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Figure 7-89. Alternative splicing of RNA transcripts of the Drosophila DSCAM gene..

Figure 7-89Alternative splicing of RNA transcripts of the Drosophila DSCAM gene.

DSCAM proteins are axon guidance receptors that help to direct growth cones to their appropriate targets in the developing nervous system. The final mRNA contains 24 exons, four of which (denoted A, B, C, and D) are present in the DSCAM gene as arrays of alternative exons. Each RNA contains 1 of 12 alternatives for exon A (red), 1 of 48 alternatives for exon B (green), 1 of 33 alternatives for exon C (blue), and 1 of 2 alternatives for exon D (yellow). If all possible splicing combinations are used, 38,016 different proteins could in principle be produced from the DSCAM gene. Only one of the many possible splicing patterns (indicated by the red line and by the mature mRNA below it) is shown. Each variant DSCAM protein would fold into roughly the same structure [predominantly a series of extracellular immunoglobulin-like domains linked to a membrane-spanning region (see Figure 24-71)], but the amino acid sequence of the domains would vary according to the splicing pattern. It is possible that this receptor diversity contributes to the formation of complex neural circuits, but the precise properties and functions of the many DSCAM variants are not yet understood. (Adapted from D.L. Black, Cell 103:367–370, 2000.)

From: Posttranscriptional Controls

Cover of Molecular Biology of the Cell
Molecular Biology of the Cell. 4th edition.
Alberts B, Johnson A, Lewis J, et al.
New York: Garland Science; 2002.
Copyright © 2002, Bruce Alberts, Alexander Johnson, Julian Lewis, Martin Raff, Keith Roberts, and Peter Walter; Copyright © 1983, 1989, 1994, Bruce Alberts, Dennis Bray, Julian Lewis, Martin Raff, Keith Roberts, and James D. Watson .

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