Three different cDNAs encoding mouse D-factor/LIF receptor

Three cDNAs for mouse differentiation-stimulating factor (D-factor)/leukemia inhibitory factor (LIF) receptor were isolated from a cDNA library prepared from the liver of a pregnant mouse. A probe for screening was prepared by the RT-PCR method using human cDNA sequences as primers. The mouse D-factor receptor cDNA encoded 1,092 amino acids, which had a marked homology with the human counterpart and consisted of signal sequence, extracellular, transmembrane, and cytoplasmic domains. The WSXWS motif found in members of the cytokine receptor family was also present in the extracellular domain of the mouse D-factor receptor. A second form of cDNA that had a 501 bp insertion was isolated. The insertion introduced a stop codon so that the mRNA encoded the soluble receptor lacking transmembrane and intracellular domains. Because the insertion contained polyadenylation signals, two different sizes of mRNA encoding the soluble receptor were produced, depending on whether or not it utilized these signals. Transcripts utilizing these signals were 2.6-3 kb in size, and were very abundantly expressed in the liver. Transcripts that did not use these signals were longer than 5 kb and of similar size to the mRNA for the cellular receptor.