Rare Copy Number Variants Intersecting Parkinson’s-associated Genes in a Cohort of children With Autism Spectrum Disorders

Abstract

Autism spectrum disorders (ASDs) are neurodevelopmental conditions characterized by important clinical and genetic heterogeneity. Recent studies suggested an overlap between ASD and Parkinson's disease (PD) in terms of clinical manifestation and underlying genetic defects. Our aim was to assess using a chromosomal microarray assay the frequency of rare exonic deletions that overlap with PD associated genes in a pediatric ASD group. Three hundred and five children diagnosed with ASD were enrolled in a study focused on deep phenotyping and genomic profiling by chromosomal microarrays. In the investigated group, four children with ASD harbored deletions encompassing genes involved in Mendelian forms of PD or contributing to PD risk. Deletions of Parkin RBR E3 ubiquitin protein ligase (PRKN) and synuclein alpha interacting protein (SNCAIP) were found in one patient, each; two other patients showed intragenic deletions of Rab9 effector protein with kelch motifs (RABEPK). Our study found that deletions involving genes associated with PD are rare events, as we identified approximately 1% in the ASD cohort of children. Our data adds to the previous reports of rare genomic imbalances of PD associated genes in ASD, further supporting the hypothesis that these conditions might share molecular mechanisms of pathogenesis.

Keywords

Autistic behavior movement disorders copy number variants monogenic Parkinson’s disease

Introduction

Autism spectrum disorders (ASDs) and Parkinson’s disease (PD) are complex disorders with neuropsychiatric manifestations and composite pathophysiology. From a developmental perspective, ASDs and PD occupy opposite ends of the spectrum, ASDs disrupting early neurodevelopment while PD occurs mostly at an advanced age due to neurodegeneration.

ASDs are neurodevelopmental conditions (NDC) characterized by impairment of social interactions, restricted interests, and repetitive behaviors. ASDs are clinically multisystemic complex entities, with many comorbidities described to date.^1-3 Among the challenges faced by individuals with ASDs are motor problems, which occur very early in life and can persist throughout life. These problems consist of delayed gross and fine motor development, muscle hypotonia, and gait problems (especially toe walking).^4-6 In this regard, several studies reported phenotypic overlap between ASDs and PD, mostly in the category of repetitive behaviors; other Parkinson’s symptoms observed in individuals with ASDs include: gait freezing, bradykinesia, rigidity, repetitive behaviors, and hypomimia.^7,8

ASDs pathophysiology has an important genetic component; both rare genetic variants with major phenotypic effects and common variants with small impact have been found to play a role in the occurrence of these conditions.⁹ A wide array of rare de novo or inherited genomic imbalances and sequence variants that involve neurodevelopmental genes have been reported in cohorts of individuals with ASDs.^10-12 Several of these genes are also known to cause early-onset, mendelian PD^13,14 or contribute to an increased risk for idiopathic, sporadic PD.^15,16 Moreover, adults with ASDs seem to be at greater risk of developing PD compared to the general population in similar age intervals.¹⁷

Our aim was to assess the frequency of rare exonic deletions that intersect PD associated genes in a pediatric ASD group of 305 children and to correlate these genotypes with the developmental trajectories, behavior, and occurrence of different co-morbidities of the respective children.

Methods

The patient group, consecutively enrolled from September 2019 to February 2022 for genomic profiling, included 305 pediatric patients (<18 years) diagnosed with ASD. The clinical protocol included neurologic, psychiatric, and psychological assessment with standardized tools according to the age of the child. The diagnosis of ASD was established according to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5TR) criteria, using specific psychological tests for ASD: Autism Diagnostic Interview-Revised (ADI-R) and Autism Disorder Observation Schedule (ADOS).

Array-based comparative genomic hybridization (array-CGH) was performed on whole blood gDNA using Agilent SurePrint G3 Human CGH Microarray Kit (Agilent Technologies, Santa Clara, CA, USA). Copy number variants (CNVs) were stratified by their clinical relevance using ACMG criteria in benign (B), likely benign (LB), variants of uncertain significance (VOUS), likely pathogenic (LP), and pathogenic (P).¹⁸

The inheritance studies were performed in families with children harboring CNVs involving PD associated genes when parental blood samples were available, following the protocol below. Quantitative Real-Time Polymerase Chain Reaction (qPCR) was performed on 7500 Fast PCR machine (Applied Biosystems, Foster City, CA, USA) using Power SYBR Green PCR Master Mix and primers targeting the regions of interest.

To screen for PD associated genes, the gene content of deletions with (potential) clinical impact (P, LP and VOUS) found in our ASDs group, encompassing at least one exon, was manually compared to several gene lists. These lists were compiled from Online Mendelian Inheritance in Man - OMIM database (omim.org - “Parkinson disease” search term), Movement Disorder Society Genetic mutation - MDSGene database (mdsgene.org - “Parkinson disease” search term) and a dedicated database and analytic platform for Parkinson disease Gene4PD (http://genemed.tech/gene4pd/source), and literature (search term “Parkinson disease AND gene name”).^19-21

The study was reviewed and approved by the Ethics Committee of Prof. Dr. Alexandru Obregia Clinical Hospital of Psychiatry (Approval no 33/26.11.2019) and of Victor Babes National Institute of Pathology (Approval no 76/3.12.2019). Written informed consent was obtained from all the parents of enrolled individuals for participation in the study and for data publication, before inclusion in the study.

Results

Genetic analysis

Array-CGH detected 218 rare CNVs classified as P, LP or VOUS in our group of children diagnosed with ASDs. Among these, four exonic deletions, classified as VOUS, encompassed genes associated with PD (Table 1). Considering the greater detrimental effect of genetic material loss compared to duplications, we chose to only focus on the deletions found in our exploration of genomic imbalances in PD linked genes. Moreover, the functional impact of duplications, apart from that of genes with triplosensitivity, is more difficult to predict.

Table 1.

Summary of genetic findings of the patients harboring deletions of PD associated genes.

Pt.	Gender	CNV type	Genomic coordinates (GRCh37)	Size (kb)	OMIM Genes	Effect	Classification
1	F	Del	chr6:162525376-162636361	111	PRKN (NM_004562.3)	Deletion of exon 4 and partial deletion of flanking sequences from introns 3 and 4. Predicted out of frame	VOUS in relation to NDC phenotype; recessive allele (Parkinson disease juvenile type 2 – AR - OMIM # 600116)
2	F	Del	chr5:120064176-121792041	1727.8	FTMT, SRFBP1, LOX, SNCAIP (NM_005460.4), ZNF474	Large deletion including several genes. SNCAIP gene deletion spans 5’UTR, exons 1-7 and the flanking region from intron 7.	VOUS; pathogenic CNV due to LOX deletion (Aortic aneurysm, familial thoracic 10 – AD - OMIM # 617168), incidental finding
3	M	Del	chr9:127963344-127980239	16.8	RABEPK (NM_001174152.2)	Deletion of exons 3 - 5, partial deletion of introns 2 and 5. Predicted out of frame	VOUS
4	F	Del	chr9:127963344-127980239	16.8	RABEPK (NM_001174152.2)	Deletion of exons 3 - 5, partial deletion of introns 2 and 5. Predicted out of frame	VOUS

AD, autosomal dominant; AR, autosomal recessive; Del, deletion; kb, kilobase; NDC, neurodevelopmental conditions; OMIM, Online Mendelian Inheritance in Man Database; PD, Parkinson Disease; VOUS, variant of uncertain significance.

Parkin RBR E3 ubiquitin protein ligase (PRKN) genetic defects are known to be causal for a form of juvenile PD which is highly penetrant and has an autosomal recessive inheritance.²² In addition, the PRKN gene has been proposed to contribute to various NDCs, ASDs included.^13,23-26 Microarray testing identified an intragenic deletion of PRKN (6q26) in patient 1, spanning 111 kb, which includes exon 4 and sequences of flanking introns 3 and 4 (Table 1), inherited from the healthy father. Although CNVs inherited from a healthy parent are less likely to be detrimental, incomplete penetrance and clinical variability were reported for various pathogenic CNVs in NDCs.^27,28 No other rare CNVs with potential relevance for the phenotype were found.

Synuclein alpha interacting protein (SNCAIP) is proposed as a risk factor for idiopathic PD.²⁹ SNCAP, the protein encoded by SNCAIP, is the interacting protein of α-Synuclein, the pathology of which is a major feature in PD.³⁰ Moreover, SNCAIP has been identified in large cohorts with ASDs as a candidate gene for this condition.^31,32 Microarray testing revealed, in patient 2, a large deletion (~1.7 Mb) on 5q23.1-23.2 including four OMIM genes. SNCAIP is partially encompassed by the deletion (Table 1). The deletion was the only CNV with potential relevance. Due to the lack of biological samples from the parents, no inheritance data were available for this CNV. Thus, the significance of this CNV remains VOUS.

Ras analog in brain 9 (Rab9) effector protein with kelch motifs gene (RABEPK) codes for the effector protein of RAB9 which belongs to a family of genes involved in PD pathogenesis; reports of RABEPK gene alteration in ASDs are exceedingly rare.³³ Microarray testing of patients 3 and 4 revealed a deletion of ~17 kb on 9q33.3 which encompasses three exons (3, 4 and 5) of RABEPK (Table 1). Inheritance data were partially available for patient 3 - the healthy mother is not a carrier of this CNV, while the father was unavailable for sampling. No inheritance data were available for this CNV in patient 4, due to the lack of biological samples from the parents. No other rare CNVs with potential relevance for NDC were found in patients 3 and 4.

Patient 3, a boy, was also screened for CGG expansion in the Fragile X messenger ribonucleoprotein 1 gene (FMR1) associated with Fragile X syndrome. The methylation pattern and the number of triplet repetitions were in the normal range (data not shown). The clinical interpretation of this CNV has remained VOUS.

Clinical reports

Ninety percent of the patients from our cohort of 305 children aged 2 to 18 years were diagnosed with unexplained ASDs, with no genetic causes identified by chromosomal microarray and Fragile X testing and without clinical descriptions suggestive of a well-defined genetic syndrome. These patients presented with different degrees of ASDs severity, ranging from mild to severe, and in many cases associated with other neuropsychiatric conditions, such as intellectual disability or developmental delay, speech problems, hyperkinesia, and sleep disorders. Fifteen patients with unexplained ASDs were diagnosed with high-functioning ASD.

Genetic variants considered explanatory for the neurodevelopmental phenotypes were found in the rest of 10% of the patients (data not shown). Only one of these patients was high-functioning.

All four children harboring deletions involving PD associated genes belong to the unexplained ASDs category; they were unrelated, and born from healthy nonconsanguineous parents.

Patient 1 is a girl of 7 years who harbors an intragenic deletion of the PRKN gene. She was born at 38 weeks by caesarian section from a pregnancy with placenta praevia, in breech presentation and reduced fetal movements. Her birth weight was 2500 g and length 50 cm. The neonate Apgar score was 2; she was admitted into the intensive care department for 1 month with apnea episodes and feeding difficulties. She had a delayed psychomotor development: she sat down at 3 years, walked with support at 6 years, said her first syllables at 19 months and first words at 30 months. At the age of 4 years, she presented her first epileptic seizures – epileptic spasms, atypical absences, with partial seizure control with levetiracetam. The actual clinical examination showed normal morphometric measurements and dysmorphic facial features (Table 2). Neurological evaluation showed ataxic gait only with support, hypotonia, severe speech delay (she says only syllables, no complete words); severe intellectual disability (IQ 30), autistic behavior (poor eye contact, stereotypic movements, very poor interest in toys and other persons). ADOS test showed mild autistic behavior (a total score of 8). Electroencephalogram (EEG) showed generalized epileptiform discharges. Brain Magnetic Resonance Imaging (MRI), electromyogram, heart, and abdominal ultrasound evaluations were normal. Metabolic tests were in the normal range.

Table 2.

Clinical findings - auxological, dysmorphological, electrophysiological and neuroimaging - of the children with ASD and genetic variants in PD-associated genes.

Pt	Age (years/months)	Gender	Morphometric parameters			Dysmorphic features	Epilepsy/EEG characteristics	MRI
Pt	Age (years/months)	Gender	Weight - kg (per Centile or SD)	Height – cm (percentile or SD)	OFC -cm value (percentile or SD)	Dysmorphic features	Epilepsy/EEG characteristics	MRI
1	7	F	20 (16)	118 (26)	51 (15)	up slanting palpebral fissures, hypertelorism, broad nasal bridge, anteverted nostrils, micrognathia	Yes/ generalized epileptiform discharges	normal
2	5	F	17 (32)	105 (28)	47.5 cm (3)	big, malformed protruding ears, up-slanting palpebral fissures, partial palpebral ptosis bilaterally, long eyelashes, anteverted nostrils, short nasal philtrum, high palatal arch, micrognathia, single transvers palmar crease at the left hand, finger pads	No/normal	Normal
3	4/10	M	15 (6)	110 (72)	OFC 47 (<-3.4 SD)	big, malformed ears, partial palpebral ptosis bilaterally, broad nasal bridge, anteverted nostrils, high palatal arch, micrognathia	Yes/ ESES	mild temporal atrophy
4	5/7	F	19.5 (50)	111 (43)	52.5 (85)	-	No/ NP	NP

ASD, autism spectrum disorders; ESSES, electrical status epilepticus in sleep; NP, not performed; PD, Parkinson Disease; SD, standard deviation.

Patient 2 is a girl aged 5 years, found by our study to have a deletion that encompasses SNCAIP, besides the other three OMIM genes. She was born at 38 weeks, weighing 2010 g, with feeding difficulties in the first month of life (gavage feeding). The psychomotor development was delayed: head control at 12 months, sitting at 18 months, unsupported walking at 3 years, first syllables at 3 years, first words at 4 years. She was included in a program of therapy (physical and speech therapy) starting at the age of 6 months. The clinical evaluation at 5 years showed normal growth parameters and craniofacial and upper limbs dysmorphic features (Table 2). Neurological examination showed chewing difficulties, poor gross and fine motor skills, brisk reflexes at lower limbs, speech delay (she says only words, no sentences); autistic behavior (echolalia, stereotypic movements, difficulties in social interaction). The psychological evaluation showed mild developmental delay (DQ 58) and moderate autistic behavior (ADI-R score 30).

Patient 3 is a boy, 4 years, and 10 months old, in whom chromosomal microarray showed a small intragenic deletion in the RABEPK gene. He was born at 36 weeks with normal physical development, after an uncomplicated pregnancy. He had a mild motor delay (sat down at 8 months, and walked unsupported at 17 months) and severe speech delay (no syllables at the last follow-up). At the age of 2 years 6 months, he started to present generalized epileptic seizures; sleep and wake EEG studies in the conscious state and in sleep revealed generalized sharp-waves and poly-sharp-waves discharges with activation in sleep (pattern of electrical status epilepticus in sleep, ESES). Brain MRI showed mild temporal atrophy. He received anti-seizure drugs (valproate, levetiracetam, clonazepam) and cortico-therapy, with partial seizure control but with persistence of an EEG pattern of ESES. The present examination revealed microcephaly (below 3SD), normal weight and height, and facial dysmorphic features. Neurological and psychological examination showed chewing difficulties, ataxic gait, hypotonia, poor gross and fine motor skills, no bladder control, severe speech delay (she says only sounds), severe autistic behavior (no eye contact, stereotypic movements, ADOS score of 17), and severe developmental delay (DQ 34).

Patient 4 is a girl, 5 years, and 7 months old, with the same small intragenic deletion in RABEPK gene. She was born at 36 weeks by caesarian section after a pregnancy complicated by maternal blood hypertension, with normal physical development. She had a delayed psychomotor development: she sat down at 8 months, walked unsupported at 17 months, said first syllables at 2 years and first words at 3 years. The present clinical examination showed normal growth parameters (Table 2). The neurological examination showed speech delay (poorly developed speech, dyslalia, echolalia; mild intellectual disability (IQ 65) and severe autistic behavior (poor eye contact, stereotypic movements, difficulties in social interaction; ADOS score 19).

Table 2 summarizes additional clinical aspects observed in our patient group.

Discussion

We report the results of a study focused on screening for deletions of PD associated genes in Romanian children diagnosed with ASD, obtained from a larger study including 305 subjects. Four deletions were thus detected; although the genes involved are promising candidates for NDC or interact with NDC genes, the functional impact of these deletions at the protein level and subsequently the significance for the neurodevelopmental phenotypes is uncertain (VOUS).

ASDs and PD are conditions with complex pathogenesis, which involves a genetic component.^11,34-36 Recent reports suggested an overlap between ASD and PD in terms of underlying genetic defects and clinical manifestation.^8,25,37 ASDs are neurodevelopmental conditions with life-long, multi-systemic health issues, social interaction difficulties, and deficits in adaptive functioning.^2,3 The genetic causes and liability of ASDs are well known.^10-12 Complex molecular pathomechanisms, including disruption of neurogenesis, neuronal differentiation and communication, underlie ASDs. This leads to the impairment of brain development with onset in fetal life.^11,38,39 At the opposite end of the spectrum, PD is a neurodegenerative disorder characterized by progressive and selective substantia nigra dopaminergic neuron loss, as the main culprit for symptomatology.⁴⁰ PD is a complex neurodegenerative condition in which the individual genetic background acts in synergy with other contributing factors (i.e. age and environmental insults).³⁶ More than 20 genes were reported to cause specific forms of familial, early-onset PD (SNCA, PRKN and PINK1) or to contribute to an increased risk for idiopathic, sporadic PD (LRRK2).^20,41 Seventy-eight loci were found to be robustly associated with PD in genome-wide association studies performed on populations with diverse ancestries.⁴²

ASDs and PD are disorders with an important clinical heterogeneity that reflects the underlying diversity of biological pathomechanisms and complex genetic architecture. Understanding the molecular basis is instrumental for the delineation of more homogeneous patient groups within ASDs and PD, respectively, which may lead to patient tailored therapeutic strategies. Various research work starting from genome-wide association studies data sets obtained from individuals with ASDs^43,44, schizophrenia⁴⁵, and PD⁴⁶ revealed links between neurodevelopment and neurodegeneration in protein-protein interaction networks, gene regulatory networks and biological networks. Moreover, both PD and ASDs showed alterations of common essential biological processes, such as mitochondrial biogenesis and functions, oxidative metabolism, and dopaminergic pathway.^37,44,47,48 The identification of common dysregulated pathways provided the rationale for developing new therapies or repurposing the existing ones with the aim of improving the management of both ASDs and PD.

Among the various levels of overlap, clinical commonalities between ASDs and PD have also been noted. The motor symptoms include rigidity, bradykinesia, gait freezing, and hypomimia.⁸ Hollander et al.⁷ observed common obsessive-compulsive (OC) and related phenomena, such as pathological repetition, including preoccupations, rituals, or inflexible activity.⁷ Moreover, a higher incidence of PD and Parkinson’s symptoms was reported in ASD adult individuals compared to the general population.^17,49

Considering all the above, we consider that neurological evaluation with special attention on the detection of signs and symptoms specific to PD, using standardized clinical tools, would be beneficial in individuals with ASD, especially in those who carry gene variants associated with PD. Periodic neurological follow-up of all patients with ASD during their lifespan starting from early adulthood is also warranted for the identification of PD signs and progression of the disease. By adding new cases with NDC whose genomic profiles contain variations in PD associated genes and gathering cross-sectional and longitudinal clinical data, valuable data for both conditions can be generated.

Regarding the genes reported in this paper, PRKN and SNCAIP, were previously described in association with both ASDs and PD. They are known candidate genes for NDC, ASD included, recorded in dedicated databases.^32,50 PRKN is a well-known cause of early-onset PD while SNCAIP is proposed as a candidate gene for PD. RABEPK has been indirectly linked to PD and ASDs by its interaction with neuronal RAB protein RAB9. RAB9 gene has been proposed to be involved in the development and differentiation of neurons.⁵¹

PRKN gene, found by us to have an intragenic deletion in patient 1, encodes parkin, known to be involved in protein degradation dependent on proteasome. Parkin is a pleiotropic molecule due to its ability to ubiquitinate an array of protein substrates that are involved in many biological processes at the cellular level.⁵² PRKN plays an important role in mitochondrial homeostasis,⁵³ disruption of PRKN being associated with ubiquitination defects and impaired mitophagy.⁵⁴ PRKN defects are the most frequent genetic causes of early-onset PD, the alterations of mitochondrial functions being positioned at the core of disease pathogenesis.⁵⁵ Biallelic pathogenic variants in the PRKN gene are known to be associated with Parkinson’s disease juvenile type 2 (OMIM # 600116) by a loss of function mechanism.^19,22 However, the association of heterozygous variants in PRKN with an increased risk for PD is still actively debated.^56,57

Extended studies have shown that heterozygous CNVs involving PRKN, de novo or inherited from healthy parents, are also found in NDCs, including ASDs.^13,23-26 PRKN is recorded in the Simon Foundation Autism Research Initiative (SFARI) database as a strong candidate for ASD (score 2).³² Studies performed on PRKN mutant neurons derived from a human fibroblast cell line supported Parkin roles in neuronal homeostasis, specifically neurite growth and maturation.⁵⁸ Furthermore, other evidence supported the role of Parkin in synapse functions, namely localization in neuronal bodies as well as axons and dendrites, association with synaptic vesicles and ubiquitination of synaptic proteins.^52,59-61 Similarly, Huo et al (2022) found evidence that supports the involvement of Prkn in brain development in murine models, the loss of Parkin being associated with a reduction in dendritic arborization and synapse density as well as alterations of synaptic proteins.⁶² Moreover, the same study found autistic-like behaviors in Prkn knockout mice.⁶²

The deletion identified in patient 2 encompasses the SNCAIP gene which encodes a protein harboring several protein-protein interaction domains, synphilin-1, an interactor of alpha-synuclein (SNCA). The gene is known to be involved in cell death, regulation of inclusion body assembly and regulation of neurotransmitter secretion mainly by ubiquitin protein ligase binding and protein binding.⁶³ Synphilin-1 interacts with SNCA and other proteins involved in PD, such as parkin,⁶⁴ however, its physiological functions are not completely understood. Synphilin-1 seems to play a neuroprotective role for dopaminergic neurons, as proven by in vitro and in vivo studies;^65,66 however, synphilin-1 neurotoxicity was also detected in PD experimental models.⁶⁷

Synphilin-1 is expressed in the brain, predominantly in neurons; its presence in synapses suggests that synphilin-1 mediates SNCA synaptic effects.⁶⁸ The same study, that was performed on rat models, found evidence for accumulation of synphilin-1 in presynaptic nerve terminals during development.⁶⁸ However, few studies focused on synphilin-1 role in neurodevelopment. SNCAIP has been only recently proposed as a candidate gene in ASD^31,69 and listed in the SFARI database.³² CNVs altering SNCAIP have been reported in NDC databases such as DECIPHER; three CNVs were associated with ASDs, however, these were large CNVs (over 3 Mb) that have a rich gene content besides SINCAP.⁷⁰

RABEPK gene, harboring intragenic deletions in patients 3 and 4, encodes Rab9 effector protein with kelch motifs, a Rab associated protein. RABEPK acts as the effector of Rab9 GTPase. RABEPK encodes a protein involved in protein binding with important roles in vesicle trafficking from endosomes to the trans-Golgi network.⁷¹ Rab signaling and membrane trafficking have been recently proposed to contribute to PD risk.⁷² Moreover, members of the Rab family, such as RAB32 and RAB39B were found to be involved in PD pathogenicity.^73-75 Recent studies have also revealed the close association and interactions between Rab GTPases and other proteins with pivotal roles in PD pathogenesis, such as LRRK2, VPS35 and PINK1.^73,76

RABEPK gene expression in brain cells (neuronal and non-neuronal) was found to be dysregulated in autosomal dominant forms of another neurodegenerative disorder, Alzheimer's dementia (AD).⁷⁷ Transcriptomic studies of PD and Hutchinson-Gilford progeria detected RABEPK among differentially expressed genes in both disorders, the authors suggesting a potential impact of this gene on disease liability.⁷⁸ Variants in the RABEPK gene were rarely reported in ASDs patients.³³ To date, the gene is not included in the SFARI database or other curated lists of NDC and autism, such and GeneTrek.⁵⁷ Nevertheless, RABEPK loss has been shown to destabilize RAB9 and perturb its intracellular localization⁷⁹ having thus the potential to alter RAB9 functions. Rab9, a neuronal GTPase with preferential localization in synapse as demonstrated in a Drosophila model,⁸⁰ takes part in synaptic membrane trafficking. Further studies are needed to advance the knowledge on RAB9 and its mediators, such as RABEPK, and to understand the impact of their disruption on human health and disease.

Our data brings to attention two prevalent conditions, ASDs and PD, that share many clinical particularities such as the multifactorial and multisystemic nature, and that co-occur in certain subjects, as PD seems to affect the individuals with ASDs more often compared to the general population.⁵⁷ The observed overlap of causal or risk genetic factors between the two conditions sparked the interest in understanding the neurodevelopmental component of PD^81,82 with implications for the management of both NDC and PD. Further studies are needed to fully comprehend the impact of CNVs affecting PD associated genes on the development of pediatric neuropsychiatric phenotypes; these studies become possible only with the accumulation of data from novel patients. Another important question, besides the contribution to neurodevelopmental problems, is whether these variants elevate the risk for PD. In our patients, no motor signs specific to PD were observed; however, they are still in early childhood. Clinical follow-up of our patients, as well as of other individuals with ASDs harboring rare CNVs that encompass PD genes, may offer valuable data regarding the occurrence of Parkinson's manifestations throughout the lifespan.

By exploring the common clinical features and daily challenges of the patients as well as the shared alterations of molecular pathways underlying neurodevelopmental and neurodegenerative disorders, such as ASD and PD, new opportunities to improve clinical management may be found. Therapeutic interventions and pharmacotherapy may be extrapolated from one condition to the other, while the identification of common molecular targets may pave the way for further development of treatments that address both conditions.

A limitation of our study, besides the short time of patient follow-up to date (considering their age range of 4-7 years old), is represented by the absence of data regarding the sequence variants with potential clinical relevance.

Conclusions

We report four children with ASD harboring deletions of PD-associated genes, detected in a larger study of 305 children with this condition. Our data adds to the previous reports of genomic imbalances of PD genes in ASD, further supporting the hypothesis that these conditions are interlinked by shared molecular mechanisms of pathogenesis and symptomatology. Thus, the understanding of ASD genetics impact on PD risk may open the way toward tailored clinical monitoring plans, such as periodic neurological follow-ups of young adults with ASD, to detect early signs of Parkinsonism. First author AE advances her PhD thesis with the title Genomic structural variation in autism spectrum disorders and the presented results will be part of the original section of the PhD thesis.

Footnotes

Acknowledgements

The authors thank the patients and their families for participating in the study.

ORCID iD

Sorina Mihaela Papuc

Ethical considerations

The study was reviewed and approved by the Ethics Committee of Prof. Dr. Alexandru Obregia Clinical Hospital of Psychiatry (Approval no 33/26.11.2019) and the Ethics Committee of Victor Babes National Institute of Pathology (Approval no 76/3.12.2019).

Consent to participate

Written informed consent was obtained from all the parents of enrolled individuals for participation in the study, before inclusion in the study.

Consent for publication

Written informed consent was obtained from all the parents of enrolled individuals for data publication, before inclusion in the study.

Author Contributions

Conceptualization, A.E,A.A.,S.M.P.,M.B.,M.E.H.,M.N.; methodology, A.E,M.B,M.D., S.M.P.,A.A.; validation, A.E.,M.D.,A.A.,S.M.P.,M.B.,C.I; formal analysis, A.E.,M.B.,C.I.,A.A.,S.M.P.; investigation, M.B.,A.E.,M.D.,S.M.P.,A.A.; writing—original draft preparation, A.E.,M.B.,M.D,S.M.P.,A.A.,M.E.H.,M.N.; writing—review and editing, A.E.,M.B.,S.M.P.,A.A.,M.E.H.,M.N.; supervision, M.B.,A.A.,M.E.H.,M.N.; funding acquisition, M.B.,A.A. All authors have read and agreed to the published version of the manuscript.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The research leading to these results has received funding from the EEA Grant 2014-2021, under the project contract No 6/2019 and Core Program within the National Research, Development, and Innovation Plan, 2022–2027, with the support of MCID, project no. 10N/01.01.2023, PN 23.16.02.03.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Data Availability Statement

The main data generated and analyzed in our study are included in this article.

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