heparitin-sulfate and Disorders-of-Sex-Development

The unc-52 gene encodes the nematode homologue of mammalian perlecan, the major heparan sulfate proteoglycan of the extracellular matrix. This is a large complex protein with regions similar to low-density lipoprotein receptors, laminin, and neural cell adhesion molecules (NCAMs). In this study, we extend our earlier work and demonstrate that a number of complex isoforms of this protein are expressed through alternative splicing. We identified three major classes of perlecan isoforms: a short form lacking the NCAM region and the C-terminal agrin-like region; a medium form containing the NCAM region, but still lacking the agrin-like region; and a newly identified long form that contains all five domains present in mammalian perlecan. Using region-specific antibodies and unc-52 mutants, we reveal a complex spatial and temporal expression pattern for these UNC-52 isoforms. As well, using a series of mutations affecting different regions and thus different isoforms of UNC-52, we demonstrate that the medium NCAM-containing isoforms are sufficient for myofilament lattice assembly in developing nematode body-wall muscle. Neither short isoforms nor isoforms containing the C-terminal agrin-like region are essential for sarcomere assembly or muscle cell attachment, and their role in development remains unclear.

Topics: Agrin; Alternative Splicing; Amino Acid Sequence; Animals; Caenorhabditis elegans; Caenorhabditis elegans Proteins; Cloning, Molecular; Disorders of Sex Development; Fluorescent Antibody Technique; Gene Expression Regulation, Developmental; Helminth Proteins; Heparan Sulfate Proteoglycans; Heparitin Sulfate; Membrane Proteins; Microscopy, Confocal; Molecular Sequence Data; Muscle Development; Mutation; Neural Cell Adhesion Molecules; Protein Isoforms; Proteoglycans; Sequence Alignment; Sequence Deletion