An evolutionarily conserved aspect of nervous system development is the migration of undifferentiated cells, termed neuroblasts, to specific locations where they differentiate into neurons. Mutations that cause changes to these processes, whether they are an altered migration pattern or change in cell fate, can create development defects. Recently, we isolated a mutant strain of Caenorhabditis elegans in which the PQR, an oxygen-sensing sensory tail neuron, is aberrantly located in the head. This suggests that there is a defect in neuroblast migration. The mutant animals also have a "dumpy" (Dpy) phenotype that is unrelated to neuroblast migration. To learn more about how the mutation (cnj1) impacts neuroblast migration, we sought to identify the gene affected by the mutation. Four experiments suggest that cnj1 is a mutant allele of the dpy-19 gene. First, we used single nucleotide polymorphisms and mapped cnj1 to a region left of the center of chromosome III, which is near the dpy-19 gene. This was notable because cnj1 displays a temperature sensitive Dpy phenotype identical to a well-characterized allele of dpy-19, dpy-19(e1259). Second, when cnj1 was crossed to dpy-19 mutant animals for complementation, dpy-19(e1314) and dpy-19(e1259), the progeny displayed PQR defects and a Dpy phenotype. Third, injection of a wild type copy of dpy-19 from two Fosmids, WRM0621aG11 and WRM0634dD07, into heterozygous cnj1 mutant animals rescued the PQR defect and Dpy phenotype. Fourth, sequencing of genomic DNA from cnj1 mutants revealed a large deletion that removes most of the dpy-19 open reading frame. Previous studies have shown that dpy-19 is important for the initial polarization of the QL/R parent cells, however, our data shows that dpy-19 is also important for the migration of each of their lineages. dpy-19 encodes a C-mannosyltransferase that acts by glycosylating the thrombospondin repeats of cell surface receptors, specifically tryptophan residues. This catalyzation event has been interpreted as an essential process for proper secretion of protein MIG-21 during Q lineage migration. The implications of DPY-19 function postulates that lack-there-of disrupts the migration patterns of the QL lineage. DPY-19 is present in humans as four homologues, DPY19L1-4, suggesting conserved molecular function. Dpy19l1, a mouse homologue, is activated in glutamatergic neurons of the developing brain, while in humans, DPY19L1 and DPY19L3 are C-mannosyltransferases with substrate specificities (Watanabe et al. 2011; Morishita et al. 2017; Shcherbakova et al. 2017). Elucidating that DPY-19 may act as a transmembrane (nuclear or bilayer) signaling molecule and protein folder for neuron migration across species.