The GRIN2B Disorder
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What are genes?
Genes are the biological templates the body uses to make the structural proteins and enzymes needed to build and maintain tissues and organs. They are made up of strands of genetic code, denoted by the letters G, C, T and A. Humans have about 30,000 genes bundled into 46 chromosomes all coiled up in the nucleus of nearly every cell in the body.
What are G,C,T and A
The letters of the genetic code refer to the molecules guanine (G), cytosine (C), thymine (T) and adenine (A). In DNA, these molecules pair up: G with C and T with A. These “base pairs” become the rungs of the familiar DNA double helix. Each of us inherits about 60 new mutations from our parents, so actually having a mutation is extremely common! Unfortunately, in the case of our GRIN2B children, the pinpoint mutation of only one nucleotide out of 6 billion was in such a critical place that it causes a disease.
NMDA receptors are responsible for sending messages between nerve cells and has a critical role in learning and memory functions in the brain. The GRIN2B gene encodes the GluN2B subunit of NMDARs. Changes in this gene, referred to as a varation or mutation, has been implicated in a neurodevelopmental disorder characterized by hypotonia, developmental delay, intellectual disability, epileptic encephalopathies, and language and motor disorders. It has also been linked to Autism Spectrum Disorder and Attention Deficit Hyperactivity Disorder.
The terminology we often use
- Gain of Function (GOF) – When there is over-activity of the Receptor
- Lost of Function (LOF) – When there is under-activity of the Receptor
- Missense Mutation – When a single nucleotide is changed, and as a result a different protein is produced (more)
- Deletion Mutation – When the entire or part of the gene is missing (more)
Why and how does a mutation happen?
There are several causes for the GRIN2B mutations, the most common is called de novo, which means it happens spontaneously at the early stages of pregnancy.
Every human being has about 60 such mutations, since every human has more than 6 billion nucleotides (think about it as a book composed of 6 billion characters) the probability a mutation will happen in one of the critical area of the GRIN2B gene is very low.
A much less common cause for a GRIN2B disorder is an inherent mutation from one of the parents.
Currently, there are less than 500 known people living with GRIN2B disorder, worldwide. As Whole Exome Sequencing (WES test) becomes more accessible, we will see the number of individuals diagnosed with a GRIN2B- increase.
What are the possible symptoms?
Most of the patients with GRIN2B-disorder will have a normal life span.
With your loved ones’ genetic test (WES) results, you should contact (email) one of the centers that perform functional testing, which will most likely provide you with a detailed projection for your children’s specific mutation.
You can also search this list of known variants if the exact same variant has been documented.
The most common symptoms are: Global developmental delays, Epilepsy (seizures), Hypotonia (low muscle tone), Intellectual disability, Nonverbal (or delayed speech) and more.
Is there a cure?
GRIN2B-Related Neurodevelopmental Disorder is ultra-rare and there is currently no cure. We are working to change that.
What are the treatment options?
Although there is currently no cure for GRIN Disorders, symptoms may be improved with various therapies. Please see the Families section for more information.
Be sure to join the GRIN parent support groups, see links at the Families section.
Although not doctors, other parents are often one of the best sources of information and support\
The GRIN2B Disorder Research Foundation (GDRF) is dedicated to finding a cure for GRIN2B-Related Neurodevelopmental Disorder. We do this by promoting, coordinating and funding translational and clinical research. We are a team of parents and advocates who are fiercely focused on searching for a cure for our loved ones, as quickly as possible.
The GRIN Disorders Research Foundation (GDRF) is dedicated to finding a cure for GRIN genes disorders. We do this by funding translational and clinical research and building awareness.We are a team of parents and advocates who are fiercely focused on finding a cure for our loved ones, as quickly as possible.