relationships,
repetitive language, collecting objects and poor mannerisms. The other case of
France was recorded by a physician who treated a twelve-year-old boy who was in
the woods. In the recorded data, the boy could not speak but instead produced
bizarre noises, he had poor social skills and showed impulsive and overactive
traits. Frith observed in her work that the symptoms would be classified as
autism as they are the same one people with what has been diagnosed in the
modern-day autism display (Lubetsky,
Handen & McGonigle, 2017).
Andrew
Wakefield from Britain and twelve other researchers published a paper in 1998
in The Lancet, linking autism to childhood vaccination for rubella, measles,
and mumps. As a result, many parents in the U.S and Britain resorted to denying
their children the vital vaccines hence putting them at risk of contracting the
diseases. Scientist found flaws in the paper and finally in 2007 ten of the
co-authors denounced their findings. Consequently, The Lancet retracted the
paper in 2010. The same year the British Medical Council revoked Andrew’s
medical license following The Lancet decision. There have been studies over the
years, and no causal link has been found between childhood vaccination and
autism. Many scientists have termed Wakefield’s research as a cause of fear of
childhood vaccination and a drag on the autism research (Barna, 2017).
An array
of researches have since been done to not only define the disorder but also to
try and find the cause, the treatment, and management of the disorder. Through
the research, it is quite clear who between men and women are more prone to
this among many other elements.
Genetics of Autism Spectrum Disorder
In
discussing the genetics of Autism Spectrum Disorder contrasting syndromic and
non-syndromic is crucial as it elaborates deeper on the aspects.
Syndromic
ASD
The
Syndromic ASD consists of identifiable syndromes with genetic causes that are
known. They may include but not limited to Fragile-X syndrome, and Tuberous
Sclerosis. Syndromic ASD is characterized by dysmorphic features like
anatomical brain abnormalities, seizures, chromosomal abnormalities intellectual
disability (ID). It is approximated that 10% of children evaluated for Autism
Spectrum Disorder are found to be having a medical condition with a genetic
lesion such as tuberous or Fragile X. 10% more are found to have copy number
variation related to ASD or have a chromosomal structural abnormality (Lubetsky,
Handen & McGonigle 2017).
According
to data compiled by Lubetsky, Handen & McGonigle (2017), of 15q
duplication-Angelman syndrome, the number of individuals with the syndrome and
have ASD is more than 40% and that of patients with ASD and have the signs is
between one and two percent. The Gene associated with this syndrome is UBE3A.
In 16p11 deletion syndrome, the number of patients with this syndrome and have
ASD, is high while the number of individuals with an ASD that have the syndrome
is approximately 1%. The Gene associated with this syndrome is however unknown.
22q deletion as a syndrome related to the SHANKS Gene and the number of
patients with this syndrome and high ASD is high. There is a rare occurrence in
patients with an ASD and have the syndrome (Lubetsky, Handen & McGonigle
2017).
From
recent genome-wide scans, it is apparent that a little chromosomal duplication
or deletion could be the origin of ASD. Through various studies, it is
estimated that at least 2% of familial and10% of sporadic ASD may be due to de
novo copy number variation (CNV). The list of know ASD- related CNVs may
increase with the advancement in microarray technology (Buxbaum & Hof,
2013).
Non-syndromic
ASD
The
non-syndromic ASD of cases with or without identifiable duplication or deletion
in the DNA. The microgenetic alterations are found within the abnormal
chromosomal regions in the syndromic ASD thus the link between syndromic and
non-syndromic. People with the non-syndromic ASD are most likely to be male.
The ratio of female to male on the prevalence of non-syndromic ASD IS 1:4
(Lubetsky, Handen & McGonigle 2017).
The
distinction between syndromic and non-syndromic ASDs is starting to thin in
that the genes associated with non-syndromic ASD are found within chromosomal regions
or abnormal chromosomes which result in syndromic ASD.
Neuroscience of Autism Spectrum
Disorder
In 1943
when Leo Kanner published his work on Autism, he noted that out of 11 of the
patients her diagnosed with autism, five of them had a brain enlargement from
the ordinary which triggered the study of the circumference of the brain. The
study conducted during the time yielded little to no results as there were no
techniques to better the study. However, with technological advancement there
came the magnetic resonance imaging (MRI) which allowed the study of the brain
structure and function of an individual with ASD (Buxbaum & Hof, 2013).
Study of
the brain prior the introduction of MRI suggested that there was a significant
process in age-dependent brain growth abnormality in an individual with autism.
There have been studied implying that the size of the brain of a young child
with autism increased by 5-10%. Year of study in this area has consistently
suggested that there has been a correlation between an increased brain volume
and the severity of autism symptoms. The child’s brain size returns to normal
or smaller by the time they are adolescents heading to adulthood. Various
studies have also suggested that several brain regions play a role in ASD and these
areas may increase or decrease in size compared to those children without the
ASD (Buxbaum & Hof, 2013)..
Summary of Autism Spectrum Disorder
Autism
Spectrum Disorder is a condition that is not physiological but emanates from
the brain. Various studies have shown that variation in the size of the brain
and some parts of it that affect the way of life are the most crucial in
determining the causal elements. It is also apparent that gene duplication and
deletion of de novo copy number variation can cause various syndromes
associated with ASD. However, as much as individuals with the disorder have
traits like repetitive patterns of interests and behavior, social and
communication restrictions, they could lead a normal lifestyle. The lifestyle
could be achieved through proper management from a tender age through
activities behavior therapy for 25 hours a week, contemporary alternatives life
fine art or medicine (Sanchack & Thomas, 2016).
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