威廉斯症候群：過於友善的人

Williams Syndrome is a rare genetic condition that makes people very friendly and loving towards others. Imagine walking down the street and feeling a warm connection with every person you see. This is a common experience for individuals with Williams Syndrome, who often treat strangers as if they are their best friends. They are known for their affectionate nature, being very talkative, and having a strong desire to connect with others. However, this extreme friendliness can sometimes lead to challenges. People with Williams Syndrome may struggle with feelings of loneliness and isolation, as their trusting nature can make them vulnerable to those who may not have good intentions. Alysson Muotri, a professor at the University of California, San Diego, explains that individuals with this condition are often too trusting. They may not recognize when someone poses a danger, which can lead to unfortunate situations. This highlights an important aspect of human evolution: our brains have developed to be cautious around new people to protect ourselves. In addition to their social challenges, people with Williams Syndrome often face various health issues. They may experience developmental delays and learning disabilities, which can affect their growth and learning compared to their peers. For instance, many individuals with this condition have distinct physical features, such as a small, upturned nose and a wide mouth. Over the years, scientists have been studying Williams Syndrome to gain insights into the genetic and neurological factors that contribute to its characteristics. Humans typically have 46 chromosomes, organized into 23 pairs. During the formation of sperm and egg cells, a process called recombination occurs, where genetic material is exchanged between matching chromosomes. However, in the case of Williams Syndrome, a section of DNA from one copy of chromosome seven is accidentally deleted. This deletion results in the loss of between 25 to 27 genes, which play crucial roles in various bodily functions. For example, one gene called ELN is responsible for producing a protein called elastin, which helps maintain the flexibility of blood vessels. Without elastin, individuals with Williams Syndrome may experience cardiovascular issues. Another gene, BAZ1B, is involved in the growth of stem cells that eventually develop into various tissues in the body. The physical features associated with Williams Syndrome, such as a small nose and wide mouth, are also linked to these genetic changes. Scientists are particularly interested in understanding why people with Williams Syndrome are so friendly. One theory suggests that the neural connections in their brains may differ from those of typical individuals. Some researchers believe that the gene GTF2I could play a significant role in this increased sociability. Studies have shown that animals lacking GTF2I tend to be more social than their counterparts. For instance, mice without this gene are more likely to approach other mice, and dogs possess a variant of GTF2I that may contribute to their friendly behavior. In contrast, individuals with autism often exhibit social phobia, which is quite different from the behavior seen in those with Williams Syndrome. The exact mechanisms by which GTF2I influences sociability are still being explored. The protein produced by GTF2I helps regulate the expression of many other genes, which may impact social behavior. One area of interest is the myelin sheath, which insulates nerve fibers and is crucial for efficient communication between neurons. Boaz Barak, an associate professor at Tel Aviv University, has conducted research indicating that mice lacking GTF2I exhibit impaired myelination, leading to weaker communication between brain regions responsible for fear and social decision-making. This could explain why individuals with Williams Syndrome do not experience fear or mistrust towards strangers. Interestingly, a drug called clemastine, commonly used to treat allergies, has been found to improve myelination. Given that brain samples from individuals with Williams Syndrome show myelination impairments, Barak and his team are investigating the potential of clemastine as a treatment for this condition. They are currently conducting safety and effectiveness assessments in a clinical trial, which is expected to conclude in December 2025. Families of individuals with Williams Syndrome often express their love for their children's friendly nature, stating that they would not want to change their affectionate behavior. While researchers aim to develop treatments for those who seek them, they also recognize the value of the unique traits that individuals with Williams Syndrome possess. Another intriguing aspect of this research is the discovery that individuals with Williams Syndrome may have more neural connections related to reward in their brains. This could explain why they feel happy when they encounter new people. In contrast, children with autism tend to have fewer neuronal connections. This research highlights the importance of social behavior in human evolution. Scientists believe that being friendly and trusting is essential for our survival as a species, as it fosters collaboration and cooperation among individuals. They suggest that evolution has fine-tuned the expression of the GTF2I gene to strike a balance between being too friendly and not friendly enough. This balance is crucial for maintaining healthy social interactions and relationships.