It is therefore possible that a polymorphism in this region effects the expression of both HTR1A and RNF180. Since we in this study observe that HTR1A might be involved in T1D susceptibility independently of RNF180, we suggest that expression studies of HTR1A should be carried out in order to fully understand its function in T1D development. Here, RNF180 is linked to type 1 diabetes mellitus.