A novel activation-induced cytidine deaminase gene mutation in a Tunisian family with hyper IgM syndrome

Mutations in activation-induced cytidine deaminase can cause an autosomal recessive form of hyper-IgM syndrome. We have examined a Tunisian family composed of six members: two healthy parents, their two healthy daughters and two affected sons. We found a homozygous transversion G to T in the two sons while heterozygosity for the mutation was found in all other family members. This alteration is localised in intron 2 at the +1 position resulting in defective splicing. Use of various intronic cryptic splice-sites led to expression of various aberrant mRNA species. Conclusion:This is a novel mutation found in the gene encoding for activation-induced cytidine deaminase in a Tunisian family with hyper-IgM type 2 syndrome. This alteration leads to the use of two cryptic splicing sites causing the formation of two different mRNA species.C. Fiorini and S. Jilani contributed equally to this work.