SIGLEC11 (sialic acid binding Ig-like lectin 11)

The gene encoding Siglec-11 underwent a human specific gene conversion event involving an adjacent pseudogene, resulting in a new amino-terminal sequence and promoter region. This resulted in the first reported "human-specific" protein. A consequence of this event was a significant change in the binding properties of the molecule, along with new expression in the microglia of the brain. The gene conversion event involved a small part of the 5' untranslated sequences of SIGLEC11. Studies are underway to determine if this could explain the new expression in microglia seen only in humans. The significance of this event for human brain evolution is unknown at this time. It is also of interest that microglia are prominent apparently human-specific diseases such as Alzheimer's diesease and AIDS associated dementia.  In this regard, it is interesting that SIglec-11 is capable of suppressing inflammatory responses in microglia.  The recent discovery of a paired activating receptor (Siglec-16) present only in some humans further complicates the picture.