Background
Cluster Headache (CH) is a severe primary headache, with a poorly understood pathophysiology. Complex genetic factors are likely to play a role in CH etiology; however, no confirmed gene ...associations have been identified. The aim of this study is to identify genetic variants influencing risk to CH and to explore the potential pathogenic mechanisms.
Methods
We have performed a genome-wide association study (GWAS) in a clinically well-defined cohort of 99 Italian patients with CH and in a control sample of 360 age-matched sigarette smoking healthy individuals, using the Infinium PsychArray (Illumina), which combines common highly-informative genome-wide tag SNPs and exonic SNPs. Genotype data were used to carry out a genome-wide single marker case-control association analysis using common SNPs, and a gene-based association analysis focussing on rare protein altering variants in 745 candidate genes with a putative role in CH.
Results
Although no single variant showed statistically significant association at the genome-wide threshold, we identified an interesting suggestive association (
P
= 9.1 × 10
−6
) with a common variant of the PACAP receptor gene (
ADCYAP1R1
). Furthermore, gene-based analysis provided significant evidence of association (
P
= 2.5 × 10
−5
) for a rare potentially damaging missense variant in the
MME
gene, encoding for the membrane metallo-endopeptidase neprilysin.
Conclusions
Our study represents the first genome-wide association study of common SNPs and rare exonic variants influencing risk for CH. The most interesting results implicate
ADCYAP1R1
and
MME
gene variants in CH susceptibility and point to a role for genes involved in pain processing. These findings provide new insights into the pathogenesis of CH that need further investigation and replication in larger CH samples.
Synesthesia, a neurological condition affecting between 0.05%–1% of the population, is characterized by anomalous sensory perception and associated alterations in cognitive function due to ...interference from synesthetic percepts. A stimulus in one sensory modality triggers an automatic, consistent response in either another modality or a different aspect of the same modality. Familiality studies show evidence of a strong genetic predisposition; whereas initial pedigree analyses supported a single-gene X-linked dominant mode of inheritance with a skewed F:M ratio and a notable absence of male-to-male transmission, subsequent analyses in larger samples indicated that the mode of inheritance was likely to be more complex. Here, we report the results of a whole-genome linkage scan for auditory-visual synesthesia with 410 microsatellite markers at 9.05 cM density in 43 multiplex families (n = 196) with potential candidate regions fine-mapped at 5 cM density. Using NPL and HLOD analysis, we identified four candidate regions. Significant linkage at the genome-wide level was detected to chromosome 2q24 (HLOD = 3.025, empirical genome-wide p = 0.047). Suggestive linkage was found to chromosomes 5q33, 6p12, and 12p12. No support was found for linkage to the X chromosome; furthermore, we have identified two confirmed cases of male-to-male transmission of synesthesia. Our results demonstrate that auditory-visual synesthesia is likely to be an oligogenic disorder subject to multiple modes of inheritance and locus heterogeneity. This study comprises a significant step toward identifying the genetic substrates underlying synesthesia, with important implications for our understanding of the role of genes in human cognition and perception.
Autism spectrum disorder (ASD) is a clinically heterogeneous class of neurodevelopmental conditions with a strong, albeit complex, genetic basis. The genetic architecture of ASD includes different ...genetic models, from monogenic transmission at one end, to polygenic risk given by thousands of common variants with small effects at the other end. The mitochondrial DNA (mtDNA) was also proposed as a genetic modifier for ASD, mostly focusing on maternal mtDNA, since the paternal mitogenome is not transmitted to offspring. We extensively studied the potential contribution of mtDNA in ASD pathogenesis and risk through deep next generation sequencing and quantitative PCR in a cohort of 98 families. While the maternally-inherited mtDNA did not seem to predispose to ASD, neither for haplogroups nor for the presence of pathogenic mutations, an unexpected influence of paternal mtDNA, apparently centered on haplogroup U, came from the Italian families extrapolated from the test cohort (n = 74) when compared to the control population. However, this result was not replicated in an independent Italian cohort of 127 families and it is likely due to the elevated paternal age at time of conception. In addition, ASD probands showed a reduced mtDNA content when compared to their unaffected siblings. Multivariable regression analyses indicated that variants with 15%–5% heteroplasmy in probands are associated to a greater severity of ASD based on ADOS-2 criteria, whereas paternal super-haplogroups H and JT were associated with milder phenotypes. In conclusion, our results suggest that the mtDNA impacts on ASD, significantly modifying the phenotypic expression in the Italian population. The unexpected finding of protection induced by paternal mitogenome in term of severity may derive from a role of mtDNA in influencing the accumulation of nuclear
de novo
mutations or epigenetic alterations in fathers’ germinal cells, affecting the neurodevelopment in the offspring. This result remains preliminary and needs further confirmation in independent cohorts of larger size. If confirmed, it potentially opens a different perspective on how paternal non-inherited mtDNA may predispose or modulate other complex diseases.
Autism Spectrum Disorder (ASD) is a highly heterogeneous neuropsychiatric disorder with a strong genetic component. The genetic architecture is complex, consisting of a combination of common low-risk ...and more penetrant rare variants. Voltage-gated calcium channels (VGCCs or Ca
) genes have been implicated as high-confidence susceptibility genes for ASD, in accordance with the relevant role of calcium signaling in neuronal function. In order to further investigate the involvement of VGCCs rare variants in ASD susceptibility, we performed whole genome sequencing analysis in a cohort of 105 families, composed of 124 ASD individuals, 210 parents and 58 unaffected siblings. We identified 53 rare inherited damaging variants in Ca
genes, including genes coding for the principal subunit and genes coding for the auxiliary subunits, in 40 ASD families. Interestingly, biallelic rare damaging missense variants were detected in the
gene, coding for the T-type Ca
3.2 channel, in ASD probands from two different families. Thus, to clarify the role of these
variants on calcium channel activity we performed electrophysiological analysis using whole-cell patch clamp technology. Three out of four tested variants were shown to mildly affect Ca
3.2 channel current density and activation properties, possibly leading to a dysregulation of intracellular Ca
ions homeostasis, thus altering calcium-dependent neuronal processes and contributing to ASD etiology in these families. Our results provide further support for the role of
in neurodevelopmental disorders and suggest that rare
variants may be involved in ASD development, providing a high-risk genetic background.
Autism spectrum disorder (ASD) is a complex neurodevelopmental condition with a strong genetic component in which rare variants contribute significantly to risk. We performed whole genome and/or ...exome sequencing (WGS and WES) and SNP-array analysis to identify both rare sequence and copy number variants (SNVs and CNVs) in 435 individuals from 116 ASD families. We identified 37 rare potentially damaging de novo SNVs (pdSNVs) in the cases (n = 144). Interestingly, two of them (one stop-gain and one missense variant) occurred in the same gene, BRSK2. Moreover, the identification of 8 severe de novo pdSNVs in genes not previously implicated in ASD (AGPAT3, IRX5, MGAT5B, RAB8B, RAP1A, RASAL2, SLC9A1, YME1L1) highlighted promising candidates. Potentially damaging CNVs (pdCNVs) provided support to the involvement of inherited variants in PHF3, NEGR1, TIAM1 and HOMER1 in neurodevelopmental disorders (NDD), although mostly acting as susceptibility factors with incomplete penetrance. Interpretation of identified pdSNVs/pdCNVs according to the ACMG guidelines led to a molecular diagnosis in 19/144 cases, although this figure represents a lower limit and is expected to increase thanks to further clarification of the role of likely pathogenic variants in ASD/NDD candidate genes not yet established. In conclusion, our study highlights promising ASD candidate genes and contributes to characterize the allelic diversity, mode of inheritance and phenotypic impact of de novo and inherited risk variants in ASD/NDD genes.
Intellectual disability (ID) and autism spectrum disorders (ASDs) are complex neuropsychiatric conditions, with overlapping clinical boundaries in many patients. We identified a novel intragenic ...deletion of maternal origin in two siblings with mild ID and epilepsy in the CADPS2 gene, encoding for a synaptic protein involved in neurotrophin release and interaction with dopamine receptor type 2 (D2DR). Mutation screening of 223 additional patients (187 with ASD and 36 with ID) identified a missense change of maternal origin disrupting CADPS2/D2DR interaction. CADPS2 allelic expression was tested in blood and different adult human brain regions, revealing that the gene was monoallelically expressed in blood and amygdala, and the expressed allele was the one of maternal origin. Cadps2 gene expression performed in mice at different developmental stages was biallelic in the postnatal and adult stages; however, a monoallelic (maternal) expression was detected in the embryonal stage, suggesting that CADPS2 is subjected to tissue‐ and temporal‐specific regulation in human and mice. We suggest that CADPS2 variants may contribute to ID/ASD development, possibly through a parent‐of‐origin effect.
Synopsis
Monoallelic and tissue‐specific expression of novel CADPS2 gene variants was identified in two siblings with borderline cognitive decline and epilepsy, suggesting a role for CADPS2 in intellectual disability and autism spectrum disorders.
Two rare variants of maternal origin (an intragenic deletion and a missense change) were identified in CADPS2 in a cohort of patients with neurodevelopmental abnormalities; the p. Asp1113Asn variant was shown to disrupt the interaction with dopamine receptor type 2 (D2DR).
Differentially methylated sites were identified in CADPS2 first intron, in blood and amygdala, but they did not show a parent‐of‐origin methylation pattern typical of an imprinted gene.
Tissue‐specific, monoallelic maternal expression of CADPS2 in blood and in the amygdala plays a key role in regulating social interactions and supports the importance of a fine modulation of CADPS2 for human behavior.
CADPS2 variants may contribute to intellectual disability and autism susceptibility, and their role should be interpreted in light of possible parent‐of‐origin effect.
Monoallelic and tissue‐specific expression of novel CADPS2 gene variants was identified in two siblings with borderline cognitive decline and epilepsy, suggesting a role for CADPS2 in intellectual disability and autism spectrum disorders.
Recent findings revealed rare copy number variants and missense changes in the X-linked gene PTCHD1 in autism spectrum disorder (ASD) and intellectual disability (ID). Here, we aim to explore the ...contribution of common PTCHD1 variants in ASD and gain additional evidence for the role of rare variants of this gene in ASD and ID. A two-stage case-control association study investigated 28 tag single nucleotide polymorphisms (SNPs) in 994 ASD cases and 1035 controls from four European populations. Mutation screening was performed in 673 individuals who included 240 ASD cases, 183 ID patients and 250 controls. The case-control association study showed a significant association with rs7052177 (P=6.13E-4) in the ASD discovery sample that was replicated in an independent sample (P=0.03). A Mantel-Haenszel meta-analysis for rs7052177T considering the four European populations showed an odds ratio of 0.58 (P=7E-05). This SNP is predicted to be located in a transcription factor binding site. No rare missense PTCHD1 variants were found in our ASD cohort and only one was identified in the ID sample. A duplication (27 bp) in the promoter region, absent from 590 controls, was found in three ASD patients (Fisher exact test, P=0.024). A gene reporter assay showed a significant decrease in the transcriptional activity (26%) driven by this variant. Moreover, we found that the longest allele of a trinucleotide repeat located upstream from PTCHD1 was associated with ASD (P=0.003, permP=0.0186). Our results further support the involvement of PTCHD1 in ASD, suggesting that both common and rare variants contribute to the disorder.
We examined the potential benefits of neuroimaging measurements across the first 5 years of life in detecting early comorbid or etiological signs of autism spectrum disorder (ASD). In particular, we ...analyzed the prevalence of neuroradiologic findings in routine magnetic resonance imaging (MRI) scans of a group of 117 ASD children younger than 5 years old. These data were compared to those reported in typically developing (TD) children. MRI findings in children with ASD were analyzed in relation to their cognitive level, severity of autistic symptoms, and the presence of electroencephalogram (EEG) abnormalities. The MRI was rated abnormal in 55% of children with ASD with a significant prevalence in the high-functioning subgroup compared to TD children. We report significant incidental findings of mega cisterna magna, ventricular anomalies and abnormal white matter signal intensity in ASD without significant associations between these MRI findings and EEG features. Based on these results we discuss the role that brain MRI may play in the diagnostic procedure of ASD.
Autism spectrum disorders: molecular genetic advances Bacchelli, Elena; Maestrini, Elena
American journal of medical genetics. Part C, Seminars in medical genetics,
15 February 2006, Letnik:
142C, Številka:
1
Journal Article
Despite the strong genetic basis of autism spectrum disorders (ASD), research efforts in the last decade have not been successful in the identification of confirmed susceptibility genes. We review ...the present status of genetic linkage, candidate gene, and association studies, pointing out the limitations of these approaches and the challenge of dealing with the clinical and genetic complexity of autism. Finally, we outline how recent technological and bioinformatic advances, together with an increasing understanding of the structure of the human genome, have set the stage to perform more comprehensive and well powered studies, possibly leading to a turning point in the understanding of the genetic basis of this devastating disorder.
Autism spectrum disorders (ASDs) are a group of neurodevelopmental disorders with high heritability, although their underlying genetic factors are still largely unknown. Here we present a ...comprehensive genetic characterization of two ASD siblings from Sardinia by genome-wide copy number variation analysis and whole exome sequencing (WES), to identify novel genetic alterations associated with this disorder. Single nucleotide polymorphism (SNP) array data revealed a rare microdeletion involving
,
and
genes, in both siblings.
encodes for a postsynaptic density (PSD) protein known to regulate spine morphogenesis and synaptic formation. The reduced
mRNA and protein expression levels in ASD patients, in the presence of hemizygosity or a particular genetic and/or epigenetic background, highlighted the functional relevance of
as a candidate gene for ASD. WES analysis led to the identification in both affected siblings of a rare frameshift mutation in
, a gene intolerant to loss of function mutation, encoding for a voltage-dependent anion channel localized on PSD. Moreover, four missense damaging variants were identified in genes intolerant to loss of function variation encoding for PSD proteins:
,
,
and
. This study identifies
and
as candidate genes and provides additional support for genes encoding PSD proteins in ASD susceptibility.
PDF
