Antenatal Magnesium Sulfate Benefits Female Preterm Infants but Results in Poor Male Outcomes.

Magnesium sulfate (MagSul) is used clinically to prevent eclamptic seizures during pregnancy and as a tocolytic for preterm labor. More recently, it has been implicated as offering neural protection in utero for at-risk infants. However, evidence is mixed. Some studies found that MagSul reduced the incidence of cerebral palsy (CP) but did not improve other measures of neurologic function. Others did not find any improvement in outcomes. Inconsistencies in the literature may reflect the fact that sex effects are largely ignored, despite evidence that MagSul shows sex effects in animal models of neonatal brain injury. The current study used retrospective infant data to assess differences in developmental outcomes as a function of sex and MagSul treatment. We found that on 18-month neurodevelopmental cognitive and language measures, preterm males treated with MagSul (n = 209) had significantly worse scores than their untreated counterparts (n = 135; p < 0.05). Female preterm infants treated with MagSul (n = 220), on the other hand, showed a cognitive benefit relative to untreated females (n = 123; p < 0.05). No significant effects of MagSul were seen among females on language (p > 0.05). These results have tremendous implications for risk-benefit considerations in the ongoing use of MagSul and may explain why benefits have been hard to identify in clinical trials when sex is not considered.

A novel approach to the assessment of higher-order rule learning in male mice.

Historically, the development of valid and reliable methods for assessing higher-order cognitive abilities (e.g., rule learning and transfer) has been difficult in rodent models. To date, limited evidence supports the existence of higher cognitive abilities such as rule generation and complex decision-making in mice, rats, and rabbits. To this end, we sought to develop a task that would require mice to learn and transfer a rule. We trained mice to visually discriminate a series of images (image set, six total) of increasing complexity following three stages: (1) learn a visual target, (2) learn a rule (ignore any new images around the target), and finally (3) apply this rule in abstract form to a comparable but new image set. To evaluate learning for each stage, we measured (1) days (and performance by day) to discriminate the original target at criterion, (2) days (and performance by day) to get back to criterion when images in the set were altered by the introduction of distractors (rule learning), and (3) overall days (and performance by day) to criterion when experienced versus naïve cohorts of mice were tested on the same image set (rule transfer). Twenty-seven wild-type male C57 mice were tested using Bussey-Saksida touchscreen operant conditioning boxes (Lafayette Instruments). Two comparable black-white image sets were delivered sequentially (counterbalanced for order) to two identical cohorts of mice. Results showed that all mice were able to effectively learn their initial target image and could recall it >80 d later. We also found that mice were able to quickly learn and apply a "rule" : Ignore new distractors and continue to identify their visual target embedded in more complex images. The presence of rule learning was supported because performance criterion thresholds were regained much faster than initial learning when distractors were introduced. On the other hand, mice appeared unable to transfer this rule to a new set of stimuli. This is supported because visual discrimination curves for a new image set were no better than an initial (naïve) learning by a matched cohort of mice. Overall results have important implications for phenotyping research and particularly for the modeling of complex disorders in mice.

Rapid auditory processing and medial geniculate nucleus anomalies in Kiaa0319 knockout mice.

Developmental dyslexia is a common neurodevelopmental disorder characterized by difficulties in reading and writing. Although underlying biological and genetic mechanisms remain unclear, anomalies in phonological processing and auditory processing have been associated with dyslexia. Several candidate risk genes have also been identified, with KIAA0319 as a main candidate. Animal models targeting the rodent homolog (Kiaa0319) have been used to explore putative behavioral and anatomic anomalies, with mixed results. For example after downregulation of Kiaa0319 expression in rats via shRNA, significant adult rapid auditory processing impairments were reported, along with cortical anomalies reflecting atypical neuronal migration. Conversely, Kiaa0319 knockout (KO) mice were reported to have typical adult auditory processing, and no visible cortical anomalies. To address these inconsistencies, we tested Kiaa0319 KO mice on auditory processing tasks similar to those used previously in rat shRNA knockdown studies. Subsequent neuroanatomic analyses on these same mice targeted medial geniculate nucleus (MGN), a receptive communication-related brain structure. Results confirm that Kiaa0319 KO mice exhibit significant auditory processing impairments specific to rapid/brief stimuli, and also show significant volumetric reductions and a shift toward fewer large and smaller neurons in the MGN. The latter finding is consistent with post mortem MGN data from human dyslexic brains. Combined evidence supports a role for KIAA0319 in the development of auditory CNS pathways subserving rapid auditory processing functions critical to the development of speech processing, language, and ultimately reading. Results affirm KIAA0319 variation as a possible risk factor for dyslexia specifically via anomalies in central acoustic processing pathways.

Peripheral Anomalies in USH2A Cause Central Auditory Anomalies in a Mouse Model of Usher Syndrome and CAPD.

Central auditory processing disorder (CAPD) is associated with difficulties hearing and processing acoustic information, as well as subsequent impacts on the development of higher-order cognitive processes (i.e., attention and language). Yet CAPD also lacks clear and consistent diagnostic criteria, with widespread clinical disagreement on this matter. As such, identification of biological markers for CAPD would be useful. A recent genome association study identified a potential CAPD risk gene, USH2A. In a homozygous state, this gene is associated with Usher syndrome type 2 (USH2), a recessive disorder resulting in bilateral, high-frequency hearing loss due to atypical cochlear hair cell development. However, children with heterozygous USH2A mutations have also been found to show unexpected low-frequency hearing loss and reduced early vocabulary, contradicting assumptions that the heterozygous (carrier) state is "phenotype free". Parallel evidence has confirmed that heterozygous Ush2a mutations in a transgenic mouse model also cause low-frequency hearing loss (Perrino et al., 2020). Importantly, these auditory processing anomalies were still evident after covariance for hearing loss, suggesting a CAPD profile. Since usherin anomalies occur in the peripheral cochlea and not central auditory structures, these findings point to upstream developmental feedback effects of peripheral sensory loss on high-level processing characteristic of CAPD. In this study, we aimed to expand upon the mouse behavioral battery used in Perrino et al. (2020) by evaluating central auditory brain structures, including the superior olivary complex (SOC) and medial geniculate nucleus (MGN), in heterozygous and homozygous Ush2a mice. We found that heterozygous Ush2a mice had significantly larger SOC volumes while homozygous Ush2a had significantly smaller SOC volumes. Heterozygous mutations did not affect the MGN; however, homozygous Ush2a mutations resulted in a significant shift towards more smaller neurons. These findings suggest that alterations in cochlear development due to USH2A variation can secondarily impact the development of brain regions important for auditory processing ability.

Behavioral and neuroanatomical outcomes following altered serotonin expression in a hypoxic-ischemic injury neonate rodent model.

BACKGROUND: Children born prematurely (<37 gestational weeks) are at risk for a variety of adverse medical events. They may experience ischemic and/or hemorrhagic events leading to negative neural sequelae. They are also exposed to repeated stressful experiences as part of life-saving care within the neonatal intensive care unit (NICU). These experiences have been associated with methylation of SLC6A4, a gene which codes for serotonin transport proteins, and is associated with anxiety, depression, and increased incidence of autism spectrum disorders.The purpose of this study was to examine the effects of altered serotonin levels on behavioral and neuroanatomical outcomes in a neonatal rodent model with or without exposure to hypoxic-ischemic (HI) injury. METHODS: Wistar rat pups were randomly assigned to either HI injury or sham groups. Pups within each group were treated with a chronic SSRI (Citalopram HBr) to simulate the effects of SLC6A4 methylation, or saline (NS). Subjects were assessed on behavioral tasks and neuropathologic indices. RESULTS: HI injured subjects performed poorly on behavioral tasks. SSRI subjects did not display significantly greater anxiety. HI + SSRI subjects learned faster than HI+NS. Histologically, SSRI subjects had predominantly larger brain volumes than NS. CONCLUSION: SSRI treated subjects without injury showed patterns of increased anxiety, consistent with theories of SLC6A4 methylation. The paradoxical trend to improved cognition in HI+SSRI subjects relative to HI alone, may reflect an unexpected SSRI neuroprotective effect in the presence of injury, and may be related to serotonin-induced neurogenesis.

Effort-related decision making in humanized COMT mice: Effects of Val158Met polymorphisms and possible implications for negative symptoms in humans.

Catechol-o-methyltransferase (COMT) is an enzyme that metabolizes catecholamines, and is crucial for clearance of dopamine (DA) in prefrontal cortex. Val158Met polymorphism, which causes a valine (Val) to methionine (Met) substitution at codon 158, is reported to be associated with human psychopathologies in some studies. The Val/Val variant of the enzyme results in higher dopamine metabolism, which results in reduced dopamine transmission. Thus, it is important to investigate the relation between Val158Met polymorphisms using rodent models of psychiatric symptoms, including negative symptoms such as motivational dysfunction. In the present study, humanized COMT transgenic mice with two genotype groups (Val/Val (Val) and Met/Met (Met) homozygotes) and wild-type (WT) mice from the S129 background were tested using a touchscreen effort-based choice paradigm. Mice were trained to choose between delivery of a preferred liquid diet that reinforced panel pressing on various fixed ratio (FR) schedules (high-effort alternative), vs. intake of pellets concurrently available in the chamber (low-effort alternative). Panel pressing requirements were controlled by varying the FR levels (FR1, 2, 4, 8, 16) in ascending and descending sequences across weeks of testing. All mice were able to acquire the initial touchscreen operant training, and there was an inverse relationship between the number of reinforcers delivered by panel pressing and pellet intake across different FR levels. There was a significant group x FR level interaction in the ascending limb, with panel presses in the Val group being significantly lower than the WT group in FR1-8, and lower than Met in FR4. These findings indicate that the humanized Val allele in mice modulates FR/pellet-choice performance, as marked by lower levels of panel pressing in the Val group when the ratio requirement was moderately high. These studies may contribute to the understanding of the role of COMT polymorphisms in negative symptoms such as motivational dysfunctions in schizophrenic patients.

Multi-level evidence of an allelic hierarchy of USH2A variants in hearing, auditory processing and speech/language outcomes.

Language development builds upon a complex network of interacting subservient systems. It therefore follows that variations in, and subclinical disruptions of, these systems may have secondary effects on emergent language. In this paper, we consider the relationship between genetic variants, hearing, auditory processing and language development. We employ whole genome sequencing in a discovery family to target association and gene x environment interaction analyses in two large population cohorts; the Avon Longitudinal Study of Parents and Children (ALSPAC) and UK10K. These investigations indicate that USH2A variants are associated with altered low-frequency sound perception which, in turn, increases the risk of developmental language disorder. We further show that Ush2a heterozygote mice have low-level hearing impairments, persistent higher-order acoustic processing deficits and altered vocalizations. These findings provide new insights into the complexity of genetic mechanisms serving language development and disorders and the relationships between developmental auditory and neural systems.

Pharmacological studies of effort-related decision making using mouse touchscreen procedures: effects of dopamine antagonism do not resemble reinforcer devaluation by removal of food restriction.

RATIONALE: Effort-based decision-making tasks offer animals choices between preferred reinforcers that require high effort to obtain vs. low effort/low reward options. The neural mechanisms of effort-based choice are widely studied in rats, and evidence indicates that mesolimbic dopamine (DA) and related neural systems play a key role. Fewer studies of effort-based choice have been performed in mice. OBJECTIVES: The present studies used touchscreen operant procedures (Bussey-Saksida boxes) to assess effort-based choice in mice. METHODS: CD1 mice were assessed on a concurrent fixed ratio 1 panel pressing/choice procedure. Mice were allowed to choose between rearing to press an elevated panel on the touchscreen for a preferred food (strawberry milkshake) vs. consuming a concurrently available less preferred alternative (high carbohydrate pellets). RESULTS: The DA D2 antagonist haloperidol (0.05-0.15 mg/kg IP) produced a dose-related decrease in panel pressing. Intake of food pellets was not reduced by haloperidol, and in fact, there was a significant quadratic trend, indicating a tendency for pellet intake to increase at low/moderate doses. In contrast, reinforcer devaluation by removing food restriction substantially decreased both panel pressing and pellet intake. In free-feeding choice tests, mice strongly preferred milkshake vs. pellets. Haloperidol did not affect food intake or preference. CONCLUSION: Haloperidol reduced the tendency to work for food, but this reduction was not due to decreases in primary food motivation or preference. Mouse touchscreen procedures demonstrate effects of haloperidol that are similar but not identical to those shown in rats. These rodent studies may be relevant for understanding motivational dysfunctions in humans.

Evaluation of visual motion perception ability in mice with knockout of the dyslexia candidate susceptibility gene Dcdc2.

Developmental dyslexia is a heritable disability characterized by difficulties in learning to read and write. The neurobiological and genetic mechanisms underlying dyslexia remain poorly understood; however, several dyslexia candidate risk genes have been identified. One of these candidate risk genes-doublecortin domain containing 2 (DCDC2)-has been shown to play a role in neuronal migration and cilia function. At a behavioral level, variants of DCDC2 have been associated with impairments in phonological processing, working memory and reading speed. Additionally, a specific mutation in DCDC2 has been strongly linked to deficits in motion perception-a skill subserving reading abilities. To further explore the relationship between DCDC2 and dyslexia, a genetic knockout (KO) of the rodent homolog of DCDC2 (Dcdc2) was created. Initial studies showed that Dcdc2 KOs display deficits in auditory processing and working memory. The current study was designed to evaluate the association between DCDC2 and motion perception, as these skills have not yet been assessed in the Dcdc2 KO mouse model. We developed a novel motion perception task, utilizing touchscreen technology and operant conditioning. Dcdc2 KOs displayed deficits on the Pairwise Discrimination task specifically as motion was added to visual stimuli. Following behavioral assessment, brains were histologically prepared for neuroanatomical analysis of the lateral geniculate nucleus (LGN). The cumulative distribution showed that Dcdc2 KOs exhibited more small neurons and fewer larger neurons in the LGN. Results compliment findings that DCDC2 genetic alteration results in anomalies in visual motion pathways in a subpopulation of dyslexic patients.

Shank3B mutant mice display pitch discrimination enhancements and learning deficits.

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder characterized by a core set of atypical behaviors in social-communicative and repetitive-motor domains. Individual profiles are widely heterogeneous and include language skills ranging from nonverbal to hyperlexic. The causal mechanisms underlying ASD remain poorly understood but appear to include a complex combination of polygenic and environmental risk factors. SHANK3 (SH3 and multiple ankyrin repeat domains 3) is one of a subset of well-replicated ASD-risk genes (i.e., genes demonstrating ASD associations in multiple studies), with haploinsufficiency of SHANK3 following deletion or de novo mutation seen in about 1% of non-syndromic ASD. SHANK3 is a synaptic scaffolding protein enriched in the postsynaptic density of excitatory synapses. In order to more closely evaluate the contribution of SHANK3 to neurodevelopmental expression of ASD, a knockout mouse model with a mutation in the PDZ domain was developed. Initial research showed compulsive/repetitive behaviors and impaired social interactions in these mice, replicating two core ASD features. The current study was designed to further examine Shank3B heterozygous and homozygous knockout mice for behaviors that might map onto atypical language in ASD (e.g., auditory processing, and learning/memory). We report findings of repetitive and atypical aggressive social behaviors (replicating prior reports), novel evidence that Shank3B KO mice have atypical auditory processing (low-level enhancements that might have a direct relationship with heightened pitch discrimination seen in ASD), as well as robust learning impairments.

A comparison of biofluid cytokine markers across platform technologies: Correspondence or divergence?

BACKGROUND: Quantification of biofluid cytokines is a rapidly growing area of translational research. However, comparability across the expanding number of available assay platforms for detection of the same proteins remains to be determined. We aimed to directly compare a panel of commonly measured cytokines in plasma of typically aging adults across two high sensitivity quantification platforms, Meso Scale Discovery high performance electrochemiluminiscence (HPE) and single-molecule immunosorbent assays (Simoa) by Quanterix. METHODS: 57 community-dwelling older adults completed a blood draw, neuropsychological assessment, and brain MRI as part of a healthy brain aging study. Plasma samples from the same draw dates were analyzed for IL-10, IP-10, IL-6, TNFα, and IL-1ß on HPE and Simoa, separately. Reliable detectability (coefficient of variance (CV) < 20% and outliers 3 interquartiles above the median removed), intra-assay precision, absolute concentrations, reproducibility across platforms, and concurrent associations with external variables of interest (e.g., demographics, peripheral markers of vascular health, and brain health) were examined. RESULTS: The proportion of cytokines reliably measured on HPE (87.7-93.0%) and Simoa (75.4-93.0%) did not differ (ps > 0.32), with the exception of IL-1ß which was only reliably measured using Simoa (68.4%). On average, CVs were acceptable at <8% across both platforms. Absolute measured concentrations were higher using Simoa for IL-10, IL-6, and TNFα (ps < 0.05). HPE and Simoa shared only small-to-moderate proportions of variance with one another on the same cytokine proteins (range: r = 0.26 for IL-10 to r = 0.64 for IL-6), though platform agreement did not dependent on cytokine concentrations. Cytokine ratios within each platform demonstrated similar relative patterns of up- and down-regulation across HPE and Simoa, though still significantly differed (ps < 0.001). Supporting concurrent validity, all 95% confidence intervals of the correlations between cytokines and external variables overlapped between the two platforms. Moreover, most associations were in expected directions and consistently so across platforms (e.g., IL-6 and TNFα), though with several notable exceptions for IP-10 and IL-10. CONCLUSIONS: HPE and Simoa showed comparable detectability and intra-assay precision measuring a panel of commonly examined cytokine proteins, with the exception of IL-1ß which was not reliably detected on HPE. However, Simoa demonstrated overall higher concentrations and the two platforms did not show agreement when directly compared against one another. Relative cytokine ratios and associations demonstrated similar patterns across platforms. Absolute cytokine concentrations may not be directly comparable across platforms, may be analyte dependent, and interpretation may be best limited to discussion of relative associations.

Behavioral and neuroanatomical outcomes in a rat model of preterm hypoxic-ischemic brain Injury: Effects of caffeine and hypothermia.

The current study investigated behavioral and post mortem neuroanatomical outcomes in Wistar rats with a neonatal hypoxic-ischemic (HI) brain injury induced on postnatal day 6 (P6; Rice-Vannucci HI method; Rice et al., 1981). This preparation models brain injury seen in premature infants (gestational age (GA) 32-35 weeks) based on shared neurodevelopmental markers at time of insult, coupled with similar neuropathologic sequelae (Rice et al., 1981; Workman et al., 2013). Clinically, HI insult during this window is associated with poor outcomes that include attention deficit hyperactivity disorder (ADHD), motor coordination deficits, spatial memory deficits, and language/learning disabilities. To assess therapies that might offer translational potential for improved outcomes, we used a P6 HI rat model to measure the behavioral and neuroanatomical effects of two prospective preterm neuroprotective treatments - hypothermia and caffeine. Hypothermia (aka "cooling") is an approved and moderately efficacious intervention therapy for fullterm infants with perinatal hypoxic-ischemic (HI) injury, but is not currently approved for preterm use. Caffeine is a respiratory stimulant used during removal of infants from ventilation but has shown surprising long-term benefits, leading to consideration as a therapy for HI of prematurity. Current findings support caffeine as a preterm neuroprotectant; treatment significantly improved some behavioral outcomes in a P6 HI rat model and partially rescued neuropathology. Hypothermia treatment (involving core temperature reduction by 4 °C for 5 h), conversely, was found to be largely ineffective and even deleterious for some measures in both HI and sham rats. These results have important implications for therapeutic intervention in at-risk preterm populations, and promote caution in the application of hypothermia protocols to at-risk premature infants without further research.

Deficits in learning and memory in mice with a mutation of the candidate dyslexia susceptibility gene Dyx1c1.

Dyslexia is a learning disability characterized by difficulty learning to read and write. The underlying biological and genetic etiology remains poorly understood. One candidate gene, dyslexia susceptibility 1 candidate 1 (DYX1C1), has been shown to be associated with deficits in short-term memory in dyslexic populations. The purpose of the current study was to examine the behavioral phenotype of a mouse model with a homozygous conditional (forebrain) knockout of the rodent homolog Dyx1c1. Twelve Dyx1c1 conditional homozygous knockouts, 7 Dyx1c1 conditional heterozygous knockouts and 6 wild-type controls were behaviorally assessed. Mice with the homozygous Dyx1c1 knockout showed deficits on memory and learning, but not on auditory or motor tasks. These findings affirm existing evidence that DYX1C1 may play an underlying role in the development of neural systems important to learning and memory, and disruption of this function could contribute to the learning deficits seen in individuals with dyslexia.

Effects of Sex and Mild Intrainsult Hypothermia on Neuropathology and Neural Reorganization following Neonatal Hypoxic Ischemic Brain Injury in Rats.

Hypoxia ischemia (HI) is a recognized risk factor among late-preterm infants, with HI events leading to varied neuropathology and cognitive/behavioral deficits. Studies suggest a sex difference in the incidence of HI and in the severity of subsequent behavioral deficits (with better outcomes in females). Mechanisms of a female advantage remain unknown but could involve sex-specific patterns of compensation to injury. Neuroprotective hypothermia is also used to ameliorate HI damage and attenuate behavioral deficits. Though currently prescribed only for HI in term infants, cooling has potential intrainsult applications to high-risk late-preterm infants as well. To address this important clinical issue, we conducted a study using male and female rats with a postnatal (P) day 7 HI injury induced under normothermic and hypothermic conditions. The current study reports patterns of neuropathology evident in postmortem tissue. Results showed a potent benefit of intrainsult hypothermia that was comparable for both sexes. Findings also show surprisingly different patterns of compensation in the contralateral hemisphere, with increases in hippocampal thickness in HI females contrasting reduced thickness in HI males. Findings provide a framework for future research to compare and contrast mechanisms of neuroprotection and postinjury plasticity in both sexes following a late-preterm HI insult.

Horner's Syndrome after Scalene Block and Carotid Dissection.

BACKGROUND: Horner's syndrome refers to the clinical triad of ptosis, miosis, and anhidrosis resulting from disruption of the ocular and facial sympathetic pathways. A myriad of etiologies can lead to Horner's syndrome; awareness of the underlying anatomy can assist physicians in identifying potential causes and initiating appropriate care. CASE REPORT: Two patients presented to our Nashville-area hospital in 2014. Patient 1 was a 26-year-old man who noticed facial asymmetry one day after an outpatient orthopedic procedure. His symptoms were attributed to his posterior interscalene anesthesia device; with deactivation of this device, the symptoms rapidly resolved. Patient 2 was a 42-year-old man who presented to our emergency department with persistent headache and ptosis over several weeks. Computed tomography angiography revealed ipsilateral carotid dissection and the patient was admitted for further management. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: The pathologies underlying Horner's syndrome are exceedingly diverse. Although classic teaching often focuses on neoplastic causes, and more specifically Pancoast tumors, neoplasms are discovered only in a small minority of Horner's syndrome cases. Other etiologies include trauma, cervical artery dissection, and infarction. With a better understanding of the pertinent anatomy and array of possible etiologies, emergency physicians may have more success in identifying and treating the causes of Horner's syndrome.

Learning delays in a mouse model of Autism Spectrum Disorder.

Autism Spectrum Disorder (ASD) is a heterogeneous neurodevelopmental disorder with core symptoms of atypical social interactions and repetitive behaviors. It has also been reported that individuals with ASD have difficulty with multisensory integration, and this may disrupt higher-order cognitive abilities such as learning and social communication. Impairments in the integration of sensory information could in turn reflect diminished cross-modal white matter connectivity. Moreover, the genetic contribution in ASD appears to be strong, with heritability estimates as high as 90%. However, no single gene has been identified, and over 1000 risk genes have been reported. One of these genes - contactin-associated-like-protein 2 (CNTNAP2) - was first associated with Specific Language Impairment, and more recently has been linked to ASD. CNTNAP2 encodes a cell adhesion protein regulating synaptic signal transmission. To better understand the behavioral and biological underlying mechanisms of ASD, a transgenic mouse model was created with a genetic knockout (KO) of the rodent homolog Cntnap2. Initial studies on this mouse revealed poor social interactions, behavioral perseveration, and reduced vocalizations-all strongly resembling human ASD symptoms. Cntnap2 KO mice also show abnormalities in myelin formation, consistent with a hypo-connectivity model of ASD. The current study was designed to further assess the behavioral phenotype of this mouse model, with a focus on learning and memory. Cntnap2 KO and wild-type mice were tested on a 4/8 radial arm water maze for 14 consecutive days. Error scores (total, working memory, reference memory, initial and repeated reference memory), latency and average turn angle were independently assessed using a 2×14 repeated measures ANOVA. Results showed that Cntnap2 KO mice exhibited significant deficits in working and reference memory during the acquisition period of the task. During the retention period (i.e., after asymptote in errors), Cntnap2 KO mice performed comparably to wild-type mice. These findings suggest that CNTNAP2 may influence the development of neural systems important to learning and cross-modal integration, and that disruption of this function could be associated with delayed learning in ASD.

Mutation of the Dyslexia-Associated Gene Dcdc2 Enhances Glutamatergic Synaptic Transmission Between Layer 4 Neurons in Mouse Neocortex.

Variants in DCDC2 have been associated with reading disability in humans, and targeted mutation of Dcdc2 in mice causes impairments in both learning and sensory processing. In this study, we sought to determine whether Dcdc2 mutation affects functional synaptic circuitry in neocortex. We found mutation in Dcdc2 resulted in elevated spontaneous and evoked glutamate release from neurons in somatosensory cortex. The probability of release was decreased to wild-type level by acute application of N-methyl-d-aspartate receptor (NMDAR) antagonists when postsynaptic NMDARs were blocked by intracellular MK-801, and could not be explained by elevated ambient glutamate, suggesting altered, nonpostsynaptic NMDAR activation in the mutants. In addition, we determined that the increased excitatory transmission was present at layer 4-layer 4 but not thalamocortical connections in Dcdc2 mutants, and larger evoked synaptic release appeared to enhance the NMDAR-mediated effect. These results demonstrate an NMDAR activation-gated, increased functional excitatory connectivity between layer 4 lateral connections in somatosensory neocortex of the mutants, providing support for potential changes in cortical connectivity and activation resulting from mutation of dyslexia candidate gene Dcdc2.

Auditory processing and morphological anomalies in medial geniculate nucleus of Cntnap2 mutant mice.

Genetic epidemiological studies support a role for CNTNAP2 in developmental language disorders such as autism spectrum disorder, specific language impairment, and dyslexia. Atypical language development and function represent a core symptom of autism spectrum disorder (ASD), with evidence suggesting that aberrant auditory processing-including impaired spectrotemporal processing and enhanced pitch perception-may both contribute to an anomalous language phenotype. Investigation of gene-brain-behavior relationships in social and repetitive ASD symptomatology have benefited from experimentation on the Cntnap2 knockout (KO) mouse. However, auditory-processing behavior and effects on neural structures within the central auditory pathway have not been assessed in this model. Thus, this study examined whether auditory-processing abnormalities were associated with mutation of the Cntnap2 gene in mice. Cntnap2 KO mice were assessed on auditory-processing tasks including silent gap detection, embedded tone detection, and pitch discrimination. Cntnap2 knockout mice showed deficits in silent gap detection but a surprising superiority in pitch-related discrimination as compared with controls. Stereological analysis revealed a reduction in the number and density of neurons, as well as a shift in neuronal size distribution toward smaller neurons, in the medial geniculate nucleus of mutant mice. These findings are consistent with a central role for CNTNAP2 in the ontogeny and function of neural systems subserving auditory processing and suggest that developmental disruption of these neural systems could contribute to the atypical language phenotype seen in autism spectrum disorder.

Whole-genome sequencing suggests a chemokine gene cluster that modifies age at onset in familial Alzheimer's disease.

We have sequenced the complete genomes of 72 individuals affected with early-onset familial Alzheimer's disease caused by an autosomal dominant, highly penetrant mutation in the presenilin-1 (PSEN1) gene, and performed genome-wide association testing to identify variants that modify age at onset (AAO) of Alzheimer's disease. Our analysis identified a haplotype of single-nucleotide polymorphisms (SNPs) on chromosome 17 within a chemokine gene cluster associated with delayed onset of mild-cognitive impairment and dementia. Individuals carrying this haplotype had a mean AAO of mild-cognitive impairment at 51.0 ± 5.2 years compared with 41.1 ± 7.4 years for those without these SNPs. This haplotype thus appears to modify Alzheimer's AAO, conferring a large (~10 years) protective effect. The associated locus harbors several chemokines including eotaxin-1 encoded by CCL11, and the haplotype includes a missense polymorphism in this gene. Validating this association, we found plasma eotaxin-1 levels were correlated with disease AAO in an independent cohort from the University of California San Francisco Memory and Aging Center. In this second cohort, the associated haplotype disrupted the typical age-associated increase of eotaxin-1 levels, suggesting a complex regulatory role for this haplotype in the general population. Altogether, these results suggest eotaxin-1 as a novel modifier of Alzheimer's disease AAO and open potential avenues for therapy.