Targeted gene therapy for FOXP1

Targeted gene therapy for FOXP1

A deletion or mutation on the FoxP1 gene is a genetic disorder that can occur spontaneously (de novo) as well as be hereditary. An altered protein structure causes a syndrome with different symptoms, which influences the neurological development: This gene generates a wrong protein which causes problems for the whole mental and physical development.

All milestones that come naturally to any other child like walking, talking, reading, and writing are enormously challenging for children and adults with FOXP1 syndrome.

LUMC’s mission is  to cure hereditary diseases and genetic abnormalities, such as FOXP1, and has developed a line of research for this.

Internationally there is great interest for this research program. A treatment or cure for the FoxP1 syndrome would mean a significant advancement in finding a treatment or cure for a vast majority of other genetic disorders.

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What does FOXP1 syndrome mean for a patient like Fenn

What does FOXP1 syndrome mean for a patient like Fenn

Meet Fenn!

When Fenn was a baby, we noticed that he startled and became anxious easily. He also didn’t meet any of the normal baby milestones like grabbing toys, making a sound, or rolling over. In fact, none of these milestones were even slightly present. Swallowing was hard for him, and sleeping during the night was a disaster. Overall, things weren’t really developing as they should, but we weren’t worried. 

It wasn’t until 8 months when our physician had to refer Fenn to a neurologist because he started developing a strange kind of seizure that completely strained him in which he was unable to make contact and would perspire enormously. This led to a complete medical circus….

After countless checkups with a neurologist, a geneticist, and our physician, we finally got Fenns’ diagnoses around the age of three. “Well, we finally found something”; we were told in a phone call.  Fenn had a genetic mutation on the FoxP1 gene.

The only answer they were able to give us when we asked what this means was;

“Developmental delay and mental disability, but we really don’t have any answers, because we simply don’t know much about this rare genetic condition. He just has a little baking error. It could be that he will never walk or talk, but we just don’t know. We wish you all the best and have fun with him.”

That’s it?! And now what? All your dreams and expectations of a normal life are out the window. Days, weeks, months of disbelief, silent grieve, anxiety and searching on the internet followed.

Cancelling the “normal” daycare center and giving up on a normal school were such difficult tasks. Looking into the world of special needs schools and being confronted with all these different special needs children was extremely difficult for us. Was this our future? Every time you say goodbye to a normal life bit by bit.

Every day we see Fenn (now nine years old) struggling and doing his best to participate in all the activities at school and at home that are not always easy for him. Some days his eyes don't work well which makes him anxious and makes him want to hold your hand all the time. Or, he tries to run and falls for the tenth time that day. Nothing comes naturally and everything takes a lot of effort for him. He’s easily overstimulated and has been suffering from irrational fears for a few years now. It’s so special that despite all his struggles, he often has a cheerful smile on his face. But how great would it be if everything was just a little easier for him. Even the smallest chance of a solution means that you would do literally everything as a parent to make this possible.

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What does FOXP1 syndrome mean for a patient like Fenn

Genetic Study by Willeke van Roon-Mom, Phd, LUMC

Genetic Study by Willeke van Roon-Mom, Phd, LUMC

There are indications that a possible repair of effects of the FoxP1 syndrome is conceivable.

In this project we want to study how a mutation in the DNA binding domain of FOXP1 can influence the neurological development. We use the ‘Brain-in-a-Dish’ technology where it is possible to create 3D brainorganoids (mini brain). 

By creating organoids with and without the FOXP1 mutation, we can study where and when changes in development of the brain occur.

This cell model will be important for further studies on the development of FOXP1 syndrome and the development of therapies.

Exploratory studies will also be done to be able to remove the error in the DNA that causes FOXP1 syndrome with the so-called Adenine Base Editors. These Base Editors is a form of genome editing CRISPR/Cas.

Internationally there is great interest in this research.

The solution for FOXP1 syndrome could have a major impact on a solution for many other genetic mutations.

Many have the same effects on the human system, because of the production of the altered proteins.

Rare diseases rely on private initiatives to work towards a cure. In just over a year, the Kind Beter Foundation has raised more than 90,000 Euros through private initiatives. The Bontius Foundation has decided to make a case for the remaining amount to also make the second year of this research possible.

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Genetic Study by Willeke van Roon-Mom, Phd, LUMC

Video item LUMC

Clinical study by Dr. Saskia Koene

Dr. Saskia Koene, clinical geneticist in training, Leiden Universitair Medisch Centrum (LUMC), started mapping the possibilities and limitations of FOXP1 patients in order to determine how we can help children with FOXP1 syndrome develop in the best way possible.

In collaboration with the USA and Australia a questionnaire is being developed.

In the attached video a short explanation by Dr. Saskia Koene; what is FoxP1 syndrome and what does it mean.

FOXP1 symptoms

FOXP1 symptoms

The severity of the symptoms are different and vary for each patient. Some of them just need some extra help and can lead almost normal lives. Unfortunately, others need 24-hour care and guidance throughout their entire lives.

A deviation on the FoxP1 gene can cause several different symptoms:

  • Intellectual disability
  • Speech disorder
  • Poor fine and gross motor skills development
  • Autism or autistic like features
  • Strong diminished immune system
  • Visual problems
  • High Sensitivity
  • Anxiety
  • Poor concentration skills
  • Hyperactivity
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Charitable gift from abroad

Charitable gift from abroad

Is your organisation or foundation headed in another country? It is possible to donate with tax deductability or Gift Aid. Please email us by clicking one of the buttons below. The right details will be sent to you immediately.


United Kingdom

United States of America


For more information, please contact Ms. Ambika Lucassen from LUMC Research Foundation +31 (0)71 526 57 49.

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Charitable gift from abroad

Donation as a fund or company

Donation as a fund or company

Would you like more information, or do you have information about how you can co-finance?

Please contact our Relationship Manager Ambika Lucassen of the Bontius Foundation | LUMC Research Foundation via telephone number 071 526 5749 or donate directly using the following account number NL03 INGB 0657 9199 26 stating: FOXP1

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Donation as a fund or company


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