title: A phylogenetic analysis of the L1 family of neural cell adhesion molecules.
abstract: L1-type genes form one of several distinct gene families that encode adhesive proteins, which are predominantly expressed in developing and mature metazoan nervous systems. These proteins have a multitude of different important cellular functions in neuronal and glial cells. L1-type gene products are transmembrane proteins with a characteristic extracellular domain structure consisting of six immunoglobulin and three to five fibronectin type III protein folds. As reported here, L1-type proteins can be identified in most metazoan phyla with the notable exception of Porifera (sponges). This puts the origin of L1-type genes at a point in time when primitive cellular neural networks emerged, approximately 1,200 to 1,500 million years ago. Subsequently, several independent gene duplication events generated multiple paralogous L1-type genes in some phyla, allowing for a considerable diversification of L1 structures and the emergence of new functional features and molecular interactions. One such evolutionary newer feature is the appearance of RGD integrin-binding motifs in some vertebrate L1 family members.
authors.affiliation: Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA.
authors.forename: Rula
authors.initials: R
authors.lastname: Mualla
authors.forename: Kakanahalli
authors.initials: K
authors.lastname: Nagaraj
authors.forename: Michael
authors.initials: M
authors.lastname: Hortsch
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D020440:Gene Duplication; D006801:Humans; D007136:Immunoglobulins / Q000737:chemistry / Q000235:genetics; D039842:Neural Cell Adhesion Molecule L1 / Q000737:chemistry / Q000235:genetics*; D009842:Oligopeptides / Q000235:genetics; D010802:Phylogeny; D017434:Protein Structure, Tertiary
chemical_list: D007136:Immunoglobulins; D039842:Neural Cell Adhesion Molecule L1; D009842:Oligopeptides; C047981:arginyl-glycyl-aspartic acid