Optic Atrophy Panel

Last modified: Jun 12, 2018

Summary

  • Is a 19 gene panel that includes assessment of non-coding variants
  • Is ideal for patients with a clinical suspicion / diagnosis of isolated or syndromic optic atrophy. Genes on this panel are included in the Neuro-Ophthalmology Panel.

Analysis methods

  • PLUS
  • SEQ
  • DEL/DUP

Availability

4 weeks

Number of genes

19

Test code

OP0301

Panel size

Small

CPT codes

SEQ 81405
SEQ 81406
SEQ 81407
DEL/DUP 81479

Summary

The Blueprint Genetics Optic Atrophy Panel (test code OP0301):

  • Is a 19 gene panel that includes assessment of selected non-coding disease-causing variants
  • Is available as PLUS analysis (sequencing analysis and deletion/duplication analysis), sequencing analysis only or deletion/duplication analysis only

ICD codes

Commonly used ICD-10 code(s) when ordering the Optic Atrophy Panel

ICD-10 Disease
H47.20 Optic atrophy

Sample Requirements

  • EDTA blood, min. 1 ml
  • Purified DNA, min. 3μg
  • Saliva (Oragene DNA OG-500 kit)

Label the sample tube with your patient’s name, date of birth and the date of sample collection.

Note that we do not accept DNA samples isolated from formalin-fixed paraffin-embedded (FFPE) tissue.

Optic atrophy is a condition that affects the optic nerve, which carries impulses from the eye to the brain. Optic atrophy type 1 (OA1) is clinically characterized by progressive decrease in visual acuity from early childhood onwards. Clinical presentation can be highly variable. The visual impairment is usually moderate, but ranges from severe (legal blindness with acuity <1/20) to mild, accompanied by visual field and color vision defects. OA1 is characterized by the preferential loss of retinal ganglion cells and is inherited in an autosomal dominant manner. Approximately 80% of the familial and 50% of the sporadic cases with OA1 are explained by variants in OPA1, which encodes a mitochondrial inner membrane protein. Optic atrophy can also be syndromic. For example, deafness-dystonia-optic neuronopathy (DDON) syndrome (Mohr-Tranebjaerg syndrome) is inherited in an X-linked manner and caused by variants in TIMM8A. Biallelic variants in WFS1 are associated with optic atrophy as part of the autosomal recessive Wolfram syndrome. Autosomal dominant Charcot-Marie-Tooth hereditary neuropathy type 2A is caused by variants in MFN2. Variants in C12ORF65 are implicated in autosomal recessive hereditary spastic paraplegias.

Genes in the Optic Atrophy Panel and their clinical significance

Gene Associated phenotypes Inheritance ClinVar HGMD
ACO2 Optic atrophy, Infantile cerebellar-retinal degeneration AR 16 13
C12ORF65 Spastic paraplegia, Combined oxidative phosphorylation deficiency AR 10 11
CISD2* Wolfram syndrome 2 AR 2 4
FDXR Auditory neuropathy and optic atrophy AR 5 17
MFN2 Hereditary motor and sensory neuropathy, Charcot-Marie-Tooth disease AD/AR 59 220
NDUFS1 Mitochondrial complex I deficiency AR 22 27
NR2F1 Bosch-Boonstra optic atrophy syndrome AD 20 31
OPA1 Optic atrophy, Optic atrophy 1, Optic atrophy with or without deafness, Ophthalmoplegia, myopathy, ataxia, and neuropathy, Behr synrome, Mitochondrial DNA depletion syndrome 14 AD/AR 97 387
OPA3 Optic atrophy, 3-methylglutaconic aciduria AD/AR 9 15
POLG POLG-related ataxia neuropathy spectrum disorders, Sensory ataxia, dysarthria, and ophthalmoparesis, Alpers syndrome, Progressive external ophthalmoplegia with mitochondrial DNA deletions, Mitochondrial DNA depletion syndrome AD/AR 90 280
PRPS1* Deafness, Phosphoribosylpyrophosphate synthetase I superactivity, Arts syndrome, Charcot-Marie-Tooth disease, X-linked recessive, 5, Nonsyndromic sensorineural deafness, 2, X-linked XL 27 31
RTN4IP1 Optic atrophy 10 with or without ataxia, mental retardation, and seizures AR 2 12
SLC25A46 Neuropathy, hereditary motor and sensory, type VIB AR 12 13
SLC52A2 Brown-Vialetto-Van Laere syndrome AR 26 22
SNX10 Osteopetrosis, autosomal recessive 8 AR 3 13
SPG7 Spastic paraplegia AR 64 108
TIMM8A* Mohr-Tranebjaerg syndrome, Jensen syndrome, Opticoacoustic nerve atrophy with dementia XL 10 21
TMEM126A Optic atrophy AR 2 1
WFS1 Wolfram syndrome, Deafness, Wolfram-like syndrome, autosomal dominant, Deafness, autosomal dominant 6/14/38, Cataract 41 AD/AR 68 351

* Some, or all, of the gene is duplicated in the genome. Read more.

# The gene has suboptimal coverage (means <90% of the gene’s target nucleotides are covered at >20x with mapping quality score (MQ>20) reads).

The sensitivity to detect variants may be limited in genes marked with an asterisk (*) or number sign (#)

Gene refers to the HGNC approved gene symbol; Inheritance refers to inheritance patterns such as autosomal dominant (AD), autosomal recessive (AR), X-linked (XL), X-linked dominant (XLD) and X-linked recessive (XLR); ClinVar refers to the number of variants in the gene classified as pathogenic or likely pathogenic in this database (ClinVar); HGMD refers to the number of variants with possible disease association in the gene listed in Human Gene Mutation Database (HGMD). The list of associated, gene specific phenotypes are generated from CGD or Orphanet databases.

Non-coding variants covered by the panel

Gene Genomic location HG19 HGVS RefSeq RS-number
OPA1 Chr3:193374829 c.2179-40G>C NM_130837.2
OPA1 Chr3:193335986 c.610+360G>A NM_130837.2
OPA1 Chr3:193335990 c.610+364G>A NM_130837.2
TIMM8A ChrX:100601671 c.133-23A>C NM_004085.3 rs869320666
WFS1 Chr4:6271704 c.-43G>T NM_006005.3

Test strength

The strengths of this test include:
  • CAP and ISO-15189 accreditations covering all operations at Blueprint Genetics including all Whole Exome Sequencing, NGS panels and confirmatory testing
  • CLIA-certified personnel performing clinical testing in a CLIA-certified laboratory
  • Powerful sequencing technologies, advanced target enrichment methods and precision bioinformatics pipelines ensure superior analytical performance
  • Careful construction of clinically effective and scientifically justified gene panels
  • Our Nucleus online portal providing transparent and easy access to quality and performance data at the patient level
  • Our publically available analytic validation demonstrating complete details of test performance
  • ~1,500 non-coding disease causing variants in Blueprint WES assay (please see below ‘Non-coding disease causing variants covered by this panel’)
  • Our rigorous variant classification based on modified ACMG variant classification scheme
  • Our systematic clinical interpretation workflow using proprietary software enabling accurate and traceable processing of NGS data
  • Our comprehensive clinical statements

Test limitations

This test does not detect the following:
  • Complex inversions
  • Gene conversions
  • Balanced translocations
  • Mitochondrial DNA variants
  • Repeat expansion disorders unless specifically mentioned
  • Non-coding variants deeper than ±20 base pairs from exon-intron boundary unless otherwise indicated (please see above Panel Content / non-coding variants covered by the panel).

This test may not reliably detect the following:

  • Low level mosaicism (variant with a minor allele fraction of 14.6% is detected with 90% probability)
  • Stretches of mononucleotide repeats
  • Indels larger than 50bp
  • Single exon deletions or duplications
  • Variants within pseudogene regions/duplicated segments

The sensitivity of this test may be reduced if DNA is extracted by a laboratory other than Blueprint Genetics.

For additional information, please refer to the Test performance section and see our Analytic Validation.

The Blueprint Genetics optic atrophy panel covers classical genes associated with Mohr-Tranebjaerg syndrome, Wolfram syndrome, optic atrophy, Autosomal dominant Charcot-Marie-tooth disease type 2A2, autosomal recessive optic atrophy and autosomal recessive spastic paraplegia type 55. The genes on the panel have been carefully selected based on scientific literature, mutation databases and our experience.

Our panels are sliced from our high-quality whole exome sequencing data. Please see our sequencing and detection performance table for different types of alterations at the whole exome level (Table).

Assays have been validated for different starting materials including EDTA-blood, isolated DNA (no FFPE), saliva and dry blood spots (filter card) and all provide high-quality results. The diagnostic yield varies substantially depending on the assay used, referring healthcare professional, hospital and country. Blueprint Genetics' Plus Analysis (Seq+Del/Dup) maximizes the chance to find a molecular genetic diagnosis for your patient although Sequence Analysis or Del/Dup Analysis may be a cost-effective first line test if your patient's phenotype is suggestive of a specific mutation type.

Performance of Blueprint Genetics Whole Exome Sequencing (WES) assay. All individual panels are sliced from WES data.

Sensitivity % (TP/(TP+FN) Specificity %
Single nucleotide variants 99.65% (412,456/413,893) >99.99%
Insertions, deletions and indels by sequence analysis
1-10 bps 96.94% (17,070/17,608) >99.99%
11-50 bps 99.07% (957/966) >99.99%
Copy number variants (exon level dels/dups)
Clinical samples (small CNVs, n=52)
1 exon level deletion 92.3% (24/26) NA
2 exons level deletion/duplication 100.0% (11/11) NA
3-7 exons level deletion/duplication 93.3% (14/15) NA
Microdeletion/-duplication sdrs (large CNVs, n=37))
Size range (0.1-47 Mb) 100% (37/37)
Simulated CNV detection
2 exons level deletion/duplication 90.98% (7,357/8,086) 99.96%
5 exons level deletion/duplication 98.63% (7,975/8,086) 99.98%
     
The performance presented above reached by WES with the following coverage metrics
     
Mean sequencing depth at exome level 174x
Nucleotides with >20x sequencing coverage (%) 99.4%

Bioinformatics

The target region for each gene includes coding exons and ±20 base pairs from the exon-intron boundary. In addition, the panel includes non-coding variants if listed above (Non-coding variants covered by the panel). Some regions of the gene(s) may be removed from the panel if specifically mentioned in the ‘Test limitations” section above. The sequencing data generated in our laboratory is analyzed with our proprietary data analysis and annotation pipeline, integrating state-of-the art algorithms and industry-standard software solutions. Incorporation of rigorous quality control steps throughout the workflow of the pipeline ensures the consistency, validity and accuracy of results. Our pipeline is streamlined to maximize sensitivity without sacrificing specificity. We have incorporated a number of reference population databases and mutation databases such as, but not limited, to 1000 Genomes Project, gnomAD, ClinVar and HGMD into our clinical interpretation software to make the process effective and efficient. For missense variants, in silico variant prediction tools such as SIFT, PolyPhen, MutationTaster are used to assist with variant classification. Through our online ordering and statement reporting system, Nucleus, the customer has an access to details of the analysis, including patient specific sequencing metrics, a gene level coverage plot and a list of regions with inadequate coverage if present. This reflects our mission to build fully transparent diagnostics where customers have easy access to crucial details of the analysis process.

Clinical interpretation

We provide customers with the most comprehensive clinical report available on the market. Clinical interpretation requires a fundamental understanding of clinical genetics and genetic principles. At Blueprint Genetics, our PhD molecular geneticists, medical geneticists and clinical consultants prepare the clinical statement together by evaluating the identified variants in the context of the phenotypic information provided in the requisition form. Our goal is to provide clinically meaningful statements that are understandable for all medical professionals regardless of whether they have formal training in genetics.

Variant classification is the corner stone of clinical interpretation and resulting patient management decisions. Our classifications follow the Blueprint Genetics Variant Classification Schemes based on the ACMG guideline 2015. Minor modifications were made to increase reproducibility of the variant classification and improve the clinical validity of the report. Our experience with tens of thousands of clinical cases analyzed at our laboratory allowed us to further develop the industry standard.

The final step in the analysis of sequence variants is confirmation of variants classified as pathogenic or likely pathogenic using bi-directional Sanger sequencing. Variant(s) fulfilling all of the following criteria are not Sanger confirmed: 1) the variant quality score is above the internal threshold for a true positive call, 2) an unambiguous IGV in-line with the variant call and 3) previous Sanger confirmation of the same variant at least three times at Blueprint Genetics. Reported variants of uncertain significance are confirmed with bi-directional Sanger sequencing only if the quality score is below our internally defined quality score for true positive call. Reported copy number variations with a size <10 exons are confirmed by orthogonal methods such as qPCR if the specific CNV has been seen less than three times at Blueprint Genetics.

Our clinical statement includes tables for sequencing and copy number variants that include basic variant information (genomic coordinates, HGVS nomenclature, zygosity, allele frequencies, in silico predictions, OMIM phenotypes and classification of the variant). In addition, the statement includes detailed descriptions of the variant, gene and phenotype(s) including the role of the specific gene in human disease, the mutation profile, information about the gene’s variation in population cohorts and detailed information about related phenotypes. We also provide links to the references used, congress abstracts and mutation databases to help our customers further evaluate the reported findings if desired. The conclusion summarizes all of the existing information and provides our rationale for the classification of the variant.

Identification of pathogenic or likely pathogenic variants in dominant disorders or their combinations in different alleles in recessive disorders are considered molecular confirmation of the clinical diagnosis. In these cases, family member testing can be used for risk stratification within the family. In the case of variants of uncertain significance (VUS), we do not recommend family member risk stratification based on the VUS result. Furthermore, in the case of VUS, we do not recommend the use of genetic information in patient management or genetic counseling.

Our interpretation team analyzes millions of variants from thousands of individuals with rare diseases. Thus, our database, and our understanding of variants and related phenotypes, is growing by leaps and bounds. Our laboratory is therefore well positioned to re-classify previously reported variants as new information becomes available. If a variant previously reported by Blueprint Genetics is re-classified, our laboratory will issue a follow-up statement to the original ordering health care provider at no additional cost.