Turner syndrome patients with bicuspid aortic valves and renal malformations exhibit abnormal expression of X-linked inhibitor of apoptosis protein (XIAP).

OBJECTIVE: We analyzed mRNA expression of X-linked inhibitor of apoptosis protein (XIAP) in patients with Turner syndrome (TS) and examined its association with phenotypic features. SUBJECTS AND METHODS: XIAP mRNA expression levels were investigated in 98 patients with TS in total RNA extracted from blood leucocytes by real time quantitative polymerase chain reaction. RESULTS: Levels of XIAP mRNA were significantly lower in patients with bicuspid aortic valves (BAV; n=13) than those without (log XIAP -1.17±0.3 vs. -0.94±0.2, p=0.002). Significantly higher expression of XIAP mRNA was seen in patients with a mosaic karyotype and renal malformations (log XIAP -0.79±0.3 vs. -1.0±0.3, p=0.03). No correlations were seen between XIAP and other manifestations. CONCLUSION: Abnormal expression of XIAP may be an important underlying mechanism in the development of BAV and renal malformations in TS. However, abnormal XIAP mRNA expression, as determined from peripheral mononuclear cells, does not appear to explain all the somatic and visceral stigmata of TS.