MEF2C Awareness Day Date in the current year: May 14, 2026

MEF2C stands for “myocyte-specific enhancer factor 2C”, which is a type of transcription factor protein. These proteins control the activation and deactivation of other genes, ensuring they are expressed in the right cells, at the right time, and in the right amount. MEF2C specifically regulates the expression of nearly 2,000 genes that participate in the development of multiple organs and systems, including the brain and nervous system, heart and vascular system, immune system, and skeletal muscles.

Mutations or deletions in the MEF2C gene cause MEF2C-related disorders, a group of neurodevelopmental conditions also known as MEF2C haploinsufficiency syndrome. “Haploinsufficiency” means that one copy of the gene is inactive or missing, and the remaining copy is insufficient for normal function. The mutation is usually de novo, meaning it arose spontaneously and was not inherited from a parent.

MEF2C haploinsufficiency syndrome is considered a severe form of autism spectrum disorder (ASD). Its common symptoms include:

• Global developmental delay
• Sleeping and feeding difficulties
• Moderate to severe intellectual disability
• Severely delayed or absent speech
• Early-onset seizures or epilepsy
• Low muscle tone (hypotonia) in infancy
• Autistic-like behaviors, including stereotypical and repetitive movements and poor social skills
• Significant motor delay (about half of the affected individuals are unable to walk independently)

Like most rare genetic disorders, MEF2C haploinsufficiency syndrome is incurable. Management is supportive and includes seizure control, physical therapy, speech therapy, and developmental support. The life expectancy of individuals with this condition is unclear because it is rare and understudied. Generally, it is believed that individuals whose epilepsy is well-managed and who do not develop significant medical complications will likely survive into adulthood with proper care; however, they will require lifelong support and medical management. Living fully independently with MEF2C haploinsufficiency syndrome is rare due to significant intellectual disability and absent or very limited speech.

May 14 was chosen as MEF2C Awareness Day in reference to MEF2C’s location: 5q14.3 (region 1, band 4, subband 3 on the long arm of chromosome 5). It is supported and promoted by various organization that raise awareness of MEF2C-related disorders, including the MEF2C Foundation UK, the US MEF2C Foundation, and the MEF2C Family Foundation.

There are many ways to participate in MEF2C Awareness Day. You can learn more about this rare disorder and share what you’ve learned with others; donate to an organization that supports affected families or funds research; wear blue to show solidarity with the MEF2C community and start conversations; spread the word on social media with the hashtag #MEF2CAwarenessDay.