Preliminary Evidence for Aortopathy and an X-Linked Parent-of-Origin Effect on Aortic Valve Malformation in a Mouse Model of Turner Syndrome

Turner syndrome (TS), most frequently caused by X-monosomy (45,X), is characterized in part by cardiovascular abnormalities, including aortopathy and bicuspid aortic valve (BAV). There is a need for animal models that recapitulate the cardiovascular manifestations of TS. Extracellular matrix (ECM) organization and morphometrics of the aortic valve and proximal aorta were examined in adult 39,XO mice (where the parental origin of the single X was paternal (39,X(P)O) or maternal (39,X(M)O)) and 40,XX controls. Aortic valve morphology was normal (tricuspid) in all of the 39,X(P)O and 40,XX mice studied, but abnormal (bicuspid or quadricuspid) in 15% of 39,X(M)O mice. Smooth muscle cell orientation in the ascending aorta was abnormal in all 39,X(P)O and 39,X(M)O mice examined, but smooth muscle actin was decreased in 39,X(M)O mice only. Aortic dilation was present with reduced penetrance in 39,XO mice. The 39,XO mouse demonstrates aortopathy and an X-linked parent-of-origin effect on aortic valve malformation, and the candidate gene FAM9B is polymorphically expressed in control and diseased human aortic valves. The 39,XO mouse model may be valuable for examining the mechanisms underlying the cardiovascular findings in TS, and suggest there are important genetic modifiers on the X chromosome that modulate risk for nonsyndromic BAV and aortopathy.