HERV-Derived Is Conserved in Simiiformes, Exhibiting Expression in Hematopoietic Cell Lineages Including Macrophages.

(1) Background: The gene in humans is derived from an envelope () gene of a human endogenous retrovirus group, HERV-P(b). The gene reportedly has a conserved open reading frame (ORF) in Old World monkeys. Although its forced expression led to cell-fusion in an ex vivo cell culture system, like other -derived genes such as and - its mRNA expression is not placenta-specific, but almost ubiquitous, albeit being quite low in human tissues and organs, implying a distinct role for . (2) Methods: To elucidate the cell lineage(s) in which the ERVPb1 protein is translated in human development, we developed a novel, highly sensitive system for detecting HERV-derived proteins/peptides expressed in the tissue differentiation process of human induced pluripotent stem cells (iPSCs). (3) Results: We first determined that is also conserved in New World monkeys. Then, we showed that the ERVPb1 protein is translated from a uniquely spliced transcript in hematopoietic cell lineages, including a subset of macrophages, and further showed that its mRNA expression is upregulated by lipopolysaccharide (LPS) stimulation in primary human monocytes. (4) Conclusions: is unique to Simiiformes and actually translated in hematopoietic cell lineages, including a subset of macrophages.