scholarly journals De novo structural mutation rates and gamete-of-origin biases revealed through genome sequencing of 2,396 families

2020 ◽  
Author(s):  
Jonathan R. Belyeu ◽  
Harrison Brand ◽  
Harold Wang ◽  
Xuefang Zhao ◽  
Brent S. Pedersen ◽  
...  
Keyword(s):  
De Novo ◽  
Genome Structure ◽  
Point Mutations ◽  
Large Family ◽  
Germline Mutations ◽  
Autism Spectrum ◽  
Parental Age ◽  
Single Nucleotide Variants ◽  
Multiple Testing Correction ◽  
Structural Mutations

AbstractEach human genome includes de novo mutations that arose during gametogenesis. While these germline mutations represent a fundamental source of new genetic diversity, they can also create deleterious alleles that impact fitness. The germline mutation rate for single nucleotide variants and factors that significantly influence this rate, such as parental age, are now well established. However, far less is known about the frequency, distribution, and features that impact de novo structural mutations. We report a large, family-based study of germline mutations, excluding aneuploidy, that affect genome structure among 572 genomes from 33 families in a multigenerational CEPH-Utah cohort and 2,363 cases of non-familial autism spectrum disorder (ASD), 1,938 unaffected siblings, and both parents (9,599 genomes in total). We find that de novo structural mutations detected by alignment-based, short-read WGS occurred at an overall rate of at least 0.160 events per genome in unaffected individuals and was significantly higher (0.206 per genome) in ASD cases. In both probands and unaffected samples, nearly 73% of de novo structural mutations arose in paternal gametes, and predict most de novo structural mutations to be caused by mutational mechanisms that do not require sequence homology. After multiple testing correction we did not observe a statistically significant correlation between parental age and the rate of de novo structural variation in offspring. These results highlight that a spectrum of mutational mechanisms contribute to germline structural mutations, and that these mechanisms likely have markedly different rates and selective pressures than those leading to point mutations.

scholarly journals The Landscape of Mutational Mosaicism in Autistic and Normal Human Cerebral Cortex

2020 ◽  
Author(s):  
Rachel E. Rodin ◽  
Yanmei Dou ◽  
Minseok Kwon ◽  
Maxwell A. Sherman ◽  
Alissa M. D’Gama ◽  
...  
Keyword(s):  
Human Brain ◽  
Somatic Mutations ◽  
De Novo ◽  
Germline Mutations ◽  
Autism Spectrum ◽  
Single Nucleotide Variants ◽  
Human Cerebral Cortex ◽  
Single Nucleotide ◽  
Normal Human ◽  
Enhancer Sequences

AbstractAlthough somatic mutations have well-established roles in cancer and certain focal epilepsies, the extent to which mutational mosaicism shapes the developing human brain is poorly understood. Here we characterize the landscape of somatic mutations in the human brain using ultra-deep (~250×) whole-genome sequencing of brains from 59 autism spectrum disorder (ASD) cases and 15 controls. We observe a mean of 26 (±10, range 10-60) somatic single nucleotide variants (sSNVs) per brain present in ≥4% of cells, with enrichment of mutations in coding and putative regulatory regions. Our analysis reveals that the first cell division after fertilization produces ~3.4 mutations, followed by 2-3 mutations in subsequent generations. This rate suggests that a typical individual possesses ~80 sSNVs present in ≥2% of cells—comparable to the number of de novo germline mutations per generation—with about half of individuals having at least one potentially function-altering somatic mutation somewhere in the cortex. Although limited by sample size, ASD brains show an excess of somatic mutations in neural enhancer sequences compared to controls, suggesting that mosaic enhancer mutations may contribute to ASD risk.

scholarly journals Recent Advances in Understanding the Genetic Architecture of Autism

2020 ◽  
Vol 21 (1) ◽  
pp. 289-304 ◽  
Author(s):  
Caroline M. Dias ◽  
Christopher A. Walsh
Keyword(s):  
Genetic Architecture ◽  
De Novo ◽  
Clinical Care ◽  
Copy Number Variants ◽  
Autism Spectrum ◽  
Loss Of Function ◽  
Single Nucleotide Variants ◽  
Single Nucleotide ◽  
Recent Advances ◽  
Insight Into

Recent advances in understanding the genetic architecture of autism spectrum disorder have allowed for unprecedented insight into its biological underpinnings. New studies have elucidated the contributions of a variety of forms of genetic variation to autism susceptibility. While the roles of de novo copy number variants and single-nucleotide variants—causing loss-of-function or missense changes—have been increasingly recognized and refined, mosaic single-nucleotide variants have been implicated more recently in some cases. Moreover, inherited variants (including common variants) and, more recently, rare recessive inherited variants have come into greater focus. Finally, noncoding variants—both inherited and de novo—have been implicated in the last few years. This work has revealed a convergence of diverse genetic drivers on common biological pathways and has highlighted the ongoing importance of increasing sample size and experimental innovation. Continuing to synthesize these genetic findings with functional and phenotypic evidence and translating these discoveries to clinical care remain considerable challenges for the field.

scholarly journals Exonic Mosaic Mutations Contribute Risk for Autism Spectrum Disorder

2017 ◽  
Author(s):  
Deidre R. Krupp ◽  
Rebecca A. Barnard ◽  
Yannis Duffourd ◽  
Sara A. Evans ◽  
Ryan M. Mulqueen ◽  
...  
Keyword(s):  
Autism Spectrum Disorder ◽  
De Novo ◽  
Large Family ◽  
Recurrence Risk ◽  
Autism Spectrum ◽  
Spectrum Disorder ◽  
Sequencing Data ◽  
Full Cohort ◽  
Risk Genes ◽  
Family Based

AbstractGenetic risk factors for autism spectrum disorder (ASD) have yet to be fully elucidated. Postzygotic mosaic mutations (PMMs) have been implicated in several neurodevelopmental disorders and overgrowth syndromes. We systematically evaluated PMMs by leveraging whole-exome sequencing data on a large family-based ASD cohort, the Simons Simplex Collection. We found evidence that 11% of published single nucleotide variant (SNV) de novo mutations are potentially PMMs. We then developed a robust SNV PMM calling approach that leverages complementary callers, logistic regression modeling, and additional heuristics. Using this approach, we recalled SNVs and found that 22% of de novo mutations likely occur as PMMs in children. Unexpectedly, we found a significant burden of synonymous PMMs in probands that are predicted to alter splicing. We found no evidence of missense PMM burden in the full cohort. However, we did observe increased signal for missense PMMs in families without germline mutations in probands, which strengthens in genes intolerant to mutations. We also determined that 7-11% of parental mosaics are transmitted to children. Parental mosaic mutations make up 6.8% of all mutations newly germline in children, which has important implications for recurrence risk. PMMs intersect previously implicated high confidence and other ASD candidate risk genes, further suggesting that this class of mutations contribute to ASD risk. We also identified PMMs in novel candidate risk genes involved with chromatin remodeling or neurodevelopment. We estimate that PMMs contribute risk to 4-8% of simplex ASD cases. Overall, these findings argue for future studies of PMMs in ASD and related-disorders.

Next Generation Sequencing and Cytogenetic Based Evaluation of Indian Pierre Robin Sequence Families Reveals CNV Regions of Modest Effect and a Novel LOXL3 Mutation

2021 ◽  
pp. 105566562110527
Author(s):  
Anubhuti Sood ◽  
Uzma Shamim ◽  
Om P. Kharbanda ◽  
Madhulika Kabra ◽  
Neerja Gupta ◽  
...  
Keyword(s):  
De Novo ◽  
Tertiary Care ◽  
Family Members ◽  
Point Mutations ◽  
Copy Number Variations ◽  
Care Hospital ◽  
Pierre Robin Sequence ◽  
Single Nucleotide Variants ◽  
Robin Sequence ◽  
Pierre Robin

Background Pierre Robin Sequence (PRS) affects approximately 1 per 8500 to 14000 new-borns worldwide. Although the clinical entity is well defined, the pathogenesis of PRS is debated. The present study aims to understand the contribution of genomic imbalances and genetic variants in patients clinically diagnosed of PRS. Methodology A total of 7 independent patients with nonsyndromic PRS thoroughly evaluated by a medical geneticist at a tertiary care hospital, were included in the study. Blood samples were collected from these patients and their family members. Array CGH was performed on all 7 patients and their respective family members for detection of underlying cytogenetic defects. Whole exome sequencing (WES) was performed for 5 families to capture single nucleotide variants or small indels. Results Cytogenetic analyses did not detect any previously reported gross chromosomal aberrations for PRS in the patient cohort. However, copy number variations (CNVs) of size <1 Mb were detected in patients which may have implications in PRS. The present study provided evidence for the occurrence of de novo deletions at 7p14.1 locus in PRS patients: further validating the candidate loci susceptibility in oral clefts. WES data identified LOXL3 as candidate gene, carrying novel deleterious variant, which is suggestive of the role of point mutations in the pathogenesis of PRS. Conclusion The present study offered considerable insight into the contribution of cytogenetic defects and novel point mutation in the etiology of nonsyndromic PRS. Studies comprising large number of cases are required to fully elucidate the genetic mechanisms underlying the PRS phenotype.

scholarly journals Prevalence and Phenotypic Impact of Rare Likely Pathogenic Variants in Autism Spectrum Disorder

2020 ◽  
Author(s):  
Behrang Mahjani ◽  
Silvia De Rubeis ◽  
Christina Gustavsson Mahjani ◽  
Maureen Mulhern ◽  
Xinyi Xu ◽  
...  
Keyword(s):  
Autism Spectrum Disorder ◽  
De Novo ◽  
Strong Association ◽  
Population Sample ◽  
Population Level ◽  
Autism Spectrum ◽  
Spectrum Disorder ◽  
Single Nucleotide Variants ◽  
Pathogenic Variants ◽  
Pathogenic Cnvs

Abstract Background: Copy number variants (CNVs) and single nucleotide variants (SNVs) are sources of risk for autism spectrum disorder (ASD). The distribution of such pathogenic variants in individuals with ASD and the characterization of those who carry such variants versus those who do not are understudied at the population level. We describe a population sample from Sweden, evaluating the distribution of likely pathogenic variants and their impact on medical, neurological, and psychiatric phenotypes.Methods: The genotyped sample consisted of 1,236 children born in Sweden with autistic disorder, a severe form of ASD (International Classification of Diseases, Tenth Revision, code F84.0.) Of these individuals, CNVs were called from 997, while SNVs were called from 808. Results: Out of 997 individuals from whom CNVs were called, 104 (10.4 %) carried one or more likely pathogenic CNV, including 15q11q13 (n=8), 15q13.3 (n=5), 16p13.11 (n=5), 16p11.11 (n=5), 22q11.2 (n=5). Of 808 individuals assessed by whole-exome sequencing, 69 (8.5%) had a likely pathogenic SNV, including in GRIN2B (n = 6), POGZ (n = 5), SATB1 (n=4), DYNC1H1 (n=4), and CREBBP (n=3). Fourteen individuals carried two likely pathogenic CNVs, and 5 carried a likely pathogenic CNV and SNV. Carriers of likely pathogenic CNVs or SNVs were more likely to have intellectual disability (ID), scholastic skill disorders, and epilepsy, with odds ratios of 2.31 (95%CI, 1.55,3.47), 1.98 (95%CI, 1.19,3.21), and 1.63 (95%CI, 1.08,2.44) respectively. Carriers of likely pathogenic CNVs also showed significant increased rates of congenital anomalies. We compared rates of likely pathogenic CNVs, SNVs, and phenotypes from genotyped AD subjects with and without ID: rates were not significantly different between groups. Limitations: As a case-control cohort, we did not have de novo information to aid in classification. More broadly, there were judgment calls involved in identifying likely pathogenic variants. For these reasons, some misclassification is possible. In addition, phenotypes are defined from medical registers, which may lead to underestimates of milder findings.Conclusions: People with ASD who carry likely pathogenic CNVs or SNVs show increased rates of various comorbidities, most prominently ID. Despite the strong association with ID, conditioning on its presence explains little of the variation for other comorbidities and physical traits.

scholarly journals A De Novo Designed Esterase with p-Nitrophenyl Acetate Hydrolysis Activity

Molecules ◽  
2020 ◽  
Vol 25 (20) ◽  
pp. 4658 ◽  
Author(s):  
Guanlin Li ◽  
Li Xu ◽  
Houjin Zhang ◽  
Junjun Liu ◽  
Jinyong Yan ◽  
...  
Keyword(s):  
De Novo ◽  
Point Mutations ◽  
Large Family ◽  
Catalytic Triad ◽  
Harsh Environments ◽  
Quantum Mechanical ◽  
Expression And Purification ◽  
Oxygen Anion ◽  
Hydrolysis Activity ◽  
The Ideal

Esterases are a large family of enzymes with wide applications in the industry. However, all esterases originated from natural sources, limiting their use in harsh environments or newly- emerged reactions. In this study, we designed a new esterase to develop a new protocol to satisfy the needs for better biocatalysts. The ideal spatial conformation of the serine catalytic triad and the oxygen anion hole at the substrate-binding site was constructed by quantum mechanical calculation. The catalytic triad and oxygen anion holes were then embedded in the protein scaffold using the new enzyme protocol in Rosetta 3. The design results were subsequently evaluated, and optimized designs were used for expression and purification. The designed esterase had significant lytic activities towards p-nitrophenyl acetate, which was confirmed by point mutations. Thus, this study developed a new protocol to obtain novel enzymes that may be useful in unforgiving environments or novel reactions.

scholarly journals Association of Copy Number Variations in Autism Spectrum Disorders: A Systematic Review

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Elif Funda Sener
Keyword(s):  
Autism Spectrum Disorders ◽  
Complex Traits ◽  
Copy Number ◽  
De Novo ◽  
Genome Structure ◽  
Autism Spectrum ◽  
Copy Number Variations ◽  
Repetitive Behaviors ◽  
Wide Range ◽  
Spectrum Disorders

Autism spectrum disorders (ASDs) are characterized by language impairments, social deficits, and repetitive behaviors. The onset of symptoms occurs by the age of 3 and shows a lifelong persistence. Genetics plays a major role in the etiology of ASD. Except genetics, several potential risk factors (environmental factors and epigenetics) may contribute to ASD. Copy number variations (CNVs) are the most widespread structural variations in the human genome. These variations can alter the genome structure either by deletion or by duplication. CNVs can be de novo or inherited. Chromosomal rearrangements have been detected in 5–10% of the patients with ASD and recently copy number changes ranging from a few kilobases (kb) to several megabases (Mb) in size have been reported. Recent data have also revealed that submicroscopic CNVs can have a role in ASD, and de novo CNVs seem to be a more common risk factor in sporadic compared with inherited forms of ASD. CNVs are being implicated as a contributor to the pathophysiology of complex neurodevelopmental disorders and they can affect a wide range of human phenotypes including mental retardation (MR), autism, neuropsychiatric disorders, and susceptibility to other complex traits such as HIV, Crohn’s disease, and psoriasis. This review emphasizes the major CNVs reported to date in ASD.

scholarly journals In vitro zinc supplementation alters synaptic deficits caused by autism spectrum disorder-associated Shank2 point mutations in hippocampal neurons

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Yukti Vyas ◽  
Yewon Jung ◽  
Kevin Lee ◽  
Craig C. Garner ◽  
Johanna M. Montgomery
Keyword(s):  
Hippocampal Neurons ◽  
Fluorescent Protein ◽  
Zinc Supplementation ◽  
Point Mutations ◽  
Autism Spectrum ◽  
Single Nucleotide Variants ◽  
Single Nucleotide ◽  
Green Fluorescent ◽  
The Impact

AbstractAutism Spectrum Disorders (ASDs) are neurodevelopmental disorders characterised by deficits in social interactions and repetitive behaviours. ASDs have a strong genetic basis with mutations involved in the development and function of neural circuitry. Shank proteins act as master regulators of excitatory glutamatergic synapses, and Shank mutations have been identified in people with ASD. Here, we have investigated the impact of ASD-associated Shank2 single nucleotide variants (SNVs) at the synaptic level, and the potential of in vitro zinc supplementation to prevent synaptic deficits. Dissociated rat hippocampal cultures expressing enhanced green fluorescent protein (EGFP) tagged Shank2-Wildtype (WT), and ASD-associated Shank2 single nucleotide variants (SNVs: S557N, V717F, and L1722P), were cultured in the absence or presence of 10 μM zinc. In comparison to Shank2-WT, ASD-associated Shank2 SNVs induced significant decreases in synaptic density and reduced the frequency of miniature excitatory postsynaptic currents. These structural and functional ASD-associated synaptic deficits were prevented by chronic zinc supplementation and further support zinc supplementation as a therapeutic target in ASD.

scholarly journals Genetic contributions to autism spectrum disorder

2021 ◽  
pp. 1-14
Author(s):  
A. Havdahl ◽  
M. Niarchou ◽  
A. Starnawska ◽  
M. Uddin ◽  
C. van der Merwe ◽  
...  
Keyword(s):  
Autism Spectrum Disorder ◽  
Rare Variants ◽  
De Novo ◽  
Point Mutations ◽  
Autism Spectrum ◽  
Repetitive Behaviors ◽  
Spectrum Disorder ◽  
Individual Risk ◽  
Future Research ◽  
Risk Genes

Abstract Autism spectrum disorder (autism) is a heterogeneous group of neurodevelopmental conditions characterized by early childhood-onset impairments in communication and social interaction alongside restricted and repetitive behaviors and interests. This review summarizes recent developments in human genetics research in autism, complemented by epigenetic and transcriptomic findings. The clinical heterogeneity of autism is mirrored by a complex genetic architecture involving several types of common and rare variants, ranging from point mutations to large copy number variants, and either inherited or spontaneous (de novo). More than 100 risk genes have been implicated by rare, often de novo, potentially damaging mutations in highly constrained genes. These account for substantial individual risk but a small proportion of the population risk. In contrast, most of the genetic risk is attributable to common inherited variants acting en masse, each individually with small effects. Studies have identified a handful of robustly associated common variants. Different risk genes converge on the same mechanisms, such as gene regulation and synaptic connectivity. These mechanisms are also implicated by genes that are epigenetically and transcriptionally dysregulated in autism. Major challenges to understanding the biological mechanisms include substantial phenotypic heterogeneity, large locus heterogeneity, variable penetrance, and widespread pleiotropy. Considerable increases in sample sizes are needed to better understand the hundreds or thousands of common and rare genetic variants involved. Future research should integrate common and rare variant research, multi-omics data including genomics, epigenomics, and transcriptomics, and refined phenotype assessment with multidimensional and longitudinal measures.

scholarly journals Quantification of autism recurrence risk by direct assessment of paternal sperm mosaicism

2017 ◽  
Author(s):  
Martin W. Breuss ◽  
Morgan Kleiber ◽  
Renee D. George ◽  
Danny Antaki ◽  
Kiely N. James ◽  
...  
Keyword(s):  
Single Molecule ◽  
De Novo ◽  
Recurrence Risk ◽  
Autism Spectrum ◽  
Causative Mutation ◽  
Single Nucleotide Variants ◽  
Single Nucleotide ◽  
Germline Mosaicism ◽  
Spectrum Disorders ◽  
Low Levels

SummaryDe novo genetic mutations represent a major contributor to pediatric disease, including autism spectrum disorders (ASD), congenital heart disease, and muscular dystrophies1,2, but there are currently no methods to prevent or predict them. These mutations are classically thought to occur either at low levels in progenitor cells or at the time of fertilization1,3 and are often assigned a low risk of recurrence in siblings4,5. Here, we directly assess the presence of de novo mutations in paternal sperm and discover abundant, germline-restricted mosaicism. From a cohort of ASD cases, employing single molecule genotyping, we found that four out of 14 fathers were germline mosaic for a putatively causative mutation transmitted to the affected child. Three of these were enriched or exclusively present in sperm at high allelic fractions (AF; 7-15%); and one was recurrently transmitted to two additional affected children, representing clinically actionable information. Germline mosaicism was further assessed by deep (>90x) whole genome sequencing of four paternal sperm samples, which detected 12/355 transmitted de novo single nucleotide variants that were mosaic above 2% AF, and more than two dozen additional, non-transmitted mosaic variants in paternal sperm. Our results demonstrate that germline mosaicism is an underestimated phenomenon, which has important implications for clinical practice and in understanding the basis of human disease. Genetic analysis of sperm can assess individualized recurrence risk following the birth of a child with a de novo disease, as well as the risk in any male planning to have children.

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