Clinical and Genetic Characterization of 26 Tunisian Patients with Allgrove Syndrome.

BACKGROUND AND AIMS: Allgrove syndrome is characterized by achalasia, alacrima, and adrenal insufficiency as well as being associated with progressive neurological signs. This is an autosomal recessive disorder due to mutations in the AAAS gene located on chromosome 12q13. The AAAS gene encodes a protein of 546 amino acids, ALADIN. Mutations in this genwere reported in families from North Africa and Europe. Our objective is to conduct a clinical, molecular and genetic study of 26 Tunisian patients with Allgrove syndrome. METHODS: We report 26 Tunisian patients with between two and four clinical features associated with Allgrove syndrome. Blood samples were collected and isolated DNA derived from subjects was amplified. The entire sequence of the AAAS gene was analyzed by PCR and sequencing. PCR-RFLP method was performed to identify the frequent mutations found. RESULTS: Sequencing of the AAAS gene revealed a major homozygous mutation (c.1331+1G>A) in 25 patients and R286X mutation in one patient. The presence of a major mutation in several unrelated affected individuals suggests the presence of a founder effect in Tunisia and allows for a fast and targeted molecular diagnosis. CONCLUSIONS: We created an easy and rapid molecular enzymatic protocol based on PCR-RFLP using MvaI restriction enzyme that directly targets this major mutation and can be used for prenatal diagnosis and genetic counseling for Tunisian families at risk. To the best of our knowledge, this is the first major series report of Allgrove syndrome in Tunisia.

Contribution of PTPN22, CD28, CTLA-4 and ZAP-70 variants to the risk of type 1 diabetes in Tunisians.

Type 1 diabetes (T1D) is caused by an immune-mediated destruction of the insulin-producing ß-cells. Several studies support the involvement of T cell activation molecules. In order to underline the role of the genes involved in this pathway, we investigated, using the Sequenom MassARRAY platform, polymorphisms of sixteen single-nucleotide polymorphisms (SNPs) belonging to PTPN22, CD28, CTLA-4, and ZAP-70 genes in 76 T1D patients and 162 unrelated healthy controls from Southern Tunisia. We confirmed the association with PTPN22 (rs2476601, Corrected P (Pcorr)=0.002, OR=6.20) and CD28 gene (rs1879877, Pcorr=0.003; OR=4.27 and rs3181096, Pcorr=0.02; OR=1.73). We also identified an association with rs17695937 of ZAP-70 gene (Pcorr=0.02, OR=1.87). Our results suggest a significant effect on T1D susceptibility for A-C-A-G-C and T-C-C-T-A-C haplotypes, of ZAP-70 and CD28 genes, respectively. In addition, (A-G-C) combination of ZAP-70/CD28 gene was significantly increased in T1D patients as compared to controls, suggesting the possible interaction between these genes. These results confirm the involvement of PTPN22 and CD28 genes in the genetic susceptibility to T1D. Interestingly, ZAP-70 seems to contribute to the susceptibility to the disease in our population. However, this finding has to be confirmed in further studies.