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Intellectual Disability via the GRIK2 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
GRIK2 81479 81479,81479 $990
Test Code Test Copy Genes Test CPT Code Gene CPT Codes Copy CPT Code Base Price
10475GRIK281479 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


  • Renee Bend, PhD

Clinical Features and Genetics

Clinical Features

Intellectual Disability (ID) is a heterogeneous group of neurodevelopmental disorders, characterized by congenital limitation in intellectual functioning (intelligence quotient, IQ ≤70), and adaptive behavior. It is diagnosed in ~1–3% of the population before 18 years of age (American Association of Intellectual and Developmental Disabilities, AAIDD).

Deficiency of Glutamate receptor ionotropic kainite 2 (GRIK2) primarily leads to mental retardation type 6 (MRT6); however there is at least one report of a gain of function pathogenic variant in GRIK2. GRIK-related intellectual disability can be both non-syndromic and syndromic. The clinical features may include (but may not be limited to) intellectual disability, developmental delay, motor and speech delay, epilepsy, ataxia, hypotonia, dystonia, microcephaly, behavioral problems including autism, happy demeanor, short attention span, stereotypic behavior, and bouts of laughter (Motazacker et al. 2007. PubMed ID: 17847003; Najmabadi et al. 2007. PubMed ID: 17120046; Cordoba et al. 2015. PubMed ID: 25039795; Guzmán et al. 2017. PubMed ID: 28180184; Monies et al. 2017. PubMed ID: 28600779; https://gene.sfari.org/database/human-gene/GRIK2).


GRIK2-related (also described as GLUR6) intellectual disability is primarily transmitted in autosomal recessive manner; however there is at least one report of a de novo pathogenic variant (Guzmán et al. 2017. PubMed ID: 28180184). GRIK2 maps to chromosome 6q16.3 and encodes a 908 amino acid polypeptide subunit of kainate receptors (KARs). Glutamate receptor ionotropic kainite 2 (GRIK2) is a SUMO (small ubiquitin-like modifier protein) substrate and is presumed to play role in excitatory neurotransmission in the brain, induction of long-term potentiation and axonal Ca++ homeostasis (Contractor et al. 2001. PubMed ID: 11182092; Martin et al. 2007. PubMed ID: 17486098; Ouardouz et al. 2009. PubMed ID: 19224535). To date, missense, nonsense and splice site variants have been reported, and there is at least one report of a complex rearrangement (Human Gene Mutation Database).

Clinical Sensitivity - Sequencing with CNV PGxome

This test is predicted to detect pathogenic variants in <0.1% of individuals with intellectual disability (ID). In this context, it is important to note that although pathological variants over 800 genes have been identified in individuals with ID, a genetic diagnosis is still lacking in most cases due to extreme clinical and genetic heterogeneity of the condition (Vissers et al. 2016. PubMed ID: 26503795).

Testing Strategy

This test provides full coverage of all coding exons of the GRIK2 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

Targeted Sanger sequencing in GRIK2 is appropriate for the family members of patients with GRIK2 pathogenic variants. Of note, a panel (or exome/genome) sequencing test would nearly always be more appropriate for patients with intellectual disabilities, unless previous clinical knowledge implicates the GRIK2 gene. Prenatal testing is possible if the genetic diagnosis has been firmly established in an affected family member. This test may also be considered for the reproductive partners of individuals who carry pathogenic variants in GRIK2.


Official Gene Symbol OMIM ID
GRIK2 138244
Inheritance Abbreviation
Autosomal Dominant AD
Autosomal Recessive AR
X-Linked XL
Mitochondrial MT


Name Inheritance OMIM ID
Mental Retardation, Autosomal Recessive 6 AR 611092


  • Contractor et al. 2001. PubMed ID: 11182092
  • Cordoba et al. 2015. PubMed ID: 25039795
  • Guzmán et al. 2017. PubMed ID: 28180184
  • Human Gene Mutation Database (Bio-base).
  • Martin et al. 2007. PubMed ID: 17486098
  • Monies et al. 2017. PubMed ID: 28600779
  • Motazacker et al. 2007. PubMed ID: 17847003
  • Najmabadi et al. 2007. PubMed ID: 17120046
  • Ouardouz et al. 2009. PubMed ID: 19224535
  • Vissers et al. 2016. PubMed ID: 26503795


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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View Ordering Instructions

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2) Select Additional Test Options

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Note: acceptable specimen types are whole blood and DNA from whole blood only.
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