RCCX

RCCX is a genetic module in humans that is notable for its complexity and potential role in disease susceptibility. The RCCX module is located on chromosome 6 in the Major Histocompatibility Complex (MHC) region, and is unique to primates. It is named for the four genes it contains: RP1, Complement C4, CYP21A2, and TNXB.

Structure

The RCCX module is a tandem repeat, meaning that its sequence of genes can be repeated multiple times in a row. The number of repeats varies between individuals, with most people having two or three. Each repeat contains one copy of RP1, one or two copies of C4 (which can be either the C4A or C4B subtype), one copy of CYP21A2, and one copy of TNXB.

Function

The genes within the RCCX module are involved in a variety of biological processes. RP1 is a regulator of complement activation, C4 is a key component of the immune system, CYP21A2 is involved in steroid metabolism, and TNXB is involved in connective tissue integrity.

Clinical significance

Variations in the RCCX module have been associated with a number of diseases. For example, deletions of C4A are associated with systemic lupus erythematosus, while duplications of C4B are associated with age-related macular degeneration. Mutations in CYP21A2 can cause congenital adrenal hyperplasia, and mutations in TNXB can cause Ehlers-Danlos syndrome.

See also

• Major Histocompatibility Complex
• Complement system
• Congenital adrenal hyperplasia
• Ehlers-Danlos syndrome