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European Journal of Applied Sciences – Vol. 12, No. 1

Publication Date: February 25, 2024

DOI:10.14738/aivp.121.16177

Sanyour, A., & Alhazmi, S. (2024). Giant Platelets as Potential Biomarker for Autism Spectrum Disorder. European Journal of

Applied Sciences, Vol - 12(1). 255-267.

Services for Science and Education – United Kingdom

Giant Platelets as Potential Biomarker for Autism Spectrum

Disorder

Aya Sanyour

Department of Biological Sciences,

King Abdulaziz University, Jeddah, Saudi Arabia

Safiah Alhazmi

Department of Biological Sciences, King Abdulaziz University,

Jeddah, Saudi Arabia and Immunology Unit, King Fahad Medical

Research Centre, King Abdulaziz University, Jeddah, Saudi Arabia

ABSTRACT

Introduction: Platelet hyperserotonemia has been repeatedly observed in

individuals with autism spectrum disorder (ASD). Ras p21 protein activator 3

(RASA3) is essential in forming and differentiating blood cells, especially platelets.

Therefore, this study aims to evaluate the expression of RASA3 and examine the

platelet morphology in addition measuring the plateletcrit and platelet count in all

samples. Methods: RNA was extracted from 12 autistic children and four control

samples then qPCR was used to determine the expression of RASA3. Platelet

morphology was examined under light microscope. In addition, Complete blood

count (CBC) test with automated haematology analysers was done for all children

to determine the platelet count and the plateletcrit (PCT). Results: The qPCR result

showed differential expression patterns of RASA3 between autistic and normal

samples. The platelet morphology revealed large and giant platelets in all autistic

samples and the plateletcrit percentage was increased in 10 out of 12 ASD samples.

Conclusions: There is a correlation between dysregulated RASA3 and the large and

giant platelets in ASD cases which could explain the platelet hyperserotonemia in

this disorder and could be used as an early biomarker for ASD diagnosis or may be

used for early interventions.

Keywords: RASA3, ASD, DNA methylation, Plateletcrit, Hyperserotonemia,

INTRODUCTION

ASD is a persistent impairment in social communication and interaction, as well as restricted

and repetitive patterns of behavior, interests, or activities. Indeed, the prevalence of ASD has

increased worldwide, and it is considered one of the most common disorders in the Gulf

Cooperation Council (GCC) countries (Almandil et al., 2019). However, ASD is considered a

heritable neurodevelopmental disorder due to the large differences in concordance rates

between monozygotic (60–92%) and dizygotic twins (0–10%) where the risk for ASD in

siblings is much higher than that in the general population (Elagoz Yuksel et al., 2016).

On the other hand, the diagnosis of autism still relies on expert judgment, observation, and

assessment of behavior and cognition to detect a significant impairment in the core behavioral

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European Journal of Applied Sciences (EJAS) Vol. 12, Issue 1, February-2024

domains when there is no exact biomarker for ASD is identified (American Psychiatric

Association, 2013). Therefore, ASD is usually appeared in the developmental period, often

during the second year of life, and it is in varying degrees of limitations, but if developmental

delay is severe, it may be seen earlier than 12 months, or later than 24 months if symptoms are

simple (Schaefer and Mendelsohn, 2013). However, earlier detection, intervention,

compensation, and current support for individuals with ASD could lead to a major long-term

positive effect on the symptoms (American Psychiatric Association, 2013).

However, in the 1950s, platelets (PLTs) studies had been an intriguing aspect for studying

neurodevelopmental disorders since the discovery of these tiny fragments of cells as storage

reservoirs for circulating serotonin (Maclean and Schoenwaelder, 2019). Therefore, the

researchers' interest has increased in using the platelets as a model cell for studying

neuropathology and also as a biomarker for the diagnosis of complex neurological disorders

(Padmakumar et al., 2019, Goubau et al., 2014). Platelets or thrombocytes are small blood cells

that stop bleeding by forming clots. In humans, platelets have an average life span of 8-14 days

then eliminated in the spleen and liver, they are originally derived from megakaryocytes in the

bone marrow that originate numerous cellular extensions called proplatelets resulting in the

release of thousands of platelets at once (Maclean and Schoenwaelder, 2019, Sharathkumar and

Shapiro, 2008). In addition, platelets size is 1-2 μm, six to eight times smaller than red cells

under the microscope, or 1.5 to 3 μm in greatest diameter (Handtke and Thiele, 2020, Palmer

et al., 2015). Although the basic function of platelets is to be activated when a blood vessel is

damaged to form a clot, hemostasis and blood coagulation is not the exclusive function of

platelets, they also play many pivotal roles in disease pathophysiology (van der Meijden and

Heemskerk, 2019, Ghoshal and Bhattacharyya, 2014). For instance, A previous study reported

that when platelet contains high amounts of serotonin it leads to dysfunction of the

serotoninergic system and the development of several behavioral disorders (Ehrlich and

Humpel, 2012). In general, dysfunction, abnormal activation, and morphological alteration of

platelets have been implicated in many complex neurological disorders such as schizophrenia,

migraine, Parkinson's disease, Alzheimer's disease, and autism (Goubau et al., 2014).

In normal conditions, serotonin or 5-hydroxytryptamine (5-HT) modulates a wide range of

neuropsychological processes, and it has important roles in controlling behavior and sociality.

In addition, alterations of serotonin metabolism have been linked to several neurological

disorders such as schizophrenia, migraine, Alzheimer’s disease, and ASD (Bijl et al., 2015). For

example, increased platelet activity has been described during migraine attacks and is related

to releasing serotonin (Goubau et al., 2014). Furthermore, several studies found that platelet

serotonin concentrations were significantly elevated in patients with chronic schizophrenia

(Asor and Ben-Shachar, 2012). Indeed, increased the level of serotonin in platelet of patients

with autism (platelet hyperserotonemia) was repeatedly observed, it seems to be the most

biochemical aberration that persistently appears in patients with ASD (Hranilovic and Blazevic,

2014, Janušonis, 2008). A previous study reported increased levels of serotonin in platelet-rich

plasma of ASD patients and their first-degree relatives (unaffected siblings, mothers, and

fathers), also a decrease in the secretion of adenosine triphosphate (ATP) from platelet dense

granules after stimulation. Moreover, the study has been reported an increase in the platelet

counts in ASD patients and their unaffected siblings compared to the normal controls (Bijl et

al., 2015). Nevertheless, platelets themselves are unable to produce serotonin, they take up

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Sanyour, A., & Alhazmi, S. (2024). Giant Platelets as Potential Biomarker for Autism Spectrum Disorder. European Journal of Applied Sciences, Vol -

12(1). 255-267.

URL: http://dx.doi.org/10.14738/aivp.121.16177

serotonin from the plasma into their dense granules via the serotonin transporter where it is

released upon activation. Consequently, it has been speculated that platelets’ function is to keep

the concentration of circulating serotonin at the normal level (Maclean and Schoenwaelder,

2019).

On the other hand, the blood-brain barrier (BBB), which tightly controls the passage of ions,

molecules, and cells between the blood and the brain tissue, is virtually impermeable to 5-HT.

In early studies on the role of serotonin in ASD, it has been assumed that biological factors that

lead to platelet hyperserotonemia may influence the autistic brain in the early development

stages when the blood-brain barrier is not yet fully formed (Janušonis, 2008, Karande, 2006).

A recent study suggested that platelets may facilitate communication between the blood and

the brain (Leiter and Walker, 2019). To date, there is no direct explanation to elucidate the

association between altered serotonin levels and a variant gene that regulated serotonin

metabolism in autism cases (Padmakumar et al., 2019, Goubau et al., 2014).

DNA methylation is the major and well-studied epigenetic mechanism that regulates gene

expression and has a critical role in normal brain development and stem cell differentiation

(Moore et al., 2013, Berdasco and Esteller, 2011). DNA methylation is essential for the

maintenance of hematopoietic stem cell (HSC) homeostasis. Additionally, aberrant DNA

methylation has been associated with several diseases such as leukemia, autoimmune disease,

and neurological diseases (Jiang et al., 2019, Jin and Liu, 2018). Moreover, aberrant methylation

of RASA3 is correlated with its differentially expressed and is implicated in neurological

disorders such as Schizophrenia and Alzheimer (Broce et al., 2019, Pidsley et al., 2014).

RASA3 is a member of the GAP1 subfamily and is also known as (Ras GTPase-Activating Protein

3, GAP1IP4 Binding Protein, Ins (1,3,4,5) P4-Binding Protein, and R-Ras GAP or GAP III). The

GAP1 family of RasGAPs comprises RASA2, RASA3, RASA4, RASAL1 (King et al., 2013). RASA3

functions as an important negative regulator of the small guanosine triphosphatases (GTPase)

Ras and Rap signaling pathways. Moreover, membrane localization of RASA3 is required for

GAP activity to downregulate RAS and RAP which plays roles in cell differentiation and

development (Chang, 2014).

Small GTPases also known as small G-proteins are molecular switches that cycle between

inactive (GDP)-bound and active (GTP)-bound states, they are deactivated by GTPase- activating proteins (GAPs), where they are activated by guanine-nucleotide exchange factors

(GEFs) (Toma-Fukai and Shimizu, 2019). Ras GTPase superfamily has obtained medical

attention due to its involvement in several diseases such as cancer, cardiovascular disorders,

aging, neurodegeneration, and developmental syndromes (Goitre et al., 2014). However, it’s

well-known that all blood cells are derived from hematopoietic stem cells that are

differentiated into progenitor cells that develop into mature circulating cells. Interestingly,

studies on mouse models have demonstrated the crucial role of RASA3 in hematopoiesis.

Moreover, RASA3 was originally purified from the plasma membrane of human platelets in

1994 and the study found that RASA3 has a pivotal role in platelet activation (Robledo et al.,

2020;Stefanini and Bergmeier, 2016). According to the above, understanding the role of RASA3

in the platelets of individuals with autism is important for enhancing our understanding of the

etiology underlying ASD.