Development of the N400 for Word Learning in the First 2 Years of Life: A Systematic Review.

The N400 ERP component is a direct neural index of word meaning. Studies show that the N400 component is already present in early infancy, albeit often delayed. Many researchers capitalize on this finding, using the N400 component to better understand how early language acquisition unfolds. However, variability in how researchers quantify the N400 makes it difficult to set clear predictions or build theory. Not much is known about how the N400 component develops in the first 2 years of life in terms of its latency and topographical distributions, nor do we know how task parameters affect its appearance. In the current paper we carry out a systematic review, comparing over 30 studies that report the N400 component as a proxy of semantic processing elicited in infants between 0 and 24 months old who listened to linguistic stimuli. Our main finding is that there is large heterogeneity across semantic-priming studies in reported characteristics of the N400, both with respect to latency and to distributions. With age, the onset of the N400 insignificantly decreases, while its offset slightly increases. We also examined whether the N400 appears different for recently-acquired novel words vs. existing words: both situations reveal heterogeneity across studies. Finally, we inspected whether the N400 was modulated differently with studies using a between-subject design. In infants with more proficient language skills the N400 was more often present or showed itself here with earlier latency, compared to their peers; but no consistent patterns were observed for distribution characteristics of the N400. One limitation of the current review is that we compared studies that widely differed in choice of EEG recordings, pre-processing steps and quantification of the N400, all of which could affect the characteristics of the infant N400. The field is still missing research that systematically tests development of the N400 using the same paradigm across infancy.

A Structure-Function-Inhibition Analysis of the Pseudomonas aeruginosa Type III Secretion Needle Protein PscF.

The Pseudomonas aeruginosa type III secretion system (T3SS) needle comprised of multiple PscF subunits is essential for the translocation of effector toxins into human cells, facilitating the establishment and dissemination of infection. Mutations in the pscF gene provide resistance to the phenoxyacetamide (PhA) series of T3SS inhibitory chemical probes. To better understand PscF functions and interactions with PhA, alleles of pscF with 71 single mutations altering 49 of the 85 residues of the encoded protein were evaluated for their effects on T3SS phenotypes. Of these, 37% eliminated and 63% maintained secretion, with representatives of both evenly distributed across the entire protein. Mutations in 14 codons conferred a degree of PhA resistance without eliminating secretion, and all but one were in the alpha-helical C-terminal 25% of PscF. PhA-resistant mutants exhibited no cross-resistance to two T3SS inhibitors with different chemical scaffolds. Two mutations caused constitutive T3SS secretion. The pscF allele at its native locus, whether wild type (WT), constitutive, or PhA resistant, was dominant over other pscF alleles expressed from nonnative loci and promoters, but mixed phenotypes were observed in chromosomal ΔpscF strains with both WT and mutant alleles at nonnative loci. Some PhA-resistant mutants exhibited reduced translocation efficiency that was improved in a PhA dose-dependent manner, suggesting that PhA can bind to those resistant needles. In summary, these results are consistent with a direct interaction between PhA inhibitors and the T3SS needle, suggest a mechanism of blocking conformational changes, and demonstrate that PscF affects T3SS regulation, as well as carrying out secretion and translocation.IMPORTANCEP. aeruginosa effector toxin translocation into host innate immune cells is critical for the establishment and dissemination of P. aeruginosa infections. The medical need for new anti-P. aeruginosa agents is evident by the fact that P. aeruginosa ventilator-associated pneumonia is associated with a high mortality rate (40 to 69%) and recurs in >30% of patients, even with standard-of-care antibiotic therapy. The results described here confirm roles for the PscF needle in T3SS secretion and translocation and suggest that it affects regulation, possibly by interaction with T3SS regulatory proteins. The results also support a model of direct interaction of the needle with PhA and suggest that, with further development, members of the PhA series may prove useful as drugs for P. aeruginosa infection.

Abnormalities in early visual processes are linked to hypersociability and atypical evaluation of facial trustworthiness: An ERP study with Williams syndrome.

Accurate assessment of trustworthiness is fundamental to successful and adaptive social behavior. Initially, people assess trustworthiness from facial appearance alone. These assessments then inform critical approach or avoid decisions. Individuals with Williams syndrome (WS) exhibit a heightened social drive, especially toward strangers. This study investigated the temporal dynamics of facial trustworthiness evaluation in neurotypic adults (TD) and individuals with WS. We examined whether differences in neural activity during trustworthiness evaluation may explain increased approach motivation in WS compared to TD individuals. Event-related potentials were recorded while participants appraised faces previously rated as trustworthy or untrustworthy. TD participants showed increased sensitivity to untrustworthy faces within the first 65-90 ms, indexed by the negative-going rise of the P1 onset (oP1). The amplitude of the oP1 difference to untrustworthy minus trustworthy faces was correlated with lower approachability scores. In contrast, participants with WS showed increased N170 amplitudes to trustworthy faces. The N170 difference to low-high-trust faces was correlated with low approachability in TD and high approachability in WS. The findings suggest that hypersociability associated with WS may arise from abnormalities in the timing and organization of early visual brain activity during trustworthiness evaluation. More generally, the study provides support for the hypothesis that impairments in low-level perceptual processes can have a cascading effect on social cognition.

Discovery of bacterial fatty acid synthase type II inhibitors using a novel cellular bioluminescent reporter assay.

Novel, cellular, gain-of-signal, bioluminescent reporter assays for fatty acid synthesis type II (FASII) inhibitors were constructed in an efflux-deficient strain of Pseudomonas aeruginosa and based on the discovery that FASII genes in P. aeruginosa are coordinately upregulated in response to pathway disruption. A screen of 115,000 compounds identified a series of sulfonamidobenzamide (SABA) analogs, which generated strong luminescent signals in two FASII reporter strains but not in four control reporter strains designed to respond to inhibitors of pathways other than FASII. The SABA analogs selectively inhibited lipid biosynthesis in P. aeruginosa and exhibited minimal cytotoxicity to mammalian cells (50% cytotoxic concentration [CC50] ≥ 80 µM). The most potent SABA analogs had MICs of 0.5 to 7.0 µM (0.2 to 3.0 µg/ml) against an efflux-deficient Escherichia coli (ΔtolC) strain but had no detectable MIC against efflux-proficient E. coli or against P. aeruginosa (efflux deficient or proficient). Genetic, molecular genetic, and biochemical studies revealed that SABA analogs target the enzyme (AccC) catalyzing the biotin carboxylase half-reaction of the acetyl coenzyme A (acetyl-CoA) carboxylase step in the initiation phase of FASII in E. coli and P. aeruginosa. These results validate the capability and the sensitivity of this novel bioluminescent reporter screen to identify inhibitors of E. coli and P. aeruginosa FASII.

Novel Small Molecule Entry Inhibitors of Ebola Virus.

BACKGROUND: The current Ebola virus (EBOV) outbreak has highlighted the troubling absence of available antivirals or vaccines to treat infected patients and stop the spread of EBOV. The EBOV glycoprotein (GP) plays critical roles in the early stage of virus infection, including receptor binding and membrane fusion, making it a potential target for the development of anti-EBOV drugs. We report the identification of 2 novel EBOV inhibitors targeting viral entry. METHODS: To identify small molecule inhibitors of EBOV entry, we carried out a cell-based high-throughput screening using human immunodeficiency virus-based pseudotyped viruses expressing EBOV-GP. Two compounds were identified, and mechanism-of-action studies were performed using immunoflourescence, AlphaLISA, and enzymatic assays for cathepsin B inhibition. RESULTS: We report the identification of 2 novel entry inhibitors. These inhibitors (1) inhibit EBOV infection (50% inhibitory concentration, approximately 0.28 and approximately 10 µmol/L) at a late stage of entry, (2) induce Niemann-Pick C phenotype, and (3) inhibit GP-Niemann-Pick C1 (NPC1) protein interaction. CONCLUSIONS: We have identified 2 novel EBOV inhibitors, MBX2254 and MBX2270, that can serve as starting points for the development of an anti-EBOV therapeutic agent. Our findings also highlight the importance of NPC1-GP interaction in EBOV entry and the attractiveness of NPC1 as an antifiloviral therapeutic target.

Mapping genetically controlled neural circuits of social behavior and visuo-motor integration by a preliminary examination of atypical deletions with Williams syndrome.

In this study of eight rare atypical deletion cases with Williams-Beuren syndrome (WS; also known as 7q11.23 deletion syndrome) consisting of three different patterns of deletions, compared to typical WS and typically developing (TD) individuals, we show preliminary evidence of dissociable genetic contributions to brain structure and human cognition. Univariate and multivariate pattern classification results of morphometric brain patterns complemented by behavior implicate a possible role for the chromosomal region that includes: 1) GTF2I/GTF2IRD1 in visuo-spatial/motor integration, intraparietal as well as overall gray matter structures, 2) the region spanning ABHD11 through RFC2 including LIMK1, in social cognition, in particular approachability, as well as orbitofrontal, amygdala and fusiform anatomy, and 3) the regions including STX1A, and/or CYLN2 in overall white matter structure. This knowledge contributes to our understanding of the role of genetics on human brain structure, cognition and pathophysiology of altered cognition in WS. The current study builds on ongoing research designed to characterize the impact of multiple genes, gene-gene interactions and changes in gene expression on the human brain.

Synthesis and antibacterial evaluation of new, unsymmetrical triaryl bisamidine compounds.

Herein we describe the synthesis and antibacterial evaluation of a new, unsymmetrical triaryl bisamidine compound series, [Am]-[indole]-[linker]-[HetAr/Ar]-[Am], in which [Am] is an amidine or amino group, [linker] is a benzene, thiophene or pyridine ring, and [HetAr/Ar] is a benzimidazole, imidazopyridine, benzofuran, benzothiophene, pyrimidine or benzene ring. When the [HetAr/Ar] unit is a 5,6-bicyclic heterocycle, it is oriented such that the 5-membered ring portion is connected to the [linker] unit and the 6-membered ring portion is connected to the [Am] unit. Among the 34 compounds in this series, compounds with benzofuran as the [HetAr/Ar] unit showed the highest potencies. Introduction of a fluorine atom or a methyl group to the triaryl core led to the more potent analogs. Bisamidines are more active toward bacteria while the monoamidines are more active toward mammalian cells (as indicated by low CC50 values). Importantly, we identified compound P12a (MBX 1887) with a relatively narrow spectrum against bacteria and a very high CC50 value. Compound P12a has been scaled up and is currently undergoing further evaluations for therapeutic applications.

New small molecule entry inhibitors targeting hemagglutinin-mediated influenza a virus fusion.

Influenza viruses are a major public health threat worldwide, and options for antiviral therapy are limited by the emergence of drug-resistant virus strains. The influenza virus glycoprotein hemagglutinin (HA) plays critical roles in the early stage of virus infection, including receptor binding and membrane fusion, making it a potential target for the development of anti-influenza drugs. Using pseudotype virus-based high-throughput screens, we have identified several new small molecules capable of inhibiting influenza virus entry. We prioritized two novel inhibitors, MBX2329 and MBX2546, with aminoalkyl phenol ether and sulfonamide scaffolds, respectively, that specifically inhibit HA-mediated viral entry. The two compounds (i) are potent (50% inhibitory concentration [IC50] of 0.3 to 5.9 µM); (ii) are selective (50% cytotoxicity concentration [CC(50)] of >100 µM), with selectivity index (SI) values of >20 to 200 for different influenza virus strains; (iii) inhibit a wide spectrum of influenza A viruses, which includes the 2009 pandemic influenza virus A/H1N1/2009, highly pathogenic avian influenza (HPAI) virus A/H5N1, and oseltamivir-resistant A/H1N1 strains; (iv) exhibit large volumes of synergy with oseltamivir (36 and 331 µM(2) % at 95% confidence); and (v) have chemically tractable structures. Mechanism-of-action studies suggest that both MBX2329 and MBX2546 bind to HA in a nonoverlapping manner. Additional results from HA-mediated hemolysis of chicken red blood cells (cRBCs), competition assays with monoclonal antibody (MAb) C179, and mutational analysis suggest that the compounds bind in the stem region of the HA trimer and inhibit HA-mediated fusion. Therefore, MBX2329 and MBX2546 represent new starting points for chemical optimization and have the potential to provide valuable future therapeutic options and research tools to study the HA-mediated entry process.

Mutational analysis of quinolone resistance protein QnrB1.

Alanine substitutions and selected deletions have been used to localize amino acids in QnrB essential for its protective activity. Essential amino acids are found at positions i and i(-2) in the pentapeptide repeat module and in the larger of two loops, where deletion of only a single amino acid compromises activity. Deletion of 10 amino acids at the N terminus is tolerated, but removal of 3 amino acids in the C-terminal dimerization unit destroys activity.

Vowels in early words: an event-related potential study.

Previous behavioural research suggests that infants possess phonologically detailed representations of the vowels and consonants in familiar words. These tasks examine infants' sensitivity to mispronunciations of a target label in the presence of a target and distracter image. Sensitivity to the mispronunciation may, therefore, be contaminated by the degree of mismatch between the distracter label and the heard mispronounced label. Event-related potential (ERP) studies allow investigation of infants' sensitivity to the relationship between a heard label (correct or mispronounced) and the referent alone using single picture trials. ERPs also provide information about the timing of lexico-phonological activation in infant word recognition. The current study examined 14-month-olds' sensitivity to vowel mispronunciations of familiar words using ERP data from single picture trials. Infants were presented with familiar images followed by a correct pronunciation of its label, a vowel mispronunciation or a phonologically unrelated non-word. The results support and extend previous behavioural findings that 14-month-olds are sensitive to mispronunciations of the vowels in familiar words using an ERP task. We suggest that the presence of pictorial context reinforces infants' sensitivity to mispronunciations of words, and that mispronunciation sensitivity may rely on infants accessing the cross-modal associations between word forms and their meanings.

Language and sociability: insights from Williams syndrome.

One of the most compelling features of Williams syndrome (WS) is the widely reported excessive sociability, accompanied by a relative proficiency in expressive language, which stands in stark contrast with significant intellectual and nonverbal impairments. It has been proposed that the unique language skills observed in WS are implicated in the strong drive to interact and communicate with others, which has been widely documented in WS. Nevertheless, this proposition has yet to be empirically examined. The present study aimed at investigating the relationship between a brain index of language processing and judgments of approachability of faces, as a proxy for sociability, in individuals with WS as contrasted to typical controls. Results revealed a significant and substantial association between the two in the WS, but not in the control group, supporting the hitherto untested notion that language use in WS might be uniquely related to their excessive social drive.

Identification of a small-molecule entry inhibitor for filoviruses.

Ebola virus (EBOV) causes severe hemorrhagic fever, for which therapeutic options are not available. Preventing the entry of EBOV into host cells is an attractive antiviral strategy, which has been validated for HIV by the FDA approval of the anti-HIV drug enfuvirtide. To identify inhibitors of EBOV entry, the EBOV envelope glycoprotein (EBOV-GP) gene was used to generate pseudotype viruses for screening of chemical libraries. A benzodiazepine derivative (compound 7) was identified from a high-throughput screen (HTS) of small-molecule compound libraries utilizing the pseudotype virus. Compound 7 was validated as an inhibitor of infectious EBOV and Marburg virus (MARV) in cell-based assays, with 50% inhibitory concentrations (IC(50)s) of 10 µM and 12 µM, respectively. Time-of-addition and binding studies suggested that compound 7 binds to EBOV-GP at an early stage during EBOV infection. Preliminary Schrödinger SiteMap calculations, using a published EBOV-GP crystal structure in its prefusion conformation, suggested a hydrophobic pocket at or near the GP1 and GP2 interface as a suitable site for compound 7 binding. This prediction was supported by mutational analysis implying that residues Asn69, Leu70, Leu184, Ile185, Leu186, Lys190, and Lys191 are critical for the binding of compound 7 and its analogs with EBOV-GP. We hypothesize that compound 7 binds to this hydrophobic pocket and as a consequence inhibits EBOV infection of cells, but the details of the mechanism remain to be determined. In summary, we have identified a novel series of benzodiazepine compounds that are suitable for optimization as potential inhibitors of filoviral infection.

Contrasting patterns of language-associated brain activity in autism and Williams syndrome.

Two neurodevelopmental disorders, Williams syndrome (WS) and autism, are both commonly described as having opposite social profiles: social avoidance in autism vs hypersociability in individuals with WS. The goal of this study was to contrast the brain activity associated with language processing in these two populations, in order to understand the very likely interplay between the use of language and the sociability dimension, on which these disorders diverge. Towards this aim, the N400 component of the event-related potentials was used to quantify the processing of semantic integration in these two populations. Results revealed that individuals with WS showed a significantly larger N400 effect, as compared to both typical controls and individuals with autism, while the latter group demonstrated the smallest N400 effect. The findings demonstrate quite opposite profiles of neural correlates of language processing in WS and autism, mirroring their contrasting social phenotypes.

The fusiform face area is enlarged in Williams syndrome.

Williams syndrome (WS) is a genetic condition characterized by atypical brain structure, cognitive deficits, and a life-long fascination with faces. Face recognition is relatively spared in WS, despite abnormalities in aspects of face processing and structural alterations in the fusiform gyrus, part of the ventral visual stream. Thus, face recognition in WS may be subserved by abnormal neural substrates in the ventral stream. To test this hypothesis, we used functional magnetic resonance imaging and examined the fusiform face area (FFA), which is implicated in face recognition in typically developed (TD) individuals, but its role in WS is not well understood. We found that the FFA was approximately two times larger among WS than TD participants (both absolutely and relative to the fusiform gyrus), despite apparently normal levels of face recognition performance on a Benton face recognition test. Thus, a larger FFA may play a role in face recognition proficiency among WS.

Affiliative behavior in Williams syndrome: social perception and real-life social behavior.

A frequently noted but largely anecdotal behavioral observation in Williams syndrome (WS) is an increased tendency to approach strangers, yet the basis for this behavior remains unknown. We examined the relationship between affect identification ability and affiliative behavior in participants with WS relative to a neurotypical comparison group. We quantified social behavior from self-judgments of approachability for faces, and from parent/other evaluations of real life. Relative to typical individuals, participants with WS were perceived as more sociable by others, exhibited perceptual deficits in affect identification, and judged faces of strangers as more approachable. In WS, high self-rated willingness to approach strangers was correlated with poor affect identification ability, suggesting that these two findings may be causally related. We suggest that the real-life hypersociability in WS may arise at least in part from abnormal perceptual processing of other people's faces, rather than from an overall bias at the level of behavior. While this did not achieve statistical significance, it provides preliminary evidence to suggest that impaired social-perceptual ability may play a role in increased approachability in WS.

Intelligence in Williams Syndrome is related to STX1A, which encodes a component of the presynaptic SNARE complex.

Although genetics is the most significant known determinant of human intelligence, specific gene contributions remain largely unknown. To accelerate understanding in this area, we have taken a new approach by studying the relationship between quantitative gene expression and intelligence in a cohort of 65 patients with Williams Syndrome (WS), a neurodevelopmental disorder caused by a 1.5 Mb deletion on chromosome 7q11.23. We find that variation in the transcript levels of the brain gene STX1A correlates significantly with intelligence in WS patients measured by principal component analysis (PCA) of standardized WAIS-R subtests, r = 0.40 (Pearson correlation, Bonferroni corrected p-value = 0.007), accounting for 15.6% of the cognitive variation. These results suggest that syntaxin 1A, a neuronal regulator of presynaptic vesicle release, may play a role in WS and be a component of the cellular pathway determining human intelligence.

A preliminary study of orbitofrontal activation and hypersociability in Williams Syndrome.

Individuals with Williams syndrome (WS) demonstrate an abnormally positive social bias. However, the neural substrates of this hypersociability, i.e., positive attribution bias and increased drive toward social interaction, have not fully been elucidated. METHODS: We performed an event-related functional magnetic resonance imaging study while individuals with WS and typically developing controls (TD) matched positive and negative emotional faces. WS compared to TD showed reduced right amygdala activation during presentation of negative faces, as in the previous literature. In addition, WS showed a unique pattern of right orbitofrontal cortex activation. While TD showed medial orbitofrontal cortex activation in response to positive, and lateral orbitofrontal cortex activation to negative, WS showed the opposite pattern. In light of the general notion of a medial/lateral gradient of reward/punishment processing in the orbitofrontal cortex, these findings provide an additional biological explanation for, or correlate of positive attribution bias and hypersociability in WS.

High-throughput screening of viral entry inhibitors using pseudotyped virus.

Virus entry into a host cell is an attractive target for therapy because propagation of virus can be blocked at an early stage, minimizing chances for the virus to acquire drug resistance. Anti-infective drug discovery for BSL-4 viruses like Ebola or Lassa hemorrhagic fever virus presents challenges due to the requirement for a BSL-4 laboratory containment facility. Pseudotyped viruses provide a surrogate model in which the native envelope glycoprotein of a BSL-2 level virus (e.g., vesicular stomatitis virus) is replaced with envelope glycoprotein of a foreign BSL-4 virus (e.g., Ebola virus). Because the envelope glycoprotein determines interaction of virus with its cellular receptors, pseudotyped viruses can mimic the viral entry process of the original virus. Moreover, they are competent for only a single cycle of infection, and therefore can be used in BSL-2 facilities. Pseudotyped viruses have been used in high-throughput screening of entry inhibitors for a number of BSL-4 level viruses. This unit includes protocols for preparing pseudotyped viruses using lentiviral vectors and use of pseudotyped viruses for high-throughput screening of viral entry inhibitors.

Cross-modal influences of affect across social and non-social domains in individuals with Williams syndrome.

The Williams syndrome (WS) cognitive profile is characterized by relative strengths in face processing, an attentional bias towards social stimuli, and an increased affinity and emotional reactivity to music. An audio-visual integration study examined the effects of auditory emotion on visual (social/non-social) affect identification in individuals with WS and typically developing (TD) and developmentally delayed (DD) controls. The social bias in WS was hypothesized to manifest as an increased ability to process social than non-social affect, and a reduced auditory influence in social contexts. The control groups were hypothesized to perform similarly across conditions. The results showed that while participants with WS exhibited indistinguishable performance to TD controls in identifying facial affect, DD controls performed significantly more poorly. The TD group outperformed the WS and DD groups in identifying non-social affect. The results suggest that emotionally evocative music facilitated the ability of participants with WS to process emotional facial expressions. These surprisingly strong facial-processing skills in individuals with WS may have been due to the effects of combining social and music stimuli and to a reduction in anxiety due to the music in particular. Several directions for future research are suggested.

Atypical hemispheric asymmetry in the perception of negative human vocalizations in individuals with Williams syndrome.

Williams syndrome is a neurological condition associated with high levels of auditory reactivity and emotional expression combined with impaired perception of prosody. Yet, little is currently known about the neural organization of affective auditory processing in individuals with this disorder. The current study examines auditory emotion processing in individuals with Williams syndrome. Hemispheric organization for positive and negative human non-linguistic sound processing was compared in participants with and without the disorder using a dichotic listening paradigm. While controls exhibited an expected right cerebral hemisphere advantage for processing negative sounds, those with Williams syndrome showed the opposite pattern. No differences between the groups emerged for the positive stimuli. The results suggest aberrant processing of negative auditory information in Williams syndrome.