Incorporated into fibronectin-containing matrix fibers. Plays a role in cell adhesion and migration along protein fibers within the extracellular matrix (ECM). Important for certain developmental processes and contributes to the supramolecular organization of ECM architecture, in particular to those of basement membranes. Involved in regulating the shape and adhesion of cells in the developing pharynx, intestine, body-wall muscle and gonadal tissue (PubMed:16120639). During gonadogenesis, regulates the width of gonads and the migration of distal tip cells (DTC) (PubMed:15556862, PubMed:17043142, PubMed:22298704). Together with type IV collagen let-2 and downstream of metalloprotease mig-17, recruits nidogen nid-1 to the gonad basement membrane thereby inducing basement membrane remodeling required for the directional migration of DTCs (PubMed:15556863, PubMed:19104038). Acts antagonistically with metalloprotease gon-1 to maintain optimal levels of type IV collagen emb-9 in the gonad basement membrane during gonadogenesis (PubMed:15556862, PubMed:17043142, PubMed:22298704). Required for larval development (PubMed:17043142). Involved in the assembly of the flexible hemicentin-containing tracks found joining the pharynx and body-wall-muscle basement membranes. Homomultimerizes and interacts with various extracellular matrix components. Expressed in head muscle cells, anterior and posterior intestinal cells (PubMed:15556862). Isoform a: Expressed in male and hermaphrodite gonad, anterior and posterior intestine and pharyngeal basement membranes, body-wall muscle, GLR cells, uterine attachment and mechanosensory neurons (PubMed:15556863, PubMed:16120639, PubMed:17043142). Isoform c: Expressed on ALM/PLM mechanosensory neuron attachments, in flexible tracks connecting the pharyngeal, body-wall-muscle basement membranes and in uterine attachments (PubMed:16120639). Expressed from late embryonic stage onwards. Gonads have short and swollen arms. Pharyngeal defects. Movement is lethargic. Although involved in the same pathway as gon-1 and mig-17, it is probably not cleaved by these metalloproteases. Belongs to the fibulin family.