Evidence of digenic inheritance in autoinflammation-associated genes

Familial Mediterranean fever (FMF) has traditionally been considered as a monogenic autosomal recessive disorder caused by mutations in the MEFV gene with highest incidence among Mediterranean populations. In a considerable number of patients with typical FMF, only one MEFV mutation was identified and the possibility that more than one autoinflammatory gene may be responsible for their disease was investigated. In the present study, an extensive search for possible mutations in three hereditary recurrent fever (HRF) genes was performed in 128 MEFV heterozygous Greek–Cypriots clinically diagnosed based on their phenotype with FMF-like disease from a previous study. Sequence analysis was performed for MVK, TNFRSF1A and NLRP3 genes which is also known to cause HRFs. In total, three patients were identified with heterozygous mutations and a second mutation in an autoinflammatory gene. Two patients carried a MEFV mutation and a NLRP3 mutation, and an additional third carried a MEFV mutation and a TNFRSF1A mutation. Patient 1 carried MEFV p.[Val726Ala] (NM_000243.2:c.2177T >C) and NLRP3 p.[Val198Met] (NM_001243133.1:c.592G >A) variants and patient 2 carried MEFV p.[Glu148Gln] (NM_000243.2:c.442G >C) variant which is of uncertain significance and NLRP3 p.[Arg176Trp] (NM_001243133.1:c.526C >T). Lastly, patient 3 was identified to carry MEFV p.[Met694Val] (NM_000243.2:c.2080A >G) and TNFRSF1A p.[Arg121Gln] (NM_001065.3:c.362G >A) variants. The results from this study indicate that screening of genes known to cause HRFs in patients already identified with a single MEFV mutation, can reveal quite rare but potentially causative mutational combinations at different loci. Such interaction provide further evidence for possible locus–locus interactions and phenotypes resulting from digenic inheritance.     

<Emphasis Type="Italic">CDKN2A</Emphasis> and <Emphasis Type="Italic">MC1R</Emphasis> variants found in Cypriot patients diagnosed with cutaneous melanoma

The prevalence of genetic variants associated to cutaneous melanoma (CM) has never been determined within Cypriot melanomas. This study evaluates the frequency of variants in cyclin-dependent kinase inhibitor 2A (CDKN2A) and melanocortin-1 receptor (MC1R) in 32 patients diagnosed with CM. Other characteristics and risk factors were also assessed. CDKN2A p.Ala148Thr was detected in three of 32 patients, while the control group revealed no variations within CDKN2A. MC1R screening in 32 patients revealed the following variations: p.Val60Leu in 11 patients, p.Arg142His in four patients, p.Thr314Thr in one patient, p.Arg160Trp in one patient, p.Val92Met/p.Thr314Thr in one patient and p.Val92Met/p.Arg142His/p.Thr314Thr in one patient. The control group revealed only p.Val60Leu (in 10 of 45 individuals), which is frequently found in general populations. Two unrelated patients carried CDKN2A p.Ala148Thr in combination with MC1R p.Arg142His, suggesting digenic inheritance that may provide evidence of different gene variants acting synergistically to contribute for CM development. This study confirms the presence of CDKN2A and MC1R variants among Cypriot melanomas and supports existing evidence of a role for these variants in susceptibility to melanoma.