Locus-specific Databases Research Articles

Locus Reference Genomic: reference sequences for the reporting of clinically relevant sequence variants

Locus Reference Genomic (LRG; http://www.lrg-sequence.org/) records contain internationally recognized stable reference sequences designed specifically for reporting clinically relevant sequence variants. Each LRG is contained within a single file consisting of a stable ‘fixed’ section and a regularly updated ‘updatable’ section. The fixed section contains stable genomic DNA sequence for a genomic region, essential transcripts and proteins for variant reporting and an exon numbering system. The updatable section contains mapping information, annotation of all transcripts and overlapping genes in the region and legacy exon and amino acid numbering systems. LRGs provide a stable framework that is vital for reporting variants, according to Human Genome Variation Society (HGVS) conventions, in genomic DNA, transcript or protein coordinates. To enable translation of information between LRG and genomic coordinates, LRGs include mapping to the human genome assembly. LRGs are compiled and maintained by the National Center for Biotechnology Information (NCBI) and European Bioinformatics Institute (EBI). LRG reference sequences are selected in collaboration with the diagnostic and research communities, locus-specific database curators and mutation consortia. Currently >700 LRGs have been created, of which >400 are publicly available. The aim is to create an LRG for every locus with clinical implications.

Familial hypercholesterolaemia (FH) in Wales is genetically heterogeneous

Familial hypercholesterolaemia (FH) in Wales is genetically heterogeneous

Platelet Functional and Morphological Abnormalities In a Case Of Arthrogryposis, Renal Dysfunction and Cholestasis (ARC) Syndrome With a Novel Genetic Profile

ARC syndrome is a severe autosomal recessive multisystem disorder characterized by arthrogryposis, neonatal cholestatic jaundice, renal tubular acidosis, failure to thrive, dysmorphic features, congenital heart disease, cerebral malformation, hypotonia, recurrent febrile illness and a bleeding disorder. It is associated with consanguinity and most patients do not survive beyond the first year of life. ARC syndrome is linked to loss of function in either VPS33B or VIPAS39, respectively encoding VPS33B and VPS16B, which we have shown to be interaction partners within a multiprotein complex involved in intracellular vesicular trafficking (Urban et al, Blood. 2012 Dec 13;120(25):5032-40). Earlier we determined that bleeding problems in ARC syndrome patients (where platelet aggregation abnormalities have been observed) arise from abnormal function of normally abundant platelets lacking α-granules (Lo et al, Blood. 2005;106(13):4159-66). Detailed studies of ARC syndrome platelets have been hampered by limited availability.A term 4-month old boy was observed to have significant epistaxis and petechiae requiring multiple transfusions of plasma, packed red blood cells, tranexamic acid, vitamin K and nasal packing twice, with final success over control of bleeding. INR was 1.8 and PTT was 40 with a normal platelet count of 319 during this episode. Intermittent episodes of bleeding continued throughout his course, with difficulty in stopping the bleeding. The patient was found to have jaundice with scleral icterus, cholestasis and giant cell hepatitis seen on liver biopsy. A metabolic work-up revealed significant aminoaciduria and proximal tubular acidosis. He also had failure to thrive, feeding intolerance, severe bilateral sensorineural hearing loss, limb contractures, right rocker bottom foot and clubbed left foot. MRI of the brain showed abnormal corpus callosum with non-visualization of the anterior commissure. On abdominal ultrasound, the liver was enlarged and mildly echogenic with no evidence of portal hypertension and patent vessels. Echogenic kidneys were present with nephrocalcinosis. He was referred for evaluation and possible liver transplantation.Blood film examination revealed pale-appearing platelets and transmission electron microscopy confirmed the complete absence of α-granules, making a diagnosis of ARC syndrome highly probable. Immunofluorescence confocal microscopy detected abnormalities in patient platelets with regards to: 1) size (larger than normal); 2) morphology of the tubulin ring cytoskeleton (loosely organized compared to normal); and 3) intracellular distribution of CD63 (more abundant and widely dispersed than normal). Sequencing of patient DNA detected normal VIPAS39 and apparent homozygosity for a single base pair deletion (c.1531delT, p.Tyr511ThrfsStop10) in exon 20 of VPS33B, predicted to cause a frame shift and premature translation stop codon. Gene sequencing of the parents detected the identical VPS33B mutation in the mother heterozygous to a normal allele; no mutation was found in the father. Array comparative genomic hybridization (aCGH) – which allows detection of deletions and amplification mutations of one or more exons within a given gene – uncovered an approximately 140 kb deletion mutation encompassing the entire VPS33B gene in our patient (g.91,478,004 – proximal to g.91,618.247 – distal), confirming compound heterozygosity. According to the online locus-specific ARC database (https://grenada.lumc.nl/LOVD2/ARC), this is the first association of this mutation combination with ARC syndrome.Unusually for ARC syndrome, bleeding indicative of platelet dysfunction was a major presenting symptom in this patient. While the genetic profile is unusual, the pathological platelet hallmarks of ARC syndrome were present: hypogranular platelets on blood film and absence of α-granules via electron microscopy. We were also able to detect other platelet abnormalities via immunofluorescence microscopy. These observations lead us to suspect that ARC syndrome may represent the most severe class within a possible spectrum of platelet function disorders associated with mutations in VPS33B and/or VIPAS39, a possibility that requires further study. Disclosures:No relevant conflicts of interest to declare.

Updates of the HbVar database of human hemoglobin variants and thalassemia mutations

HbVar (http://globin.bx.psu.edu/hbvar) is one of the oldest and most appreciated locus-specific databases launched in 2001 by a multi-center academic effort to provide timely information on the genomic alterations leading to hemoglobin variants and all types of thalassemia and hemoglobinopathies. Database records include extensive phenotypic descriptions, biochemical and hematological effects, associated pathology and ethnic occurrence, accompanied by mutation frequencies and references. Here, we report updates to >600 HbVar entries, inclusion of population-specific data for 28 populations and 27 ethnic groups for α-, and β-thalassemias and additional querying options in the HbVar query page. HbVar content was also inter-connected with two other established genetic databases, namely FINDbase (http://www.findbase.org) and Leiden Open-Access Variation database (http://www.lovd.nl), which allows comparative data querying and analysis. HbVar data content has contributed to the realization of two collaborative projects to identify genomic variants that lie on different globin paralogs. Most importantly, HbVar data content has contributed to demonstrate the microattribution concept in practice. These updates significantly enriched the database content and querying potential, enhanced the database profile and data quality and broadened the inter-relation of HbVar with other databases, which should increase the already high impact of this resource to the globin and genetic database community.

Large numbers of genetic variants considered to be pathogenic are common in asymptomatic individuals.

It is now affordable to order clinically interpreted whole-genome sequence reports from clinical laboratories. One major component of these reports is derived from the knowledge base of previously identified pathogenic variants, including research articles, locus-specific, and other databases. While over 150,000 such pathogenic variants have been identified, many of these were originally discovered in small cohort studies of affected individuals, so their applicability to asymptomatic populations is unclear. We analyzed the prevalence of a large set of pathogenic variants from the medical and scientific literature in a large set of asymptomatic individuals (N = 1,092) and found 8.5% of these pathogenic variants in at least one individual. In the average individual in the 1000 Genomes Project, previously identified pathogenic variants occur on average 294 times (σ = 25.5) in homozygous form and 942 times (σ = 68.2) in heterozygous form. We also find that many of these pathogenic variants are frequently occurring: there are 3,744 variants with minor allele frequency (MAF) ≥ 0.01 (4.6%) and 2,837 variants with MAF ≥ 0.05 (3.5%). This indicates that many of these variants may be erroneous findings or have lower penetrance than previously expected.

UMD-MLH1/MSH2/MSH6 databases: description and analysis of genetic variations in French Lynch syndrome families

Lynch syndrome is an autosomal dominant disease caused by germ line heterozygous mutations mainly involving the MSH2, MLH1 and MSH6 genes that belong to the DNA MisMatch Repair (MMR) genes family. The French network counting the 16 licensed laboratories involved in Lynch syndrome genetic testing developed three locus-specific databases with the UMD® software (www.umd.be/MLH1/, www.umd.be/MSH2/ and www.umd.be/MSH6/) that presently contain a total of 7047 sequence variations including 707 distinct variations of a priori unknown functional significance (VUS) that were identified through complete mutation screening or targeted predictive testing. Mutation carriers are at high risk for developing early-onset colorectal and endometrial adenocarcinomas. Consensus clinical guidelines have been proposed, allowing the efficient detection of curable lesions. The major challenge of genetic testing is to reliably classify the genomic variations in those patients who seek genetic counseling. Combining the interactive tools of the software, the relevant published data and mainly original information produced by the French MisMatch Repair network, the UMD-MLH1/MSH2/MSH6 databases provide interpretation data for the 707 VUS that were classified according to the IARC 5-Class system. These public databases are regularly updated to improve the classification of all registered VUS, exploring their role in cancer pre-disposition based on structural and functional approaches.

Using Reference Databases of Genetic Variation to Evaluate the Potential Pathogenicity of Candidate Disease Variants

The potential pathogenicity of genetic variants identified in disease-based resequencing studies is often overlooked where variants have previously been reported in dbSNP, the 1000 genomes project, or the National Heart, Lung and Blood Institute Exome Sequencing Project (ESP). In this work, we estimate that collectively, these databases capture ∼52% of mutations (dbSNP 50.4%; 1000 genomes 4.8%; and ESP 10.2%) reported as disease causing within phenotype-based locus-specific databases (LSDBs). To investigate whether these mutations may simply represent benign population variants, we evaluated whether the carrier frequencies associated with mutations implicated in amyotrophic lateral sclerosis were higher than what could be accounted for by high-penetrance disease models. In doing so, we have questioned the veracity of 51 mutations, but also demonstrated that each of the three databases included credible disease variants. Our results demonstrate the benefits of using databases such as dbSNP, the 1000 genomes project, and the ESP to evaluate the pathogenicity of putative disease variants, and suggest that many disease mutations reported across LSDBs may not actually be pathogenic. However, they also demonstrate that even in the context of rare Mendelian disorders, the potential pathogenicity of variants reported by these databases should not be overlooked without proper evaluation.

The CDC Hemophilia A Mutation Project (CHAMP) Mutation List: A New Online Resource

Genotyping efforts in hemophilia A (HA) populations in many countries have identified large numbers of unique mutations in the Factor VIII gene (F8). To assist HA researchers conducting genotyping analyses, we have developed a listing of F8 mutations including those listed in existing locus-specific databases as well as those identified in patient populations and reported in the literature. Each mutation was reviewed and uniquely identified using Human Genome Variation Society (HGVS) nomenclature standards for coding DNA and predicted protein changes as well as traditional nomenclature based on the mature, processed protein. Listings also include the associated hemophilia severity classified by International Society of Thrombosis and Haemostasis (ISTH) criteria, associations of the mutations with inhibitors, and reference information. The mutation list currently contains 2,537 unique mutations known to cause HA. HA severity caused by the mutation is available for 2,022 mutations (80%) and information on inhibitors is available for 1,816 mutations (72%). The CDC Hemophilia A Mutation Project (CHAMP) Mutation List is available at http://www.cdc.gov/hemophiliamutations for download and search and will be updated quarterly based on periodic literature reviews and submitted reports.

A first RDF implementation of the COSMIC database on mutations in cancer

Motivation and Objectives Within a living organism, genome and proteome variations may influence many molecular interactions and biochemical pathways, leading to deleterious effects in the proper activity of cells, tissues, and organs; ultimately, this may be the cause of many syndromes and diseases. It is now well known that tumors may arise as a result of a series of DNA sequence abnormalities and mutations. It is then not surprising that there is a vast amount of information available in the scientific literature and that a lot of information systems devoted to the management of related data exist. Among these, of particular interest are the many Locus Specific Data Bases (LSDB) and the COSMIC (Catalogue of Somatic Mutations in Cancer) database (Forbes et al., 2011). Such data, however, are not yet sufficiently integrated with other molecular, biomedical, and clinical databases. New efforts are therefore needed in this direction. Data retrieval, search and integration solutions in bioinformatics are increasingly making use of a set of standards and technologies which are the basis of the Semantic Web (Berners-Lee et al., 2001) framework. This framework is intended to evolve the web into a distributed knowledge-base and a first step in this evolution is the generation of a Web of Data (Bizer et al., 2009). In this view, we can see Linked Data as an approach to data integration that employs ontologies, terminologies, Uniform Resource Identifiers (URIs), and the Resource Description Framework (RDF) to connect pieces of data, information and knowledge on the Semantic Web (Belleau et al., 2008). In particular, RDF describes semantic rich information on the web through a composition of simple triples (predicates), such as (‘Subject’, ‘Property’, ‘Object’), that link entities through relations which are expressed by using ontologies, and are defined by using URIs. See the RDF reference site: http://www.w3.org/RDF/, last accessed on October 3, 2012). A relevant contribution to this vision comes from the conversion of data stored in relational databases (RDB) into RDF. There is a vast amount of information on human variation in the literature and several mutation and variation databases, but, to our knowledge, this kind of information is still scarce in the Web of Data. Various motivations can be depicted for using Semantic Web technologies and publishing Linked Data life sciences datasets; this allows to improve data and information integration, share ability of openly accessible data through standard and programmatic interfaces, semantic normalization, data discoverability and query federation from distributed sources. A first work carried out by our group led to the implementation of an RDF version (Zappa et al., 2012) of the IARC TP53 Somatic Mutation database (IARCDB) (Petitjean et al., 2007). Here, we present the initial development of an RDF version of the COSMIC (Catalogue of Somatic Mutations in Cancer) database by means of Semantic Web technologies.

Disease‐specific databases: Why we need them and some recommendations from the Human Variome Project Meeting, May 28, 2011

The need for Locus-Specific Databases, with disease-specific experts and curators, is an essential ingredient in a process to enable the benefits of the advances in sequencing and mutational analysis to be realized across the genome. Next generation sequencing provides both astounding opportunities and challenges, especially for genetic counsellors. An approach coordinated at a genome wide, international level, supported by well-organized disease-specific respected organizations is a model most likely to be successful, but committed resourceful professionals working in local poorly resourced environments can make valuable contributions that can grow. Bioinformatic tools to sift and integrate multiple domains of information are being developed, and play a major part in meeting the challenges. Regulation of providers, including a requirement for them to submit mutational information to central databases, also should assist to reach the goals needed to realize the opportunities. There is also a need to agree on governance of Locus-Specific Databases (LSDBs) at an international level, and for adequate international funding to support this need, to ensure humanity reaps the benefits of the current molecular genetic revolution. The Human Variome Project offers this, working also with the other major initiatives with similar objectives. This report concludes with Recommendations for the Human Variome Project stemming from the presentations and discussions at the meeting.

Expanding the MTM1 mutational spectrum: novel variants including the first multi-exonic duplication and development of a locus-specific database

Myotubular myopathy (MIM#310400), the X-linked form of Centronuclear myopathy (CNM) is mainly characterized by neonatal hypotonia and inability to maintain unassisted respiration. The MTM1 gene, responsible for this disease, encodes myotubularin - a lipidic phosphatase involved in vesicle trafficking regulation and maturation. Recently, it was shown that myotubularin interacts with desmin, being a major regulator of intermediate filaments. We report the development of a locus-specific database for MTM1 using the Leiden Open Variation database software (http://www.lovd.nl/MTM1), with data collated for 474 mutations identified in 472 patients (by June 2012). Among the entries are a total of 25 new mutations, including a large deletion encompassing introns 2-15. During database implementation it was noticed that no large duplications had been reported. We tested a group of eight uncharacterized CNM patients for this specific type of mutation, by multiple ligation-dependent probe amplification (MLPA) analysis. A large duplication spanning exons 1-5 was identified in a boy with a mild phenotype, with results pointing toward possible somatic mosaicism. Further characterization revealed that this duplication causes an in-frame deletion at the mRNA level (r.343_444del). Results obtained with a next generation sequencing approach suggested that the duplication extends into the neighboring MAMLD1 gene and subsequent cDNA analysis detected the presence of a MTM1/MAMLD1 fusion transcript. A complex rearrangement involving the duplication of exon 10 has since been reported, with detection also enabled by MLPA analysis. It is thus conceivable that large duplications in MTM1 may account for a number of CNM cases that have remained genetically unresolved.

Spinocerebellar ataxias: An example of the challenges associated with genetic databases for dynamic mutations

Locus-specific databases are an important source of information for diagnostic laboratories and a valued means of improving quality of genetic testing. Although increasingly frequent, databases for oligonucleotide repeat expansions are still scarce, due to factors that make them different and the building of databases much more difficult. Definition of what constitutes "the repeat" to measure is not a simple matter and correct sizing is not always straightforward. Reference ranges and penetrance classes are not easy to establish. Acceptable margins of error depend on the disease and allele-size distribution, and vary according to size range and pathogenic significance. Inter- and intralaboratorial variance is well documented and allele distribution may vary among populations. The spinocerebellar ataxias, used only as an example of those difficulties, are also a highly heterogeneous group, which includes loci with both pathogenic repeat expansions and point mutations or insertions/deletions. They display a variable, but often overlapping phenotype, where genotype-phenotype correlation is difficult or nonexistent. Standard (Human Genome Variation Society) nomenclature is not appropriate for oligonucleotide repeats, as established at harmonization among all EMQN (European Molecular Genetics Network) external quality assessment (EQA) schemes for "repeat disorders." Curation of such databases is a difficult task, but one that needs to be addressed adequately and without much delay.

Systematic curation and analysis of genomic variations and their potential functional consequences in snoRNA loci

Small nucleolar RNAs (snoRNAs) are a class of noncoding functional RNAs which are involved in RNA modifications, like methylation and pseudouridylation of other RNAs. The snoRNA species of RNAs are characterized by conserved structural motifs they harbor which are also intricately related to their functionality. Though there have been reports of the involvement of snoRNAs in disease processes and anecdotal reports of genomic variations in snoRNA loci and their effects in modulating snoRNA function, there has been no systematic collection and analysis of variations in snoRNA loci. In this manuscript, we present the most comprehensive curation of genomic single nucleotide variations in human snoRNA loci, and their systematic computational analysis to reveal potential single nucleotide variations which could have functional effects. We show six single nucleotide variations in snoRNA loci could significantly alter snoRNA structure and could have potential implications in their functions. The compilation is available at the snoRNA locus specific variation database: http://genome.igib.res.in/snolovd conforming to the HGVS standards for nomenclature of genomic variants.

The inherited ataxias: Genetic heterogeneity, mutation databases, and future directions in research and clinical diagnostics

The inherited cerebellar ataxias are a diverse group of clinically and genetically heterogeneous neurodegenerative disorders. Inheritance patterns of these disorders can be complex with autosomal dominant, autosomal recessive, X-linked, and mitochondrial inheritance demonstrated by one or more ataxic syndromes. The broad range of mutation types found in inherited ataxia contributes to the complex genetic etiology of these disorders. The majority of inherited ataxias are caused by repeat expansions; however, conventional mutations are important causes of the rarer dominant and recessive ataxias. Advances in sequencing technology have allowed for much broader testing of these rare ataxia genes. This is relevant to the aims of the Human Variome Project, which aims to collate and store gene variation data through mutation databases. Variant data is currently located in a range of public and commercial resources. Few locus-specific databases have been created to catalogue variation in the dominant ataxia genes although there are several databases for some recessive genes. Developing these resources will facilitate a better understanding of the complex genotype-phenotype relationships in these disorders and assist interpretation of gene variants as testing for rarer ataxia genes becomes commonplace.

Toward a mtDNA locus-specific mutation database using the LOVD platform.

The Human Variome Project (HVP) is a global effort to collect and curate all human genetic variation affecting health. Mutations of mitochondrial DNA (mtDNA) are an important cause of neurogenetic disease in humans; however, identification of the pathogenic mutations responsible can be problematic. In this article, we provide explanations as to why and suggest how such difficulties might be overcome. We put forward a case in support of a new Locus Specific Mutation Database (LSDB) implemented using the Leiden Open-source Variation Database (LOVD) system that will not only list primary mutations, but also present the evidence supporting their role in disease. Critically, we feel that this new database should have the capacity to store information on the observed phenotypes alongside the genetic variation, thereby facilitating our understanding of the complex and variable presentation of mtDNA disease. LOVD supports fast queries of both seen and hidden data and allows storage of sequence variants from high-throughput sequence analysis. The LOVD platform will allow construction of a secure mtDNA database; one that can fully utilize currently available data, as well as that being generated by high-throughput sequencing, to link genotype with phenotype enhancing our understanding of mitochondrial disease, with a view to providing better prognostic information.

WS8.5 Help for the interpretation of unclassified variants: example of the UMD-CFTR-France Locus Specific Database

WS8.5 Help for the interpretation of unclassified variants: example of the UMD-CFTR-France Locus Specific Database

Phenotype-optimized sequence ensembles substantially improve prediction of disease-causing mutation in cystic fibrosis

Cystic fibrosis transmembrane conductance regulator (CFTR) mutation is associated with a phenotypic spectrum that includes cystic fibrosis (CF). The disease liability of some common CFTR mutations is known, but rare mutations are seen in too few patients to categorize unequivocally, making genetic diagnosis difficult. Computational methods can predict the impact of mutation, but prediction specificity is often below that required for clinical utility. Here, we present a novel supervised learning approach for predicting CF from CFTR missense mutation. The algorithm begins by constructing custom multiple sequence alignments called phenotype-optimized sequence ensembles (POSEs). POSEs are constructed iteratively, by selecting sequences that optimize predictive performance on a training set of CFTR mutations of known clinical significance. Next, we predict CF disease liability from a different set of CFTR mutations (test-set mutations). This approach achieves improved prediction performance relative to popular methods recently assessed using the same test-set mutations. Of clinical significance, our method achieves 94% prediction specificity. Because databases such as HGMD and locus-specific mutation databases are growing rapidly, methods that automatically tailor their predictions for a specific phenotype may be of immediate utility. If the performance achieved here generalizes to other systems, the approach could be an excellent tool to help establish genetic diagnoses.

Mutation update on the CHD7 gene involved in CHARGE syndrome

CHD7 is a member of the chromodomain helicase DNA-binding (CHD) protein family that plays a role in transcription regulation by chromatin remodeling. Loss-of-function mutations in CHD7 are known to cause CHARGE syndrome, an autosomal-dominant malformation syndrome in which several organ systems, for example, the central nervous system, eye, ear, nose, and mediastinal organs, are variably involved. In this article, we review all the currently described CHD7 variants, including 183 new pathogenic mutations found by our laboratories. In total, we compiled 528 different pathogenic CHD7 alterations from 508 previously published patients with CHARGE syndrome and 294 unpublished patients analyzed by our laboratories. The mutations are equally distributed along the coding region of CHD7 and most are nonsense or frameshift mutations. Most mutations are unique, but we identified 94 recurrent mutations, predominantly arginine to stop codon mutations. We built a locus-specific database listing all the variants that is easily accessible at www.CHD7.org. In addition, we summarize the latest data on CHD7 expression studies, animal models, and functional studies, and we discuss the latest clinical insights into CHARGE syndrome.

The androgen receptor gene mutations database: 2012 update

The current version of the androgen receptor gene (AR) mutations database is described. A major change to the database is that the nomenclature and numbering scheme now conforms to all Human Genome Variation Society norms. The total number of reported mutations has risen from 605 to 1,029 since 2004. The database now contains a number of mutations that are associated with prostate cancer (CaP) treatment regimens, while the number of AR mutations found in CaP tissues has more than doubled from 76 to 159. In addition, in a number of androgen insensitivity syndrome (AIS) and CaP cases, multiple mutations have been found within the same tissue samples. For the first time, we report on a disconnect within the AIS phenotype-genotype relationship among our own patient database, in that over 40% of our patients with a classic complete AIS or partial AIS phenotypes did not appear to have a mutation in their AR gene. The implications of this phenomenon on future locus-specific mutation database (LSDB) development are discussed, together with the concept that mutations can be associated with both loss- and gain-of-function, and the effect of multiple AR mutations within individuals. The database is available on the internet (http://androgendb.mcgill.ca), and a web-based LSDB with the variants using the Leiden Open Variation Database platform is available at http://www.lovd.nl/AR.

Update of PAX2 mutations in renal coloboma syndrome and establishment of a locus-specific database

Renal coloboma syndrome, also known as papillorenal syndrome is an autosomal-dominant disorder characterized by ocular and renal malformations. Mutations in the paired-box gene, PAX2, have been identified in approximately half of individuals with classic findings of renal hypoplasia/dysplasia and abnormalities of the optic nerve. Prior to 2011, there was no actively maintained locus-specific database (LSDB) cataloguing the extent of genetic variation in the PAX2 gene and phenotypic variation in individuals with renal coloboma syndrome. Review of published cases and the collective diagnostic experience of three laboratories in the United States, France, and New Zealand identified 55 unique mutations in 173 individuals from 86 families. The three clinical laboratories participating in this collaboration contributed 28 novel variations in 68 individuals in 33 families, which represent a 50% increase in the number of variations, patients, and families published in the medical literature. An LSDB was created using the Leiden Open Variation Database platform: www.lovd.nl/PAX2. The most common findings reported in this series were abnormal renal structure or function (92% of individuals), ophthalmological abnormalities (77% of individuals), and hearing loss (7% of individuals). Additional clinical findings and genetic counseling implications are discussed.