let-4 encodes an extracellular leucine-rich repeat only protein; let-4 was originally identified in a screen for essential genes, and let-4 mutants exhibit early larval lethality; let-4 is required for organization of the apical extracellular matrix, and is involved in excretory cell canal morphology and renal function as mutants exhibit excretory canal cysts and impaired renal function.
Involved in several processes, including epithelial cell development; nematode larval development; and positive regulation of membrane permeability. Located in apical part of cell. Expressed in excretory system; hypodermis; rectal epithelial cell; and vulva.