Which are the causes of Floating-Harbor syndrome?

Floating-Harbor syndrome is a rare genetic disorder caused by specific mutations in the SRCAP gene, which provides instructions for making a protein involved in regulating gene expression. This condition is typically not inherited from parents but occurs as a de novo (new) mutation in the affected individual, meaning it happens spontaneously during early development.

What is the primary genetic cause of Floating-Harbor syndrome?

The scientific community has identified that Floating-Harbor syndrome is primarily caused by heterozygous mutations in the SRCAP gene (Snf2-related CREBBP activator protein). Think of the SRCAP gene as a master conductor in an orchestra; its job is to help turn other genes "on" or "off" at the right time. When this gene is mutated, the "conductor" cannot properly regulate the expression of various other genes, which leads to the characteristic physical and developmental features associated with Floating-Harbor syndrome.

Is Floating-Harbor syndrome an inherited condition?

In the vast majority of documented cases, Floating-Harbor syndrome is not inherited from a parent. Instead, it arises as a de novo mutation. This means the genetic change occurs for the first time in the affected individual, either in the egg or sperm cell or very early in embryonic development. Because it is a de novo event, the recurrence risk for parents who have one child with Floating-Harbor syndrome is very low, though it is still recommended that families consult with a clinical geneticist to review their specific family history.

What are the specific mutation patterns in the SRCAP gene?

Research indicates that the mutations causing Floating-Harbor syndrome are almost exclusively located in a specific region of the SRCAP gene. These mutations are typically "truncating," meaning they lead to a shortened, non-functional protein. Key facts regarding the genetic mechanism include:

• Location: The mutations are clustered in the terminal exons of the SRCAP gene.


• Mechanism: The resulting protein is unable to properly incorporate into the chromatin-remodeling complex, which is essential for reading DNA.


• Impact: Because the body produces a mix of normal and dysfunctional protein, the condition follows an autosomal dominant pattern of inheritance if it were to be passed down.

Are there environmental or external triggers for Floating-Harbor syndrome?

There is no evidence to suggest that Floating-Harbor syndrome is caused by environmental factors, toxins, maternal health choices, or infections during pregnancy. It is strictly a genetic condition. It is important to distinguish between "causes" and "risk factors" in this context: while a "risk factor" might be something like maternal age for certain chromosomal conditions, Floating-Harbor syndrome has no identified lifestyle or environmental risk factors. It is a biological event that occurs independently of external influence.

How is current research improving our understanding of the etiology?

While the link between the SRCAP gene and Floating-Harbor syndrome is well-established, researchers are currently focused on understanding exactly how the loss of this protein affects neurodevelopment and skeletal growth. By studying these molecular pathways, scientists hope to eventually identify potential therapeutic targets. Currently, 11 people with Floating-Harbor syndrome have shared their experiences on DiseaseMaps.org, providing valuable anecdotal data that supports clinical researchers in mapping the spectrum of this rare condition.

Next steps

• Consult with a clinical geneticist to confirm a diagnosis through molecular genetic testing (specifically sequencing of the SRCAP gene).


• Schedule a comprehensive evaluation with a pediatric endocrinologist to monitor growth and development.


• Connect with the DiseaseMaps community to share experiences with others navigating a diagnosis of Floating-Harbor syndrome.


• Request a referral to a speech-language pathologist, as communication challenges are common in this population.

Medical disclaimer: This information is for educational purposes only and does not constitute medical advice, diagnosis, or treatment; always seek the guidance of a qualified healthcare provider with any questions regarding a medical condition.

References

• NIH Genetic and Rare Diseases Information Center (GARD): Floating-Harbor syndrome.


• Online Mendelian Inheritance in Man (OMIM): #136140 Floating-Harbor Syndrome.


• Orphanet: Floating-Harbor syndrome (ORPHA:352).


• Hood, R. L., et al. (2012). "Mutations in the transcriptional regulator SRCAP cause Floating-Harbor syndrome." American Journal of Human Genetics.