ABSTRACT
<p><b>OBJECTIVE</b>To perform phenotypic identification and characteristic analysis of a new zebrafish mutant 1276 defective in primitive myelopoiesis.</p><p><b>METHODS</b>The AB strain male zebrafish were mutagenized with N-ethyl N-nitrosourea (ENU) to induce mutations in the spermatogonial cells, and the mutations were transmitted to the offsprings. The F3 embryos were screened by neutral red staining for identifying the mutants defective in primitive myelopoiesis. One of the myeloid mutants 1276 was further studied by cytochemistry and whole mount in stiu hybridization (WISH) with different lineage markers.</p><p><b>RESULTS</b>A total of 2140 mutagenized genomes from the 1296 F2 families were analyzed, and 12 mutants were identified to show abnormal signal by neutral red staining. In the primitive hematopoiesis stage, the mutant 1276 showed the absence of neutral red staining-positive cells in the whole body. The expression of microglia marker apoe was totally lost in the head of the mutant, and the expression of the macrophage marker l-plastin was slightly decreased in the head and remained normal in the ventral dorsal aorta region, but the granulocytes and erythrocytes developed normally. in the definitive hematopoiesis stage, the mutant 1276 still showed abnormal macrophages as found in the primitive hematopoiesis stage, but the granulocytes, erythrocytes and lymphocytes appeared normal.</p><p><b>CONCLUSION</b>The zebrafish mutant 1276 shows abnormalities in the function, development and migration of the macrophages in the primitive hematopoiesis stage, which can not be compensated in the definitive hematopoiesis stage.</p>