Inherited human complement C5 deficiency. Nonsense mutations in exons 1 (Gln1 to Stop) and 36 (Arg1458 to Stop) and...

Area of Science:

• Immunology
• Genetics
• Molecular Biology

Background:

• Hereditary C5 deficiency (C5D) is a rare genetic disorder affecting the complement system.
• Previous reports identified C5D in various ethnic groups, but the underlying molecular genetic defects remained largely unknown.
• Understanding the genetic basis of C5D is crucial for diagnosing and potentially treating related immune deficiencies.

Purpose of the Study:

• To investigate the molecular genetic basis of C5 deficiency in African-American families.
• To identify specific mutations in the C5 gene responsible for C5D in this population.

Main Methods:

• Sequencing of C5 gene exons and intron/exon boundaries in three C5-deficient African-American families.
• Utilized allele-specific PCR and sequence analyses to confirm mutation presence and inheritance patterns.
• Screened European and Caucasian-American C5D individuals for the identified mutations.

Main Results:

• Identified two distinct nonsense mutations in the C5 gene: one in exon 1 (C84AG to TAG) and another in exon 36 (C4521GA to TGA).
• The exon 1 mutation affects the C5 beta-chain, while the exon 36 mutation impacts the C5 alpha-chain.
• These mutations were found to be present in compound heterozygous states in all studied African-American C5D families and were absent in European/Caucasian-American C5D individuals.

Conclusions:

• Hereditary C5 deficiency results from diverse molecular genetic defects.
• Two specific nonsense mutations in exons 1 and 36 of the C5 gene partially explain C5 deficiency in the African-American population.
• Compound heterozygosity for these mutations is a common genetic mechanism underlying C5D in these families.