Gelatinous Drop-Like Corneal Dystrophy (GDLD) via the TACSTD2 Gene
Summary and Pricing 
Test Method
Exome Sequencing with CNV Detection
| Test Code | Test Copy Genes | Test CPT Code | Gene CPT Codes Copy CPT Code | Base Price | |
|---|---|---|---|---|---|
| 8985 | TACSTD2 | 81479 | 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.
Clinical Features and Genetics
Clinical Features
Gelatinous drop-like corneal dystrophy (GDLD) is a rare autosomal recessive disorder. However, it is more prevalent in Japan with estimated prevalence of 1 in 300,000. GDLD is a form of primary corneal amyloidosis leading to blindness. Clinically, GDLD is characterized by grayish, mulberry-like protruding corneal depositions of amyloid with a prominent hyperfluorescence of the cornea that results in severely impaired visual acuity. These symptoms usually appear in the first decade of life. Most patients require corneal transplantation (Tsujikawa et al. 1998; Kawasaki and Kinoshita 2011; Tsujikawa 2012).
Genetics
Autosomal recessive GDLD is caused by mutation in the TACSTD2 (tumor-associated calcium signal transducer 2) gene (previously known as M1S1 and also TROP2) located at chromosome 1p32. TACSTD2 encoded protein is a monomeric cell surface glycoprotein, which is shown to be localized at the cell-to-cell borders of all epithelial layers and also in other stratified epithelia-type tissues such as conjunctiva, skin, pharynx, esophagus, uterine cervix and vagina (Nakatsukasa et al. 2010). High protein expression levels were found in human carcinomas (Ripani et al. 1998). This protein likely functions as a cell-to-cell adhesion receptor, which explains the impaired corneal epithelium barrier function in GDLD patients. This protein may also play a role in regulating the growth of carcinoma cells and act as a calcium signal transducer (Fornaro et al. 1995; Ripani et al. 1998). The mutation c.352C>T(p.Gln118*) was reported as a founder mutation in Japanese GDLD patients (Tsujikawa et al. 1998).
Clinical Sensitivity - Sequencing with CNV PGxome
A mutation screening in 26 affected members of 20 Japanese GDLD families identified TACSTD2 mutations in homozygous or compound heterozygous state in all 26 individuals. A founder mutation c.352C>T(p.Gln118*) was found in 33 out of of 40 (82.5%) disease alleles (Tsujikawa et al.1999).
Testing Strategy
This test provides full coverage of all coding exons of the TACSTD2 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 corneal amyloidosis are candidates. This test may also be considered for the reproductive partners of individuals who carry pathogenic variants in TACSTD2.
All patients with symptoms suggestive of corneal amyloidosis are candidates. This test may also be considered for the reproductive partners of individuals who carry pathogenic variants in TACSTD2.
Gene
| Official Gene Symbol | OMIM ID |
|---|---|
| TACSTD2 | 137290 |
| Inheritance | Abbreviation |
|---|---|
| Autosomal Dominant | AD |
| Autosomal Recessive | AR |
| X-Linked | XL |
| Mitochondrial | MT |
Disease
| Name | Inheritance | OMIM ID |
|---|---|---|
| Lattice Corneal Dystrophy Type III | AR | 204870 |
Citations
- Fornaro M, Dell’Arciprete R, Stella M, Bucci C, Nutini M, Capri MG, Alberti S. 1995. Cloning of the gene encoding Trop-2, a cell-surface glycoprotein expressed by human carcinomas. Int. J. Cancer 62: 610–618. PubMed ID: 7665234
- Kawasaki S, Kinoshita S. 2011. Clinical and basic aspects of gelatinous drop-like corneal dystrophy. Dev Ophthalmol 48: 97–115. PubMed ID: 21540633
- Nakatsukasa M, Kawasaki S, Yamasaki K, Fukuoka H, Matsuda A, Tsujikawa M, Tanioka H, Nagata-Takaoka M, Hamuro J, Kinoshita S. 2010. Tumor-Associated Calcium Signal Transducer 2 Is Required for the Proper Subcellular Localization of Claudin 1 and 7. The American Journal of Pathology 177: 1344–1355. PubMed ID: 20651236
- Ripani E, Sacchetti A, Corda D, Alberti S. 1998. Human Trop-2 is a tumor-associated calcium signal transducer. Int. J. Cancer 76: 671–676. PubMed ID: 9610724
- Tsujikawa M, Kurahashi H, Tanaka T, Nishida K, Shimomura Y, Tano Y, Nakamura Y. 1999. Identification of the gene responsible for gelatinous drop-like corneal dystrophy. Nat. Genet. 21: 420–423. PubMed ID: 10192395
- Tsujikawa M, Kurahashi H, Tanaka T, Okada M, Yamamoto S, Maeda N, Watanabe H, Inoue Y, Kiridoshi A, Matsumoto K, Ohashi Y, Kinoshita S, Shimomura Y, Nakamura Y, Tano Y. 1998. Homozygosity mapping of a gene responsible for gelatinous drop-like corneal dystrophy to chromosome 1p. Am J Hum Genet 63: 1073–1077. PubMed ID: 9758629
- Tsujikawa M. 2012. Gelatinous drop-like corneal dystrophy. Cornea 31 Suppl 1: S37–40. PubMed ID: 23038033
Ordering/Specimens
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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ORDER OPTIONS
View Ordering Instructions1) Select Test Type
2) Select Additional Test Options
No Additional Test Options are available for this test.