Publications by authors named "Ludwine Messiaen"

107 Publications

Constitutional mismatch repair deficiency is the diagnosis in 0.41% of pathogenic NF1/SPRED1 variant negative children suspected of sporadic neurofibromatosis type 1.

Genet Med 2020 Dec 10;22(12):2081-2088. Epub 2020 Aug 10.

Institute of Human Genetics, Medical University of Innsbruck, Innsbruck, Austria.

Purpose: Biallelic germline mismatch repair (MMR) gene pathogenic variants (PVs) cause constitutional MMR deficiency (CMMRD), a highly penetrant childhood cancer syndrome phenotypically overlapping with neurofibromatosis type 1 (NF1). CMMRD testing in suspected NF1 children without NF1/SPRED1 PVs enables inclusion of CMMRD positives into monitoring programs prior to tumor onset. However, testing is associated with potential harms and the prevalence of CMMRD among these children is unknown.

Methods: Using a simple and scalable microsatellite instability (MSI) assay of non-neoplastic leukocyte DNA to detect CMMRD, we retrospectively screened >700 children suspected of sporadic NF1 but lacking NF1/SPRED1 PVs.

Results: For three of seven MSI-positive patients germline MMR gene PVs confirmed the diagnosis of CMMRD. Founder variants NM_000535.5(PMS2):c.736_741delinsTGTGTGTGAAG, prevalent in Europe and North America, and NM_000179.2(MSH6):c.10C>G, affecting 1:400 French Canadians, represented two of five PVs. The prevalence of CMMRD was 3/735 (0.41%, 95% confidence interval [CI]: 0.08-1.19%).

Conclusion: Our empirical data provide reliable numbers for genetic counseling and confirm previous prevalence estimations, on which Care for CMMRD consortium guidelines are based. These advocate CMMRD testing of preselected patients rather than offering reflex testing to all suspected sporadic NF1 children lacking NF1/SPRED1 PVs. The possibility of founder effects should be considered alongside these testing guidelines.
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http://dx.doi.org/10.1038/s41436-020-0925-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7708300PMC
December 2020

AG-exclusion zone revisited: Lessons to learn from 91 intronic NF1 3' splice site mutations outside the canonical AG-dinucleotides.

Hum Mutat 2020 Jun 11;41(6):1145-1156. Epub 2020 Mar 11.

Department of Genetics, University of Alabama at Birmingham, Birmingham, Alabama.

Uncovering frequent motives of action by which variants impair 3' splice site (3'ss) recognition and selection is essential to improve our understanding of this complex process. Through several mini-gene experiments, we demonstrate that the pyrimidine (Y) to purine (R) transversion NM_000267.3(NF1):c.1722-11T>G, although expected to weaken the polypyrimidine tract, causes exon skipping primarily by introducing a novel AG in the AG-exclusion zone (AGEZ) between the authentic 3'ss AG and the branch point. Evaluation of 90 additional noncanonical intronic NF1 3'ss mutations confirmed that 63% of all mutations and 89% (49/55) of the single-nucleotide variants upstream of positions -3 interrupt the AGEZ. Of these AGEZ-interrupting mutations, 24/49 lead to exon skipping suggesting that absence of AG in this region is necessary for accurate 3'ss selection already in the initial steps of splicing. The analysis of 91 noncanonical NF1 3'ss mutations also shows that 90% either introduce a novel AG in the AGEZ, cause a Y>R transversion at position -3 or remove ≥2 Ys in the AGEZ. We confirm in a validation cohort that these three motives distinguish spliceogenic from splice-neutral variants with 85% accuracy and, therefore, are generally applicable to select among variants of unknown significance those likely to affect splicing.
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http://dx.doi.org/10.1002/humu.24005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7317903PMC
June 2020

Clinical spectrum of individuals with pathogenic NF1 missense variants affecting p.Met1149, p.Arg1276, and p.Lys1423: genotype-phenotype study in neurofibromatosis type 1.

Authors:
Magdalena Koczkowska Tom Callens Yunjia Chen Alicia Gomes Alesha D Hicks Angela Sharp Eric Johns Kim Armfield Uhas Linlea Armstrong Katherine Armstrong Bosanko Dusica Babovic-Vuksanovic Laura Baker Donald G Basel Mario Bengala James T Bennett Chelsea Chambers Lola K Clarkson Maurizio Clementi Fanny M Cortés Mitch Cunningham M Daniela D'Agostino Martin B Delatycki Maria C Digilio Laura Dosa Silvia Esposito Stephanie Fox Mary-Louise Freckmann Christine Fauth Teresa Giugliano Sandra Giustini Allison Goetsch Yael Goldberg Robert S Greenwood Cristin Griffis Karen W Gripp Punita Gupta Eric Haan Rachel K Hachen Tamara L Haygarth Concepción Hernández-Chico Katelyn Hodge Robert J Hopkin Louanne Hudgins Sandra Janssens Kory Keller Geraldine Kelly-Mancuso Aaina Kochhar Bruce R Korf Andrea M Lewis Jan Liebelt Angie Lichty Robert H Listernick Michael J Lyons Isabelle Maystadt Mayra Martinez Ojeda Carey McDougall Lesley K McGregor Daniela Melis Nancy Mendelsohn Malgorzata J M Nowaczyk June Ortenberg Karin Panzer John G Pappas Mary Ella Pierpont Giulio Piluso Valentina Pinna Eniko K Pivnick Dinel A Pond Cynthia M Powell Caleb Rogers Noa Ruhrman Shahar S Lane Rutledge Veronica Saletti Sarah A Sandaradura Claudia Santoro Ulrich A Schatz Allison Schreiber Daryl A Scott Elizabeth A Sellars Ruth Sheffer Elizabeth Siqveland John M Slopis Rosemarie Smith Alberto Spalice David W Stockton Haley Streff Amy Theos Gail E Tomlinson Grace Tran Pamela L Trapane Eva Trevisson Nicole J Ullrich Jenneke Van den Ende Samantha A Schrier Vergano Stephanie E Wallace Michael F Wangler David D Weaver Kaleb H Yohay Elaine Zackai Jonathan Zonana Vickie Zurcher Kathleen B M Claes Marica Eoli Yolanda Martin Katharina Wimmer Alessandro De Luca Eric Legius Ludwine M Messiaen

Hum Mutat 2020 01 26;41(1):299-315. Epub 2019 Oct 26.

Department of Genetics, University of Alabama at Birmingham, Birmingham, Albama.

We report 281 individuals carrying a pathogenic recurrent NF1 missense variant at p.Met1149, p.Arg1276, or p.Lys1423, representing three nontruncating NF1 hotspots in the University of Alabama at Birmingham (UAB) cohort, together identified in 1.8% of unrelated NF1 individuals. About 25% (95% confidence interval: 20.5-31.2%) of individuals heterozygous for a pathogenic NF1 p.Met1149, p.Arg1276, or p.Lys1423 missense variant had a Noonan-like phenotype, which is significantly more compared with the "classic" NF1-affected cohorts (all p < .0001). Furthermore, p.Arg1276 and p.Lys1423 pathogenic missense variants were associated with a high prevalence of cardiovascular abnormalities, including pulmonic stenosis (all p < .0001), while p.Arg1276 variants had a high prevalence of symptomatic spinal neurofibromas (p < .0001) compared with "classic" NF1-affected cohorts. However, p.Met1149-positive individuals had a mild phenotype, characterized mainly by pigmentary manifestations without externally visible plexiform neurofibromas, symptomatic spinal neurofibromas or symptomatic optic pathway gliomas. As up to 0.4% of unrelated individuals in the UAB cohort carries a p.Met1149 missense variant, this finding will contribute to more accurate stratification of a significant number of NF1 individuals. Although clinically relevant genotype-phenotype correlations are rare in NF1, each affecting only a small percentage of individuals, together they impact counseling and management of a significant number of the NF1 population.
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http://dx.doi.org/10.1002/humu.23929DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6973139PMC
January 2020

Child Neurology: Spastic paraparesis and dystonia with a novel mutation.

Neurology 2019 09;93(11):510-514

From the Departments of Neurology (M.D., D.G.S.) and Genetics (L.M., B.R.K.) and Division of Pediatric Neurology, Department of Pediatrics (S.R.), University of Alabama at Birmingham; and HudsonAlpha Institute for Biotechnology (G.M.C., M.D.A.), Huntsville, AL.

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http://dx.doi.org/10.1212/WNL.0000000000008089DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6746208PMC
September 2019

First International Conference on RASopathies and Neurofibromatoses in Asia: Identification and advances of new therapeutics.

Am J Med Genet A 2019 06 25;179(6):1091-1097. Epub 2019 Mar 25.

Institute of Medical Genetics, Cardiff University, Cardiff, United Kingdom.

The neurofibromatoses, which include neurofibromatosis type I (NF1), neurofibromatosis type II (NF2), and schwannomatosis, are a group of syndromes characterized by tumor growth in the nervous system. The RASopathies are a group of syndromes caused by germline mutations in genes that encode components of the RAS/mitogen-activated protein kinase (MAPK) pathway. The RASopathies include NF1, Noonan syndrome, Noonan syndrome with multiple lentigines, Costello syndrome, cardio-facio-cutaneous syndrome, Legius syndrome, capillary malformation arterio-venous malformation syndrome, and SYNGAP1 autism. Due to their common underlying pathogenetic etiology, all these syndromes have significant phenotypic overlap of which one common feature include a predisposition to tumors, which may be benign or malignant. Together as a group, they represent one of the most common multiple congenital anomaly syndromes estimating to affect approximately one in 1000 individuals worldwide. The subcontinent of India represents one of the largest populations in the world, yet remains underserved from an aspect of clinical genetics services. In an effort to bridge this gap, the First International Conference on RASopathies and Neurofibromatoses in Asia: Identification and Advances of New Therapeutics was held in Kochi, Kerala, India. These proceedings chronicle this timely and topical international symposium directed at discussing the best practices and therapies for individuals with neurofibromatoses and RASopathies.
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http://dx.doi.org/10.1002/ajmg.a.61125DOI Listing
June 2019

From process to progress-2017 International Conference on Neurofibromatosis 1, Neurofibromatosis 2 and Schwannomatosis.

Am J Med Genet A 2019 06 25;179(6):1098-1106. Epub 2019 Mar 25.

Division of Neuroscience, Oregon National Primate Research Center, and Department of Cell, Developmental and Cancer Biology, Oregon Health & Science University, Portland, Oregon.

The neurofibromatoses are inherited, tumor suppressor disorders that are characterized by multiple, benign peripheral nerve sheath tumors and other nervous system tumors. Each disease is associated with a distinct genetic mutation and with a different pathogenesis and clinical course. Neurofibromatosis 1 (NF1) is common and epitomized by multiple neurofibromas with widespread complications. NF2 and schwannomatosis are rare diseases that are typified by multiple schwannomas that are particularly painful in people with schwannomatosis. Since 1985, the Children's Tumor Foundation (formerly the National Neurofibromatosis Foundation) has hosted an international Neurofibromatosis Conference, bringing together international participants who are focused on NF research and clinical care. The 2017 Conference, held in Washington, DC, was among the largest gatherings of NF researchers to date and included presentations from clinicians and basic scientists, highlighting new data regarding the molecular and cellular mechanisms underlying each of these diseases as well as results from clinical studies and clinical trials. This article summarizes the findings presented at the meeting and represents the current state-of-the art for NF research.
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http://dx.doi.org/10.1002/ajmg.a.61112DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6488427PMC
June 2019

Ultra-deep amplicon sequencing indicates absence of low-grade mosaicism with normal cells in patients with type-1 NF1 deletions.

Hum Genet 2019 Jan 26;138(1):73-81. Epub 2018 Nov 26.

Institute of Human Genetics, University of Ulm, Albert-Einstein-Allee 11, 89081, Ulm, Germany.

Different types of large NF1 deletion are distinguishable by breakpoint location and potentially also by the frequency of mosaicism with normal cells lacking the deletion. However, low-grade mosaicism with fewer than 10% normal cells has not yet been excluded for all NF1 deletion types since it is impossible to assess by the standard techniques used to identify such deletions, including MLPA and array analysis. Here, we used ultra-deep amplicon sequencing to investigate the presence of normal cells in the blood of 20 patients with type-1 NF1 deletions lacking mosaicism according to MLPA. The ultra-deep sequencing entailed the screening of 96 amplicons for heterozygous SNVs located within the NF1 deletion region. DNA samples from three previously identified patients with type-2 NF1 deletions and low-grade mosaicism with normal cells as determined by FISH or microsatellite marker analysis were used to validate our methodology. In these type-2 NF1 deletion samples, proportions of 5.3%, 6.6% and 15.0% normal cells, respectively, were detected by ultra-deep amplicon sequencing. However, using this highly sensitive method, none of the 20 patients with type-1 NF1 deletions included in our analysis exhibited low-grade mosaicism with normal cells in blood, thereby supporting the view that the vast majority of type-1 deletions are germline deletions.
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http://dx.doi.org/10.1007/s00439-018-1961-5DOI Listing
January 2019

Constitutional mismatch repair deficiency as a differential diagnosis of neurofibromatosis type 1: consensus guidelines for testing a child without malignancy.

J Med Genet 2019 02 10;56(2):53-62. Epub 2018 Nov 10.

Division of Human Genetics, Medical University Innsbruck, Innsbruck, Austria.

Constitutional mismatch repair deficiency (CMMRD) is a rare childhood cancer predisposition syndrome caused by biallelic germline mutations in one of four mismatch-repair genes. Besides very high tumour risks, CMMRD phenotypes are often characterised by the presence of signs reminiscent of neurofibromatosis type 1 (NF1). Because NF1 signs may be present prior to tumour onset, CMMRD is a legitimate differential diagnosis in an otherwise healthy child suspected to have NF1/Legius syndrome without a detectable underlying / germline mutation. However, no guidelines indicate when to counsel and test for CMMRD in this setting. Assuming that CMMRD is rare in these patients and that expected benefits of identifying CMMRD prior to tumour onset should outweigh potential harms associated with CMMRD counselling and testing in this setting, we aimed at elaborating a strategy to preselect, among children suspected to have NF1/Legius syndrome without a causative / mutation and no overt malignancy, those children who have a higher probability of having CMMRD. At an interdisciplinary workshop, we discussed estimations of the frequency of CMMRD as a differential diagnosis of NF1 and potential benefits and harms of CMMRD counselling and testing in a healthy child with no malignancy. Preselection criteria and strategies for counselling and testing were developed and reviewed in two rounds of critical revisions. Existing diagnostic CMMRD criteria were adapted to serve as a guideline as to when to consider CMMRD as differential diagnosis of NF1/Legius syndrome. In addition, counselling and testing strategies are suggested to minimise potential harms.
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http://dx.doi.org/10.1136/jmedgenet-2018-105664DOI Listing
February 2019

Genetically engineered minipigs model the major clinical features of human neurofibromatosis type 1.

Commun Biol 2018 2;1:158. Epub 2018 Oct 2.

Recombinetics Inc., 1246 University Avenue W., Suite 301, St. Paul, MN, 55104, USA.

Neurofibromatosis Type 1 (NF1) is a genetic disease caused by mutations in (). NF1 patients present with a variety of clinical manifestations and are predisposed to cancer development. Many NF1 animal models have been developed, yet none display the spectrum of disease seen in patients and the translational impact of these models has been limited. We describe a minipig model that exhibits clinical hallmarks of NF1, including café au lait macules, neurofibromas, and optic pathway glioma. Spontaneous loss of heterozygosity is observed in this model, a phenomenon also described in NF1 patients. Oral administration of a mitogen-activated protein kinase/extracellular signal-regulated kinase inhibitor suppresses Ras signaling. To our knowledge, this model provides an unprecedented opportunity to study the complex biology and natural history of NF1 and could prove indispensable for development of imaging methods, biomarkers, and evaluation of safety and efficacy of NF1-targeted therapies.
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http://dx.doi.org/10.1038/s42003-018-0163-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6168575PMC
October 2018

Correction: Expanding the clinical phenotype of individuals with a 3-bp in-frame deletion of the NF1 gene (c.2970_2972del): an update of genotype-phenotype correlation.

Genet Med 2019 03;21(3):764-765

Department of Genetics, University of Alabama at Birmingham, Birmingham, AL, USA.

A correction has been published to this Article. The PDF and HTML have been updated accordingly.
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http://dx.doi.org/10.1038/s41436-018-0326-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7608433PMC
March 2019

Expanding the clinical phenotype of individuals with a 3-bp in-frame deletion of the NF1 gene (c.2970_2972del): an update of genotype-phenotype correlation.

Genet Med 2019 04 7;21(4):867-876. Epub 2018 Sep 7.

Department of Genetics, University of Alabama at Birmingham, Birmingham, Alabama, USA.

Purpose: Neurofibromatosis type 1 (NF1) is characterized by a highly variable clinical presentation, but almost all NF1-affected adults present with cutaneous and/or subcutaneous neurofibromas. Exceptions are individuals heterozygous for the NF1 in-frame deletion, c.2970_2972del (p.Met992del), associated with a mild phenotype without any externally visible tumors.

Methods: A total of 135 individuals from 103 unrelated families, all carrying the constitutional NF1 p.Met992del pathogenic variant and clinically assessed using the same standardized phenotypic checklist form, were included in this study.

Results: None of the individuals had externally visible plexiform or histopathologically confirmed cutaneous or subcutaneous neurofibromas. We did not identify any complications, such as symptomatic optic pathway gliomas (OPGs) or symptomatic spinal neurofibromas; however, 4.8% of individuals had nonoptic brain tumors, mostly low-grade and asymptomatic, and 38.8% had cognitive impairment/learning disabilities. In an individual with the NF1 constitutional c.2970_2972del and three astrocytomas, we provided proof that all were NF1-associated tumors given loss of heterozygosity at three intragenic NF1 microsatellite markers and c.2970_2972del.

Conclusion: We demonstrate that individuals with the NF1 p.Met992del pathogenic variant have a mild NF1 phenotype lacking clinically suspected plexiform, cutaneous, or subcutaneous neurofibromas. However, learning difficulties are clearly part of the phenotypic presentation in these individuals and will require specialized care.
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http://dx.doi.org/10.1038/s41436-018-0269-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6752285PMC
April 2019

Germline and Somatic Alterations Are Linked to Increased HER2 Expression in Breast Cancer.

Cancer Prev Res (Phila) 2018 10 13;11(10):655-664. Epub 2018 Aug 13.

Wayne State University, Detroit, Michigan.

germline mutation predisposes to breast cancer. mutations have also been proposed as oncogenic drivers in sporadic breast cancers. To understand the genomic and histologic characteristics of these breast cancers, we analyzed the tumors with germline mutations and also examined the genomic and proteomic profiles of unselected tumors. Among 14 breast cancer specimens from 13 women affected with neurofibromatosis type 1 (NF1), 9 samples (NF + BrCa) underwent genomic copy number (CN) and targeted sequencing analysis. Mutations of were identified in two samples and were in three. No mutation was detected in , and HER2 (ErbB2) overexpression was detected by IHC in 69.2% (9/13) of the tumors. CN gain/amplification of was detected in 4 of 9 with DNA analysis. By evaluating HER2 expression and alterations in unselected invasive breast cancers in TCGA datasets, we discovered that among samples with CN gain/amplification, the HER2 mRNA and protein expression were much more pronounced in -mutated/deleted samples in comparison with -unaltered samples. This finding suggests a synergistic interplay between these two genes, potentially driving the development of breast cancer harboring mutation and CN gain/amplification. gene loss of heterozygosity was observed in 4 of 9 NF + BrCa samples. appeared to have more CN gain in NF + BrCa and exhibited increased mRNA expression in TCGA -altered samples. .
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http://dx.doi.org/10.1158/1940-6207.CAPR-18-0072DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6905494PMC
October 2018

Extreme clustering of type-1 NF1 deletion breakpoints co-locating with G-quadruplex forming sequences.

Hum Genet 2018 Jul 10;137(6-7):511-520. Epub 2018 Jul 10.

Institute of Human Genetics, University of Ulm, Albert-Einstein-Allee 11, 89081, Ulm, Germany.

The breakpoints of type-1 NF1 deletions encompassing 1.4-Mb are located within NF1-REPa and NF1-REPc, which exhibit a complex structure comprising different segmental duplications in direct and inverted orientation. Here, we systematically assessed the proportion of type-1 NF1 deletions caused by nonallelic homologous recombination (NAHR) and those mediated by other mutational mechanisms. To this end, we analyzed 236 unselected type-1 deletions and observed that 179 of them (75.8%) had breakpoints located within the NAHR hotspot PRS2, whereas 39 deletions (16.5%) had breakpoints located within PRS1. Sixteen deletions exhibited breakpoints located outside of these NAHR hotspots but were also mediated by NAHR. Taken together, the breakpoints of 234 (99.2%) of the 236 type-1 NF1 deletions were mediated by NAHR. Thus, NF1-REPa and NF1-REPc are strongly predisposed to recurrent NAHR, the main mechanism underlying type-1 NF1 deletions. We also observed a non-random overlap between type-1 NF1-deletion breakpoints and G-quadruplex forming sequences (GQs) as well as regions flanking PRDM9 binding-sites. These findings imply that GQs and PRDM9 binding-sites contribute to the clustering of type-1 deletion breakpoints. The co-location of both types of sequence was at its highest within PRS2, indicative of their synergistic contribution to the greatly increased NAHR activity within this hotspot.
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http://dx.doi.org/10.1007/s00439-018-1904-1DOI Listing
July 2018

High-Throughput Tabular Data Processor - Platform independent graphical tool for processing large data sets.

PLoS One 2018 12;13(2):e0192858. Epub 2018 Feb 12.

Department of Biology and Pharmaceutical Botany, Medical University of Gdansk, Gdansk, Poland.

High-throughput technologies generate considerable amount of data which often requires bioinformatic expertise to analyze. Here we present High-Throughput Tabular Data Processor (HTDP), a platform independent Java program. HTDP works on any character-delimited column data (e.g. BED, GFF, GTF, PSL, WIG, VCF) from multiple text files and supports merging, filtering and converting of data that is produced in the course of high-throughput experiments. HTDP can also utilize itemized sets of conditions from external files for complex or repetitive filtering/merging tasks. The program is intended to aid global, real-time processing of large data sets using a graphical user interface (GUI). Therefore, no prior expertise in programming, regular expression, or command line usage is required of the user. Additionally, no a priori assumptions are imposed on the internal file composition. We demonstrate the flexibility and potential of HTDP in real-life research tasks including microarray and massively parallel sequencing, i.e. identification of disease predisposing variants in the next generation sequencing data as well as comprehensive concurrent analysis of microarray and sequencing results. We also show the utility of HTDP in technical tasks including data merge, reduction and filtering with external criteria files. HTDP was developed to address functionality that is missing or rudimentary in other GUI software for processing character-delimited column data from high-throughput technologies. Flexibility, in terms of input file handling, provides long term potential functionality in high-throughput analysis pipelines, as the program is not limited by the currently existing applications and data formats. HTDP is available as the Open Source software (https://github.com/pmadanecki/htdp).
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0192858PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5809091PMC
April 2018

Genotype-Phenotype Correlation in NF1: Evidence for a More Severe Phenotype Associated with Missense Mutations Affecting NF1 Codons 844-848.

Am J Hum Genet 2018 01 28;102(1):69-87. Epub 2017 Dec 28.

Department of Genetics, University of Alabama at Birmingham, Birmingham, AL 35294, USA. Electronic address:

Neurofibromatosis type 1 (NF1), a common genetic disorder with a birth incidence of 1:2,000-3,000, is characterized by a highly variable clinical presentation. To date, only two clinically relevant intragenic genotype-phenotype correlations have been reported for NF1 missense mutations affecting p.Arg1809 and a single amino acid deletion p.Met922del. Both variants predispose to a distinct mild NF1 phenotype with neither externally visible cutaneous/plexiform neurofibromas nor other tumors. Here, we report 162 individuals (129 unrelated probands and 33 affected relatives) heterozygous for a constitutional missense mutation affecting one of five neighboring NF1 codons-Leu844, Cys845, Ala846, Leu847, and Gly848-located in the cysteine-serine-rich domain (CSRD). Collectively, these recurrent missense mutations affect ∼0.8% of unrelated NF1 mutation-positive probands in the University of Alabama at Birmingham (UAB) cohort. Major superficial plexiform neurofibromas and symptomatic spinal neurofibromas were more prevalent in these individuals compared with classic NF1-affected cohorts (both p < 0.0001). Nearly half of the individuals had symptomatic or asymptomatic optic pathway gliomas and/or skeletal abnormalities. Additionally, variants in this region seem to confer a high predisposition to develop malignancies compared with the general NF1-affected population (p = 0.0061). Our results demonstrate that these NF1 missense mutations, although located outside the GAP-related domain, may be an important risk factor for a severe presentation. A genotype-phenotype correlation at the NF1 region 844-848 exists and will be valuable in the management and genetic counseling of a significant number of individuals.
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http://dx.doi.org/10.1016/j.ajhg.2017.12.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5777934PMC
January 2018

Breast cancer risk and germline genomic profiling of women with neurofibromatosis type 1 who developed breast cancer.

Genes Chromosomes Cancer 2018 01 30;57(1):19-27. Epub 2017 Sep 30.

Molecular Medicine and Genetics, Wayne State University, Detroit, Michigan.

NF1 mutations predispose to neurofibromatosis type 1 (NF1) and women with NF1 have a moderately elevated risk for breast cancer, especially under age 50. Germline genomic analysis may better define the risk so screening and prevention can be applied to the individuals who benefit the most. Survey conducted in several neurofibromatosis clinics in the United States has demonstrated a 17.2% lifetime risk of breast cancer in women affected with NF1. Cumulated risk to age 50 is estimated to be 9.27%. For genomic profiling, fourteen women with NF1 and a history of breast cancer were recruited and underwent whole exome sequencing (WES), targeted genomic DNA based and RNA-based analysis of the NF1 gene. Deleterious NF1 pathogenic variants were identified in each woman. Frameshift mutations because of deletion/duplication/complex rearrangement were found in 50% (7/14) of the cases, nonsense mutations in 21% (3/14), in-frame splice mutations in 21% (3/14), and one case of missense mutation (7%, 1/14). No deleterious mutation was found in the following high/moderate-penetrance breast cancer genes: ATM, BRCA1, BRCA2, BARD1, BRIP1, CDH1, CHEK2, FANCC, MRE11A, NBN, PALB2, PTEN, RAD50, RAD51C, TP53, and STK11. Twenty-five rare or common variants in cancer related genes were discovered and may have contributed to the breast cancers in these individuals. Breast cancer predisposition modifiers in women with NF1 may involve a great variety of molecular and cellular functions.
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http://dx.doi.org/10.1002/gcc.22503DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7771338PMC
January 2018

panelcn.MOPS: Copy-number detection in targeted NGS panel data for clinical diagnostics.

Hum Mutat 2017 07 16;38(7):889-897. Epub 2017 May 16.

Division of Human Genetics, Medical University Innsbruck, Innsbruck, Austria.

Targeted next-generation-sequencing (NGS) panels have largely replaced Sanger sequencing in clinical diagnostics. They allow for the detection of copy-number variations (CNVs) in addition to single-nucleotide variants and small insertions/deletions. However, existing computational CNV detection methods have shortcomings regarding accuracy, quality control (QC), incidental findings, and user-friendliness. We developed panelcn.MOPS, a novel pipeline for detecting CNVs in targeted NGS panel data. Using data from 180 samples, we compared panelcn.MOPS with five state-of-the-art methods. With panelcn.MOPS leading the field, most methods achieved comparably high accuracy. panelcn.MOPS reliably detected CNVs ranging in size from part of a region of interest (ROI), to whole genes, which may comprise all ROIs investigated in a given sample. The latter is enabled by analyzing reads from all ROIs of the panel, but presenting results exclusively for user-selected genes, thus avoiding incidental findings. Additionally, panelcn.MOPS offers QC criteria not only for samples, but also for individual ROIs within a sample, which increases the confidence in called CNVs. panelcn.MOPS is freely available both as R package and standalone software with graphical user interface that is easy to use for clinical geneticists without any programming experience. panelcn.MOPS combines high sensitivity and specificity with user-friendliness rendering it highly suitable for routine clinical diagnostics.
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http://dx.doi.org/10.1002/humu.23237DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5518446PMC
July 2017

Predicting neurofibromatosis type 1 risk among children with isolated café-au-lait macules.

J Am Acad Dermatol 2017 Jun 18;76(6):1077-1083.e3. Epub 2017 Mar 18.

Medical Genomics Laboratory, Department of Genetics, University of Alabama, Birmingham, Alabama.

Background: Although isolated cafe-au-lait macules (CALMs) are a common skin finding, they are an early feature of neurofibromatosis type 1 (NF1).

Objective: We sought to develop an algorithm determining the risk of children with CALMs to have constitutional NF1.

Methods: We conducted a retrospective study of patients with isolated CALMs. Diagnosis of NF1 was based on detecting NF1 mutation in blood or fulfilling clinical criteria.

Results: In all, 170 of 419 (41%) and 21 of 86 (24%) children with isolated CALMs who underwent molecular testing and clinical follow-up, respectively, were given a diagnosis of NF1. Presence of fewer than 6 CALMs at presentation or atypical CALMs was associated with not having NF1 (P < .001). An algorithm based on age, CALMs number, and presence of atypical macules predicted NF1 in both cohorts. According to the algorithm, children older than 29 months with at least 1 atypical CALM or less than 6 CALMs have a 0.9% (95% confidence interval 0%-2.6%) risk for constitutional NF1 whereas children younger than 29 months with 6 or more CALMs have a high risk (80.4%, 95% confidence interval 74.6%-86.2%).

Limitations: The study was designed to detect constitutional NF1 and not NF1 in mosaic form.

Conclusions: A simple algorithm enables categorization of children with isolated CALMs as being at low or high risk for having NF1.
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http://dx.doi.org/10.1016/j.jaad.2017.02.027DOI Listing
June 2017

Alternative outcomes of pathogenic complex somatic structural variations in the genomes of NF1 and NF2 patients.

Neurogenetics 2017 Jul 11;18(3):169-174. Epub 2017 Mar 11.

Medical Genomics Laboratory, Department of Genetics, University of Alabama at Birmingham, Birmingham, AL, USA.

Multiplex ligation-dependent probe amplification (MLPA) has been widely used to identify copy-number variations (CNVs), but MLPA's sensitivity and specificity in mosaic CNV detection are largely unknown. Here, we present two mosaic deletions identified by MLPA as NF1 deletion of exons 17-21 and NF2 deletion of exons 9-10. Through cDNA analysis, genomic breakpoint-spanning PCR and Sanger sequencing, we found however both NF1 and NF2 deletions are each composed of two consecutive deletions, which cannot be differentiated by MLPA. Importantly, these consecutive deletions are most likely originating from a single genomic rearrangement and have been preserved independently in different populations of cells.
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http://dx.doi.org/10.1007/s10048-017-0512-xDOI Listing
July 2017

Analysis of copy number variants in 11 pairs of monozygotic twins with neurofibromatosis type 1.

Am J Med Genet A 2017 Mar 14;173(3):647-653. Epub 2016 Nov 14.

Division of Human Genetics, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio.

Phenotypic variability among individuals with neurofibromatosis type 1 (NF1) has long been a challenge for clinicians and an enigma for researchers. Members of the same family and even identical twins with NF1 often demonstrate variable disease expression. Many mechanisms for this variability have been proposed. We have performed an exploratory study of copy number variants (CNVs) as a possible source of phenotypic variability in NF1. We enrolled 11 pairs of monozygotic (MZ) twins with NF1 and their parents, catalogued their clinical characteristics, and utilized a single nucleotide polymorphism (SNP) microarray to identify CNVs in blood and saliva. The 11 twin pairs showed high concordance for presence and number of café-au-lait spots, cutaneous neurofibromas, IQ, and ADHD. They were more likely to be discordant for optic pathway glioma, plexiform neurofibromas, skeletal manifestations, and malignancy. Microarray analysis identified a total of 81 CNVs meeting our conservative criteria, 37 of which overlap known genes. Of interest, three CNVs were previously unreported. Microarray analysis failed to ascertain any CNV differences within twin pairs, between twins and parents, or between tissues in any one individual. Results of this small pilot study did not demonstrate any de novo CNV events in our MZ twin pairs, nor were de novo CNVs overrepresented in these individuals with NF1. A much larger sample size would be needed to form any conclusions about the role of CNVs in NF1 variable expressivity. Alternative explanations for discordant phenotypes include epigenetic changes, smaller genetic alterations, or environmental factors. © 2016 Wiley Periodicals, Inc.
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http://dx.doi.org/10.1002/ajmg.a.38058DOI Listing
March 2017

Mice with missense and nonsense NF1 mutations display divergent phenotypes compared with human neurofibromatosis type I.

Dis Model Mech 2016 07 2;9(7):759-67. Epub 2016 Jun 2.

Department of Genetics, The University of Alabama at Birmingham, Birmingham, AL 35294, USA

Neurofibromatosis type 1 (NF1) is a common genetic disorder characterized by the occurrence of nerve sheath tumors and considerable clinical heterogeneity. Some translational studies have been limited by the lack of animal models available for assessing patient-specific mutations. In order to test therapeutic approaches that might restore function to the mutated gene or gene product, we developed mice harboring NF1 patient-specific mutations including a nonsense mutation (c.2041C>T; p.Arg681*) and a missense mutation (c.2542G>C; p.Gly848Arg). The latter is associated with the development of multiple plexiform neurofibromas along spinal nerve roots. We demonstrate that the human nonsense NF1(Arg681*) and missense NF1(Gly848Arg) mutations have different effects on neurofibromin expression in the mouse and each recapitulates unique aspects of the NF1 phenotype, depending upon the genetic context when assessed in the homozygous state or when paired with a conditional knockout allele. Whereas the missense Nf1(Gly848Arg) mutation fails to produce an overt phenotype in the mouse, animals homozygous for the nonsense Nf1(Arg681*) mutation are not viable. Mice with one Nf1(Arg681*) allele in combination with a conditional floxed Nf1 allele and the DhhCre transgene (Nf1(4F/Arg681*); DhhCre) display disorganized nonmyelinating axons and neurofibromas along the spinal column, which leads to compression of the spinal cord and paralysis. This model will be valuable for preclinical testing of novel nonsense suppression therapies using drugs to target in-frame point mutations that create premature termination codons in individuals with NF1.
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http://dx.doi.org/10.1242/dmm.025783DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4958313PMC
July 2016

Interaction between a Domain of the Negative Regulator of the Ras-ERK Pathway, SPRED1 Protein, and the GTPase-activating Protein-related Domain of Neurofibromin Is Implicated in Legius Syndrome and Neurofibromatosis Type 1.

J Biol Chem 2016 Feb 3;291(7):3124-34. Epub 2015 Dec 3.

From the Department of Microbiology and Immunology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan,

Constitutional heterozygous loss-of-function mutations in the SPRED1 gene cause a phenotype known as Legius syndrome, which consists of symptoms of multiple café-au-lait macules, axillary freckling, learning disabilities, and macrocephaly. Legius syndrome resembles a mild neurofibromatosis type 1 (NF1) phenotype. It has been demonstrated that SPRED1 functions as a negative regulator of the Ras-ERK pathway and interacts with neurofibromin, the NF1 gene product. However, the molecular details of this interaction and the effects of the mutations identified in Legius syndrome and NF1 on this interaction have not yet been investigated. In this study, using a yeast two-hybrid system and an immunoprecipitation assay in HEK293 cells, we found that the SPRED1 EVH1 domain interacts with the N-terminal 16 amino acids and the C-terminal 20 amino acids of the GTPase-activating protein (GAP)-related domain (GRD) of neurofibromin, which form two crossing α-helix coils outside the GAP domain. These regions have been shown to be dispensable for GAP activity and are not present in p120(GAP). Several mutations in these N- and C-terminal regions of the GRD in NF1 patients and pathogenic missense mutations in the EVH1 domain of SPRED1 in Legius syndrome reduced the binding affinity between the EVH1 domain and the GRD. EVH1 domain mutations with reduced binding to the GRD also disrupted the ERK suppression activity of SPRED1. These data clearly demonstrate that SPRED1 inhibits the Ras-ERK pathway by recruiting neurofibromin to Ras through the EVH1-GRD interaction, and this study also provides molecular basis for the pathogenic mutations of NF1 and Legius syndrome.
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http://dx.doi.org/10.1074/jbc.M115.703710DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4751360PMC
February 2016

Fine mapping of meiotic NAHR-associated crossovers causing large NF1 deletions.

Hum Mol Genet 2016 Feb 27;25(3):484-96. Epub 2015 Nov 27.

Institute of Human Genetics, University of Ulm, 89081 Ulm, Germany,

Large deletions encompassing the NF1 gene and its flanking regions belong to the group of genomic disorders caused by copy number changes that are mediated by the local genomic architecture. Although nonallelic homologous recombination (NAHR) is known to be a major mutational mechanism underlying such genomic copy number changes, the sequence determinants of NAHR location and frequency are still poorly understood since few high-resolution mapping studies of NAHR hotspots have been performed to date. Here, we have characterized two NAHR hotspots, PRS1 and PRS2, separated by 20 kb and located within the low-copy repeats NF1-REPa and NF1-REPc, which flank the human NF1 gene region. High-resolution mapping of the crossover sites identified in 78 type 1 NF1 deletions mediated by NAHR indicated that PRS2 is a much stronger NAHR hotspot than PRS1 since 80% of these deletions exhibited crossovers within PRS2, whereas 20% had crossovers within PRS1. The identification of the most common strand exchange regions of these 78 deletions served to demarcate the cores of the PRS1 and PRS2 hotspots encompassing 1026 and 1976 bp, respectively. Several sequence features were identified that may influence hotspot intensity and direct the positional preference of NAHR to the hotspot cores. These features include regions of perfect sequence identity encompassing 700 bp at the hotspot core, the presence of PRDM9 binding sites perfectly matching the consensus motif for the most common PRDM9 variant, specific pre-existing patterns of histone modification and open chromatin conformations that are likely to facilitate PRDM9 binding.
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http://dx.doi.org/10.1093/hmg/ddv487DOI Listing
February 2016

Report of a patient with a constitutional missense mutation in SMARCB1, Coffin-Siris phenotype, and schwannomatosis.

Am J Med Genet A 2015 Dec 14;167A(12):3186-91. Epub 2015 Sep 14.

Division of Pediatric Hematology and Oncology, University of Minnesota Masonic Children's Hospital, Minneapolis, Minnesota.

We report a patient with a constitutional missense mutation in SMARCB1, Coffin-Siris Syndrome (CSS), and schwannomatosis. CSS is a rare congenital syndrome with characteristic clinical findings. This thirty-three-year-old man was diagnosed early in life with the constellation of moderate intellectual disability, hypotonia, mild microcephaly, coarse facies, wide mouth with full lips, hypoplasia of the digits, and general hirsutism. At age 26, he was found to have schwannomatosis after presenting with acute spinal cord compression. Blood and tissue analysis of multiple subsequent schwannoma resections revealed a germline missense mutation of SMARCB1, acquired loss of 22q including SMARCB1 and NF2 and mutation of the remaining NF2 wild-type allele-thus completing the four-hit, three-event mechanism associated with schwannomatosis. Variations in five genes have been associated with the Coffin-Siris phenotype: ARID1A, ARID1B, SMARCA4, SMARCB1, and SMARCE1. Of these genes, SMARCB1 has a well-established association with schwannomatosis and malignancy. This is the first report of a patient with a constitutional missense mutation of SMARCB1 resulting in CSS and subsequent development of schwannomatosis. This finding demonstrates that a SMARCB1 mutation may be the initial "hit" (constitutional) for a genetic disorder with subsequent risk of developing schwannomas and other malignancies, and raises the possibility that other patients with switch/sucrose non-fermenting (SWI/SNF) mutations may be at increased risk for tumors.
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http://dx.doi.org/10.1002/ajmg.a.37356DOI Listing
December 2015

Paraspinal neurofibromas and hypertrophic neuropathy in Noonan syndrome with multiple lentigines.

J Med Genet 2016 Feb 2;53(2):123-6. Epub 2015 Sep 2.

Department of Medical Genetics, Mayo Clinic, Rochester, Minnesota, USA Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota, USA.

Background: Noonan syndrome with multiple lentigines (NSML), formerly known as LEOPARD syndrome, is an autosomal-dominant disorder characterised by lentigines, EKG abnormalities, ocular hypertelorism, pulmonic stenosis, abnormal genitalia, growth retardation and deafness. There is significant clinical overlap between NSML and other disorders that result from dysregulated rat sarcoma/mitogen-activated protein kinase pathway (RASopathies). Except for neurofibromatosis type 1, other RASopathies are not known to be typically associated with neurogenic tumours.

Methods And Results: We evaluated patients from three families with pigmentary skin lesions, progressive neuropathy, enlarged nerves, massive burden of paraspinal tumours (neurofibroma was confirmed in one patient) and a clinical diagnosis of NSML. All patients had a mutation in the protein tyrosine phosphatase catalytic domain of the PTPN11 gene; two unrelated patients had the p.Thr468Met mutation, while the family consisting of two affected individuals harboured the p.Thr279Cys mutation. Molecular analysis performed on hypertrophic nerve tissue did not disclose a second somatic hit in NF1, PTPN11, NF2 or SMARCB1 genes.

Conclusions: Neurogenic tumours and hypertrophic neuropathy are unusual complications of NSML and may be an under-recognised manifestation that would warrant surveillance. Our observation may also have implications for other disorders caused by RAS-pathway dysregulation.
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http://dx.doi.org/10.1136/jmedgenet-2015-103177DOI Listing
February 2016

Hypomagnesemia due to two novel TRPM6 mutations.

J Pediatr Endocrinol Metab 2015 Nov;28(11-12):1373-8

Background: Although most hypocalcemia with hypomagenesemia in the neonatal period is due to transient neonatal hypoparathyroidism, magnesium channel defects should also be considered.

Case: We report a case of persistent hypomagnesemia in an 8-day-old Hispanic male who presented with generalized seizures. He was initially found to have hypomagnesemia, hypocalcemia, hyperphosphatemia and normal parathyroid hormone. Serum calcium normalized with administration of calcitriol and calcium carbonate. Serum magnesium improved with oral magnesium sulfate. However, 1 week after magnesium was discontinued, serum magnesium declined to 0.5 mg/dL. Magnesium supplementation was immediately restarted, and periodic seizure activity resolved after serum magnesium concentration was maintained above 0.9 mg/dL. The child was eventually weaned off oral calcium and calcitriol with persistent normocalemia. However, supraphysiologic oral magnesium doses were necessary to prevent seizures and maintain serum magnesium at the low limit of normal.

Methods And Results: As his clinical presentation suggested primary renal magnesium wastage, TRPM6 gene mutations were suspected; subsequent genetic testing revealed the child to be compound heterozygous for TRPM6 mutations.

Conclusion: Two novel TRPM6 mutations are described with a new geographic and ethnic origin. This case highlights the importance of recognizing disorders of magnesium imbalance and describing new genetic mutations.
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http://dx.doi.org/10.1515/jpem-2014-0394DOI Listing
November 2015

Concurrent DNA Copy-Number Alterations and Mutations in Genes Related to Maintenance of Genome Stability in Uninvolved Mammary Glandular Tissue from Breast Cancer Patients.

Hum Mutat 2015 Nov 14;36(11):1088-99. Epub 2015 Aug 14.

Faculty of Pharmacy, Medical University of Gdansk, Gdansk, Poland.

Somatic mosaicism for DNA copy-number alterations (SMC-CNAs) is defined as gain or loss of chromosomal segments in somatic cells within a single organism. As cells harboring SMC-CNAs can undergo clonal expansion, it has been proposed that SMC-CNAs may contribute to the predisposition of these cells to genetic disease including cancer. Herein, the gross genomic alterations (>500 kbp) were characterized in uninvolved mammary glandular tissue from 59 breast cancer patients and matched samples of primary tumors and lymph node metastases. Array-based comparative genomic hybridization showed 10% (6/59) of patients harbored one to 359 large SMC-CNAs (mean: 1,328 kbp; median: 961 kbp) in a substantial portion of glandular tissue cells, distal from the primary tumor site. SMC-CNAs were partially recurrent in tumors, albeit with considerable contribution of stochastic SMC-CNAs indicating genomic destabilization. Targeted resequencing of 301 known predisposition and somatic driver loci revealed mutations and rare variants in genes related to maintenance of genomic integrity: BRCA1 (p.Gln1756Profs*74, p.Arg504Cys), BRCA2 (p.Asn3124Ile), NCOR1 (p.Pro1570Glnfs*45), PALB2 (p.Ser500Pro), and TP53 (p.Arg306*). Co-occurrence of gross SMC-CNAs along with point mutations or rare variants in genes responsible for safeguarding genomic integrity highlights the temporal and spatial neoplastic potential of uninvolved glandular tissue in breast cancer patients.
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http://dx.doi.org/10.1002/humu.22845DOI Listing
November 2015

Decoding NF1 Intragenic Copy-Number Variations.

Am J Hum Genet 2015 Aug 16;97(2):238-49. Epub 2015 Jul 16.

Medical Genomics Laboratory, Department of Genetics, University of Alabama at Birmingham, Birmingham, AL 35294, USA. Electronic address:

Genomic rearrangements can cause both Mendelian and complex disorders. Currently, several major mechanisms causing genomic rearrangements, such as non-allelic homologous recombination (NAHR), non-homologous end joining (NHEJ), fork stalling and template switching (FoSTeS), and microhomology-mediated break-induced replication (MMBIR), have been proposed. However, to what extent these mechanisms contribute to gene-specific pathogenic copy-number variations (CNVs) remains understudied. Furthermore, few studies have resolved these pathogenic alterations at the nucleotide-level. Accordingly, our aim was to explore which mechanisms contribute to a large, unique set of locus-specific non-recurrent genomic rearrangements causing the genetic neurocutaneous disorder neurofibromatosis type 1 (NF1). Through breakpoint-spanning PCR as well as array comparative genomic hybridization, we have identified the breakpoints in 85 unrelated individuals carrying an NF1 intragenic CNV. Furthermore, we characterized the likely rearrangement mechanisms of these 85 CNVs, along with those of two additional previously published NF1 intragenic CNVs. Unlike the most typical recurrent rearrangements mediated by flanking low-copy repeats (LCRs), NF1 intragenic rearrangements vary in size, location, and rearrangement mechanisms. We propose the DNA-replication-based mechanisms comprising both FoSTeS and/or MMBIR and serial replication stalling to be the predominant mechanisms leading to NF1 intragenic CNVs. In addition to the loop within a 197-bp palindrome located in intron 40, four Alu elements located in introns 1, 2, 3, and 50 were also identified as intragenic-rearrangement hotspots within NF1.
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http://dx.doi.org/10.1016/j.ajhg.2015.06.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4573439PMC
August 2015

High Incidence of Noonan Syndrome Features Including Short Stature and Pulmonic Stenosis in Patients carrying NF1 Missense Mutations Affecting p.Arg1809: Genotype-Phenotype Correlation.

Hum Mutat 2015 Nov 21;36(11):1052-63. Epub 2015 Aug 21.

Department of Genetics, Medical Genomics Laboratory, University of Alabama at Birmingham, Birmingham, Alabama.

Neurofibromatosis type 1 (NF1) is one of the most frequent genetic disorders, affecting 1:3,000 worldwide. Identification of genotype-phenotype correlations is challenging because of the wide range clinical variability, the progressive nature of the disorder, and extreme diversity of the mutational spectrum. We report 136 individuals with a distinct phenotype carrying one of five different NF1 missense mutations affecting p.Arg1809. Patients presented with multiple café-au-lait macules (CALM) with or without freckling and Lisch nodules, but no externally visible plexiform neurofibromas or clear cutaneous neurofibromas were found. About 25% of the individuals had Noonan-like features. Pulmonic stenosis and short stature were significantly more prevalent compared with classic cohorts (P < 0.0001). Developmental delays and/or learning disabilities were reported in over 50% of patients. Melanocytes cultured from a CALM in a segmental NF1-patient showed two different somatic NF1 mutations, p.Arg1809Cys and a multi-exon deletion, providing genetic evidence that p.Arg1809Cys is a loss-of-function mutation in the melanocytes and causes a pigmentary phenotype. Constitutional missense mutations at p.Arg1809 affect 1.23% of unrelated NF1 probands in the UAB cohort, therefore this specific NF1 genotype-phenotype correlation will affect counseling and management of a significant number of patients.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5049609PMC
http://dx.doi.org/10.1002/humu.22832DOI Listing
November 2015