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Published March 1, 1992 | Published
Journal Article Open

Alternative Splicing of Micro-Exons Creates Multiple Forms of the Insect Cell Adhesion Molecule Fasciclin I

Abstract

Fasciclin I is a homophilic cell adhesion molecule in insects that is dynamically expressed on a subset of axon pathways in the embryonic nervous system, and on a variety of other cells and tissues during development. The fasciclin I protein consists of four homologous 150 amino acid domains. In this article, we describe the complete sequence of the Drosophila fasciclin I (fasI) gene. The gene consists of 15 exons and is distributed over 14 kilobases of DNA. We examine the structure and temporal expression pattern of multiple fasciclin I mRNAs that differ in the lengths of their 3′ untranslated regions. We also show that a highly conserved sequence at the end of the second domain can be altered by the addition of three or six amino acids that are encoded by two alternatively spliced 9 base pair (bp) micro-exons. In grasshopper fasciclin I mRNAs, there are 9 bp and 6 bp insertions at the same position. The first of these insertions is identical in sequence to the first fly micro-exon. The grasshopper insertions are not found together in the same mRNA, so grasshopper fasciclin I species differ by the addition of three or two extra amino acids to the second domain. The alternatively spliced mRNAs are differentially expressed during embryogenesis, and all three of them are present in nerve cord preparations. We suggest that the amino acids inserted by alternative micro-exon splicing may alter the binding specificity of fasciclin I.

Additional Information

© 1992 by Society for Neuroscience. For the first six months after publication SfN's license will be exclusive. Beginning six months after publication the Work will be made freely available to the public on SfN's website to copy, distribute, or display under a Creative Commons Attribution 4.0 International (CC BY 4.0) license (https://creativecommons.org/licenses/by/4.0/). Received July 22, 1991; revised Oct. 14, 1991; accepted Oct. 18, 1991. We thank Ann Begovitch and Jayne Danska for help and advice with the PCR experiments, Beth Blankemeir for technical assistance in sequencing the PCR products, Ken Burtis for his Drosophila codon bias database, and John Tamkun and Matt Scott for the cosmid library. K.Z was supported by a Helen Hay Whitney postdoctoral fellowship for part of the period during which these experiments were performed. This work was supported by the Howard Hughes Medical Institute and by grants from the NIH to C.S.G. and K.Z.

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August 20, 2023
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