L1TD1 Is a Marker for Undifferentiated Human Embryonic Stem Cells

Abstract

BackgroundHuman embryonic stem cells (hESC) are stem cells capable of differentiating into cells representative of the three primary embryonic germ layers. There has been considerable interest in understanding the mechanisms regulating stem cell pluripotency, which will ultimately lead to development of more efficient methods to derive and culture hESC. In particular, Oct4, Sox2 and Nanog are transcription factors known to be important in maintenance of hESC. However, many of the downstream targets of these transcription factors are not well characterized. Furthermore, it remains unknown whether additional novel stem cell factors are involved in the establishment and maintenance of the stem cell state.Methodology/Principal FindingsHere we show that a novel gene, L1TD1 (also known as FLJ10884 or ECAT11), is abundantly expressed in undifferentiated hESC. Differentiation of hESC via embryoid body (EB) formation or BMP4 treatment results in the rapid down-regulation of L1TD1 expression. Furthermore, populations of undifferentiated and differentiated hESC were sorted using the stem cell markers SSEA4 and TRA160. Our results show that L1TD1 is enriched in the SSEA4-positive or TRA160-positive population of hESC. Using chromatin immunoprecipitation we found enriched association of Nanog to the predicted promoter region of L1TD1. Furthermore, siRNA-mediated knockdown of Nanog in hESC also resulted in downregulation of L1TD1 expression. Finally, using luciferase reporter assay we demonstrated that Nanog can activate the L1TD1 upstream promoter region. Altogether, these results provide evidence that L1TD1 is a downstream target of Nanog.Conclusion/SignificanceTaken together, our results suggest that L1TD1 is a downstream target of Nanog and represents a useful marker for identifying undifferentiated hESC.

Embryonic Stem Cell-Related Protein L1TD1 Is Required for Cell Viability, Neurosphere Formation, and Chemoresistance in Medulloblastoma

“…Since the RHA-Lin28 complex regulates OCT4 translation in mouse ESC [23], L1TD1 might be a novel component of the protein complex required for pluripotency maintenance in hESC. Indeed, L1TD1 knockdown in hESC resulted in lower OCT4 protein levels [17,18].…”

“…Under physiological conditions, basal L1TD1 expression is rapidly downregulated along the in vitro differentiation of hESC into embryoid bodies, without any noticeable decay in cell viability [17]. A dramatic L1TD1 downregulation, reaching nearly 99% of repression, was also detected in hESC during induced neural differentiation [18]. Furthermore, cells of most healthy adult somatic tissues do not show expression of L1TD1, including brain cells [16].…”

“…The authors also found that, athough upregulated by the enforced expression of the Yamanaka pluripotency factors in somatic cells, L1TD1 was dispensable for mouse induced pluripotent stem (iPS) cell generation [16]. In humans, however, L1TD1 was reported to be a target of the transcription factor circuitry comprised by Nanog, OCT4 and SOX2, and an important regulator of hESC self-renewal [17,18]. Interestingly, L1TD1 was also recently reported to be involved in proliferation of embryonal carcinoma and seminoma cell lines [17], although its role in cancer is still largely unknown.…”

Reviewing and Updating the Major Molecular Markers for Stem Cells

“…In silico analysis revealed that it is restricted to the blastocyst stage, where its expression is downregulated during differentiation in a pattern similar to that observed for Oct-4, Nanog, and Sox-2. In addition, L1TD1 is a downstream target for Nanog protein [78].…”

RNA-binding proteins in pluripotency, differentiation, and reprogramming

“…L1td1 (or Ecat11) is another RBP whose expression is rapidly downregulated upon differentiation (Wong et al, 2011). In contrast to mouse ESCs, L1td1 is required for maintenance of self-renewal in human ESCs (Iwabuchi et al, 2011; Närvä et al, 2012).…”