Pentanucleotide repeat (TTTTA)n polymorphism in the 5' control region of the apoliprotein (A) gene and atherothrombotic serum lipoprotein (A) concentration, in a pediatric population

Lipoprotein (a) [Lp(a)] is a complex of apolipoprotein (a) [apo(a)] and low density lipoprotein, which is an independent major risk factor associated with atherothrombotic disease 1. Unlike other lipoproteins, interindividual differences in Lp(a) plasma concentration is almost entirely due to inheritance, most of them being attributed to sequence differences linked to the apo(a) locus.2,3,4 The primary structure of apo(a) encompasses a protease domain, a kringle V domain and a variable number of kringle IV repeats, which is homologous to the same domain in the plasminogen molecule and is thought to be responsible for the antifibrinolytic activity of Lp(a). The gene contains a pentanucleotide repeat (TTTTA)n polymorphism, 1.4 Kb upstream from the apo(a) gene reading frame. Eight different alleles have been detected to date, with the number of TTTTA repeats ranging from 5 to 12.5 This polymorphism, first described by Wade et al in 1993,6 has been suggested to be important in the control of apo(a) gene expression. Alleles containing more repeats were generally associated with lower plasma Lp(a) concentration