Explaining Angelman Syndrome and Its Variations

By Danielle Bradshaw from In The Cloud Copy

Angelman syndrome is a rare genetic disorder that is a combination of multiple physical and mental disabilities. 1 in every 15,000 people have it and the complications of the disease can range from speech and balance issues, some degree of intellectual disability, developmental delays (which typically begin around 6 to 12 years old), and seizures. People with Angelman syndrome can often be seen constantly smiling and laughing; they are generally cheerful and enthusiastic.

Other symptoms include:

  • Problems going to or staying asleep
  • Rigid, stiff movements
  • Tongue wriggling and thrusting
  • Fair colored eyes, hair, and skin
  • Small, flat (in the back) head
  • Odd movements, like having arms lifted while walking and waving the hands around

Although Angelman syndrome is accompanied by many physical and mental complications, it doesn’t negatively impact the lifespans of those that have it. While there is no cure, it is very possible to live a long and healthy life with this illness. People can, however, seek treatments to help with any problems that they may have with sleep, medical, and developmental issues.

What Causes Angelman Syndrome?

The basic cause of this genetic illness is either due to improper functionality or a mutation within the UBE3A gene. Everyone has two of these particular genes; one comes from our mother, and the other from our father. There are areas within our brains where we use only the UBE3A gene that we get from the maternal portion of our DNA; the gene we get from our father is inert.

What the UBE3A gene actually does is help mark proteins that have been used within our body’s cells for recycling. When the mutation occurs, this function doesn’t take place as it’s supposed to and some proteins are still “working” long after they should have been recycled – which results in Angelman syndrome.

There are different variations of Angelman syndrome and what version a person has depends on what’s going on with their UBE3A gene, specifically.

Angelman Syndrome Variants

Missing maternal UBE3A Genes

This is the most common cause of Angelman syndrome (approximately 70% of cases) and as the title suggests, it is the result of a lack of UBE3A from the mother’s DNA – also known as chromosome 15. In these cases, the brain – or rather, certain parts of the brain – are unable to make UBE3A proteins regardless of a healthy paternal copy of the gene.

Mutated UBE3A Genes

Gene mutations are the second most common cause of Angelman syndrome – around 11% of cases are the result of changes within the gene. Mutations can affect how the body’s cells make the protein (the UBE3A is created with defects) or they can cause the cells to not produce the protein at all.

Defective Imprinting

It’s been found that about 5% of people that have Angelman syndrome undergo a transformation of sorts in the UBE3A gene inherited from their mother that causes it to go silent – much like the paternal version. This is what’s known as an imprinting center defect.

Mosaicism

This is among the rarer causes of the genetic disorder, occurring when some cells have a normally functioning UBE3A gene while others are defective and inhibit the creation of normal protein. Because some cells in their bodies have normal UBE3A, these patients tend to have less severe symptoms as the protein is only defective in “patches”.

Uni-parental Disomy

This is by far the rarest cause of Angelman syndrome, affecting roughly 1% of those with the disorder. Uni-parental disomy is what happens when someone inherits two copies of UBE3A from their father. As stated before, the paternal gene is inert, so the brain doesn’t have any of the protein, even if the UBE3A genes themselves are healthy.

Cases with No Known Causes

This isn’t as rare as other cases, but 10% or so of people that seemingly have Angelman syndrome symptoms can’t be confirmed as actually having the illness. It may be possible that they have an entirely new type of Angelman syndrome that hasn’t been scientifically documented.


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