Abstract
Mouse embryonic stem (ES) cells can be maintained in an undifferentiated state in the presence of leukemia inhibitory factor (LIF), a member of the interleukin-6 cytokine family. In other mammals, this is not possible with LIF alone. Chicken ES-like cells (blastodermal cells) have only been cultured with mouse LIF because chicken LIF was not available. However the culture system is imperfect and chicken ES-like cells equivalent to mouse ES cells were not observed. In the present study, we cloned the cDNA-encoding chicken LIF using mRNA subtraction and RACE methodology. The chicken LIF cDNA encodes a protein with approximately 40% sequence identity to mouse LIF. It has 211 amino acids including a putative N-terminal signal peptide of 24 residues. Chicken blastodermal cells were cultured in the presence of bacterially expressed chicken LIF or mouse LIF. The expression of alkaline phosphatase and embryonal carcinoma cell monoclonal antibody-1 and stage-specific embryonic antigen-1 and the activation of STAT3 were examined, all of which are indices of the undifferentiated state. Exposure in the blastodermal cells to recombinant chicken LIF but not to mouse LIF maintained the expression of these various markers. After 9 days of incubation, the blastodermal cells formed cystic embryoid bodies in the presence of mouse LIF but not in the presence of recombinant chicken LIF. We conclude that chicken LIF is able to maintain chicken ES cell cultures in the undifferentiated state.
Highlights
Mouse embryonic stem (ES) cells can be maintained in an undifferentiated state in the presence of leukemia inhibitory factor (LIF), a member of the interleukin-6 cytokine family
We cloned the cDNA of the chicken homologue of mammalian LIF and compared the effect of recombinant chicken LIF (chLIF) and mouse LIF (mLIF) on chicken ES-like cells
1,000 clones of the resulting cDNA library were screened by differential display, and we eventually identified 122 cDNA fragments that appeared to originate from differentially expressed genes
Summary
Mouse embryonic stem (ES) cells can be maintained in an undifferentiated state in the presence of leukemia inhibitory factor (LIF), a member of the interleukin-6 cytokine family. In other mammals, this is not possible with LIF alone. The challenge has been to isolate and characterize cells with similar properties from other species It was a number of years before ES and/or embryonic germ (EG) cells were isolated from non-murine mammalian species including the medaka [7], rabbit [8], pig [9], monkey [10], and human [11] but germ line transmission has only been successfully demonstrated in the mouse. It has been thought that this cytokine is only able to inhibit differentiation of mouse ES cells
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