Moreover, of the 34 autoantibodies identified in the first step of the current study (e.g., with a 2-fold increase in their MFI in RA vs. controls), 4 antigenic targets have previously been reported in independent RA patient cohorts [18]: “Heterogeneous Nuclear Ribonucleoprotein A1-like 2” (HNRNPA1), “Period homolog 1” (PER1), “family with sequence similarity 234 member A” (FAM234A), and “Non-POU domain containing, octamer binding” (NONO)—HNRNPA1 is a well-characterized, ubiquitously expressed RNA-binding protein which is involved in gene expression and translation [35]. Here, PER1 is linked to rheumatoid arthritis.