Abstract
Ultrastructual features of a human erythroidcell line (YN-1) were studied before and fater induction of erythroid differentiation. YN-1 was estabsished by us from a patient with Ph1 chromosome-positive chronic myelocytic leukemia who had undergone an erythroblastic transformation. YN-1 cells lacked the membrane characteristics of lymphocytes and myelomonocytic cells and carried on their surface glycophorin A. Analysis of the hemoglobin by isoelectric focusing indicated major bands in the region of embryonic hemoglobin. Erythroid differentiation of YN-1 cells was induced by hemin, cytosine arabinoside and actinomycin D. When they were cultured in the liguid media during exponential growth without inducer of erythroid differentiation, most cells were circular or oval with a few microvilli. The nucleus of them were circular showing the euchromatic pattern with a few prominent nucleoli. Numerous polysomes were dispersed throughout the cytoplasm. A small number of mitochondria and undeveloped Golgi apparatus were observed. A few micropinocytic vesicles and siderosomes were seen. After induction of erythroid differntiation by hemin, YN-1 cells had a low nuclear hytoplasmic ratio and exhibited aggregation of nuclear chromatin. Organelles such as mitochondria, Golgi apparatus and siderosome were developed and increasing number of micropinucytic vesicles were seen. Increased cytoplasmic electron density was observed, and it was correlated with the strength of pseudeperoxidase in DAB procedure, indicating hemoglobin synthesis.
From these results, relation of functional differentiation and morphological differentiation was discussed.
