VLK was identified as a novel protein kinase that was induced after the differentiation of cultured embryonic stem cells into mesendoderm. It has no homologs in invertebrates, but is highly conserved in vertebrate species although it does not belong to any known protein kinase groups. VLK is initially expressed in E-cadherin-positive anterior visceral endoderm and mesendoderm, but its expression is later confined to E-cadherin-negative mesenchyme. It is enriched in the Golgi apparatus and is thought to regulate the rate of protein export from the Golgi. Targeted disruption of VLK in mice leads to a defect in lung development and neonatal lethality. It has been suggested that mutations in VLK may be associated with the allergic condition atopy.