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The amygdala is enlarged in children but not adolescents with autism; the hippocampus is enlarged at all ages.

Autism is a neurodevelopmental disorder characterized by impairments in reciprocal social interaction, deficits in verbal and nonverbal communication, and a restricted repertoire of activities or interests. We performed a magnetic resonance imaging study to better define the neuropathology of autistic spectrum disorders. Here we report findings on the amygdala and the hippocampal formation. Borders of the amygdala, hippocampus, and cerebrum were defined, and their volumes were measured in male children (7.5-18.5 years of age) in four diagnostic groups: autism with mental retardation, autism without mental retardation, Asperger syndrome, and age-matched typically developing controls. Although there were no differences between groups in terms of total cerebral volume, children with autism (7.5-12.5 years of age) had larger right and left amygdala volumes than control children. There were no differences in amygdala volume between the adolescent groups (12.75-18.5 years of age). Interestingly, the amygdala in typically developing children increases substantially in volume from 7.5 to 18.5 years of age. Thus, the amygdala in children with autism is initially larger, but does not undergo the age-related increase observed in typically developing children. Children with autism, with and without mental retardation, also had a larger right hippocampal volume than typically developing controls, even after controlling for total cerebral volume. Children with autism but without mental retardation also had a larger left hippocampal volume relative to controls. These cross-sectional findings indicate an abnormal program of early amygdala development in autism and an abnormal pattern of hippocampal development that persists through adolescence. The cause of amygdala and hippocampal abnormalities in autism is currently unknown.

Adolescent↗

Learning and memory and synaptic plasticity are impaired in a mouse model of Rett syndrome.

Loss-of-function mutations or abnormal expression of the X-linked gene encoding methyl CpG binding protein 2 (MeCP2) cause a spectrum of postnatal neurodevelopmental disorders including Rett syndrome (RTT), nonsyndromic mental retardation, learning disability, and autism. Mice expressing a truncated allele of Mecp2 (Mecp2(308)) reproduce the motor and social behavior abnormalities of RTT; however, it is not known whether learning deficits are present in these animals. We investigated learning and memory, neuronal morphology, and synaptic function in Mecp2(308) mice. Hippocampus-dependent spatial memory, contextual fear memory, and social memory were significantly impaired in Mecp2(308) mutant males (Mecp2(308/Y)). The morphology of dendritic arborizations, the biochemical composition of synaptosomes and postsynaptic densities, and brain-derived neurotrophic factor expression were not altered in these mice. However, reduced postsynaptic density cross-sectional length was identified in asymmetric synapses of area CA1 of the hippocampus. In the hippocampus of symptomatic Mecp2(308/Y) mice, Schaffer-collateral synapses exhibited enhanced basal synaptic transmission and decreased paired-pulse facilitation, suggesting that neurotransmitter release was enhanced. Schaffer-collateral long-term potentiation (LTP) was impaired. LTP was also reduced in the motor and sensory regions of the neocortex. Finally, very early symptomatic Mecp2(308/Y) mice had increased basal synaptic transmission and deficits in the induction of long-term depression. These data demonstrate a requirement for MeCP2 in learning and memory and suggest that functional and ultrastructural synaptic dysfunction is an early event in the pathogenesis of RTT.

Animals↗

Necdin downregulates CDC2 expression to attenuate neuronal apoptosis.

The cell cycle-regulatory transcription factor E2F1 induces apoptosis of postmitotic neurons in developmental and pathological situations. E2F1 transcriptionally activates many proapoptotic genes including the cyclin-dependent protein kinase cell division cycle 2 (Cdc2). Necdin is a potent mitotic suppressor expressed predominantly in postmitotic neurons and interacts with E2F1 to suppress E2F1-mediated gene transcription. The necdin gene NDN is maternally imprinted and expressed only from the paternal allele. Deletion of the paternal NDN is implicated in the pathogenesis of Prader-Willi syndrome, a genomic imprinting-associated neurodevelopmental disorder. Here, we show that paternally expressed necdin represses E2F1-dependent cdc2 gene transcription and attenuates apoptosis of postmitotic neurons. Necdin was abundantly expressed in differentiated cerebellar granule neurons (CGNs). Neuronal activity deprivation elevated the expression of both E2F1 and Cdc2 in primary CGNs prepared from mice at postnatal day 6, whereas the necdin levels remained unchanged. In chromatin immunoprecipitation analysis, endogenous necdin was associated with the cdc2 promoter containing an E2F-binding site in activity-deprived CGNs. After activity deprivation, CGNs underwent apoptosis, which was augmented in those prepared from mice defective in the paternal Ndn allele (Ndn(+m/-p)). The levels of cdc2 mRNA, protein, and kinase activity were significantly higher in Ndn(+m/-p) CGNs than in wild-type CGNs under activity-deprived conditions. Furthermore, the populations of Cdc2-immunoreactive and apoptotic cells were increased in the cerebellum in vivo of Ndn(+m/-p) mice. These results suggest that endogenous necdin attenuates neuronal apoptosis by suppressing the E2F1-Cdc2 system.

Animals↗

An experiment of nature: brain anatomy parallels cognition and behavior in Williams syndrome.

Williams syndrome (WS) is a neurogenetic-neurodevelopmental disorder characterized by a highly variable and enigmatic profile of cognitive and behavioral features. Relative to overall intellect, affected individuals demonstrate disproportionately severe visual-spatial deficits and enhanced emotionality and face processing. In this study, high-resolution magnetic resonance imaging data were collected from 43 individuals with WS and 40 age- and gender-matched healthy controls. Given the distinct cognitive-behavioral dissociations associated with this disorder, we hypothesized that neuroanatomical integrity in WS would be diminished most in regions comprising the visual-spatial system and most "preserved" or even augmented in regions involved in emotion and face processing. Both volumetric analysis and voxel-based morphometry were used to provide convergent approaches for detecting the hypothesized WS neuroanatomical profile. After adjusting for overall brain volume, participants with WS showed reduced thalamic and occipital lobe gray matter volumes and reduced gray matter density in subcortical and cortical regions comprising the human visual-spatial system compared with controls. The WS group also showed disproportionate increases in volume and gray matter density in several areas known to participate in emotion and face processing, including the amygdala, orbital and medial prefrontal cortices, anterior cingulate, insular cortex, and superior temporal gyrus. These findings point to specific neuroanatomical correlates for the unique topography of cognitive and behavioral features associated with this disorder.

Adolescent↗

Expression of 4 genes between chromosome 15 breakpoints 1 and 2 and behavioral outcomes in Prader-Willi syndrome.

Prader-Willi syndrome is a neurodevelopmental disorder that is characterized by infantile hypotonia, feeding difficulties, hypogonadism, mental deficiency, hyperphagia (leading to obesity in early childhood), learning problems, and behavioral difficulties. A paternal 15q11-q13 deletion is found in approximately 70% of patients with Prader-Willi syndrome, approximately 25% have uniparental maternal disomy 15, and the remaining 2% to 5% have imprinting defects. The proximal deletion breakpoint in the 15q11-q13 region occurs at 1 of 2 sites located within either of 2 large duplicons allowing for the identification of 2 deletion subgroups. The larger, type I (TI) deletion involves breakpoint 1, which is close to the centromere, whereas the smaller, type II (TII) deletion involves breakpoint 2, located approximately 500 kilobases distal to breakpoint 1. Breakpoint 3 is located at the distal end of the 15q11-q13 region and common to both typical deletion subgroups. Analyses of the genetic subtypes of Prader-Willi syndrome to date have primarily compared individuals with typical deletion and uniparental maternal disomy 15 without grouping the individuals with a deletion into TI or TII. Distinct differences have been reported between individuals with Prader-Willi syndrome resulting from deletion compared with uniparental maternal disomy 15 in physical, cognitive, and behavioral parameters. We previously presented the first assessment of clinical differences in individuals with Prader-Willi syndrome categorized as having type I or II deletions. Adaptive behavior, obsessive-compulsive behaviors, reading, math, and visual-motor integration assessments were generally poorer in individuals with Prader-Willi syndrome and the TI deletion compared with subjects with Prader-Willi syndrome with the TII deletion or uniparental maternal disomy 15. Four genes (NIPA1, NIPA2, CYFIP1, and GCP5) have been identified in the chromosomal region between breakpoints 1 and 2 and are implicated in compulsive behavior and lower intellectual ability observed in individuals with Prader-Willi syndrome with TI versus TII deletions. We quantified messenger-RNA levels of these 4 genes in actively growing lymphoblastoid cells derived from 8 subjects with Prader-Willi syndrome with the TI deletion (4 males, 4 females; mean: age 25.2 +/- 8.9 years) and 9 with the TII deletion (3 males, 6 females; mean age: 19.5 +/- 5.8 years). Messenger-RNA levels were correlated with validated psychological and behavioral scales administered by trained psychologists blinded to genotype status. Messenger RNA from NIPA1, NIPA2, CYFIP1, and GCP5 was reduced but detectable in the subjects with Prader-Willi syndrome with the TI deletion, supporting biallelic expression. For the most part, messenger-RNA values were positively correlated with assessment parameters, indicating a direct relationship between messenger-RNA levels and better assessment scores, with the highest correlation for NIPA2. The coefficient of determination indicated the quantity of messenger RNA of the 4 genes explained from 24% to 99% of the variation of the behavioral and academic parameters measured. By comparison, the coefficient of determination for deletion type alone explained 5% to 50% of the variation in the assessed parameters. Understanding the influence of gene expression on behavioral and cognitive characteristics in humans is in the early stage of research development. Additional research is needed to identify the function of these genes and their interaction with gene networks to clarify the potential role they play in central nervous system development and function.

Adaptor Proteins, Signal Transducing↗

Being on the track of thimerosal. Review.

The common preservative thimerosal is one of the most important organic mercury compounds human populations are exposed to. It has toxic effect on several cell lines, and it also induces programmed cell death in in vitro experiments. Association is suggested between application of thimerosal-containing vaccines and the occurrence of neurodevelopmental disorders, like autism. While specific recommendations were made to eliminate thimerosal from vaccines, consistent evidence is still lacking for an association of exposure and disease. Unfortunately, it is very hard to study the molecular background of complex human diseases directly; however, investigations on more simple model organisms may lead to a better understanding of thimerosal as a possible disease inducing factor.

Animals↗

Rett syndrome: clinical and epidemiological aspects in a Brazilian institution.

Rett syndrome (RS) is a neurodevelopmental disorder, preferentially found in females and specifically involving the functions on which intelligence and its expression depend--learning, hand use and speech--leaving many others intact. Mutations have been identified at Xq28 on the MECP2 gene (methyl-CpG 2), which selectively silences the expression of other genes whose location is still unknown. This is a study on clinical, diagnostic and epidemiological aspects of RS in a Brazilian sample. It included 33 female patients with chronic encephalopathy without known etiology. RS was diagnosed in 24 patients (72.7%): 17 (70.8%) had classical RS; 5 (20.8%), atypical RS and 2 (8.4%), potential RS. In 9 girls clinical data and/or laboratory studies excluded diagnosis of RS. Among the atypical RS patients, 4 were form fruste and one, congenital form. Among the girls with other encephalopathies, cerebral malformation was the most frequent finding.

Adolescent↗

[Autism and Asperger syndrome: an overview].

Autism and Asperger syndrome are diagnostic entities in a family of neurodevelopmental disorders disrupting fundamental processes of socialization, communication and learning, collectively known as pervasive developmental disorders. This group of conditions is among the most common developmental disorders, affecting 1 in every 200 or so individuals. They are also the most strongly genetically related among developmental disorders, with recurrence risks within sibships of the order of 2 to 15% if a broader definition of affectedness is adopted. Their early onset, symptom profile, and chronicity implicate fundamental biological mechanisms involved in social adaptation. Advances in their understanding are leading to a new social neuroscience perspective of normative socialization processes and specific disruptions thereof. These processes may lead to the emergence of the highly heterogeneous phenotypes associated with autism, the paradigmatic pervasive developmental disorder, and its variants. This overview focuses on the history, nosology, and the clinical and associated features of the two most well-known pervasive developmental disorders - autism and Asperger syndrome.

Asperger Syndrome↗

[Autism: neuroimaging].

Autism is a neurodevelopmental disorder with a range of clinical presentations. These presentations vary from mild to severe and are referred to as autism spectrum disorders. The most common clinical sign of autism spectrum disorders is social interaction impairment, which is associated with verbal and non-verbal communication deficits and stereotyped and repetitive behaviors. Thanks to recent brain imaging studies, scientists are getting a better idea of the neural circuits involved in autism spectrum disorders. Indeed, functional brain imaging, such as positron emission tomography, single foton emission tomography and functional MRI have opened a new perspective to study normal and pathological brain functioning. Three independent studies have found anatomical and rest functional temporal lobe abnormalities in autistic patients. These alterations are localized in the superior temporal sulcus bilaterally, an area which is critical for perception of key social stimuli. In addition, functional studies have shown hypoactivation of most areas implicated in social perception (face and voice perception) and social cognition (theory of mind). These data suggest an abnormal functioning of the social brain network in autism. The understanding of the functional alterations of this important mechanism may drive the elaboration of new and more adequate social re-educative strategies for autistic patients.

Auditory Perception↗

What is known about autism: genes, brain, and behavior.

Autism is a neurodevelopmental disorder of genetic origins, with a heritability of about 90%. Autistic disorder is classed within the broad domain of pervasive developmental disorders (PDD) that also includes Rett syndrome, childhood disintegrative disorder, Asperger syndrome, and PDD not otherwise specified (PDD-NOS). Prevalence estimates suggest a rate of 0.1-0.2% for autism and 0.6% for the range of PDD disorders. There is considerable phenotypic heterogeneity within this class of disorders as well as continued debate regarding their clinical boundaries. Autism is the prototypical PDD, and is characterized by impairments in three core domains: social interaction, language development, and patterns of behavior (restricted and stereotyped). Clinical pattern and severity of impairment vary along these dimensions, and the level of cognitive functioning of individuals with autism spans the entire range, from profound mental retardation to superior intellect. There is no single biological or clinical marker for autism, nor is it expected that a single gene is responsible for its expression; as many as 15+ genes may be involved. However, environmental influences are also important, as concordance in monozygotic twins is less than 100% and the phenotypic expression of the disorder varies widely, even within monozygotic twins. Multiple susceptibility factors are being explored using varied methodologies, including genome-wide linkage studies, and family- and case-control candidate gene association studies. This paper reviews what is currently known about the genetic and environmental risk factors, neuropathology, and psychopharmacology of autism. Discussion of genetic factors focuses on the findings from linkage and association studies, the results of which have implicated the involvement of nearly every chromosome in the human genome. However, the most consistently replicated linkage findings have been on chromosome 7q, 2q, and 15q. The positive associations from candidate gene studies are largely unreplicated, with the possible exceptions of the GABRB3 and serotonin transporter genes. No single region of the brain or pathophysiological mechanism has yet been identified as being associated with autism. Postmortem findings, animal models, and neuroimaging studies have focused on the cerebellum, frontal cortex, hippocampus, and especially the amygdala. The cerebello-thalamo-cortical circuit may also be influential in autism. There is evidence that overall brain size is increased in some individuals with autism. Presently there are no drugs that produce major improvements in the core social or pragmatic language deficits in autism, although several have limited effects on associated behavioral features. The application of new techniques in autism research is being proposed, including the investigation of abnormal regulation of gene expression, proteomics, and the use of MRI and postmortem analysis of the brain.

Animals↗

The Autism Genome Project: goals and strategies.

Autism is a complex neurodevelopmental disorder with a broad spectrum of symptoms and varying severity. Currently, no biological diagnosis exists. Although there has been a significant increase in autism genetics research recently, validated susceptibility genes for the most common, sporadic forms of autistic disorder, as well as familial autism, have yet to be identified. The identification of autism-susceptibility genes will not only assist in the identification and/or development of better medications that can help improve the health and neurodevelopment of children with autism, but will also allow for better perinatal diagnosis. The Autism Genome Project (AGP) is a large-scale, collaborative genetics research project initiated by the National Alliance for Autism Research and the National Institutes of Health, and is aimed at sifting through the human genome in search of autism-susceptibility genes. Phase I of the AGP will consist of genome-wide scans utilizing both SNP array and microsatellite technologies. Linkage analysis will subsequently be performed on approximately 1500 pedigrees as will downstream fine-mapping and sequencing of the critical linkage intervals. Ultimately, the vision will be to identify the exact nucleotide variants within genes which give rise to predisposition. The AGP intends to move the field of autism clinical management forward by answering questions about the causal mechanisms underlying the pathophysiology of autism. From this knowledge, therapeutic targets for drug treatments, and ultimately, a newborn screening diagnostic that would allow for early intervention, can begin to be developed.

Autistic Disorder↗

[Environmental chemical hazards and child health].

OBJECTIVES: To review the recent medical literature on environmental chemical hazards to child health. SOURCES OF DATA: Articles published on this subject between 1999 and 2005 were searched in the MEDLINE database. Books, manuals and statements on child environmental health, issued by institutions such as the American Academy of Pediatrics and the World Health Organization, were also reviewed. SUMMARY OF THE FINDINGS: There has been a growing concern in the last few years with the exposure of children to environmental chemicals. Around 85,000 synthetic chemicals are produced today, and 2,800 of them are mass-produced. There is little knowledge regarding their effects on developing organisms. Children have a greater exposure to environmental pollutants than adults, because their metabolic needs and behaviors (e.g.: crawling, bringing objects to the mouth, playing closer to the ground) put them at special risk of contact with chemicals when they breathe, eat, drink or play. Heavy metals, pesticides, persistent organic pollutants and, at home, environmental tobacco smoke have been associated with the increasing number of diseases such as asthma, neurodevelopmental disorders and childhood cancer. CONCLUSION: Screening of risk situations using tools such as Environmental History has been stimulated alongside a greater commitment of pediatricians towards measures that can reduce the exposure of children and adolescents to environmental chemicals.

Adolescent↗

Relationships among age, sex, and lateral dominance for 3- to 6-year-old children performing unilateral stance.

To assess influence of age, sex, and lateral dominance on children's unilateral stance, from 6 Houston area preschools and day-care centers, 121 subjects were randomly selected and judged by teachers as normal 3- to 6-yr-old children. The children were tested for eye, hand, and foot preference and were then classified on over-all dominance. Maximal duration of unilateral stance, or up to 60 sec., was tested on each foot. Means over age groups show progressive increase in duration of unilateral stance with increasing age. No sex differences were found. A stepwise multiple correlation-regression showed stance on the nondominant foot and age as the only significant variables in stance on the dominant foot. Clinically, this study can help in evaluating children for neurodevelopmental disorders.

Child↗

Emerging infectious determinants of chronic diseases.

Evidence now confirms that noncommunicable chronic diseases can stem from infectious agents. Furthermore, at least 13 of 39 recently described infectious agents induce chronic syndromes. Identifying the relationships can affect health across populations, creating opportunities to reduce the impact of chronic disease by preventing or treating infection. As the concept is progressively accepted, advances in laboratory technology and epidemiology facilitate the detection of noncultivable, novel, and even recognized microbial origins. A spectrum of diverse pathogens and chronic syndromes emerges, with a range of pathways from exposure to chronic illness or disability. Complex systems of changing human behavioral traits superimposed on human, microbial, and environmental factors often determine risk for exposure and chronic outcome. Yet the strength of causal evidence varies widely, and detecting a microbe does not prove causality. Nevertheless, infectious agents likely determine more cancers, immune-mediated syndromes, neurodevelopmental disorders, and other chronic conditions than currently appreciated.

Bacterial Infections↗

Case Report: Early infantile drug-resistant epilepsy and gastrointestinal dysmotility associated with a de novo GNAO1 variant and a 16p13.11 microdeletion.

BACKGROUND: The GNAO1 gene is located on the long arm of chromosome 16 (16q13) and is associated with Developmental and Epileptic Encephalopathy 17. It encodes a protein involved in regulating various neurotransmitters and neuronal growth and development. The 16p13.11 microdeletion is a genomic deletion in the p13.11 region of the short arm of chromosome 16, previously reported to predispose individuals to neurodevelopmental disorders. These two regions do not overlap on the chromosome, and the 16p13.11 microdeletion does not involve the GNAO1 gene locus. CASE PRESENTATION: We reports a 1-month-old infant presenting with concurrent GNAO1 (p. G203R) gene variation and a 16p13.11 microdeletion. The patient initially presented with recurrent abdominal distension in the neonatal period, which gradually progressed to include focal seizures and intractable epileptic spasms. Interictal EEG showed multifocal discharges and burst-suppression patterns. Brain MRI revealed no abnormalities. A full gastrointestinal series suggested intestinal obstruction and gastro-esophageal reflux. Improved whole-exome sequencing identified: 1) A single nucleotide variantion: GNAO1, NM_020988.3:exon6: c.607G > A (p.Gly203Arg). 2) A copy number variation: A pathogenic 1.453 Mb deletion in the 16p13.11 region. CONCLUSIONS: We describe the developmental trajectory of an infant with overlapping features of gastrointestinal symptoms and drug-resistant epilepsy, carrying a GNAO1 variant and a 16p13.11 microdeletion. This case provides insights into the contribution of both single nucleotide variant and copy number variant to the phenotype.

16p13.11 microdeletion↗

Biological Foundation Models for Complex Disease Research and Clinical Translation.

Complex diseases, including cancer, rare genetic disorders, neurodevelopmental and psychiatric conditions, and neurodegenerative diseases, arise from interactions among genetic variation, gene regulation, and cellular states that are difficult to capture using a single data type or biological scale. Biological foundation models address this challenge by treating nucleotides and genes as tokens and learning representations that can be transferred to downstream biomedical and clinical tasks. In this review, we examine two major model classes, genomic sequence foundation models and cell foundation models, and compare their tokenization strategies, model architectures, pretraining objectives, and adaptation methods. We summarize their emerging applications in regulatory variant interpretation, disease-associated cell-state analysis, drug-response prediction, and therapeutic target discovery across complex diseases. We distinguish applications supported by experimental or retrospective validation from those that remain primarily computational or conceptual. We further discuss key challenges to clinical translation, including multimodal data integration, model interpretability, benchmarking, patient-specific prediction, and privacy protection. We highlight future opportunities to integrate biological foundation models with emerging frameworks of medical digital twins, agentic AI, and federated learning. By linking model design to translational goals, this review provides a practical framework for evaluating biological foundation models and their readiness for complex disease research and clinical use.

biological foundation model↗

The development and evaluation of a computer-based program to test and to teach the recognition of facial affect.

Autism is a chronic pervasive neurodevelopmental disorder characterized by the early onset of social and communicative impairments as well as restricted, ritualized, stereotypic behavior. The endophenotype of autism includes neuropsychological deficits, for instance a lack of "Theory of Mind" and problems recognizing facial affect. In this study, we report the development and evaluation of a computer-based program to teach and test the ability to identify basic facially expressed emotions. 10 adolescent or adult subjects with high-functioning autism or Asperger-syndrome were included in the investigation. A priori the facial affect recognition test had shown good psychometric properties in a normative sample (internal consistency: rtt=.91-.95; retest reliability: rtt=.89-.92). In a prepost design, one half of the sample was randomly assigned to receive computer treatment while the other half of the sample served as control group. The training was conducted for five weeks, consisting of two hours training a week. The trained individuals improved significantly on the affect recognition task, but not on any other measure. Results support the usefulness of the program to teach the detection of facial affect. However, the improvement found is limited to a circumscribed area of social-communicative function and generalization is not ensured.

Adolescent↗

Misregulated chromosome condensation in MCPH1 primary microcephaly is mediated by condensin II.

Autosomal recessive primary microcephaly (MCPH) is a neurodevelopmental disorder characterized by marked reduction in brain size and mental retardation. Mutations in the gene MCPH1, encoding microcephalin, cause MCPH and a unique cellular phenotype with premature chromosome condensation in early G2 phase and delayed decondensation post mitosis. Here, we show that in MCPH1 patient cells, siRNA-mediated depletions of condensin II subunits lead to a pronounced reduction of cells with the condensation defects in both G1 and G2 phases of the cell cycle. Similar results are obtained when microcephalin and condensin II are simultaneously depleted in HeLa cells. In contrast, depletions of condensin I subunits do not reverse the cellular phenotype. Consistently, condensin I stays in the cytoplasm in the prophase-like cells of MCPH1 patients. Our results offer a molecular explanation for the aberrant chromosome condensation in MCPH1-deficiency and provide additional evidence that condensin I and II are regulated by distinct pathways.

Adenosine Triphosphatases↗