Chromosomal assignment of zebrafish grn genes. Zebrafish grna is located close to genes (HoxB cluster, dlx8, pyy) that form an extensive bloc of conserved synteny with human chromosome 17 (Hsa17), indicating an orthologous relationship to human progranulin (grn). Zebrafish grnb, in contrast, maps to LG24 in a region devoid of syntenic correspondence to zebrafish LG3 or Hsa17 (data not shown). Grn1 and grn2 map to LG19, in a region that finds scattered synteny to two human chromosomes (Hsa 6 and Hsa 7). The presence of grn1 and grn2 on a zebrafish chromosome bearing the HoxA cluster, npy and dlx6 genes (i.e. paralogues of genes linked to zebrafish grna and human grn), suggests that grn1 or grn2 may have originated in concert with the mechanism leading to emergence of duplicated Hox clusters at the base of the vertebrate radiation. Map position on zebrafish chromosomes (LG) is presented in centiRays where 1 centiRay = 148 kilobases, the estimated average breakpoint frequency for the LN54 RH panel.