ACTN4 and focal segmental glomerulosclerosis: To date, more than 60 genes have been linked to SRNS-FSGS, with variants most frequently identified in key genes such as nephrin (NPHS1) and podocin (NPHS2), integral membrane proteins of the slit diaphragm; Wilms tumor protein (WT1), a transcription tumor suppressor protein; phospholipase C epsilon (PLCE1), involved in podocyte proliferation and differentiation; and alpha-actinin-4 (ACTN4), which regulates the podocyte cytoskeleton; among other genes (3, 4).