Abstract: This invention provides a method for treating a subject suffering from a disease, wherein the disease is characterized by aberrant cellular proliferation or aberrant cellular differentiation, comprising administering to the subject an antagonist of a polypeptide, wherein the polypeptide has an amino acid sequence as presented in SEQ ID NO:2. This invention also provides the use of a polynucleotide as a probe for identifying undifferentiated embryonic stem cells, wherein the polynucleotide comprises a nucleotide sequence as presented in SEQ ID NO:1. This invention further provides the use of the 76A11 polypeptide in vivo or ex vivo for expansion of adult somatic stem cells. This invention further provides the use of an antibody directed to an epitope presented by the polypeptide comprising the amino acid sequence as presented in SEQ ID NO:2 for detection of cancerous cells or of undifferentiated stem cells.