A systematic survey of LU domain-containing proteins reveals a novel human gene,LY6A,which encodes the candidate ortholog of mouse Ly-6A/Sca-1 and is aberrantly expressed in pituitary tumors

The Ly-6 and uPAR(LU)domain-containing proteins represent a large family of cell-surface markers.In particular,mouse Ly-6A/Sca-1 is a widely used marker for various stem cells;however,its human ortholog is missing.In this study,based on a systematic survey and comparative genomic study of mouse and human LU domain-containing proteins,we identified a previously unannotated human gene encoding the candidate ortholog of mouse Ly-6A/Sca-1.This gene,hereby named LY6A,reversely overlaps with a lncRNA gene in the majority of exonic sequences.We found that LY6A is aberrantly expressed in pituitary tumors,but not in normal pituitary tissues,and may contribute to tumorigenesis.Similar to mouse Ly-6A/Sca-1,human LY6A is also upregulated by interferon,suggesting a conserved transcriptional regulatory mechanism between humans and mice.We cloned the full-length LY6A cDNA,whose encoded protein sequence,domain architecture,and exon‒intron structures are all well conserved with mouse Ly-6A/Sca-1.Ectopic expression of the LY6A protein in cells demonstrates that it acts the same as mouse Ly-6A/Sca-1 in their processing and glycosylphosphatidylinositol anchoring to the cell membrane.Collectively,these studies unveil a novel human gene encoding a candidate biomarker and provide an interesting model gene for studying gene regulatory and evolutionary mechanisms.