Genetic Factors of Autism Spectrum Disorder

Genetic Factors of Autism Spectrum Disorder

Introduction

Autism spectrum disorder (ASD) is a neuro-developmental disorder, (developmental, mental disorder) with an onset in infancy or childhood, characterized by a persistent lack of ability to initiate and maintain social interaction and social connections, as well as limited interests and often repetitive behavioral actions. The prevalence of autism spectrum disorder in the United States and other countries is estimated at 1% of the population. The main characteristic of the disorder is a permanent deficit in social communication and social interaction.Autism Spectrum Disorder Assignment There are also problems in nonverbal communicative behavior: an abnormality of eye contact (it is difficult for patients to maintain eye contact; moreover, it can cause unpleasant sensations), body language or body orientation, speech intonation, or problems with using and understanding the essence of nonverbal communication. Persons with ASD can learn several functional gestures, but their repertoire is smaller than that of other people; they cannot spontaneously use gestures in the discussion. In extreme cases, it reaches the complete absence of eye contact, facial expressions or gestures. However, ASD is one of the most heterogeneous neurodevelopmental disorders, with considerable variation observed in behavioral manifestations and cognitive profiles, which makes the determination of the single most important genetic risk factor extremely difficult (Yoo, 2015). Therefore, one has to analyze the genetic background and its effect on people with the autism spectrum disorder, taken from a plethora of studies and surveys.

In-Depth Discussion

The main scientific and practical areas of research into the causes and mechanisms of the formation of autism spectrum disorders are environmental, biological (namely genetics) and psychological. It is important to note that each of the theoretical orientations in the framework of these areas has a particular value for understanding certain features of autism. Chromosomal and genetic elements are of great theoretical importance for understanding the underlying mechanisms of pathogenesis, even though different researchers come to contradictory conclusions about the genetic “localization” of autism. Some associate its development with impaired replication of proteins involved in the development of sensory systems and cytoarchitectonics of the brain, others with metabolic disorders caused by genetic mechanisms, etc. (Zakia et al., 2017). Autism Spectrum Disorder Assignment Chromosomal abnormalities leading to the development of autism are more studied. Among them are the fragmented X chromosome, Ulrich-Noonan, Lesch-Nyhan, and other syndromes. It should be noted that in most cases with chromosomal genesis, the exact autistic symptoms do not always appear clearly in comparison with other disorders (somatic or intellectual), which makes it possible to attribute many such cases to the so-called para-autism.

Three groups of scientists, namely Heejeong Yoo (2015), Chaste & Leboyer (2012), and Huguet & Buorgeron (2016) independently established a link between mutations in specific genes and the likelihood of a child developing autism spectrum disorders. Researchers studied a rare mutation called “de novo.” Approximately 10% of patients with ASD, especially those with intellectual disability, are carriers of de novo copy number or single nucleotide variants affecting clinically relevant genes for ASD (Huguet & Buorgeron, 2016). These mutations are not hereditary but appear during the development of the fetus. Scientists (2012) examined blood samples of families in which children had autism, whereas their parents, brothers, and sisters did not. As a result, several children were found with the same mutation in the same gene, which was not tied by anything but a diagnosis. Despite the low frequency of de novo mutations in ASD individuals, inconsistencies in genetic analysis outcomes, and phenotypic heterogeneity, “synapse-related genes are crucial candidates of ASD and provide baseline evidence for testing compounds that can enhance synaptogenesis for the treatment of the core symptoms of ASD” (Yoo, 2015). Additionally, researchers have confirmed the theory of a direct relationship between the ages of parents, in particular, fathers, with the risk of developing autism. It turned out that the older the parents, the higher the risk of de novo mutations. It has also been found that lesions in male DNA, leading to this mutation, are four times more common than in female DNA, especially in men over 35 years of age.Autism Spectrum Disorder Assignment

The main problem faced by researchers in the study of ASD is a large number of different genetic mutations that cause mental disorder. Since they all are rare, they make it difficult to develop effective treatments for ASD. However, the staff of the Austrian Institute of Science and Technology (2016) was able not only to identify a previously unknown mutation but also to “find” a whole subspecies of such genes that act similarly. They were able to identify mutations in the SLC7A5 gene in several autistic patients born from closely related marriages. To understand how the SLC7A5 gene provokes the development of autism, scientists have made the experience in laboratory mice. They artificially removed this gene on the hematoencephalic barrier (BBB is a semi-permeable barrier between blood and nerve tissue, protecting the central nervous system from the penetration of large molecules and harmful compounds), which led to a decrease in the level of BCAA-amino acids in the brain and hindering protein synthesis in neurons. Rodents have disrupted social interaction and other changes characteristic of the ASD. Then, BCAA was delivered directly to the mice’s brain for three weeks; after that, the condition of the experimental improved significantly (Institute of Science and Technology Austria, 2016). Accordingly, scientists have proven the possibility of treating specific symptoms of ASD. However, it is too early to conduct such experiments on humans since more research is needed.