CHST6

CHST6

The CHST6 gene is located on chromosome 16.

CHST6 (Carbohydrate Sulfotransferase 6) is a gene that encodes an enzyme responsible for sulfation of carbohydrates. It is primarily associated with a rare genetic disorder known as Macular Corneal Dystrophy (MCD). This disorder affects the cornea, leading to progressive vision loss and impairment.

Gene Structure

The CHST6 gene is located on chromosome 16q22.3 and consists of 7 exons. It spans approximately 10 kilobases and encodes a protein of 436 amino acids. The protein product of CHST6 is a sulfotransferase enzyme that catalyzes the transfer of sulfate groups to specific carbohydrate structures.

Function

The CHST6 enzyme plays a crucial role in the sulfation of carbohydrates, particularly in the cornea. Sulfation is a post-translational modification process that involves the addition of sulfate groups to specific positions on carbohydrates. This modification is essential for the proper functioning of various biological processes, including cell adhesion, signaling, and tissue development.

In the cornea, sulfation of carbohydrates is necessary for maintaining the transparency and integrity of the tissue. The CHST6 enzyme specifically sulfates keratan sulfate, a type of carbohydrate found in the corneal stroma. This sulfation process contributes to the proper hydration and structural organization of the cornea, ensuring its normal function.

Macular Corneal Dystrophy

Macular Corneal Dystrophy causes clouding of the cornea.

Macular Corneal Dystrophy (MCD) is an autosomal recessive disorder characterized by the progressive accumulation of abnormal sulfated carbohydrates in the cornea. This accumulation leads to the formation of cloudy deposits, resulting in impaired vision.

MCD is primarily caused by mutations in the CHST6 gene. These mutations disrupt the normal sulfation process, leading to the abnormal accumulation of unsulfated or undersulfated keratan sulfate in the cornea. Over time, these deposits cause the cornea to become progressively cloudy, leading to vision loss.

The symptoms of MCD usually appear in childhood or early adulthood and include blurred vision, sensitivity to light, and corneal clouding. As the disease progresses, individuals may experience significant visual impairment and may require corneal transplantation to restore vision.

Diagnosis and Treatment

Diagnosis of Macular Corneal Dystrophy involves a comprehensive eye examination, including visual acuity tests, corneal imaging, and genetic testing. Genetic testing can identify mutations in the CHST6 gene, confirming the diagnosis.

Currently, there is no cure for MCD. Treatment options focus on managing the symptoms and preventing further vision loss. This may include the use of corrective lenses, contact lenses, or surgical interventions such as corneal transplantation.

Conclusion

CHST6 is a gene that encodes an enzyme responsible for sulfation of carbohydrates, particularly in the cornea. Mutations in this gene lead to Macular Corneal Dystrophy, a rare genetic disorder characterized by the progressive clouding of the cornea and vision loss. Understanding the function and role of CHST6 in normal corneal physiology is crucial for developing effective treatments for MCD and improving the quality of life for affected individuals.

See Also

• Macular Corneal Dystrophy
• Sulfation
• Cornea
• Genetic Disorder

References

1. Akama TO, Nishida K, Nakayama J, et al. Macular corneal dystrophy type I and type II are caused by distinct mutations in a new sulphotransferase gene. Nat Genet. 2000;26(2):237-241. doi:10.1038/79970

2. El-Ashry MF, Abd El-Aziz MM, Wilkins S, et al. Identification of novel mutations in the carbohydrate sulfotransferase gene (CHST6) causing macular corneal dystrophy. Invest Ophthalmol Vis Sci. 2002;43(10):377-382.

3. Klintworth GK. Advances in the molecular genetics of corneal dystrophies. Am J Ophthalmol. 1999;128(6):747-754. doi:10.1016/s0002-9394(99)00300-7