The analysis of genomic structures in the L1 family of cell adhesion molecules provides no evidence for exon shuffling events after the separation of arthropod and chordate lineages.
Members of the L1 family of neural cell adhesion molecules consist of multiple extracellular immunoglobulin and fibronectin type III domains that mediate the adhesive properties of this group of transmembrane proteins. In vertebrate genomes, these protein domains are separated by introns, and it has been suggested that L1-type genes might have been subject to exon-shuffling events during evolution. However, comparison of the human L1-CAM and the chicken neurofascin gene with the genomic structure of their Drosophila homologue, neuroglian, indicates that no major rearrangement of protein domains has taken place subsequent to the split of the arthropod and chordate phyla. The Drosophila neuroglian gene appears to have lost most of the introns that have been conserved in the human L1-CAM and the chicken neurofascin gene. Nevertheless, exon shuffling or the generation of new exons by mutational changes might have been responsible for the generation of additional, alternatively spliced exons in L1-type genes.
Zhao
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University of Michigan, Department of Anatomy, Cell Biology, Ann Arbor, MI 48109-0616, USA.
Hortsch
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D000818:Animals; D001181:Arthropods / Q000235:genetics*; D001483:Base Sequence; D015815:Cell Adhesion Molecules / Q000235:genetics; D015816:Cell Adhesion Molecules, Neuronal / Q000235:genetics*; D002645:Chickens / Q000235:genetics; D002816:Chordata, Nonvertebrate / Q000235:genetics*; D004247:DNA / Q000235:genetics / Q000302:isolation & purification; D004330:Drosophila / Q000737:chemistry / Q000235:genetics; D029721:Drosophila Proteins; D019143:Evolution, Molecular; D005091:Exons / Q000235:genetics*; D017344:Genes, Insect / Q000235:genetics*; D006801:Humans; D007438:Introns / Q000235:genetics; D039841:Leukocyte L1 Antigen Complex; D008562:Membrane Glycoproteins / Q000235:genetics*; D008969:Molecular Sequence Data; D009414:Nerve Growth Factors / Q000235:genetics; D019006:Neural Cell Adhesion Molecules / Q000235:genetics*; D017422:Sequence Analysis, DNA; D017385:Sequence Homology; D014158:Transcription, Genetic / Q000235:genetics; D014714:Vertebrates / Q000235:genetics
D015815:Cell Adhesion Molecules; D015816:Cell Adhesion Molecules, Neuronal; D029721:Drosophila Proteins; D039841:Leukocyte L1 Antigen Complex; D008562:Membrane Glycoproteins; C054305:NFASC protein, human; D009414:Nerve Growth Factors; D019006:Neural Cell Adhesion Molecules; C504595:Nfasc protein, Gallus gallus; C061745:Nrg protein, Drosophila; D004247:DNA