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Myotonic Dystrophy 2 (ZNF9/CNBP) Genetic Testing (Repeat Expansion)

CPT: 81187
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Genes Assessed


Specimen Requirements


Specimen

Blood | Extracted DNA | Cultured Fibroblasts | Muscle | Buccal Cells

Volume

4 mL, 1 swab, or 200 ng of DNA, 75 mg muscle, 90% cell confluency

Container

Blood: Lavender-Top (EDTA) Tube, Buccal Swab from MNG Kit, Tissue or Extracted DNA: Sterile screw capped vial, Cultured cells: T25 flask

Collection

Blood: Specimens should be shipped overnight in a secure container at room temperature. Extracted DNA: Should be shipped overnight at room temperature. If previously frozen, DNA can be shipped in an insulated container with wet or dry ice. Cultured Fibroblasts: T-25 flasks containing fibroblasts should be shipped in an insulated container at room temperature. Flasks should be completely filled with media and cells should be ~90% confluent. Fibroblast samples must be certified free from Mycoplasma. MNG is able to perform this service for a small charge (TC05). For NGS panels, TAT will be extended by 7-14 days if cells are not confluent upon arrival. Muscle: Samples should be shipped frozen in an insulated container with 5-7 lbs. dry ice, overnight. Buccal cells: Should be shipped overnight in a secure container at room temperature.

Storage Instructions

Blood - ship ASAP, but stable up to 5 days post-collection at room temperature. DO NOT FREEZE; Swab - 60 day post-collection room temperature stability; DNA - ship at room temperature after extraction; Fibroblasts - ship flask in insulated container at room temp or refigerated; Muscle - ship in insulated container with 5-7 lbs of dry ice

Stability Requirements

Room Temperature: Blood - 5 days, Swab - 60 days, DNA - 30 days, Muscle - 0 days, Fibroblasts - 2-3 days; Refrigerated: Blood - 5 days, Swab - 60 days, DNA - 30 days, Muscle - 0 days, Fibroblasts - 2-3 days; Frozen: Blood - DO NOT FREEZE, Swab - 60 days, DNA - Indefinitely, Muscle - Indefinitely, Fibroblasts - Indefinitely; Freeze/Thaw: None

Causes for Rejection

Extracted DNA A260:A280 ratio of outside of 1.8-2.0 range; Thawed and/or fatty muscle sample

Test Details


Use

Type 2 myotonic dystrophy results from a mutation in the CNBP gene known as a tetranucleotide repeat expansion. This mutation increases the size of the repeated CCTG segment in the CNBP gene. People with type 2 myotonic dystrophy have from 75 to more than 11,000 CCTG repeats.

Limitations

Maximum reportable sizing: 373 repeats

Methodology

Repeat-Primed PCR (QP-PCR)

Recommended MNG Kits

SINGLE Blood Genetic Testing, Buccal Swab Genetic Testing

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
620087 ZNF9/CNBP Repeat Expansion 81883-1 620166 CNBP RE Result 81883-1
620087 ZNF9/CNBP Repeat Expansion 81883-1 620089 CNBP RE Interpretaion N/A
620087 ZNF9/CNBP Repeat Expansion 81883-1 630833 PDF 80563-0