Adaptive behaviour deficits in individuals with 3q29 deletion syndrome.

BACKGROUND: 3q29 deletion syndrome (3q29del) is associated with a significantly increased risk for neurodevelopmental and neuropsychiatric phenotypes. Mild to moderate intellectual disability (ID) is common in this population, and previous work by our team identified substantial deficits in adaptive behaviour. However, the full profile of adaptive function in 3q29del has not been described nor has it been compared with other genomic syndromes associated with elevated risk for neurodevelopmental and neuropsychiatric phenotypes. METHODS: Individuals with 3q29del (n = 32, 62.5% male) were evaluated using the Vineland Adaptive Behaviour Scales, Third Edition, Comprehensive Parent/Caregiver Form (Vineland-3). We explored the relationship between adaptive behaviour and cognitive function, executive function, and neurodevelopmental and neuropsychiatric comorbidities in our 3q29del study sample, and we compared subjects with 3q29del with published data on fragile X syndrome, 22q11.2 deletion syndrome and 16p11.2 deletion and duplication syndromes. RESULTS: Individuals with 3q29del had global deficits in adaptive behaviour that were not driven by specific weaknesses in any given domain. Individual neurodevelopmental and neuropsychiatric diagnoses had a small effect on adaptive behaviour, and the cumulative number of comorbid diagnoses was significantly negatively associated with Vineland-3 performance. Both cognitive ability and executive function were significantly associated with adaptive behaviour, and executive function was a better predictor of Vineland-3 performance than cognitive ability. Finally, the severity of adaptive behaviour deficits in 3q29del was distinct from previously published data on comparable genomic disorders. CONCLUSIONS: Individuals with 3q29del have significant deficits in adaptive behaviour, affecting all domains assessed by the Vineland-3. Executive function is a better predictor of adaptive behaviour than cognitive ability in this population and suggests that interventions targeting executive function may be an effective therapeutic strategy.

A distinct cognitive profile in individuals with 3q29 deletion syndrome.

BACKGROUND: 3q29 deletion syndrome is associated with mild to moderate intellectual disability as well as comorbid psychopathology such as ADHD, anxiety, ASD and schizophrenia. A greater understanding of specific profiles that could increase risk for psychopathology is necessary in order to best understand and support individuals with 3q29 deletion syndrome. The goal of this study was to thus carefully outline the strengths and weaknesses of these individuals. A second goal was to ask whether the cognitive impact of the deletion predicted psychopathology in other domains. METHODS: We systematically evaluated cognitive ability, adaptive behaviour and psychopathology in 32 individuals with the canonical 3q29 deletion using gold-standard instruments and a standardised phenotyping protocol. RESULTS: Mean full scale IQ was 73 (range 40-99). Verbal subtest score (mean 80, range 31-106) was slightly higher and had a greater range than non-verbal subtest score (mean 75, range 53-98). Spatial ability was evaluated in a subset (n = 24) and was lower than verbal and non-verbal ability (mean 71, range 34-108). There was an average 14-point difference between verbal and non-verbal subset scores; 60% of the time the verbal subset score was higher than the non-verbal subset score. Study subjects with a verbal ability subtest score lower than the non-verbal subtest score were four times more likely to have a diagnosis of intellectual disability (suggestive, P value 0.07). The age at which a child first spoke two-word phrases was strongly associated with measures of verbal ability (P value 2.56e-07). Cognitive ability was correlated with adaptive behaviour measures (correlation 0.42, P value 0.02). However, although group means found equivalent scores, there was, on average, a 10-point gap between these skills (range -33 to 33), in either direction, in about 50% of the sample, suggesting that cognitive measures only partially inform adaptive ability. Cognitive ability scores did not have any significant relationship to cumulative burden of psychopathology nor to individual neurodevelopmental or psychiatric diagnoses. CONCLUSIONS: Individuals with 3q29 deletion syndrome have a complex pattern of cognitive disability. Two-thirds of individuals with the deletion will exhibit significant strength in verbal ability; this may mask deficits in non-verbal reasoning, leading to an overestimation of overall ability. Deficits in verbal ability may be the driver of intellectual disability diagnosis. Cognitive ability is not a strong indicator of other neurodevelopmental or psychiatric impairment; thus, individuals with 3q29 deletion syndrome who exhibit IQ scores within the normal range should receive all recommended behavioural evaluations.

Functional evaluation of a PTSD-associated genetic variant: estradiol regulation and ADCYAP1R1.

Posttraumatic stress disorder (PTSD) affects 5-10% percent of the US adult population with a higher prevalence among women compared with men. Although it remains unclear how biological sex associates with susceptibility to PTSD, one mechanism may involve a role for estrogen in a gene by environment interaction. We previously demonstrated a sex-dependent association between the pituitary adenylate cyclase-activating polypeptide type 1 receptor (PAC1) and PTSD, where carriers of a C allele at single-nucleotide polymorphism (SNP) rs2267735 within the PAC1 receptor gene (ADCYAP1R1) have increased symptoms of PTSD. This SNP is located within a predicted estrogen response element (ERE), which regulates gene transcription when bound to estradiol (E2) activated estrogen receptor alpha (ERα). In the current study, we examined E2 regulation of ADCYAP1R1 in vitro, in cell culture, and in vivo in mice and humans. We find in mice that fear conditioning and E2 additively increase ADCYAP1R1 expression. In vitro, we show that E2/ERα binds to the ADCYAP1R1 ERE, with less efficient binding to an ERE containing the C allele of rs2267735. In women with low serum E2, the CC genotype associates with lower ADCYAP1R1 expression, which further associates with higher PTSD symptoms. These findings lead to a model in which E2 induces the expression of ADCYAP1R1 through binding of ERα at the ERE as an adaptive response to stress. Inhibition of E2/ERα binding to the ERE containing the rs2267735 risk allele results in reduced expression of ADCYAP1R1, diminishing estrogen regulation as an adaptive stress response and increasing risk for PTSD.

Using large clinical data sets to infer pathogenicity for rare copy number variants in autism cohorts.

Copy number variants (CNVs) have a major role in the etiology of autism spectrum disorders (ASD), and several of these have reached statistical significance in case-control analyses. Nevertheless, current ASD cohorts are not large enough to detect very rare CNVs that may be causative or contributory (that is, risk alleles). Here, we use a tiered approach, in which clinically significant CNVs are first identified in large clinical cohorts of neurodevelopmental disorders (including but not specific to ASD), after which these CNVs are then systematically identified within well-characterized ASD cohorts. We focused our initial analysis on 48 recurrent CNVs (segmental duplication-mediated 'hotspots') from 24 loci in 31 516 published clinical cases with neurodevelopmental disorders and 13 696 published controls, which yielded a total of 19 deletion CNVs and 11 duplication CNVs that reached statistical significance. We then investigated the overlap of these 30 CNVs in a combined sample of 3955 well-characterized ASD cases from three published studies. We identified 73 deleterious recurrent CNVs, including 36 deletions from 11 loci and 37 duplications from seven loci, for a frequency of 1 in 54; had we considered the ASD cohorts alone, only 58 CNVs from eight loci (24 deletions from three loci and 34 duplications from five loci) would have reached statistical significance. In conclusion, until there are sufficiently large ASD research cohorts with enough power to detect very rare causative or contributory CNVs, data from larger clinical cohorts can be used to infer the likely clinical significance of CNVs in ASD.

Dense SNP association study for bipolar I disorder on chromosome 18p11 suggests two loci with excess paternal transmission.

Parent-of-origin effects have been implicated as mediators of genetic susceptibility for a number of complex disease phenotypes, including bipolar disorder. Specifically, evidence for linkage on chromosome 18 is modified when allelic parent-of-origin is accommodated in the analysis. Our goal was to characterize the susceptibility locus for bipolar I disorder on chromosome 18p11 and investigate this parent-of-origin hypothesis in an association context. This was achieved by genotyping single nucleotide polymorphisms (SNPs) at a high density (1 SNP/5 kb) along 13.6 megabases of the linkage region. To increase our ability to detect a susceptibility locus, we restricted the phenotype definition to include only bipolar I probands. We also restricted our study population to Ashkenazi Jewish individuals; this population has characteristics of a genetic isolate and may therefore facilitate detection of variants for complex disease. Three hundred and forty-four pedigrees (363 parent/child trios) where probands were affected with bipolar 1 disorder were genotyped. Transmission disequilibrium test analysis revealed no statistically significant association to SNPs or haplotypes within this region in this sample. However, when parent-of-origin of transmitted SNPs was taken into account, suggestive association was revealed for two separate loci.

Critical determinants of Ca(2+)-dependent inactivation within an EF-hand motif of L-type Ca(2+) channels.

L-type (alpha(1C)) calcium channels inactivate rapidly in response to localized elevation of intracellular Ca(2+), providing negative Ca(2+) feedback in a diverse array of biological contexts. The dominant Ca(2+) sensor for such Ca(2+)-dependent inactivation has recently been identified as calmodulin, which appears to be constitutively tethered to the channel complex. This Ca(2+) sensor induces channel inactivation by Ca(2+)-dependent CaM binding to an IQ-like motif situated on the carboxyl tail of alpha(1C). Apart from the IQ region, another crucial site for Ca(2+) inactivation appears to be a consensus Ca(2+)-binding, EF-hand motif, located approximately 100 amino acids upstream on the carboxyl terminus. However, the importance of this EF-hand motif for channel inactivation has become controversial since the original report from our lab implicating a critical role for this domain. Here, we demonstrate not only that the consensus EF hand is essential for Ca(2+) inactivation, but that a four-amino acid cluster (VVTL) within the F helix of the EF-hand motif is itself essential for Ca(2+) inactivation. Mutating these amino acids to their counterparts in non-inactivating alpha(1E) calcium channels (MYEM) almost completely ablates Ca(2+) inactivation. In fact, only a single amino acid change of the second valine within this cluster to tyrosine (V1548Y) supports much of the functional knockout. However, mutations of presumed Ca(2+)-coordinating residues in the consensus EF hand reduce Ca(2+) inactivation by only approximately 2-fold, fitting poorly with the EF hand serving as a contributory inactivation Ca(2+) sensor, in which Ca(2+) binds according to a classic mechanism. We therefore suggest that while CaM serves as Ca(2+) sensor for inactivation, the EF-hand motif of alpha(1C) may support the transduction of Ca(2+)-CaM binding into channel inactivation. The proposed transduction role for the consensus EF hand is compatible with the detailed Ca(2+)-inactivation properties of wild-type and mutant V1548Y channels, as gauged by a novel inactivation model incorporating multivalent Ca(2+) binding of CaM.

Inhibition of recombinant Ca2+ channels by benzothiazepines and phenylalkylamines: class-specific pharmacology and underlying molecular determinants.

To understand the molecular basis of state-dependent pharmacological blockade of voltage-gated Ca2+ channels, we systematically characterized phenylalkylamine and benzothiazepine inhibition of three molecular classes of Ca2+ channels (alpha1C, alpha1A, and alpha1E) expressed from cDNA clones transfected into HEK 293 cells. State-dependent blockade figures importantly in the therapeutically desirable property of use-dependent drug action. Verapamil (a phenylalkylamine) and diltiazem (a benzothiazepine) were imperfectly selective, so differences in the state dependence of inhibition could be compared among the various channels. We found only quantitative differences in pharmacological profile of verapamil: half-maximal inhibitory concentrations spanned a 2-fold range (70 microM for alpha1A, 100 microM for alpha1E, and 110 microM for alpha1C), and inhibition was state dependent in all channels. In contrast, diltiazem produced only state-dependent block of alpha1C channels; alpha1A and alpha1E channels demonstrated state-independent block despite similar half-maximal inhibitory concentrations (60 microM for alpha1C, 220 microM for alpha1E, and 270 microM for alpha1A). To explore the molecular basis for the sharp distinction in state-dependent inhibition by diltiazem, we constructed chimeric channels from alpha1C and alpha1A and localized the structural determinants for state dependence to repeats III and IV of alpha1C, which have been found to contain the structures required for benzothiazepine binding. We then constructed a mutant alpha1C construct by changing three amino acids in IVS6 (Y14901, A1494S, 11497M) that have been implicated as key coordinating sites for avid benzothiazepine binding. Although these mutations increased the half-maximal inhibitory concentration of diltiazem inhibition by approximately 10-fold, the state-dependent nature of inhibition was spared. This result points to the existence of physically distinct elements controlling drug binding and access to the binding site, thereby favoring a "guarded-receptor" rather than a "modulated-receptor" mechanism of drug inhibition.

Bursts of action potential waveforms relieve G-protein inhibition of recombinant P/Q-type Ca2+ channels in HEK 293 cells.

1. A variety of neurotransmitters act through G-protein-coupled receptors to decrease synaptic transmission, largely by inhibiting the voltage-gated calcium channels that trigger neurotransmitter release. However, these presynaptic calcium channels are typically inaccessible to electrophysiological characterization. We have reconstituted a part of this inhibition using recombinant P/Q-type calcium channels and M2 acetylcholine receptors in HEK 293 cells. 2. One of the most interesting features of G-protein inhibition of calcium channels is that strong step depolarization transiently relieves the inhibition. We have found that short bursts of action potential voltage waveforms can also relieve the inhibition, increasing calcium current through G-protein-inhibited channels but not through uninhibited channels. 3. The extent of this relief increased linearly with the duration of the action potential waveforms. 4. This result provides the strongest evidence to date favouring the possibility that relief of G-protein inhibition can occur during high frequency trains of action potentials. This effect may constitute a novel form of short-term synaptic plasticity that is sensitive to action potential timing and duration.