Embryonic stem cell and tissue-specific expression of a novel conserved gene, asrij.

We have identified a novel gene expressed in murine embryonic stem (ES) cells and in a restricted, tissue-specific pattern during mouse development. The gene is also expressed in blood vessels; hence, we have named it asrij (Sanskrit; asRîj= blood). The gene encodes a novel conserved, predicted transmembrane protein of 247 amino acids, which is localized to lysosomes and endosomes. During ES cell-derived blood vessel formation in vitro, Asrij expression precedes and partially overlaps with the vascular markers Flk-1 and PECAM. During development, Asrij is expressed predominantly in mouse embryonic blood vessels. The asrij transcript is alternatively spliced, and its expression is regulated in a tissue-specific manner. An asrij splice variant that is enriched in the adult mouse brain encodes a protein of 196 amino acids. Asrij can serve as an early stem cell marker that is down-regulated in nonvascular tissues. Our data indicate that Asrij belongs to a novel class of conserved proteins with a complex developmental profile and suggests multiple functions for the gene.