Evaluation of DNA repair efficiency in autistic children by molecular cytogenetic analysis and transcriptome profiling

A thematic review of autism spectrum disorder research in Saudi Arabia: Insights into diagnosis, assessment, and language considerations

This study reviews the crucial role of language in Autism Spectrum Disorder (ASD) diagnosis and assessment in Saudi Arabia. Using tailored search strings, 206 relevant documents were retrieved from the Web of Science and Scopus databases. An increasing trend in ASD research in Saudi Arabia was observed through temporal analysis. Keyword analysis identified key themes including "autism," "language," "assessment," "diagnosis," "Saudi Arabia," and "children." The focus of research has shifted over the years, from pure clinical and diagnostic aspects to a more comprehensive approach that includes language and cultural factors in ASD evaluation. The findings underscore the need for culturally and linguistically sensitive assessment tools, acknowledging the impact of bilingualism on language development, and the importance of language difficulties in diagnostic decision-making. The study highlights the necessity for further research, especially longitudinal studies examining the influence of language and cultural factors on ASD outcomes. The findings are significant for clinical practice, emphasizing the need for linguistically sensitive approaches in ASD diagnosis and assessment. This research serves as a guide for future studies by identifying the gaps in existing literature and areas of focus. The study identifies crucial gaps in existing literature, particularly the need for longitudinal studies examining the influence of language and cultural factors on ASD outcomes. The findings underscore the importance of culturally and linguistically sensitive approaches in ASD diagnosis and assessment, providing a novel insight for future research and clinical practice in Saudi Arabia.

New Views of the DNA Repair Protein Ataxia-Telangiectasia Mutated in Central Neurons: Contribution in Synaptic Dysfunctions of Neurodevelopmental and Neurodegenerative Diseases

Ataxia-Telangiectasia Mutated (ATM) is a serine/threonine protein kinase principally known to orchestrate DNA repair processes upon DNA double-strand breaks (DSBs). Mutations in the Atm gene lead to Ataxia-Telangiectasia (AT), a recessive disorder characterized by ataxic movements consequent to cerebellar atrophy or dysfunction, along with immune alterations, genomic instability, and predisposition to cancer. AT patients show variable phenotypes ranging from neurologic abnormalities and cognitive impairments to more recently described neuropsychiatric features pointing to symptoms hardly ascribable to the canonical functions of ATM in DNA damage response (DDR). Indeed, evidence suggests that cognitive abilities rely on the proper functioning of DSB machinery and specific synaptic changes in central neurons of ATM-deficient mice unveiled unexpected roles of ATM at the synapse. Thus, in the present review, upon a brief recall of DNA damage responses, we focus our attention on the role of ATM in neuronal physiology and pathology and we discuss recent findings showing structural and functional changes in hippocampal and cortical synapses of AT mouse models. Collectively, a deeper knowledge of ATM-dependent mechanisms in neurons is necessary not only for a better comprehension of AT neurological phenotypes, but also for a higher understanding of the pathological mechanisms in neurodevelopmental and degenerative disorders involving ATM dysfunctions.

Aflatoxin B1 Exacerbates Genomic Instability and Apoptosis in the BTBR Autism Mouse Model via Dysregulating DNA Repair Pathway

The pathophysiology of autism is influenced by a combination of environmental and genetic factors. Furthermore, individuals with autism appear to be at a higher risk of developing cancer. However, this is not fully understood. Aflatoxin B1 (AFB1) is a potent food pollutant carcinogen. The effects of AFB1 on genomic instability in autism have not yet been investigated. Hence, we have aimed to investigate whether repeated exposure to AFB1 causes alterations in genomic stability, a hallmark of cancer and apoptosis in the BTBR autism mouse model. The data revealed increased micronuclei generation, oxidative DNA strand breaks, and apoptosis in BTBR animals exposed to AFB1 when compared to unexposed animals. Lipid peroxidation in BTBR mice increased with a reduction in glutathione following AFB1 exposure, demonstrating an exacerbated redox imbalance. Furthermore, the expressions of some of DNA damage/repair- and apoptosis-related genes were also significantly dysregulated. Increases in the redox disturbance and dysregulation in the DNA damage/repair pathway are thus important determinants of susceptibility to AFB1-exacerbated genomic instability and apoptosis in BTBR mice. This investigation shows that AFB1-related genomic instability can accelerate the risk of cancer development. Moreover, approaches that ameliorate the redox balance and DNA damage/repair dysregulation may mitigate AFB1-caused genomic instability.

The small molecule Erk1/2 signaling pathway inhibitor PD98059 improves DNA repair in an experimental autoimmune encephalomyelitis SJL/J mouse model of multiple sclerosis

Multiple sclerosis (MS) is a demyelinating disorder in which the myelin sheath covering the central nervous system axons is damaged or lost, disrupting action potential conduction and leading to various neurological complications. The pathogenesis of MS remains unclear, and no effective therapies are currently available. MS is triggered by environmental factors in genetically susceptible individuals. DNA damage and DNA repair failure have been proposed as MS genetic risk factors; however, inconsistent evidence has been found in multiple studies. Therefore, more investigations are needed to ascertain whether DNA damage/repair is altered in this disorder. In this context, therapies that prevent DNA damage or enhance DNA repair could be effective strategies for MS treatment. The overactivation of the extracellular-signal-related kinase 1 and 2 (Erk1/2) pathway can lead to DNA damage and has been linked to MS pathogenesis. In our study, we observed substantially elevated oxidative DNA damage and slower DNA repair rates in an experimentally autoimmune encephalomyelitis animal model of MS (EAE). Moreover, statistical decreases in oxidative DNA strand breaks and faster repair rates were observed in EAE animals injected with the Erk1/2 inhibitor PD98059 (PD). Moreover, the expression of several genes associated with DNA strand breaks and repair changed in EAE mice at both the mRNA and protein levels, as revealed by the RT² Profiler PCR array and verified by RT-PCR and protein analyses. The treatment with PD mitigated these changes and improved DNA repair gene expression. Our results demonstrate clear associations between Erk1/2 activation, DNA damage/repair, and MS pathology, and further suggest that PD therapy may be a promising adjuvant therapeutic strategy.

Autistic spectrum disorder (ASD) - Gene, molecular and pathway signatures linking systemic inflammation, mitochondrial dysfunction, transsynaptic signalling, and neurodevelopment

Background

Despite advances in autism spectrum disorder (ASD) research and the vast genomic, transcriptomic, and proteomic data available, there are still controversies regarding the pathways and molecular signatures underlying the neurodevelopmental disorders leading to ASD.

Purpose

To delineate these underpinning signatures, we examined the two largest gene expression meta-analysis datasets obtained from the brain and peripheral blood mononuclear cells (PBMCs) of 1355 ASD patients and 1110 controls.

Methods

We performed network, enrichment, and annotation analyses using the differentially expressed genes, transcripts, and proteins identified in ASD patients.

Results

Transcription factor network analyses in up- and down-regulated genes in brain tissue and PBMCs in ASD showed eight main transcription factors, namely: BCL3, CEBPB, IRF1, IRF8, KAT2A, NELFE, RELA, and TRIM28. The upregulated gene networks in PBMCs of ASD patients are strongly associated with activated immune-inflammatory pathways, including interferon-α signaling, and cellular responses to DNA repair. Enrichment analyses of the upregulated CNS gene networks indicate involvement of immune-inflammatory pathways, cytokine production, Toll-Like Receptor signalling, with a major involvement of the PI3K-Akt pathway. Analyses of the downregulated CNS genes suggest electron transport chain dysfunctions at multiple levels. Network topological analyses revealed that the consequent aberrations in axonogenesis, neurogenesis, synaptic transmission, and regulation of transsynaptic signalling affect neurodevelopment with subsequent impairments in social behaviours and neurocognition. The results suggest a defense response against viral infection.

Conclusions

Peripheral activation of immune-inflammatory pathways, most likely induced by viral infections, may result in CNS neuroinflammation and mitochondrial dysfunction, leading to abnormalities in transsynaptic transmission, and brain neurodevelopment.

Aluminum (Al) causes a delayed suppression of nucleotide excision repair (NER) capacity in zebrafish (Danio rerio) embryos via disturbance of DNA lesion detection

Aluminum (Al) is extensively used for making cooking utensils and its presence in the aquatic environment may occur through acid mine drainage and wastewater discharge. Al is known to induce genotoxicity in human cells, rodents, and fish. Nucleotide excision repair (NER) eliminates helix-twisting DNA lesions such as UV-induced dipyrimidine photoproducts. Because our earlier investigation revealed the operation of NER in zebrafish (Danio rerio) embryos, this study explored if inhibition of NER could be a mechanism of Al-induced genotoxicity using zebrafish embryo as a model system. An acute fish embryo toxicity test indicated that Al (as aluminum sulfate) at 2-15 mg/L were nonlethal to zebrafish embryos, yet exposure of embryos at 1 h post fertilization (hpf) to Al at 10-15 mg/L for 71 h significantly repressed their NER capacity monitored by a transcription-based DNA repair assay. Band shift analysis indicated a higher sensitivity of (6-4) photoproduct (6-4PP) than cyclobutane pyrimidine dimer (CPD) detecting activities to Al, reflecting the preferential influence of Al on the detection of strongly distorted DNA lesions. Time-course experiments showed a delayed response of NER to Al as repair machinery was unaffected by Al at 15 mg/L following a 35-h exposure, while Al treatment for the same period obviously inhibited 6-4PP binding activities although the gene expression of damage recognition factors remained active. Inhibition of 6-4PP detection blocked downstream lesion incision/excision detected by a terminal deoxy transferase-mediated end labeling assay. As the disturbance of damage sensing preceded that of the overall repair process, Al exposure was believed to downregulate NER capacity by inhibiting the activities of lesion detection proteins. Our results revealed the ability of Al to enhance its genotoxicity by suppressing NER capacity.

Multiple exposure to methylmercury aggravates DNA damage in the BTBR T + Itpr3 tf/J autistic mouse model: the role of DNA repair efficiency

Environmental and genetic factors have been recognized to play major roles in the pathogenesis of autism. Here we examined the BTBR T⁺Itpr3^tf/J (BTBR) mice's susceptibility, an autistic model, to the genotoxic effects and DNA repair dysregulation of methylmercury. Micronuclei formation and oxidative DNA damage were analyzed using the micronucleus/fluorescence in situ hybridization test and modified comet assay, respectively. The results showed higher centromeric-positive micronuclei and oxidative DNA damage in BTBR mice exposed to methylmercury than the unexposed mice, which indicates that mutagenesis aggravated in BTBR mice after methylmercury exposure. Lipid peroxides in BTBR mice were significantly elevated, with a decrease in reduced/oxidized glutathione ratio after methylmercury exposure, indicating an augmenting oxidant-antioxidant imbalance. The expression of several genes involved in DNA repair was markedly altered in BTBR mice after methylmercury exposure as evaluated via PCR array and RT-PCR analyses. Declining of the antioxidant defense and dysregulation in DNA repair process after methylmercury exposure may explain the aggravated genotoxic susceptibility of BTBR mice. Thus, autistic individuals exposed to methylmercury must be under regular medical follow-up through standard timetabled medical laboratory inquiry to allow for early recognition of any mutagenic changes. Additionally, strategies that elevate cellular antioxidants/DNA repair efficiency may counteract methylmercury-induced genotoxicity.

Role of JAK-STAT and PPAR-Gamma Signalling Modulators in the Prevention of Autism and Neurological Dysfunctions

The Janus-kinase (JAK) and signal transducer activator of transcription (STAT) signalling pathways regulate gene expression and control various factors involved in normal physiological functions such as cell proliferation, neuronal development, and cell survival. JAK activation phosphorylates STAT3 in astrocytes and microglia, and this phosphorylation has been linked to mitochondrial damage, apoptosis, neuroinflammation, reactive astrogliosis, and genetic mutations. As a regulator, peroxisome proliferator-activated receptor gamma (PPAR-gamma), in relation to JAK-STAT signalling, prevents this phosphorylation and aids in the treatment of the above-mentioned neurocomplications. Changes in cellular signalling may also contribute to the onset and progression of autism. Thus, PPAR-gamma agonist upregulation may be associated with JAK-STAT signal transduction downregulation. It may also be responsible for attenuating neuropathological changes by stimulating SOCS3 or involving RXR or SMRT, thereby reducing transcription of the various cytokine proteins and genes involved in neuronal damage. Along with JAK-STAT inhibitors, PPAR-gamma agonists could be used as target therapeutic interventions for autism. This research-based review explores the potential involvement and mutual regulation of JAK-STAT and PPAR-gamma signalling in controlling multiple pathological factors associated with autism.

Oxidative Stress in Autism Spectrum Disorder-Current Progress of Mechanisms and Biomarkers

Autism spectrum disorder (ASD) is a type of neurodevelopmental disorder that has been diagnosed in an increasing number of children around the world. Existing data suggest that early diagnosis and intervention can improve ASD outcomes. However, the causes of ASD remain complex and unclear, and there are currently no clinical biomarkers for autism spectrum disorder. More mechanisms and biomarkers of autism have been found with the development of advanced technology such as mass spectrometry. Many recent studies have found a link between ASD and elevated oxidative stress, which may play a role in its development. ASD is caused by oxidative stress in several ways, including protein post-translational changes (e.g., carbonylation), abnormal metabolism (e.g., lipid peroxidation), and toxic buildup [e.g., reactive oxygen species (ROS)]. To detect elevated oxidative stress in ASD, various biomarkers have been developed and employed. This article summarizes recent studies about the mechanisms and biomarkers of oxidative stress. Potential biomarkers identified in this study could be used for early diagnosis and evaluation of ASD intervention, as well as to inform and target ASD pharmacological or nutritional treatment interventions.

3-Aminobenzamide alleviates elevated DNA damage and DNA methylation in a BTBR T+Itpr3tf/J mouse model of autism by enhancing repair gene expression

Little is known about genetic and epigenetic alterations in autism spectrum disorder. Moreover, the efficiency of DNA repair in autism must be improved to correct these alterations. We examined whether 3-aminobenzamide (3-AB) could reverse these alterations. We conducted experiments to clarify the molecular mechanism underlying these ameliorations. An assessment of genetic and epigenetic alterations by a modified comet assay showed elevated levels of oxidative DNA strand breaks and DNA hypermethylation in BTBR T⁺Itpr3^tf/J (BTBR) mice used as a model of autism. Oxidative DNA strand breaks and DNA methylation were further quantified fluorometrically, and the results showed similar changes. Conversely, 3-AB treated BTBR mice showed a significant reduction in these alterations compared with untreated mice. The expressions of 43 genes involved in DNA repair were altered in BTBR mice. RT² Profiler PCR Array revealed significantly altered expression of seven genes, which was confirmed by RT-PCR analyses. 3-AB treatment relieved these disturbances and significantly improved Ogg1 and Rad1 up-regulation. Moreover, autism-like behaviors were also mitigated in BTBR animals by 3-AB treatment without alterations in locomotor activities. The simultaneous effects of reduced DNA damage and DNA methylation levels as well as the regulation of repair gene expression indicate the potential of 3-AB as a therapeutic agent to decrease the levels of DNA damage and DNA methylation in autistic patients. The current data may help in the development of therapies that ultimately provide a better quality of life for individuals suffering from autism.