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Short-term low intensity parent implemented intervention studies for toddlers with autism spectrum disorder (ASD) have found it difficult to demonstrate significantly improved developmental scores or autism severity compared to community treatment. We conducted a randomized comparative intent-to-treat study of a parent implemented intervention to (1) test the effects of an enhanced version on parent and child learning, and (2) evaluate the sensitivity to change of proximal versus distal measures of child behavior. We randomized 45 children with ASD, 12-30 months of age, into one of two versions of parent-implemented Early Start Denver Model (P-ESDM), the basic model, in which we delivered 1.5 h of clinic-based parent coaching weekly, and an enhanced version that contained three additions: motivational interviewing, multimodal learning tools, and a weekly 1.5-h home visit. We delivered the intervention for 12 weeks and measured child and parent change frequently in multiple settings. We found a time-by-group interaction: parents in the enhanced group demonstrated significantly greater gains in interaction skills than did parents in the non-enhanced group. Both interventions were associated with significant developmental acceleration; however, child outcomes did not differ by group. We found a significant relationship between degree of change in parental interaction skill and rate of children's improvement on our proximal measure. Parents in both groups reported satisfaction with the intervention. These findings suggest that parent skills improved more in the enhanced group than the comparison group. Children in the two groups showed similar improvements. Rate of individual parent learning was associated with greater individual child progress on a measure quite proximal to the treatment, though not on standardized assessments.

The major innate immune responder to the DNA of pathogens is the cyclic GMP-AMP (cGAMP) synthase (cGAS) - stimulator of interferon genes (STING) pathway. Most prominently, the outcome of cGAS signalling is the activation of inflammatory transcription through interferon regulatory factor 3 (IRF3) and nuclear factor kappa B (NF-kB). In addition, the cGAS-STING pathway can lead to the direct modulation of cellular processes independently of transcription, such as activation of autophagy. Under unperturbed conditions, several mechanisms are in place to prevent the activation of cGAS by self-DNA, chiefly its sequestration on chromatin, which interferes with binding to stimulatory DNA. However, under conditions of genotoxic stress and chromosomal instability, this inhibition breaks down, resulting in the activation of cGAS, which drives sterile inflammation, as well as cell fate and immune responses in cancer. Recently, several studies have suggested that cGAS, STING, or downstream pathway components can also regulate the DNA damage response, DNA damage checkpoint signalling, DNA repair and DNA replication. Here, I review these proposed mechanisms, and discuss some unanswered questions relating to them., Competing Interests: Declaration of Competing Interest The author declares that there are no conflicts of interest., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Genome instability due to the loss of DNA repair factors can drive developmental defects, autoinflammatory disease, and cancer. Two major signaling pathways are activated by genome instability-DNA damage checkpoint signaling, leading to p53 activation, and innate immunity, largely driven by the DNA sensor cGAS. Like p53, cGAS is thought to drive cell death and senescence during genotoxic stress in addition to its canonical inflammatory functions, but its role during cellular differentiation and carcinogenesis is poorly understood. Furthermore, it is heavily debated whether the cGAS pathway primarily has tumor-suppressive or oncogenic functions. A study in this issue of Cancer Research used a hematopoietic lineage-specific knockout of the ribonucleotide repair gene Rnaseh2b to introduce genotoxic stress, resulting in severe hematopoiesis defects and increased incidence of hematologic cancers. These two effects were driven by and antagonized by p53, respectively. Surprisingly, despite increased innate immune signaling, the cGAS pathway did not seem to play a role in either process. These findings suggest that innate immune responses to genotoxic stress may be more subtle and context-specific than appreciated, indicating that a more detailed understanding of pathway activation and signaling consequences is needed. See related article by Dressel et al., p. 2858., (©2023 American Association for Cancer Research.)

The DNA sensor cyclic GMP-AMP synthase (cGAS) is critical in host antiviral immunity. Vaccinia virus (VACV) is a large cytoplasmic DNA virus that belongs to the poxvirus family. How vaccinia virus antagonizes the cGAS-mediated cytosolic DNA-sensing pathway is not well understood. In this study, we screened 80 vaccinia genes to identify potential viral inhibitors of the cGAS/Stimulator of interferon gene (STING) pathway. We discovered that vaccinia E5 is a virulence factor and a major inhibitor of cGAS. E5 is responsible for abolishing cGAMP production during vaccinia virus (Western Reserve strain) infection of dendritic cells. E5 localizes to the cytoplasm and nucleus of infected cells. Cytosolic E5 triggers ubiquitination of cGAS and proteasome-dependent degradation via interacting with cGAS. Deleting the E5R gene from the Modified vaccinia virus Ankara (MVA) genome strongly induces type I IFN production by dendritic cells (DCs) and promotes DC maturation, and thereby improves antigen-specific T cell responses., (© 2023. The Author(s).)

The cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS) senses invasion of pathogenic DNA and stimulates inflammatory signaling, autophagy, and apoptosis. Organization of host DNA into nucleosomes was proposed to limit cGAS autoinduction, but the underlying mechanism was unknown. Here, we report the structural basis for this inhibition. In the cryo-electron microscopy structure of the human cGAS-nucleosome core particle (NCP) complex, two cGAS monomers bridge two NCPs by binding the acidic patch of the histone H2A-H2B dimer and nucleosomal DNA. In this configuration, all three known cGAS DNA binding sites, required for cGAS activation, are repurposed or become inaccessible, and cGAS dimerization, another prerequisite for activation, is inhibited. Mutating key residues linking cGAS and the acidic patch alleviates nucleosomal inhibition. This study establishes a structural framework for why cGAS is silenced on chromatinized self-DNA., (Copyright © 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Cyclic GMP-AMP (cGAMP) synthase (cGAS) is a major responder to the pathogenic DNA of viruses and bacteria. Upon DNA binding, cGAS becomes enzymatically active to generate the second messenger cGAMP, leading to activation of inflammatory genes, type I interferon production, autophagy, and cell death. Following genotoxic stress, cGAS can also respond to endogenous DNA, deriving from mitochondria, endogenous retroelements, and chromosomes to affect cellular signaling, secretion, and cell fate decisions. However, under unperturbed conditions, signaling from self-DNA is largely, but not completely, inhibited. Here we review how endogenous DNA is exposed to cGAS, how signaling is attenuated but activated under pathological conditions, and how low-level signaling under unperturbed conditions might prime antipathogenic responses., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Pathogenic and other cytoplasmic DNAs activate the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway to induce inflammation via transcriptional activation by IRF3 and nuclear factor κB (NF-κB), but the functional consequences of exposing cGAS to chromosomes upon mitotic nuclear envelope breakdown are unknown. Here, we show that nucleosomes competitively inhibit DNA-dependent cGAS activation and that the cGAS-STING pathway is not effectively activated during normal mitosis. However, during mitotic arrest, low level cGAS-dependent IRF3 phosphorylation slowly accumulates without triggering inflammation. Phosphorylated IRF3, independently of its DNA-binding domain, stimulates apoptosis through alleviating Bcl-xL-dependent suppression of mitochondrial outer membrane permeabilization. We propose that slow accumulation of phosphorylated IRF3, normally not sufficient for inducing inflammation, can trigger transcription-independent induction of apoptosis upon mitotic aberrations. Accordingly, expression of cGAS and IRF3 in cancer cells makes mouse xenograft tumors responsive to the anti-mitotic agent Taxol. The Cancer Genome Atlas (TCGA) datasets for non-small cell lung cancer patients also suggest an effect of cGAS expression on taxane response., (Copyright © 2019 Elsevier Inc. All rights reserved.)

The majority of eukaryotic chromosomal DNA exists in the form of nucleosomes, where ∼147 bp DNA wraps around histone hetero-octamers, composed of histone H3, H4, H2A, and H2B. Despite their obvious importance in DNA compaction and accessibility, studying their specific roles, such as regulation of mitotic progression, in a physiological environment is associated with critical caveats because of their major contributions in transcriptional control. Through establishing a method to deplete endogenous histones H3 and H4 from frog egg extracts and complementing their functions using recombinant nucleosome arrays, we are now able to analyze their roles in mitotic progression without affecting overall transcriptomic profiles. Here we summarize advancements learned from this system, illustrating that microtubule and nuclear envelope assembly can be regulated by two major nucleosome-bound protein complexes, RCC1-Ran and the chromosomal passenger complex (CPC) containing the mitotic protein kinase Aurora B. We also discuss roles of the CPC on the proteomic composition of mitotic chromatin. The CPC promotes dissociation of a variety of nucleosome remodelers and DNA repair pathway proteins, suggesting its role in suppressing DNA processing activities on mitotic chromosomes. We speculate that this suppression particularly on chromosomes under microtubule tension may be important to preserve genome integrity., (© 2017 Funabiki et al.; Published by Cold Spring Harbor Laboratory Press.)

During DNA double-strand break (DSB) repair, the ring-shaped Ku70/80 complex becomes trapped on DNA and needs to be actively extracted, but it has remained unclear what provides the required energy. By means of reconstitution of DSB repair on beads, we demonstrate here that DNA-locked Ku rings are released by the AAA-ATPase p97. To achieve this, p97 requires ATP hydrolysis, cooperates with the Ufd1-Npl4 ubiquitin-adaptor complex, and specifically targets Ku80 that is modified by K48-linked ubiquitin chains. In U2OS cells, chemical inhibition of p97 or siRNA-mediated depletion of p97 or its adapters impairs Ku80 removal after non-homologous end joining of DSBs. Moreover, this inhibition attenuates early steps in homologous recombination, consistent with p97-driven Ku release also affecting repair pathway choice. Thus, our data answer a central question regarding regulation of Ku in DSB repair and illustrate the ability of p97 to segregate even tightly bound protein complexes for release from DNA., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Chromosomes are not only carriers of the genetic material, but also actively regulate the assembly of complex intracellular architectures. During mitosis, chromosome-induced microtubule polymerisation ensures spindle assembly in cells without centrosomes and plays a supportive role in centrosome-containing cells. Chromosomal signals also mediate post-mitotic nuclear envelope (NE) re-formation. Recent studies using novel approaches to manipulate histones in oocytes, where functions can be analysed in the absence of transcription, have established that nucleosomes, but not DNA alone, mediate the chromosomal regulation of spindle assembly and NE formation. Both processes require the generation of RanGTP by RCC1 recruited to nucleosomes but nucleosomes also acquire cell cycle stage specific regulators, Aurora B in mitosis and ELYS, the initiator of nuclear pore complex assembly, at mitotic exit. Here, we review the mechanisms by which nucleosomes control assembly and functions of the spindle and the NE, and discuss their implications for genome maintenance., (© 2015 WILEY Periodicals, Inc.)

There is a paucity of studies that have looked at factors associated with responsiveness to interventions in preschoolers with autism spectrum disorder (ASD). We investigated learning profiles associated with response to the early start Denver model delivered in a group setting. Our preliminary results from 21 preschool children with an ASD aged 2- to 5-years suggest that the children with more advanced skills in functional use of objects, goal understanding and imitation made the best developmental gains after 1 year of treatment. Cognitive abilities, social attention, intensity of the treatment and chronological age were not associated with treatment gains.

We describe a protocol with which we achieved a 93% success rate in acquiring high quality MRI scans without the use of sedation in 2.5-4.5 year old children with autism, developmental delays, and typical development. Our main strategy was to conduct MRIs during natural nocturnal sleep in the evenings after the child's normal bedtime. Alternatively, with some older and higher functioning children, the MRI was conducted while the child was awake and watching a video. Both strategies relied heavily on the creation of a child and family friendly MRI environment and the involvement of parents as collaborators in the project. Scanning very young children with autism, typical development, and developmental delays without the use of sedation or anesthesia was possible in the majority of cases.

DNA double strand breaks (DSBs) can be repaired by non-homologous end joining (NHEJ) or homology-directed repair (HR). HR requires nucleolytic degradation of 5' DNA ends to generate tracts of single-stranded DNA (ssDNA), which are also important for the activation of DNA damage checkpoints. Here we describe a quantitative analysis of DSB processing in the budding yeast Saccharomyces cerevisiae. We show that resection of an HO endonuclease-induced DSB is less extensive than previously estimated and provide evidence for significant instability of the 3' ssDNA tails. We show that both DSB resection and checkpoint activation are dose-dependent, especially during the G1 phase of the cell cycle. During G1, processing near the break is inhibited by competition with NHEJ, but extensive resection is regulated by an NHEJ-independent mechanism. DSB processing and checkpoint activation are more efficient in G2/M than in G1 phase, but are most efficient at breaks encountered by DNA replication forks during S phase. Our findings identify unexpected complexity of DSB processing and its regulation, and provide a framework for further mechanistic insights.

Background: While double-strand break (DSB) repair is vital to the survival of cells during both meiosis and mitosis, the preferred mechanism of repair differs drastically between the two types of cell cycle. Thus, during meiosis, it is the homologous chromosome rather than the sister chromatid that is used as a repair template., Results: Cells attempting to undergo meiosis in the absence of Mnd1 arrest in prophase I due to the activation of the Mec1 DNA-damage checkpoint accumulating hyperresected DSBs and aberrant synapsis. Sporulation of mnd1Delta strains can be restored by deleting RED1 or HOP1, which permits repair of DSBs by using the sister chromatid as a repair template. Mnd1 localizes to chromatin as foci independently of DSB formation, axial element (AE) formation, and synaptonemal complex (SC) formation and does not colocalize with Rad51. Mnd1 does not preferentially associate with hotspots of recombination., Conclusions: Our results suggest that Mnd1 acts specifically to promote DSB repair by using the homologous chromosome as a repair template. The presence of Rec8, Red1, or Hop1 renders Mnd1 indispensable for DNA repair, presumably through the establishment of interhomolog (IH) bias. Localization studies suggest that Mnd1 carries out this function without being specifically recruited to the sites of DNA repair. We propose a model in which Mnd1 facilitates chromatin accessibility, which is required to allow strand invasion in meiotic chromatin.

The aims of this longitudinal study were: (1) to assess the continuity and change in diagnosis, intelligence, and language skills in children with autism, Down syndrome, and other developmental delays, (2) to specify the deficits in social competence and language skills in these children, and (3) to identify precursors in the preschool period of gains in language skills and of peer engagement in the mid-school years. The initial sample consisted of 70 children with autism, 93 children with Down syndrome, 59 children with developmental delays, and 108 typically developing children, with the first three groups of children studied when they were between 2 and 6 years of age. At follow-up, 51 children with autism, 71 children with Down syndrome, and 33 children with developmental delays were assessed at mean ages around 10-13 years. The long-term follow-up showed little change in the diagnosis of autism but sizeable improvements in intellectual and language abilities within the autistic group, a pattern that was not seen in the children with Down syndrome. Unique deficits in joint attention, some forms of representational play, responsiveness to the emotions of others, and initiation of peer engagement were identified in the autistic children, whereas the children with Down syndrome seemed to have a specific deficit only in language. Joint attention skills were concurrently associated with language abilities in all groups and predicted long-term gains in expressive language for the children with autism. Children with autism, regardless of their level of functioning, were less socially engaged with classmates than the other developmentally disabled children because they infrequently initiated and accepted play bids, not because they were rebuffed by peers. Early nonverbal communication and play skills were predictors of the frequency of initiations of peer play for the children with Down syndrome as well as the extent of peer engagement of the children with autism. These results suggest that improvements in early communication and play skills may have long-term consequences for later language and social competence in these groups of children.