Search

© 2015 Macmillan Publishers Limited.Recent studies implicate chromatin modifiers in autism spectrum disorder (ASD) through the identification of recurrent de novo loss of function mutations in affected individuals. ASD risk genes are co-expressed in human

Importance: Stress and viral illness during pregnancy are associated with neurodevelopmental conditions in offspring. Autism screening positivity for children born during the pandemic remains unknown., Objective: To examine associations between prenatal exposure to the pandemic milieu and maternal SARS-CoV-2 infection with rates of positive Modified Checklist for Autism in Toddlers, Revised (M-CHAT-R) screenings., Design, Setting, and Participants: Data for this cohort study were drawn from the COVID-19 Mother Baby Outcomes (COMBO) Initiative. M-CHAT-R scores obtained from children aged 16 to 30 months during routine clinical care at Columbia University Irving Medical Center in New York City were abstracted from electronic health records (EHRs) for children born between January 2018 and September 2021 (COMBO-EHR cohort). Separately, the M-CHAT-R was administered at 18 months for children born between February 2020 and September 2021 through a prospective longitudinal study (COMBO-RSCH cohort). Prenatal pandemic exposure (birth after March 1, 2020) and maternal SARS-CoV-2 status during pregnancy was determined through EHRs. Data were analyzed from March 2022 to June 2024., Exposures: Prenatal exposures to the pandemic milieu and maternal SARS-CoV-2 infection., Main Outcomes and Measures: The primary outcome was rate of positive M-CHAT-R screenings. For all primary analyses, unadjusted χ2 tests and adjusted logistic regression models were performed., Results: The COMBO-EHR cohort included 1664 children (442 born before the pandemic and 1222 born during the pandemic; 997 SARS-CoV-2 unexposed, 130 SARS-CoV-2 exposed, and 95 with unknown SARS-CoV-2 exposure status), of whom 266 (16.0%) were Black, 991 (59.6%) were Hispanic, 400 (24.0%) were White, 1245 (74.8%) were insured through Medicaid, 880 (52.9%) were male, and 204 (12.3%) were born prematurely. The COMBO-RSCH cohort included 385 children (74 born before the pandemic and 311 born during the pandemic; 201 SARS-CoV-2 unexposed, 101 SARS-CoV-2 exposed, and 9 with unknown SARS-CoV-2 exposure status), of whom 39 (10.1%) were Black, 168 (43.6%) were Hispanic, 157 (40.8%) were White, 161 (41.8%) were insured through Medicaid, 222 (57.7%) were male, and 38 (9.9%) were born prematurely. Prenatal pandemic exposure was not associated with a higher positive M-CHAT-R screening rate in either the COMBO-EHR or COMBO-RSCH cohort. Prenatal exposure to maternal SARS-CoV-2 infection was associated with a lower rate of M-CHAT-R positivity in the COMBO-EHR cohort (12.3% [16 children] vs 24.0% [239 children]; adjusted odds ratio, 0.40; 95% CI, 0.22-0.68; P = .001), but no association was found in the COMBO-RSCH cohort (12.9% [13 children] vs 19.9% [40 children]; adjusted odds ratio, 0.51; 95% CI, 0.24-1.04; P = .07)., Conclusions and Relevance: In this cohort study of 2 groups of children with prenatal pandemic exposure and/or exposure to maternal SARS-CoV-2 infection, neither exposure was associated with greater M-CHAT-R positivity.

Disruptive variants in the chromodomain helicase CHD8 , which acts as a transcriptional regulator during neurodevelopment, are strongly associated with risk for autism spectrum disorder (ASD). Loss of CHD8 function is hypothesized to perturb gene regulatory networks in the developing brain, thereby contributing to ASD etiology. However, insight into the cell type-specific transcriptional effects of CHD8 loss of function remains limited. We used single-cell and single-nucleus RNA-sequencing to globally profile gene expression and identify dysregulated genes in the embryonic and juvenile wild type and Chd8 +/- mouse cortex, respectively. Chd8 and other ASD risk-associated genes showed a convergent expression trajectory that was largely conserved between the mouse and human developing cortex, increasing from the progenitor zones to the cortical plate. Genes associated with risk for neurodevelopmental disorders and genes involved in neuron projection development, chromatin remodeling, signaling, and migration were dysregulated in Chd8 +/- embryonic day (E) 12.5 radial glia. Genes implicated in synaptic organization and activity were dysregulated in Chd8 +/- postnatal day (P) 25 deep- and upper-layer excitatory cortical neurons, suggesting a delay in synaptic maturation or impaired synaptogenesis due to CHD8 loss of function. Our findings reveal a complex pattern of transcriptional dysregulation in Chd8 +/- developing cortex, potentially with distinct biological impacts on progenitors and maturing neurons in the excitatory neuronal lineage., Competing Interests: Competing interests. The authors declare no competing interests.

Analysis of de novo mutations (DNMs) from sequencing data of nuclear families has identified risk genes for many complex diseases, including multiple neurodevelopmental and psychiatric disorders. Most of these efforts have focused on mutations in protein-coding sequences. Evidence from genome-wide association studies (GWASs) strongly suggests that variants important to human diseases often lie in non-coding regions. Extending DNM-based approaches to non-coding sequences is challenging, however, because the functional significance of non-coding mutations is difficult to predict. We propose a statistical framework for analyzing DNMs from whole-genome sequencing (WGS) data. This method, TADA-Annotations (TADA-A), is a major advance of the TADA method we developed earlier for DNM analysis in coding regions. TADA-A is able to incorporate many functional annotations such as conservation and enhancer marks, to learn from data which annotations are informative of pathogenic mutations, and to combine both coding and non-coding mutations at the gene level to detect risk genes. It also supports meta-analysis of multiple DNM studies, while adjusting for study-specific technical effects. We applied TADA-A to WGS data of ∼300 autism-affected family trios across five studies and discovered several autism risk genes. The software is freely available for all research uses., (Copyright © 2018 American Society of Human Genetics. Published by Elsevier Inc. All rights reserved.)

Importance: Autism spectrum disorder (ASD) is a highly prevalent disorder, and community psychiatrists are likely to treat many individuals with ASD during their clinical practice. This clinical case challenge describes a routine evaluation of irritability and self-injury in a preschool-aged child who meets the criteria for ASD. The case also illustrates the importance of known risk factors for ASD, such as chromosomal deletion and prematurity. This clinical neuroscience article seeks to educate the clinician of current avenues of research that can inform and may already affect clinical practice for this patient, while providing a preview of research that may yield biological treatments for ASD within the next decade., Observations: A diagnosis of ASD is defined behaviorally; therefore, many genetic and environmental risk factors, working singly or in concert, are linked to ASD. The prenatal period of brain development is particularly sensitive to risk factors such as gene mutation or drug exposure that affect brain development and circuitry formation. Currently, neuroimaging researchers can detect changes in brain connectivity of children with ASD as young as 6 months, followed by an atypical trajectory of brain development through preschool age and ongoing connectivity inefficiencies across the lifespan. Animal and cellular model systems have provided a means for defining the molecular and cellular changes associated with risk factors for ASD. The ability to connect specific treatments to particular subgroups of people with ASD is the defining hope of precision medicine initiatives., Conclusions and Relevance: The advent of next-generation sequencing technology, advanced imaging techniques, and cutting-edge molecular techniques for modeling ASD has allowed researchers to define ASD risk-related biological pathways and circuits that may, for the first time, unify the effects of disparate risk factors into common neurobiological mechanisms. The path from these mechanisms to biological treatments that improve the lives of individuals with autism remains unclear, but the cumulative output of multiple lines of research suggests that subtyping by genetic risk factors may be a particularly tractable way to capitalize on individual differences amenable to specific treatments.

Recent studies implicate chromatin modifiers in autism spectrum disorder (ASD) through the identification of recurrent de novo loss of function mutations in affected individuals. ASD risk genes are co-expressed in human midfetal cortex, suggesting that ASD risk genes converge in specific regulatory networks during neurodevelopment. To elucidate such networks, we identify genes targeted by CHD8, a chromodomain helicase strongly associated with ASD, in human midfetal brain, human neural stem cells (hNSCs) and embryonic mouse cortex. CHD8 targets are strongly enriched for other ASD risk genes in both human and mouse neurodevelopment, and converge in ASD-associated co-expression networks in human midfetal cortex. CHD8 knockdown in hNSCs results in dysregulation of ASD risk genes directly targeted by CHD8. Integration of CHD8-binding data into ASD risk models improves detection of risk genes. These results suggest loss of CHD8 contributes to ASD by perturbing an ancient gene regulatory network during human brain development.

Background: De novo loss-of-function (dnLoF) mutations are found twofold more often in autism spectrum disorder (ASD) probands than their unaffected siblings. Multiple independent dnLoF mutations in the same gene implicate the gene in risk and hence provide a systematic, albeit arduous, path forward for ASD genetics. It is likely that using additional non-genetic data will enhance the ability to identify ASD genes., Methods: To accelerate the search for ASD genes, we developed a novel algorithm, DAWN, to model two kinds of data: rare variations from exome sequencing and gene co-expression in the mid-fetal prefrontal and motor-somatosensory neocortex, a critical nexus for risk. The algorithm casts the ensemble data as a hidden Markov random field in which the graph structure is determined by gene co-expression and it combines these interrelationships with node-specific observations, namely gene identity, expression, genetic data and the estimated effect on risk., Results: Using currently available genetic data and a specific developmental time period for gene co-expression, DAWN identified 127 genes that plausibly affect risk, and a set of likely ASD subnetworks. Validation experiments making use of published targeted resequencing results demonstrate its efficacy in reliably predicting ASD genes. DAWN also successfully predicts known ASD genes, not included in the genetic data used to create the model., Conclusions: Validation studies demonstrate that DAWN is effective in predicting ASD genes and subnetworks by leveraging genetic and gene expression data. The findings reported here implicate neurite extension and neuronal arborization as risks for ASD. Using DAWN on emerging ASD sequence data and gene expression data from other brain regions and tissues would likely identify novel ASD genes. DAWN can also be used for other complex disorders to identify genes and subnetworks in those disorders.

Autism spectrum disorder (ASD) is a complex developmental syndrome of unknown etiology. Recent studies employing exome- and genome-wide sequencing have identified nine high-confidence ASD (hcASD) genes. Working from the hypothesis that ASD-associated mutations in these biologically pleiotropic genes will disrupt intersecting developmental processes to contribute to a common phenotype, we have attempted to identify time periods, brain regions, and cell types in which these genes converge. We have constructed coexpression networks based on the hcASD "seed" genes, leveraging a rich expression data set encompassing multiple human brain regions across human development and into adulthood. By assessing enrichment of an independent set of probable ASD (pASD) genes, derived from the same sequencing studies, we demonstrate a key point of convergence in midfetal layer 5/6 cortical projection neurons. This approach informs when, where, and in what cell types mutations in these specific genes may be productively studied to clarify ASD pathophysiology., (Copyright © 2013 Elsevier Inc. All rights reserved.)

The human malaria parasite, Plasmodium falciparum, modifies the red blood cells (RBCs) that it infects by exporting proteins to the host cell. One key virulence protein, P. falciparum Erythrocyte Membrane Protein-1 (PfEMP1), is trafficked to the surface of the infected RBC, where it mediates adhesion to the vascular endothelium. We have investigated the organization and development of the exomembrane system that is used for PfEMP1 trafficking. Maurer's cleft cisternae are formed early after invasion and proteins are delivered to these (initially mobile) structures in a temporally staggered and spatially segregated manner. Membrane-Associated Histidine-Rich Protein-2 (MAHRP2)-containing tether-like structures are generated as early as 4 h post invasion and become attached to Maurer's clefts. The tether/Maurer's cleft complex docks onto the RBC membrane at ~20 h post invasion via a process that is not affected by cytochalasin D treatment. We have examined the trafficking of a GFP chimera of PfEMP1 expressed in transfected parasites. PfEMP1B-GFP accumulates near the parasite surface, within membranous structures exhibiting a defined ultrastructure, before being transferred to pre-formed mobile Maurer's clefts. Endogenous PfEMP1 and PfEMP1B-GFP are associated with Electron-Dense Vesicles that may be responsible for trafficking PfEMP1 from the Maurer's clefts to the RBC membrane., (© 2013 John Wiley & Sons Ltd.)

Transport of Plasmodium falciparum Erythrocyte Membrane Protein 1 (PfEMP1) variants to the red blood cell (RBC) surface enables malarial parasite evasion of host immunity by modifying the antigenic and adhesive properties of infected RBCs. In this study, we applied the Bxb1 integrase system to integrate transgenes encoding truncated PfEMP1-GFP fusions into cytoadherent A4 parasites and characterize their surface transport requirements. Our studies revealed that the semi-conserved head structure of PfEMP1 proteins, in combination with the predicted transmembrane region and cytoplasmic tail, encodes sufficient information for RBC surface display. In contrast, miniPfEMP1 proteins with truncated head structures were exported to the RBC cytoplasm but were not detected at the RBC surface by flow cytometry or immuno-electron microscopy. We demonstrated the absence of a mechanistic barrier to having native and miniPfEMP1 proteins displayed simultaneously at the RBC surface. However, surface-exposed miniPfEMP1 proteins did not convey cytoadherence properties to their host cells, implicating potential steric considerations in host-receptor interactions or the need for multiple domains to mediate cell binding. This study establishes a new system to investigate PfEMP1 transport and demonstrates that the PfEMP1 semi-conserved head structure is under selection for protein transport, in addition to its known roles in adhesion., (© 2010 Blackwell Publishing Ltd.)

Questions surround the mechanism of mutually exclusive expression by which Plasmodium falciparum mediates activation and silencing of var genes. These encode PfEMP1 proteins, which function as cytoadherent and immunomodulatory molecules at the surface of parasitised erythrocytes. Current evidence suggests that promoter silencing by var introns might play a key role in var gene regulation. To evaluate the impact of cis-acting regulatory regions on var silencing, we generated P. falciparum lines in which luciferase was placed under the control of an UpsA var promoter. By utilising the Bxb1 integrase system, these reporter cassettes were targeted to a genomic region that was not in apposition to var subtelomeric domains. This eliminated possible effects from surrounding telomeric elements and removed the variability inherent in episomal systems. Studies with highly synchronised parasites revealed that the UpsA element possessed minimal activity in comparison with a heterologous (hrp3) promoter. This may result from the integrated UpsA promoter being largely silenced by the neighbouring cg6 promoter. Our analyses also revealed that the DownsA 3' untranslated region further decreased the luciferase activity from both cassettes, whereas the var A intron repressed the UpsA promoter specifically. By applying multivariate analysis over the entire cell cycle, we confirmed the significance of these cis-elements and found the parasite stage to be the major factor regulating UpsA-promoter activity. Additionally, we observed that the UpsA promoter was capable of nucleating reversible silencing that spread to a downstream promoter. We believe these studies are the first to analyse promoter activity of Group A var genes, which have been implicated in severe malaria, and support the model that var introns can further suppress var expression. These data also suggest an important suppressive role for the DownsA terminator. Our findings imply the existence of multiple levels of var gene regulation in addition to intrinsic promoter-dependent silencing.

Here we report an efficient, site-specific system of genetic integration into Plasmodium falciparum malaria parasite chromosomes. This is mediated by mycobacteriophage Bxb1 integrase, which catalyzes recombination between an incoming attP and a chromosomal attB site. We developed P. falciparum lines with the attB site integrated into the glutaredoxin-like cg6 gene. Transfection of these attB(+) lines with a dual-plasmid system, expressing a transgene on an attP-containing plasmid together with a drug resistance gene and the integrase on a separate plasmid, produced recombinant parasites within 2 to 4 weeks that were genetically uniform for single-copy plasmid integration. Integrase-mediated recombination resulted in proper targeting of parasite proteins to intra-erythrocytic compartments, including the apicoplast, a plastid-like organelle. Recombinant attB x attP parasites were genetically stable in the absence of drug and were phenotypically homogeneous. This system can be exploited for rapid genetic integration and complementation analyses at any stage of the P. falciparum life cycle, and it illustrates the utility of Bxb1-based integrative recombination for genetic studies of intracellular eukaryotic organisms.

Chloroquine resistance (CQR) in Plasmodium falciparum is associated with mutations in the digestive vacuole transmembrane protein PfCRT. However, the contribution of individual pfcrt mutations has not been clarified and other genes have been postulated to play a substantial role. Using allelic exchange, we show that removal of the single PfCRT amino-acid change K76T from resistant strains leads to wild-type levels of CQ susceptibility, increased binding of CQ to its target ferriprotoporphyrin IX in the digestive vacuole and loss of verapamil reversibility of CQ and quinine resistance. Our data also indicate that PfCRT mutations preceding residue 76 modulate the degree of verapamil reversibility in CQ-resistant lines. The K76T mutation accounts for earlier observations that CQR can be overcome by subtly altering the CQ side-chain length. Together, these findings establish PfCRT K76T as a critical component of CQR and suggest that CQ access to ferriprotoporphyrin IX is determined by drug-protein interactions involving this mutant residue.

Plasmodium falciparum malaria is increasingly difficult to treat and control due to the emergence of parasite resistance to the major antimalarials, notably chloroquine. Recent work has shown that the chloroquine resistance phenotype can be conferred by multiple amino acid mutations in the parasite digestive vacuole transmembrane protein PfCRT. Here, we have addressed whether chloroquine resistance can also be affected by changes in expression levels of this protein. Transient transfection reporter assays revealed that truncation of the pfcrt 3'-untranslated region just prior to putative polyadenylation sites resulted in a 10-fold decrease in luciferase expression levels. Using allelic exchange on a chloroquine-resistant line (7G8 from Brazil), this truncated 3'-untranslated region was inserted downstream of the pfcrt coding sequence, in the place of the endogenous 3'-untranslated region. The resulting pfcrt-modified "knockdown" clones displayed a marked decrease in pfcrt transcription and an estimated 30-40% decrease in PfCRT protein expression levels. [3H]hypoxanthine incorporation assays demonstrated up to a 40% decrease in chloroquine with or without verapamil IC50 levels of pfcrt knockdown clones, relative to the 7G8 parent. Single-cell photometric analyses were consistent with an altered intracellular pH in the knockdown clones, providing further evidence for a relationship between PfCRT, pH regulation, and chloroquine resistance. Genetic truncation of 3'-untranslated regions provides a useful approach for assessing the impact of candidate genes on drug resistance or other quantifiable phenotypes in P. falciparum.

Objective: We tested the hypothesis that intrauterine bacterial inoculation induces labor via expression of the inflammatory cytokine interleukin-1 (IL-1) in a murine model., Study Design: Pregnant mice on day 14.5 of a 19-20 day gestation were inoculated with killed Escherichia coli or sterile media into either (a) the right uterine horn, (b) the right uterine horn following its surgical isolation from the contralateral horn and cervix, or (c) the kidney. Cytokine levels in gestational tissues and maternal serum were determined by use of enzyme-linked immunosorbent assay (ELISA). In a separate experiment, bacterially induced preterm delivery was compared between mice lacking a functional IL-1 receptor and wild-type control litter mates., Results: Killed E coli induced delivery within 48 hours with similar dose-response curves regardless of inoculation site (intact uterine horn, isolated uterine horn, or kidney). Bacterial inoculation of an isolated right horn caused dramatic increases in local expression of IL-1 and IL-6. However, delivery occurred from the uninjected horn without corresponding upregulation of cytokines, with the exception of a modest rise within fetal membranes. Mice lacking a functional IL-1 receptor were no different from wild-type mice in their susceptibility to bacterially induced delivery., Conclusion: Bacterially induced labor in the murine model does not require IL-1 signaling.

Objective: We propose that elucidation of the pathophysiology of preterm labor can be achieved with genome-scale analyses of differential gene expression., Study Design: CD-1 mice on day 14.5 of a 19- to 20-day gestation were assigned to one of 4 treatment groups modeling different clinical conditions (n = 5 per group): group A, infection with labor (intrauterine injection of 10(10) heat-killed Escherichia coli, which causes delivery within an average of 20 hours); group B, infection without labor (intrauterine injection of 10(7) heat-killed E coli, which leads to normal delivery at term); group C, labor without infection (ovariectomy, which causes delivery within an average of 27 hours); and group D, no infection and no labor (intrauterine injection of vehicle). Total pooled myometrial RNA was prepared 3.5 hours after surgery for groups A, B, and D and 5 hours after surgery for group C. The relative expression of 4963 genes was assayed in these pools by using DNA microarrays. Transcripts specifically involved in infection-induced labor were identified by subtracting from the list of differentially regulated genes in group A those with common expression in groups B and C., Results: In group A 68 differentially expressed transcripts (>or=2-fold upregulation or downregulation) were identified. Among these are 39 characterized genes. Fourteen (45%) are involved in inflammatory responses, 7 (18%) are involved in growth-differentiation-oncogenesis, and 3 (8%) are involved in apoptosis. Subtraction identified 13 gene products most likely to be important for bacterially induced labor, as opposed to labor without infection or bacterial exposure without labor., Conclusion: This study demonstrates the potential of the subtractive DNA microarray technique to identify transcripts important specifically for bacterially induced preterm labor.