Required for embryonic morphology and development. Plays both a functional and a structural role in the maintenance and probably biogenesis of fibrous organelles, a hemidesomosome-like junction structure, which ensures muscle stability and muscle connection to the external cuticle. Interacts with vab-10 (via plankin domain). Co=localizes with cytoplasmic intermediate filaments. Co-localizes with actin. Isoform a: Expressed in the uterus, the vulva, the rectum, mechanosensory neurons and in head and tail neurons. Isoform e: Expressed in spermatheca and weakly in the vulva. Isoform f: Expressed in spermatheca and weakly in the vulva. Isoform i: Expressed in spermatheca and weakly in the vulva. Isoform a: Expressed in dorso-ventral epidermal cells from the comma stage of embryonic development to adulthood. Isoform j: Expressed in the pharynx and head neurons from the 3-fold stage of embryonic development to adulthood. Isoform k: Expressed in dorso-ventral epidermal cells, the uterus, the vulva, the rectum and in head and tail neurons from the 3-fold stage of embryonic development to adulthood. Specifically expressed in seam cells at the 3-fold stage. Embryonic lethal with failed embryonic morphogenesis. Disrupted intracellular structural integrity from the 2-fold stage of embryogenesis resulting in thickening of the epidermis, abnormal intermediate filament distribution and detachment and collapse of muscle from the cell body, particularly in the head, tail and midbody. RNAi-mediated knockdown results in developmental defects whereby 95% embryos do not undergo morphogenesis and arrest before the two-fold stage with abnormal head and tail structures and reduced motility within the eggshell. Lethality in 40% of mutants (that survive RNAi-mediated knockdown) by the adult molting phase of development, with the remaining mutants displaying molting defects and paralysis.