Two novel isoforms of Adam23 expressed in the developmental process of mouse and human brains

A metalloprotease and disintegrin (ADAM) is a family of membrane-anchored proteins and all family members have a multi-domain structure containing a zinc metalloprotease domain and a disintegrin domain that may serve as an integrin ligand. Here we reported two novel mammalian transcripts of Adam23, named Adam23 beta and Adam23 gamma, to be involved in the development and functional activities of mammalian brains. Adam23 gamma was isolated from a 22-week human fetal brain cDNA library, using an EST homologous to Adam as a probe, and is 100% homologous to human Adam23 (Adam23 alpha) except that it lacks a fragment of 91 bp near the C-terminal, thus it could not form obvious transmembrane domain. Adam23 beta was discovered while the diversity at the transmembrane domain (TM) was analyzed. Adam23 beta has a different sequence in the 91 nucleotides and thus encode different transmembrane domain. Adam23 beta and Adam23 gamma are mainly expressed in brain like Adam23 alpha. RT-PCR experiments in mouse brain also detected the two isoforms, consistent with observation of Northern analysis of human RNAs. Furthermore, results of RT-PCR amplification of Adam23 gamma in mouse brains of different developmental stages revealed a developmentally regulated expression pattern: Adam23 gamma is expressed in embryonic and infant brain, and disappeared after the 10th postnatal day. This temporally changing expression pattern of Adam23 gamma suggests that ADAM23 gamma likely plays an important role in brain development.