Novel spliced variants of OCT4, OCT4C and OCT4C1, with distinct expression patterns and functions in pluripotent and tumor cell lines.

OCT4 is a major regulator of pluripotency which has several spliced variants and expressed pseudogenes. Here, we are reporting the existence of two additional novel spliced variants of OCT4, OCT4C and OCT4C1, which lack Exon1 (E1) but start at a novel exon (E0) located ∼14kb upstream of E2. OCT4C/C1 is highly expressed in ES and iPS cells, and their expression was sharply turned off, upon the induction of neural differentiation. The long non-coding RNA (lncRNA) PSORS1C3, is located ∼9kb downstream of the E0 of OCT4C/C1. PSORS1C3 is vigorously spliced to generate nine novel variants, however, none of its exons incorporated in alternatively spliced variants of OCT4. Interestingly, the exons of OCT4 and PSORS1C3 are intertwined, with a novel exon (E0) of PSORS1C3 located ∼4kb upstream of OCT4 E0. This exon participates in generating some more variants of PSORS1C3 (variants 10-24). OCT4C/C1 knock-down in ES and iPS cell lines caused a slight downregulation of PSORS1C3 and OCT4A, a slight upregulation of OCT4B1, and a dramatic upregulation of OCT4B. Altogether, our data revisited the current view of OCT4 gene structure and regulation, and revealed its complex genomic features and expression regulation in stem and tumor cells.