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Test Code KCNJ11 SEQ KCNJ11 Sequencing

Clinical System Name

KCNJ11 Sequencing Analysis Request

Synonyms

KIR6.2

Description

Approximately 30% of PNDM is attributed to activating mutations of KCNJ11, the gene encoding the protein Kir6.2 which is one of the two components of the beta-cell plasma membrane ATP-dependent potassium channel. KCNJ11 mutations are also found to cause TNDM. Most patients with mutations in KCNJ11 have isolated diabetes, but 20% have DEND syndrome, which is associated with neurologic features such as generalized epilepsy and developmental delay.

 Testing is appropriate for:

  • Infants with persistent hyperglycemia ± history of intrauterine growth retardation, osmotic polyuria, severe hydration and failure to thrive.
  • Older individuals with history of the above symptoms
  • Infants with hyperinsulinism 

Sample Requirements

Specimen: Whole blood, cord blood

Container(s): Lavender/EDTA, Yellow/ACD A or B

Preferred Vol: 3 mL

Minimum Vol: 1 mL

 

Note: Heparin samples (Green tops) are unacceptable.

 

Specimen: Extracted DNA

Minimum: 10µg

Note: DNA concentration minimum 50 µg/mL; 260/280 ratio 1.70-2.00

  

Specimen: Cultured cells

Acceptable:  Fibroblasts

Container(s): T-25 flasks

Preferred Vol: 2 flasks

Processing Instructions

Reject due to: Heparin

Spin: No

Aliquot: No

Temp: Refrigerate

Storage location: Molecular Genetics box in CPA refrigerator #2

 

Off-site collection: Refrigerate blood samples until ready to ship.  Transport all sample types at room temperature via overnight shipping.

Stability

Specimen Type Temperature Time
Cultured cells Room temp 3 days
Whole blood, extracted DNA Room temp 3-5 days
Whole blood, extracted DNA Refrigerated 7 days
Extracted DNA Frozen ok

 

Note: Whole blood samples > 7days may be submitted to be assessed by our lab for acceptability for testing.

Availability

STAT Performed TAT
Contact lab Monday - Friday 2-3 weeks

 

Performing Laboratory

Seattle Children's Laboratory

Department

Department:  Molecular Genetics Laboratory

Phone: 206-987-3872

 

Lab Client Services: 206-987-2617

 

Lab Genetic Counselor: LabGC@seattlechildrens.org

Reference Range

Interpretive report will be provided

Methodology

Method: Bi-directional sequencing of all exons and exon-intron boundaries

 

Limitations: Mutations in the promoter region, large deletions, large duplications, or rare recombinant mutations may not be detected by this method.

CPT Codes

81403 (updated 1/19/16 by jconta)

Requisition

Molecular Genetics

Clinical Utility

Approximately 30% of PNDM is attributed to activating mutations of KCNJ11, the gene encoding the protein Kir6.2 which is one of the two components of the beta-cell plasma membrane ATP-dependent potassium channel. KCNJ11 mutations are also found to cause TNDM. Most patients with mutations in KCNJ11 have isolated diabetes, but 20% have DEND syndrome, which is associated with neurologic features such as generalized epilepsy and developmental delay.

Neonatal diabetes mellitus (NDM) is a defect of insulin production characterized by the onset of hyperglycemia in the first six months of life. Clinical features include intrauterine growth retardation, hyperglycemia, glycosuria, osmotic polyuria, severe dehydration, and failure to thrive. It is a rare condition occurring in one of 100,000 to 500,000 live births. About half of NDM cases are classified as transient neonatal diabetes mellitus (TNDM), in which the condition disappears during infancy but can reappear later in life. ABCC8 mutations are also found to cause TNDM. 

 

The remaining cases are life-long and are called permanent neonatal diabetes mellitus (PNDM). Management may be tailored depending on the specific mutations. For example, those with KCNJ11 and ABCC8 mutations can be successfully treated with oral sulfonylureas instead of insulin.
 

KCNJ11 sequencing can be performed individually or as part of one of our diabetes panels: Congenital Hyperinsulinism Panel, MODY Panel, or Neonatal Diabetes Panel