How early organisms made the transition from unicellularity to multicellularity is unknown, although certain genes have been implicated as important players in this process. One such group is the cadherin family of genes that function in cell adhesion and cell-cell signaling. By examining the genome of the unicellular choanoflagellate Monosiga brevicollis , Abedin and King show that the genome of M. brevicollis contains 23 expressed cadherin genes--as many as several multicellular animals. At least two of the cadherins localized to the actin-filled microvilli of the protozoan feeding collar, where they may participate in the recognition and capture of bacterial prey. M. Abedin, N. King, The premetazoan ancestry of cadherins. Science 319 , 946-948 (2008). [Abstract] [Full Text]