HEM1 is a 1,127 amino acid single-pass membrane protein that localizes to the cytoplasmic side of the cell membrane. One of several members of the highly conserved HEM family of tissue-specific transmembrane proteins, HEM1 is expressed in cells of hematopoietic origin where it is thought to play an important role in oogenesis. The gene encoding HEM1 maps to human chromosome 12, which encodes over 1,100 genes and comprises approximately 4.5% of the human genome. Chromosome 12 is associated with a variety of diseases and afflictions, including hypochondrogenesis, achondrogenesis, Kniest dysplasia, Noonan syndrome and Trisomy 12p, which causes facial developmental defects and seizure disorders.