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Autosomal Dominant Retinitis Pigmentosa 31 (RP31) via the TOPORS Gene

Summary and Pricing

Test Method

Exome Sequencing with CNV Detection
Test Code Test Copy GenesTest CPT Code Gene CPT Codes Copy CPT Codes Base Price
TOPORS 81479 81479,81479 $990
Test Code Test Copy Genes Test CPT Code Gene CPT Codes Copy CPT Code Base Price
8325TOPORS81479 81479,81479 $990 Order Options and Pricing

Pricing Comments

Our favored testing approach is exome based NextGen sequencing with CNV analysis. This will allow cost effective reflexing to PGxome or other exome based tests. However, if full gene Sanger sequencing is desired for STAT turnaround time, insurance, or other reasons, please see link below for Test Code, pricing, and turnaround time information. If the Sanger option is selected, CNV detection may be ordered through Test #600.

An additional 25% charge will be applied to STAT orders. STAT orders are prioritized throughout the testing process.

Click here for costs to reflex to whole PGxome (if original test is on PGxome Sequencing platform).

Click here for costs to reflex to whole PGnome (if original test is on PGnome Sequencing platform).

The Sanger Sequencing method for this test is NY State approved.

For Sanger Sequencing click here.

Turnaround Time

3 weeks on average for standard orders or 2 weeks on average for STAT orders.

Please note: Once the testing process begins, an Estimated Report Date (ERD) range will be displayed in the portal. This is the most accurate prediction of when your report will be complete and may differ from the average TAT published on our website. About 85% of our tests will be reported within or before the ERD range. We will notify you of significant delays or holds which will impact the ERD. Learn more about turnaround times here.

Targeted Testing

For ordering sequencing of targeted known variants, go to our Targeted Variants page.


Genetic Counselors


  • Dana Talsness, PhD

Clinical Features and Genetics

Clinical Features

Retinitis pigmentosa (RP; OMIM # 609923) or rod cone dystrophies (RCDs), represent a group of hereditary retinal dystrophies with a worldwide prevalence of ~1 in 4000 (Booij et al. J Med Genet 42 (11): e67, 2005). RP is clinically characterized by retinal pigment deposits visible on fundus examination, nyctalopia (night blindness), followed by progressive degeneration of the photoreceptors, which eventually leads to blindness (van Soest et al. Surv Ophthalmol 43(4):321-334,1999; Chakarova et al. Am J Hum Genet 81(5):1098-1103, 2007). RP31 affected patients have a unique perivascular retinal pigment epithelium (RPE) atrophy phenotype in the early stages of the disease (Chakarova et al., 2007).


Nonsyndromic RP is remarkably heterogeneous both clinically and genetically and exhibits autosomal dominant (ad), autosomal recessive (ar) or X-linked (XL) inheritance. To date, over 50 loci have been linked to nonsyndromic RP and 18, 27 and 2 genes have been identified that are associated with adRP, arRP, and XLRP, respectively (RetNet). TOPORS (OMIM # 609507), which encodes topoisomerase I-binding arginine-serine rich protein, is one of the recently identified genes that is associated with RP and is responsible for 1-2% of adRP (Bowne et al. Mol Vis 14:922-927, 2008; Chakarova et al. Hum Mol Genet 20(5):975-987, 2011). Immunolocalization studies indicates that the TOPORS is localized to the basal body connecting cilium of the photoreceptor cells and may play a crucial role in regulating primary cilia-dependent photoreceptor development and function. (Chakarova et al., 2011).

There are about 10 mutations have been reported in TOPORS, which includes point mutations, small insertions and deletions (Human Gene Mutation Database). It has been reported that haploinsufficiency is a likely disease mechanism for TOPORS mutations. So far no copy number variants have been identified (Bowne et al., 2008). A recent study done by Selmer et al. (2010) identified a novel missense mutation, c.1205 A>C (p.Q402P), in TOPORS in all the affected members (19/19) in a large Norwegian family and this mutation showed complete co-segregation with the disease (Selmer et al. Acta Ophthalmol 88(3):323-328, 2010).

Clinical Sensitivity - Sequencing with CNV PGxome

TOPORS mutation frequency analysis was done with a cohort of 215 adRP probands, where 89 of them did not have mutations in other known adRP genes. Only two of the 89 probands had TOPORS mutations (~1%), which was not found in 90 unrelated normal control samples. It is been reported that the addition of TOPORS to the list of adRP associated genes, mutations can be identified in 60% of the affected adRP patients (Bowne et al. Mol Vis 14:922-927, 2008).

So far, no gross deletions or duplications have been reported in TOPORS (The Human Gene Mutation Database).

Testing Strategy

This test provides full coverage of all coding exons of the TOPORS gene plus 10 bases of flanking noncoding DNA in all available transcripts along with other non-coding regions in which pathogenic variants have been identified at PreventionGenetics or reported elsewhere. We define full coverage as >20X NGS reads or Sanger sequencing. PGnome panels typically provide slightly increased coverage over the PGxome equivalent. PGnome sequencing panels have the added benefit of additional analysis and reporting of deep intronic regions (where applicable).

Dependent on the sequencing backbone selected for this testing, discounted reflex testing to any other similar backbone-based test is available (i.e., PGxome panel to whole PGxome; PGnome panel to whole PGnome).

Indications for Test

All patients with symptoms suggestive of adRP, especially with an unusual perivascular cuff of RPE atrophy.


Official Gene Symbol OMIM ID
TOPORS 609507
Inheritance Abbreviation
Autosomal Dominant AD
Autosomal Recessive AR
X-Linked XL
Mitochondrial MT


Name Inheritance OMIM ID
Retinitis Pigmentosa 31 609923

Related Test

Retinitis Pigmentosa Panel


  • Booij JC. 2005. Identification of mutations in the AIPL1, CRB1, GUCY2D, RPE65, and RPGRIP1 genes in patients with juvenile retinitis pigmentosa. Journal of Medical Genetics 42: e67–e67. PubMed ID: 16272259
  • Bowne, S.J. et al. (2008). "Mutations in the TOPORS gene cause 1% of autosomal dominant retinitis pigmentosa." Mol Vis 14:922-927. PubMed ID: 18509552
  • Chakarova, C.F. et al. (2007). "Mutations in TOPORS cause autosomal dominant retinitis pigmentosa with perivascular retinal pigment epithelium atrophy." Am J Hum Genet 81(5):1098-1103. PubMed ID: 17924349
  • Chakarova, C.F. et al. (2011). "TOPORS, implicated in retinal degeneration, is a cilia-centrosomal protein." Hum Mol Genet 20(5):975-987. PubMed ID: 21159800
  • Human Gene Mutation Database (Bio-base).
  • RetNet
  • Selmer, K.K. et al. (2010). "Autosomal dominant pericentral retinal dystrophy caused by a novel missense mutation in the TOPORS gene." Acta Ophthalmol 88(3):323-328. PubMed ID: 19183411
  • Van Soest S., Westerveld A. 1999. Survey of ophthalmology. 43: 321-34. PubMed ID: 10025514


Ordering Options

We offer several options when ordering sequencing tests. For more information on these options, see our Ordering Instructions page. To view available options, click on the Order Options button within the test description.

myPrevent - Online Ordering

  • The test can be added to your online orders in the Summary and Pricing section.
  • Once the test has been added log in to myPrevent to fill out an online requisition form.
  • PGnome sequencing panels can be ordered via the myPrevent portal only at this time.

Requisition Form

  • A completed requisition form must accompany all specimens.
  • Billing information along with specimen and shipping instructions are within the requisition form.
  • All testing must be ordered by a qualified healthcare provider.

For Requisition Forms, visit our Forms page

If ordering a Duo or Trio test, the proband and all comparator samples are required to initiate testing. If we do not receive all required samples for the test ordered within 21 days, we will convert the order to the most effective testing strategy with the samples available. Prior authorization and/or billing in place may be impacted by a change in test code.

Specimen Types

Specimen Requirements and Shipping Details

PGxome (Exome) Sequencing Panel

PGnome (Genome) Sequencing Panel

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