Publications by authors named "Benjamin Rodriguez-Santiago"

35 Publications

CRISPR Screens in Synthetic Lethality and Combinatorial Therapies for Cancer.

Cancers (Basel) 2021 Mar 30;13(7). Epub 2021 Mar 30.

Genome Instability and DNA Repair Syndromes Group, Sant Pau Biomedical Research Institute (IIB Sant Pau) and Join Unit UAB-IR Sant Pau on Genomic Medicine, 08041 Barcelona, Spain.

Cancer is a complex disease resulting from the accumulation of genetic dysfunctions. Tumor heterogeneity causes the molecular variety that divergently controls responses to chemotherapy, leading to the recurrent problem of cancer reappearance. For many decades, efforts have focused on identifying essential tumoral genes and cancer driver mutations. More recently, prompted by the clinical success of the synthetic lethality (SL)-based therapy of the PARP inhibitors in homologous recombinant deficient tumors, scientists have centered their novel research on SL interactions (SLI). The state of the art to find new genetic interactions are currently large-scale forward genetic CRISPR screens. CRISPR technology has rapidly evolved to be a common tool in the vast majority of laboratories, as tools to implement CRISPR screen protocols are available to all researchers. Taking advantage of SLI, combinatorial therapies have become the ultimate model to treat cancer with lower toxicity, and therefore better efficiency. This review explores the CRISPR screen methodology, integrates the up-to-date published findings on CRISPR screens in the cancer field and proposes future directions to uncover cancer regulation and individual responses to chemotherapy.
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http://dx.doi.org/10.3390/cancers13071591DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8037779PMC
March 2021

Heterozygous APOE Christchurch in familial Alzheimer's disease without mutations in other Mendelian genes.

Neuropathol Appl Neurobiol 2021 Jun 5;47(4):579-582. Epub 2020 Nov 5.

Networking Research Center on Neurodegenerative Diseases (CIBERNED), Instituto de Salud Carlos III, Madrid, Spain.

We present the clinical and neuropathological findings of a patient with early onset Alzheimer's dementia (AD), heterozygous carrier of the rare Apolipoprotein E Christchurch (APOEch) variant. The patient did not harbor any pathogenic mutation in known Mendelian genes related to AD or other neurodegenerative disorders. A sibling of this patient, also carrying the APOEch variant, developed AD at the age of 66 years old. Our data suggest a possible deleterious effect of this variant, which contrast with the protective role that has been previously shown in a subject homozygous for the APOEch with he Paisa PSEN1 mutation.
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http://dx.doi.org/10.1111/nan.12670DOI Listing
June 2021

Novel Somatic Genetic Variants as Predictors of Resistance to EGFR-Targeted Therapies in Metastatic Colorectal Cancer Patients.

Cancers (Basel) 2020 Aug 11;12(8). Epub 2020 Aug 11.

U705 and U745, ISCIII Center for Biomedical Research on Rare Diseases (CIBERER), 08041 Barcelona, Spain.

Background: About 40% of wild-type metastatic colorectal cancer (mCRC) patients undergoing anti-EGFR-based therapy have poor outcomes. Treatment failure is not only associated with poorer prognosis but higher healthcare costs. Our aim was to identify novel somatic genetic variants in the primary tumor and assess their effect on anti-EGFR response.

Patients And Methods: Tumor (somatic) and blood (germline) DNA samples were obtained from two well-defined cohorts of mCRC patients, those sensitive and those resistant to EGFR blockade. Genetic variant screening of 43 EGFR-related genes was performed using targeted next-generation sequencing (NGS). Relevant clinical data were collected through chart review to assess genetic results.

Results: Among 61 patients, 38 were sensitive and 23 were resistant to treatment. We identified eight somatic variants that predicted non-response. Three were located in insulin-related genes (I668N and E1218K in , T1156M in ) and three in genes belonging to the LRIG family (T152T in , S697L in and V812M in ). The remaining two variants were found in (G115Efs*46) and (T301T). We did not identify any somatic variants related to good response.

Conclusions: This study provides evidence that novel somatic genetic variants along the EGFR-triggered pathway could modulate the response to anti-EGFR drugs in mCRC patients. It also highlights the influence of insulin-related genes and genes on anti-EGFR efficacy. Our findings could help characterize patients who are resistant to anti-EGFR blockade despite harboring wild-type tumors.
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http://dx.doi.org/10.3390/cancers12082245DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7463997PMC
August 2020

Screening of dementia genes by whole-exome sequencing in Spanish patients with early-onset dementia: likely pathogenic, uncertain significance and risk variants.

Neurobiol Aging 2020 09 18;93:e1-e9. Epub 2020 Feb 18.

Alzheimer's Disease and Other Cognitive Disorders Unit, Hospital Clínic, Fundació Clínic per a la Recerca Biomèdica, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Universitat de Barcelona, Barcelona, Spain.

Early-onset Alzheimer's disease (EOAD) and frontotemporal dementia (FTD) have a high proportion of genetically determined cases. Next-generation sequencing technologies have triggered the discovery of new mutations and genetic variants in dementia-causal genes. We performed whole-exome sequencing and selective analysis of known genes causative of EOAD and FTD in a well-characterized Spanish cohort of 103 patients (60 EOAD, 43 FTD) to find genetic variants associated to patients' phenotype. In EOAD patients, a new likely pathogenic variant in PSEN1 gene (p.G378R) was found. In FTD patients, 2 likely pathogenic variants were found, one in MAPT gene (p.P397S) and one in VCP gene (p.R159H). In our series, 2% of early-onset dementia without criteria for clinical genetic testing according to current guidelines presented a likely pathogenic mutation. We have also detected 13 additional variants of uncertain significance in causal genes, as well as rare variants in risk genes for dementia (ABCA7, SORL1, SQSTM1, and TREM2). Next-generation technologies in neurodegenerative diseases constitute a powerful tool that significantly contributes to patients' diagnosis.
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http://dx.doi.org/10.1016/j.neurobiolaging.2020.02.008DOI Listing
September 2020

Optimised molecular genetic diagnostics of Fanconi anaemia by whole exome sequencing and functional studies.

J Med Genet 2020 04 5;57(4):258-268. Epub 2019 Oct 5.

Hospital Universitario Puerta del Mar, Cadiz, Andalucía, Spain.

Purpose: Patients with Fanconi anaemia (FA), a rare DNA repair genetic disease, exhibit chromosome fragility, bone marrow failure, malformations and cancer susceptibility. FA molecular diagnosis is challenging since FA is caused by point mutations and large deletions in 22 genes following three heritability patterns. To optimise FA patients' characterisation, we developed a simplified but effective methodology based on whole exome sequencing (WES) and functional studies.

Methods: 68 patients with FA were analysed by commercial WES services. Copy number variations were evaluated by sequencing data analysis with RStudio. To test missense variants, wt FANCA cDNA was cloned and variants were introduced by site-directed mutagenesis. Vectors were then tested for their ability to complement DNA repair defects of a FANCA-KO human cell line generated by TALEN technologies.

Results: We identified 93.3% of mutated alleles including large deletions. We determined the pathogenicity of three FANCA missense variants and demonstrated that two variants reported in mutations databases as 'affecting functions' are SNPs. Deep analysis of sequencing data revealed patients' true mutations, highlighting the importance of functional analysis. In one patient, no pathogenic variant could be identified in any of the 22 known FA genes, and in seven patients, only one deleterious variant could be identified (three patients each with FANCA and FANCD2 and one patient with FANCE mutations) CONCLUSION: WES and proper bioinformatics analysis are sufficient to effectively characterise patients with FA regardless of the rarity of their complementation group, type of mutations, mosaic condition and DNA source.
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http://dx.doi.org/10.1136/jmedgenet-2019-106249DOI Listing
April 2020

Further delineation of the phenotype caused by loss of function mutations in PRMT7.

Eur J Med Genet 2019 Mar 10;62(3):182-185. Epub 2018 Jul 10.

Department of Clinical and Molecular Genetics and Rare Disease Unit, University Hospital Vall d´Hebron, Barcelona, Spain; Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), ISCIII, Barcelona, Spain. Electronic address:

PRMT7 encodes for an arginine methyltransferase that methylates arginine residues on various protein substrates and has been shown to play a role in various developmental processes. Mutations in PRMT7 have been recently shown to be implicated in a phenotype with intellectual disability, short stature and brachydactyly, and considered to be a phenocopy of pseudohypoparathyroidism. We report a patient with short stature, psychomotor delay, hearing loss and brachydactyly, for whom whole exome sequencing detected two mutations in PRMT7 and parental segregation studies detected biallelic mutation inheritance. Few patients with biallelic PRMT7 mutations have been reported so far in the literature. We report a new patient and review all reported cases to date to delineate the clinical manifestations that may help in diagnosis this disorder, known as Short Stature, Brachydactyly, Intellectual Developmental Disability, and Seizures syndrome, allowing appropriate management and genetic counselling.
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http://dx.doi.org/10.1016/j.ejmg.2018.07.007DOI Listing
March 2019

Detectable clonal mosaicism in blood as a biomarker of cancer risk in Fanconi anemia.

Blood Adv 2017 Jan 23;1(5):319-329. Epub 2017 Jan 23.

Centro de Investigación Biomédica en Red de Enfermedades Raras, Barcelona, Spain.

Detectable clonal mosaicism for large chromosomal events has been associated with aging and an increased risk of hematological and some solid cancers. We hypothesized that genetic cancer predisposition disorders, such as Fanconi anemia (FA), could manifest a high rate of chromosomal mosaic events (CMEs) in peripheral blood, which could be used as early biomarkers of cancer risk. We studied the prevalence of CMEs by single-nucleotide polymorphism (SNP) array in 130 FA patients' blood DNA and their impact on cancer risk. We detected 51 CMEs (4.4-159 Mb in size) in 16 out of 130 patients (12.3%), of which 9 had multiple CMEs. The most frequent events were gains at 3q (n = 6) and 1q (n = 5), both previously associated with leukemia, as well as rearrangements with breakpoint clustering within the major histocompatibility complex locus ( = 7.3 × 10). Compared with 15 743 age-matched population controls, FA patients had a 126 to 140 times higher risk of detectable CMEs in blood ( < 2.2 × 10). Prevalent and incident hematologic and solid cancers were more common in CME carriers (odds ratio [OR] = 11.6, 95% confidence interval [CI] = 3.4-39.3, = 2.8 × 10), leading to poorer prognosis. The age-adjusted hazard risk (HR) of having cancer was almost 5 times higher in FA individuals with CMEs than in those without CMEs. Regarding survival, the HR of dying was 4 times higher in FA individuals having CMEs (HR = 4.0, 95% CI = 2.0-7.9, = 5.7 × 10). Therefore, our data suggest that molecular karyotyping with SNP arrays in easy-to-obtain blood samples could be used for better monitoring of bone marrow clonal events, cancer risk, and overall survival of FA patients.
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http://dx.doi.org/10.1182/bloodadvances.2016000943DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5744036PMC
January 2017

Novel genes involved in severe early-onset obesity revealed by rare copy number and sequence variants.

PLoS Genet 2017 May 10;13(5):e1006657. Epub 2017 May 10.

Genetics Unit, Universitat Pompeu Fabra, Barcelona, Spain.

Obesity is a multifactorial disorder with high heritability (50-75%), which is probably higher in early-onset and severe cases. Although rare monogenic forms and several genes and regions of susceptibility, including copy number variants (CNVs), have been described, the genetic causes underlying the disease still remain largely unknown. We searched for rare CNVs (>100kb in size, altering genes and present in <1/2000 population controls) in 157 Spanish children with non-syndromic early-onset obesity (EOO: body mass index >3 standard deviations above the mean at <3 years of age) using SNP array molecular karyotypes. We then performed case control studies (480 EOO cases/480 non-obese controls) with the validated CNVs and rare sequence variants (RSVs) detected by targeted resequencing of selected CNV genes (n = 14), and also studied the inheritance patterns in available first-degree relatives. A higher burden of gain-type CNVs was detected in EOO cases versus controls (OR = 1.71, p-value = 0.0358). In addition to a gain of the NPY gene in a familial case with EOO and attention deficit hyperactivity disorder, likely pathogenic CNVs included gains of glutamate receptors (GRIK1, GRM7) and the X-linked gastrin-peptide receptor (GRPR), all inherited from obese parents. Putatively functional RSVs absent in controls were also identified in EOO cases at NPY, GRIK1 and GRPR. A patient with a heterozygous deletion disrupting two contiguous and related genes, SLCO4C1 and SLCO6A1, also had a missense RSV at SLCO4C1 on the other allele, suggestive of a recessive model. The genes identified showed a clear enrichment of shared co-expression partners with known genes strongly related to obesity, reinforcing their role in the pathophysiology of the disease. Our data reveal a higher burden of rare CNVs and RSVs in several related genes in patients with EOO compared to controls, and implicate NPY, GRPR, two glutamate receptors and SLCO4C1 in highly penetrant forms of familial obesity.
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http://dx.doi.org/10.1371/journal.pgen.1006657DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5443539PMC
May 2017

Female chromosome X mosaicism is age-related and preferentially affects the inactivated X chromosome.

Nat Commun 2016 06 13;7:11843. Epub 2016 Jun 13.

National Institute of Cancer Research, National Health Research Institutes, Zhunan 35053, Taiwan.

To investigate large structural clonal mosaicism of chromosome X, we analysed the SNP microarray intensity data of 38,303 women from cancer genome-wide association studies (20,878 cases and 17,425 controls) and detected 124 mosaic X events >2 Mb in 97 (0.25%) women. Here we show rates for X-chromosome mosaicism are four times higher than mean autosomal rates; X mosaic events more often include the entire chromosome and participants with X events more likely harbour autosomal mosaic events. X mosaicism frequency increases with age (0.11% in 50-year olds; 0.45% in 75-year olds), as reported for Y and autosomes. Methylation array analyses of 33 women with X mosaicism indicate events preferentially involve the inactive X chromosome. Our results provide further evidence that the sex chromosomes undergo mosaic events more frequently than autosomes, which could have implications for understanding the underlying mechanisms of mosaic events and their possible contribution to risk for chronic diseases.
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http://dx.doi.org/10.1038/ncomms11843DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4909985PMC
June 2016

Mosaic loss of chromosome Y is associated with common variation near TCL1A.

Nat Genet 2016 05 11;48(5):563-8. Epub 2016 Apr 11.

Department of Epidemiology, University of Texas M.D. Anderson Cancer Center, Houston, Texas, USA.

Mosaic loss of chromosome Y (mLOY) leading to gonosomal XY/XO commonly occurs during aging, particularly in smokers. We investigated whether mLOY was associated with non-hematological cancer in three prospective cohorts (8,679 cancer cases and 5,110 cancer-free controls) and genetic susceptibility to mLOY. Overall, mLOY was observed in 7% of men, and its prevalence increased with age (per-year odds ratio (OR) = 1.13, 95% confidence interval (CI) = 1.12-1.15; P < 2 × 10(-16)), reaching 18.7% among men over 80 years old. mLOY was associated with current smoking (OR = 2.35, 95% CI = 1.82-3.03; P = 5.55 × 10(-11)), but the association weakened with years after cessation. mLOY was not consistently associated with overall or specific cancer risk (for example, bladder, lung or prostate cancer) nor with cancer survival after diagnosis (multivariate-adjusted hazard ratio = 0.87, 95% CI = 0.73-1.04; P = 0.12). In a genome-wide association study, we observed the first example of a common susceptibility locus for genetic mosaicism, specifically mLOY, which maps to TCL1A at 14q32.13, marked by rs2887399 (OR = 1.55, 95% CI = 1.36-1.78; P = 1.37 × 10(-10)).
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http://dx.doi.org/10.1038/ng.3545DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4848121PMC
May 2016

NGS-Based Assay for the Identification of Individuals Carrying Recessive Genetic Mutations in Reproductive Medicine.

Hum Mutat 2016 06 15;37(6):516-23. Epub 2016 Apr 15.

Unit of Medical Genomics, Department of Obstetrics, Gynaecology and Reproduction, Dexeus Women's Health, Barcelona, Spain.

Next-generation sequencing (NGS) has the capacity of carrier screening in gamete donation (GD) programs. We have developed and validated an NGS carrier-screening test (qCarrier test) that includes 200 genes associated with 368 disorders (277 autosomal recessive and 37 X-linked). Carrier screening is performed on oocyte donation candidates and the male partner of oocyte recipient. Carriers of X-linked conditions are excluded from the GD program, whereas donors are chosen who do not carry mutations for the same gene/disease as the recipients. The validation phase showed a high sensitivity (>99% sensitivity) detecting all single-nucleotide variants, 13 indels, and 25 copy-number variants included in the validation set. A total of 1,301 individuals were analysed with the qCarrier test, including 483 candidate oocyte donors and 635 receptor couples, 105 females receiving sperm donation, and 39 couples seeking pregnancy. We identified 56% of individuals who are carriers for at least one genetic condition and 1.7% of female donors who were excluded from the program due to a carrier state of X-linked conditions. Globally, 3% of a priori assigned donations had a high reproductive risk that could be minimized after testing. Genetic counselling at different stages is essential for helping to facilitate a successful and healthy pregnancy.
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http://dx.doi.org/10.1002/humu.22989DOI Listing
June 2016

A Novel Recurrent Breakpoint Responsible for Rearrangements in the Williams-Beuren Region.

Cytogenet Genome Res 2015 18;146(3):181-6. Epub 2015 Sep 18.

x00C0;rea de Genx00E8;tica Clx00ED;nica i Molecular, Hospital Universitari Vall d'Hebron, Barcelona, Spain.

Copy number variants (CNVs) of the Williams-Beuren syndrome (WBS) 7q11.23 region are responsible for neurodevelopmental disorders with multisystem involvement and variable expressivity. We found 2 patients with a deletion and 1 patient with a duplication in this region sharing a common breakpoint located between the LIMK1 and EIF4H(WBSCR1) genes. One patient had a WBS phenotype, although testing with a commercially available FISH assay was negative for the deletion. A further test using array CGH showed an atypical WBS region deletion. The second patient showed global developmental delay, speech delay and poor motor skills with a deletion outside the WBS region. The third patient had manifestations compatible with an autism spectrum disorder showing a duplication in the WBS region. Our findings point to the existence of a previously unrecognized recurrent breakpoint responsible for rearrangements in the WBS region. Given that most commercial FISH assays include probes flanking this novel breakpoint, further testing with array CGH should be performed in patients with WBS and negative FISH results.
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http://dx.doi.org/10.1159/000439463DOI Listing
January 2016

The UBC-40 Urothelial Bladder Cancer cell line index: a genomic resource for functional studies.

BMC Genomics 2015 05 22;16:403. Epub 2015 May 22.

Epithelial Carcinogenesis Group, F BBVA Cancer Cell Biology Programme, CNIO (Spanish National Cancer Research Centre), Madrid, Spain.

Background: Urothelial bladder cancer is a highly heterogeneous disease. Cancer cell lines are useful tools for its study. This is a comprehensive genomic characterization of 40 urothelial bladder carcinoma (UBC) cell lines including information on origin, mutation status of genes implicated in bladder cancer (FGFR3, PIK3CA, TP53, and RAS), copy number alterations assessed using high density SNP arrays, uniparental disomy (UPD) events, and gene expression.

Results: Based on gene mutation patterns and genomic changes we identify lines representative of the FGFR3-driven tumor pathway and of the TP53/RB tumor suppressor-driven pathway. High-density array copy number analysis identified significant focal gains (1q32, 5p13.1-12, 7q11, and 7q33) and losses (i.e. 6p22.1) in regions altered in tumors but not previously described as affected in bladder cell lines. We also identify new evidence for frequent regions of UPD, often coinciding with regions reported to be lost in tumors. Previously undescribed chromosome X losses found in UBC lines also point to potential tumor suppressor genes. Cell lines representative of the FGFR3-driven pathway showed a lower number of UPD events.

Conclusions: Overall, there is a predominance of more aggressive tumor subtypes among the cell lines. We provide a cell line classification that establishes their relatedness to the major molecularly-defined bladder tumor subtypes. The compiled information should serve as a useful reference to the bladder cancer research community and should help to select cell lines appropriate for the functional analysis of bladder cancer genes, for example those being identified through massive parallel sequencing.
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http://dx.doi.org/10.1186/s12864-015-1450-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4470036PMC
May 2015

Integrated analysis of whole-exome sequencing and transcriptome profiling in males with autism spectrum disorders.

Mol Autism 2015 15;6:21. Epub 2015 Apr 15.

Department of Experimental and Health Sciences, Universitat Pompeu Fabra, C/Doctor Aiguader 88, 422, Barcelona, 08003 Spain ; Hospital del Mar Research Institute (IMIM), C/Doctor Aiguader 88, Barcelona, 08003 Spain ; Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBER-ER), C/ Monforte de Lemos 3-5, Madrid, 28029 Spain.

Background: Autism spectrum disorders (ASD) are a group of neurodevelopmental disorders with high heritability. Recent findings support a highly heterogeneous and complex genetic etiology including rare de novo and inherited mutations or chromosomal rearrangements as well as double or multiple hits.

Methods: We performed whole-exome sequencing (WES) and blood cell transcriptome by RNAseq in a subset of male patients with idiopathic ASD (n = 36) in order to identify causative genes, transcriptomic alterations, and susceptibility variants.

Results: We detected likely monogenic causes in seven cases: five de novo (SCN2A, MED13L, KCNV1, CUL3, and PTEN) and two inherited X-linked variants (MAOA and CDKL5). Transcriptomic analyses allowed the identification of intronic causative mutations missed by the usual filtering of WES and revealed functional consequences of some rare mutations. These included aberrant transcripts (PTEN, POLR3C), deregulated expression in 1.7% of mutated genes (that is, SEMA6B, MECP2, ANK3, CREBBP), allele-specific expression (FUS, MTOR, TAF1C), and non-sense-mediated decay (RIT1, ALG9). The analysis of rare inherited variants showed enrichment in relevant pathways such as the PI3K-Akt signaling and the axon guidance.

Conclusions: Integrative analysis of WES and blood RNAseq data has proven to be an efficient strategy to identify likely monogenic forms of ASD (19% in our cohort), as well as additional rare inherited mutations that can contribute to ASD risk in a multifactorial manner. Blood transcriptomic data, besides validating 88% of expressed variants, allowed the identification of missed intronic mutations and revealed functional correlations of genetic variants, including changes in splicing, expression levels, and allelic expression.
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http://dx.doi.org/10.1186/s13229-015-0017-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4427998PMC
May 2015

Characterization of large structural genetic mosaicism in human autosomes.

Am J Hum Genet 2015 Mar;96(3):487-97

Department of Thoracic and Cardiovascular Surgery, Cancer Research Institute, College of Medicine, Seoul National University, Seoul 151-742, Republic of Korea.

Analyses of genome-wide association study (GWAS) data have revealed that detectable genetic mosaicism involving large (>2 Mb) structural autosomal alterations occurs in a fraction of individuals. We present results for a set of 24,849 genotyped individuals (total GWAS set II [TGSII]) in whom 341 large autosomal abnormalities were observed in 168 (0.68%) individuals. Merging data from the new TGSII set with data from two prior reports (the Gene-Environment Association Studies and the total GWAS set I) generated a large dataset of 127,179 individuals; we then conducted a meta-analysis to investigate the patterns of detectable autosomal mosaicism (n = 1,315 events in 925 [0.73%] individuals). Restricting to events >2 Mb in size, we observed an increase in event frequency as event size decreased. The combined results underscore that the rate of detectable mosaicism increases with age (p value = 5.5 × 10(-31)) and is higher in men (p value = 0.002) but lower in participants of African ancestry (p value = 0.003). In a subset of 47 individuals from whom serial samples were collected up to 6 years apart, complex changes were noted over time and showed an overall increase in the proportion of mosaic cells as age increased. Our large combined sample allowed for a unique ability to characterize detectable genetic mosaicism involving large structural events and strengthens the emerging evidence of non-random erosion of the genome in the aging population.
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http://dx.doi.org/10.1016/j.ajhg.2015.01.011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4375431PMC
March 2015

Autosomal dominant oculoauriculovertebral spectrum and 14q23.1 microduplication.

Am J Med Genet A 2013 Aug 21;161A(8):2030-5. Epub 2013 Jun 21.

Unidad de Genética Médica y Dismorfología, Servicio de Pediatría, Hospital Universitario Virgen de la Arrixaca, Murcia, Spain.

Oculoauriculovertebral spectrum (OAVS; OMIM 164210) is characterized by anomalies derived from an abnormal development of the first and second branchial arches, with marked inter and intra-familial phenotypic variability. Main clinical features are defects on aural, oral, mandibular, and vertebral development. Cardiac, pulmonary, renal, skeletal, and central nervous system anomalies have also been described. Most affected individuals are isolated cases in otherwise normal families. Autosomal dominant inheritance has been observed in about 2-10% of cases and linkage analysis as well as array-CGH analysis have detected candidate loci for OAVS offering new insights into the understanding of pathogenesis of this entity. We describe a family with clinical diagnosis of OAVS, autosomal dominant inheritance pattern, and detection of a 14q23.1 duplication of 1.34 Mb in size which segregates with the phenotype. This region contains OTX2, which is involved in the development of the forebrain, eyes, and ears, and appears to be a good candidate gene for OAVS.
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http://dx.doi.org/10.1002/ajmg.a.36007DOI Listing
August 2013

Contribution of rare copy number variants to isolated human malformations.

PLoS One 2012 3;7(10):e45530. Epub 2012 Oct 3.

Unitat de Genètica, Universitat Pompeu Fabra, Barcelona, Spain.

Background: Congenital malformations are present in approximately 2-3% of liveborn babies and 20% of stillborn fetuses. The mechanisms underlying the majority of sporadic and isolated congenital malformations are poorly understood, although it is hypothesized that the accumulation of rare genetic, genomic and epigenetic variants converge to deregulate developmental networks.

Methodology/principal Findings: We selected samples from 95 fetuses with congenital malformations not ascribed to a specific syndrome (68 with isolated malformations, 27 with multiple malformations). Karyotyping and Multiplex Ligation-dependent Probe Amplification (MLPA) discarded recurrent genomic and cytogenetic rearrangements. DNA extracted from the affected tissue (46%) or from lung or liver (54%) was analyzed by molecular karyotyping. Validations and inheritance were obtained by MLPA. We identified 22 rare copy number variants (CNV) [>100 kb, either absent (n = 7) or very uncommon (n = 15, <1/2,000) in the control population] in 20/95 fetuses with congenital malformations (21%), including 11 deletions and 11 duplications. One of the 9 tested rearrangements was de novo while the remaining were inherited from a healthy parent. The highest frequency was observed in fetuses with heart hypoplasia (8/17, 62.5%), with two events previously related with the phenotype. Double events hitting candidate genes were detected in two samples with brain malformations. Globally, the burden of deletions was significantly higher in fetuses with malformations compared to controls.

Conclusions/significance: Our data reveal a significant contribution of rare deletion-type CNV, mostly inherited but also de novo, to human congenital malformations, especially heart hypoplasia, and reinforce the hypothesis of a multifactorial etiology in most cases.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0045530PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3463597PMC
April 2013

Genome-wide CNV analysis replicates the association between GSTM1 deletion and bladder cancer: a support for using continuous measurement from SNP-array data.

BMC Genomics 2012 Jul 20;13:326. Epub 2012 Jul 20.

Spanish National Cancer Research Center (CNIO), Madrid, E-28029, Spain.

Background: Structural variations such as copy number variants (CNV) influence the expression of different phenotypic traits. Algorithms to identify CNVs through SNP-array platforms are available. The ability to evaluate well-characterized CNVs such as GSTM1 (1p13.3) deletion provides an important opportunity to assess their performance.

Results: 773 cases and 759 controls from the SBC/EPICURO Study were genotyped in the GSTM1 region using TaqMan, Multiplex Ligation-dependent Probe Amplification (MLPA), and Illumina Infinium 1 M SNP-array platforms. CNV callings provided by TaqMan and MLPA were highly concordant and replicated the association between GSTM1 and bladder cancer. This was not the case when CNVs were called using Illumina 1 M data through available algorithms since no deletion was detected across the study samples. In contrast, when the Log R Ratio (LRR) was used as a continuous measure for the 5 probes contained in this locus, we were able to detect their association with bladder cancer using simple regression models or more sophisticated methods such as the ones implemented in the CNVtools package.

Conclusions: This study highlights an important limitation in the CNV calling from SNP-array data in regions of common aberrations and suggests that there may be added advantage for using LRR as a continuous measure in association tests rather than relying on calling algorithms.
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http://dx.doi.org/10.1186/1471-2164-13-326DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3425254PMC
July 2012

Detectable clonal mosaicism and its relationship to aging and cancer.

Nat Genet 2012 May 6;44(6):651-8. Epub 2012 May 6.

Division of Cancer Epidemiology and Genetics, National Cancer Institute (NCI), Rockville, Maryland, USA.

In an analysis of 31,717 cancer cases and 26,136 cancer-free controls from 13 genome-wide association studies, we observed large chromosomal abnormalities in a subset of clones in DNA obtained from blood or buccal samples. We observed mosaic abnormalities, either aneuploidy or copy-neutral loss of heterozygosity, of >2 Mb in size in autosomes of 517 individuals (0.89%), with abnormal cell proportions of between 7% and 95%. In cancer-free individuals, frequency increased with age, from 0.23% under 50 years to 1.91% between 75 and 79 years (P = 4.8 × 10(-8)). Mosaic abnormalities were more frequent in individuals with solid tumors (0.97% versus 0.74% in cancer-free individuals; odds ratio (OR) = 1.25; P = 0.016), with stronger association with cases who had DNA collected before diagnosis or treatment (OR = 1.45; P = 0.0005). Detectable mosaicism was also more common in individuals for whom DNA was collected at least 1 year before diagnosis with leukemia compared to cancer-free individuals (OR = 35.4; P = 3.8 × 10(-11)). These findings underscore the time-dependent nature of somatic events in the etiology of cancer and potentially other late-onset diseases.
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http://dx.doi.org/10.1038/ng.2270DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3372921PMC
May 2012

De novo copy number variants associated with intellectual disability have a paternal origin and age bias.

J Med Genet 2011 Nov 3;48(11):776-8. Epub 2011 Oct 3.

Department of Human Genetics, Nijmegen Centre for Molecular Life Sciences and Institute for Genetic and Metabolic Disorders, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.

Background: De novo mutations and structural rearrangements are a common cause of intellectual disability (ID) and other disorders with reduced or null reproductive fitness. Insight into the genomic and environmental factors predisposing to the generation of these de novo events is therefore of significant clinical importance.

Methods: This study used information from single nucleotide polymorphism microarrays to determine the parent-of-origin of 118 rare de novo copy number variations (CNVs) detected in a cohort of 3443 patients with ID.

Results: The large majority of these CNVs (76%, p=1.14×10(-8)) originated on the paternal allele. This paternal bias was independent of CNV length and CNV type. Interestingly, the paternal bias was less pronounced for CNVs flanked by segmental duplications (64%), suggesting that molecular mechanisms involved in the formation of rare de novo CNVs may be dependent on the parent-of-origin. In addition, a significantly increased paternal age was only observed for those CNVs which were not flanked by segmental duplications (p=0.02).

Conclusion: This indicates that rare de novo CNVs are increasingly being generated with advanced paternal age by replication based mechanisms during spermatogenesis.
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http://dx.doi.org/10.1136/jmedgenet-2011-100147DOI Listing
November 2011

De novo nonsense mutations in ASXL1 cause Bohring-Opitz syndrome.

Nat Genet 2011 Jun 26;43(8):729-31. Epub 2011 Jun 26.

Department of Human Genetics, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.

Bohring-Opitz syndrome is characterized by severe intellectual disability, distinctive facial features and multiple congenital malformations. We sequenced the exomes of three individuals with Bohring-Opitz syndrome and in each identified heterozygous de novo nonsense mutations in ASXL1, which is required for maintenance of both activation and silencing of Hox genes. In total, 7 out of 13 subjects with a Bohring-Opitz phenotype had de novo ASXL1 mutations, suggesting that the syndrome is genetically heterogeneous.
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http://dx.doi.org/10.1038/ng.868DOI Listing
June 2011

A fast and accurate method to detect allelic genomic imbalances underlying mosaic rearrangements using SNP array data.

BMC Bioinformatics 2011 May 17;12:166. Epub 2011 May 17.

Center for Research in Environmental Epidemiology, Doctor Aiguader 88, Barcelona 08003, Spain.

Background: Mosaicism for copy number and copy neutral chromosomal rearrangements has been recently identified as a relatively common source of genetic variation in the normal population. However its prevalence is poorly defined since it has been only studied systematically in one large-scale study and by using non optimal ad-hoc SNP array data analysis tools, uncovering rather large alterations (> 1 Mb) and affecting a high proportion of cells. Here we propose a novel methodology, Mosaic Alteration Detection-MAD, by providing a software tool that is effective for capturing previously described alterations as wells as new variants that are smaller in size and/or affecting a low percentage of cells.

Results: The developed method identified all previously known mosaic abnormalities reported in SNP array data obtained from controls, bladder cancer and HapMap individuals. In addition MAD tool was able to detect new mosaic variants not reported before that were smaller in size and with lower percentage of cells affected. The performance of the tool was analysed by studying simulated data for different scenarios. Our method showed high sensitivity and specificity for all assessed scenarios.

Conclusions: The tool presented here has the ability to identify mosaic abnormalities with high sensitivity and specificity. Our results confirm the lack of sensitivity of former methods by identifying new mosaic variants not reported in previously utilised datasets. Our work suggests that the prevalence of mosaic alterations could be higher than initially thought. The use of appropriate SNP array data analysis methods would help in defining the human genome mosaic map.
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http://dx.doi.org/10.1186/1471-2105-12-166DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3118168PMC
May 2011

Assessment of copy number variation using the Illumina Infinium 1M SNP-array: a comparison of methodological approaches in the Spanish Bladder Cancer/EPICURO study.

Hum Mutat 2011 Feb 25;32(2):240-8. Epub 2011 Jan 25.

Centro Nacional de Investigaciones Oncológicas (CNIO) Madrid, Spain.

High-throughput single nucleotide polymorphism (SNP)-array technologies allow to investigate copy number variants (CNVs) in genome-wide scans and specific calling algorithms have been developed to determine CNV location and copy number. We report the results of a reliability analysis comparing data from 96 pairs of samples processed with CNVpartition, PennCNV, and QuantiSNP for Infinium Illumina Human 1Million probe chip data. We also performed a validity assessment with multiplex ligation-dependent probe amplification (MLPA) as a reference standard. The number of CNVs per individual varied according to the calling algorithm. Higher numbers of CNVs were detected in saliva than in blood DNA samples regardless of the algorithm used. All algorithms presented low agreement with mean Kappa Index (KI) <66. PennCNV was the most reliable algorithm (KI(w=) 98.96) when assessing the number of copies. The agreement observed in detecting CNV was higher in blood than in saliva samples. When comparing to MLPA, all algorithms identified poorly known copy aberrations (sensitivity = 0.19-0.28). In contrast, specificity was very high (0.97-0.99). Once a CNV was detected, the number of copies was truly assessed (sensitivity >0.62). Our results indicate that the current calling algorithms should be improved for high performance CNV analysis in genome-wide scans. Further refinement is required to assess CNVs as risk factors in complex diseases.
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http://dx.doi.org/10.1002/humu.21398DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3230937PMC
February 2011

Mosaic uniparental disomies and aneuploidies as large structural variants of the human genome.

Am J Hum Genet 2010 Jul;87(1):129-38

Departament de Ciències Experimentals i de la Salut, Universitat Pompeu Fabra, E-08003 Barcelona, Spain.

Mosaicism is defined as the coexistence of cells with different genetic composition within an individual, caused by postzygotic somatic mutation. Although somatic mosaicism for chromosomal abnormalities is a well-established cause of developmental and somatic disorders and has also been detected in different tissues, its frequency and extent in the adult normal population are still unknown. We provide here a genome-wide survey of mosaic genomic variation obtained by analyzing Illumina 1M SNP array data from blood or buccal DNA samples of 1991 adult individuals from the Spanish Bladder Cancer/EPICURO genome-wide association study. We found mosaic abnormalities in autosomes in 1.7% of samples, including 23 segmental uniparental disomies, 8 complete trisomies, and 11 large (1.5-37 Mb) copy-number variants. Alterations were observed across the different autosomes with recurrent events in chromosomes 9 and 20. No case-control differences were found in the frequency of events or the percentage of cells affected, thus indicating that most rearrangements found are not central to the development of bladder cancer. However, five out of six events tested were detected in both blood and bladder tissue from the same individual, indicating an early developmental origin. The high cellular frequency of the anomalies detected and their presence in normal adult individuals suggest that this type of mosaicism is a widespread phenomenon in the human genome. Somatic mosaicism should be considered in the expanding repertoire of inter- and intraindividual genetic variation, some of which may cause somatic human diseases but also contribute to modifying inherited disorders and/or late-onset multifactorial traits.
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http://dx.doi.org/10.1016/j.ajhg.2010.06.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2896781PMC
July 2010

Autism-specific copy number variants further implicate the phosphatidylinositol signaling pathway and the glutamatergic synapse in the etiology of the disorder.

Hum Mol Genet 2009 May 26;18(10):1795-804. Epub 2009 Feb 26.

Unitat de Genètica, Universitat Pompeu Fabra, Barcelona, Spain.

Autism spectrum disorders (ASDs) constitute a group of severe neurodevelopmental conditions with complex multifactorial etiology. In order to explore the hypothesis that submicroscopic genomic rearrangements underlie some ASD cases, we have analyzed 96 Spanish patients with idiopathic ASD after extensive clinical and laboratory screening, by array comparative genomic hybridization (aCGH) using a homemade bacterial artificial chromosome (BAC) array. Only 13 of the 238 detected copy number alterations, ranging in size from 89 kb to 2.4 Mb, were present specifically in the autistic population (12 out of 96 individuals, 12.5%). Following validation by additional molecular techniques, we have characterized these novel candidate regions containing 24 different genes including alterations in two previously reported regions of chromosome 7 associated with the ASD phenotype. Some of the genes located in ASD-specific copy number variants act in common pathways, most notably the phosphatidylinositol signaling and the glutamatergic synapse, both known to be affected in several genetic syndromes related with autism and previously associated with ASD. Our work supports the idea that the functional alteration of genes in related neuronal networks is involved in the etiology of the ASD phenotype and confirms a significant diagnostic yield for aCGH, which should probably be included in the diagnostic workup of idiopathic ASD.
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http://dx.doi.org/10.1093/hmg/ddp092DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2671988PMC
May 2009

Novel SLC7A7 large rearrangements in lysinuric protein intolerance patients involving the same AluY repeat.

Eur J Hum Genet 2009 Jan 20;17(1):71-9. Epub 2008 Aug 20.

Medical and Molecular Genetics Center, IDIBELL, Hospital Duran i Reynals, L'Hospitalet de Llobregat, Barcelona, Spain.

Lysinuric protein intolerance (LPI) is a rare autosomal inherited disease caused by defective cationic aminoacid transport 4F2hc/y(+)LAT-1 at the basolateral membrane of epithelial cells in the intestine and kidney. LPI is a multisystemic disease with a variety of clinical symptoms such as hepatosplenomegaly, osteoporosis, hypotonia, developmental delay, pulmonary insufficiency or end-stage renal disease. The SLC7A7 gene, which encodes the y(+)LAT-1 protein, is mutated in LPI patients. Mutation analysis of the promoter localized in intron 1 and all exons of the SLC7A7 gene was performed in 11 patients from 9 unrelated LPI families. Point mutation screening was performed by exon direct sequencing and a new multiplex ligation probe amplification (MLPA) assay was set up for large rearrangement analysis. Eleven SLC7A7-specific mutations were identified, seven of them were novel: p.L124P, p.C425R, p.R468X, p.Y274fsX21, c.625+1G>C, DelE4-E11 and DelE6-E11. The novel large deletions originated by the recombination of Alu repeats at introns 3 and 5, respectively, with the same AluY sequence localized at the SLC7A7 3' region. The novel MLPA assay is robust and valuable for LPI molecular diagnosis. Our results suggest that genomic rearrangements of SLC7A7 play a more important role in LPI than has been reported, increasing the detection rate from 5.1 to 21.4%. Moreover, the 3' region AluY repeat could be a recombination hot spot as it is involved in 38% of all SLC7A7 rearranged chromosomes described so far.
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http://dx.doi.org/10.1038/ejhg.2008.145DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2985956PMC
January 2009

Genetic and genomic analysis modeling of germline c-MYC overexpression and cancer susceptibility.

BMC Genomics 2008 Jan 11;9:12. Epub 2008 Jan 11.

Bioinformatics and Biostatistics Unit, and Translational Research Laboratory, Catalan Institute of Oncology, IDIBELL, L'Hospitalet, Barcelona, Spain.

Background: Germline genetic variation is associated with the differential expression of many human genes. The phenotypic effects of this type of variation may be important when considering susceptibility to common genetic diseases. Three regions at 8q24 have recently been identified to independently confer risk of prostate cancer. Variation at 8q24 has also recently been associated with risk of breast and colorectal cancer. However, none of the risk variants map at or relatively close to known genes, with c-MYC mapping a few hundred kilobases distally.

Results: This study identifies cis-regulators of germline c-MYC expression in immortalized lymphocytes of HapMap individuals. Quantitative analysis of c-MYC expression in normal prostate tissues suggests an association between overexpression and variants in Region 1 of prostate cancer risk. Somatic c-MYC overexpression correlates with prostate cancer progression and more aggressive tumor forms, which was also a pathological variable associated with Region 1. Expression profiling analysis and modeling of transcriptional regulatory networks predicts a functional association between MYC and the prostate tumor suppressor KLF6. Analysis of MYC/Myc-driven cell transformation and tumorigenesis substantiates a model in which MYC overexpression promotes transformation by down-regulating KLF6. In this model, a feedback loop through E-cadherin down-regulation causes further transactivation of c-MYC.

Conclusion: This study proposes that variation at putative 8q24 cis-regulator(s) of transcription can significantly alter germline c-MYC expression levels and, thus, contribute to prostate cancer susceptibility by down-regulating the prostate tumor suppressor KLF6 gene.
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http://dx.doi.org/10.1186/1471-2164-9-12DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2244606PMC
January 2008