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A large family of Dscam genes with tandemly arrayed 5' cassettes in Chelicerata.

Yue Y, Meng Y, Ma H, Hou S, Cao G, Hong W, Shi Y, Guo P, Liu B, Shi F, Yang Y, Jin Y - Nat Commun (2016)

Bottom Line: Furthermore, extraordinary isoform diversity has been generated through a combination of alternating promoter and alternative splicing.These sDscams have a high sequence similarity with Drosophila Dscam1, and share striking organizational resemblance to the 5' variable regions of vertebrate clustered Pcdhs.Hence, our findings have important implications for understanding the functional similarities between Drosophila Dscam1 and vertebrate Pcdhs, and may provide further mechanistic insights into the regulation of isoform diversity.

View Article: PubMed Central - PubMed

Affiliation: Institute of Biochemistry, Innovation Center for Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang ZJ310058, China.

ABSTRACT
Drosophila Dscam1 (Down Syndrome Cell Adhesion Molecules) and vertebrate clustered protocadherins (Pcdhs) are two classic examples of the extraordinary isoform diversity from a single genomic locus. Dscam1 encodes 38,016 distinct isoforms via mutually exclusive splicing in D. melanogaster, while the vertebrate clustered Pcdhs utilize alternative promoters to generate isoform diversity. Here we reveal a shortened Dscam gene family with tandemly arrayed 5' cassettes in Chelicerata. These cassette repeats generally comprise two or four exons, corresponding to variable Immunoglobulin 7 (Ig7) or Ig7-8 domains of Drosophila Dscam1. Furthermore, extraordinary isoform diversity has been generated through a combination of alternating promoter and alternative splicing. These sDscams have a high sequence similarity with Drosophila Dscam1, and share striking organizational resemblance to the 5' variable regions of vertebrate clustered Pcdhs. Hence, our findings have important implications for understanding the functional similarities between Drosophila Dscam1 and vertebrate Pcdhs, and may provide further mechanistic insights into the regulation of isoform diversity.

No MeSH data available.


Related in: MedlinePlus

Each variable cassette preceded by a promoter in sDscam.(a) A schematic diagram of the expression of variable cassettes in M. martensii sDscamβ6. Symbols used are the same as in Fig. 1. Potential promoter elements (PPE) are shown as green circles. (b) Analysis of sDscam variable cassette promoter in the reporter assays. A portion of the sequence immediately preceding a given variable cassette was cloned into a luciferase reporter construct and subsequently transfected into Drosophila S2 cells. The luciferase vector containing the Drosophila Dscam2 promoter or intronic sequence of sDscamβ6 served as positive and negative controls, respectively. Schematic diagrams of mutants with the indicated sizes are depicted on the left. The deleted PPEs are shown as dashed circles. Data are expressed as a percentage of the mean±s.d. from three independent experiments. *P<0.05, **P<0.01 and ***P<0.001 (Student's t-test, two-tailed); NS, not significant.
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f4: Each variable cassette preceded by a promoter in sDscam.(a) A schematic diagram of the expression of variable cassettes in M. martensii sDscamβ6. Symbols used are the same as in Fig. 1. Potential promoter elements (PPE) are shown as green circles. (b) Analysis of sDscam variable cassette promoter in the reporter assays. A portion of the sequence immediately preceding a given variable cassette was cloned into a luciferase reporter construct and subsequently transfected into Drosophila S2 cells. The luciferase vector containing the Drosophila Dscam2 promoter or intronic sequence of sDscamβ6 served as positive and negative controls, respectively. Schematic diagrams of mutants with the indicated sizes are depicted on the left. The deleted PPEs are shown as dashed circles. Data are expressed as a percentage of the mean±s.d. from three independent experiments. *P<0.05, **P<0.01 and ***P<0.001 (Student's t-test, two-tailed); NS, not significant.

Mentions: To clarify the mechanisms by which isoforms were generated and regulated from a single sDscam gene locus, it was ascertained whether the sDscam genes applied a similar strategy to that in vertebrate Pcdhs, with the alternative use of a separate promoter upstream of each first exon of a variable region1920. In Pcdhs, each first exon is preceded by a promoter and produces a transcript in which the first exon is spliced to common exons. To determine whether each sDscam variable cassette has its own promoter, sequences immediately upstream of the transcription start site of each variable region in sDscamα and six sDscamβ genes were examined. A rich array of potential promoter elements (PPEs) was predicted to be located upstream of the 5′ end of each variable region (Fig. 4a; Supplementary Fig. 9). Therefore our data suggest that each variable cassette is generally preceded by a given promoter.


A large family of Dscam genes with tandemly arrayed 5' cassettes in Chelicerata.

Yue Y, Meng Y, Ma H, Hou S, Cao G, Hong W, Shi Y, Guo P, Liu B, Shi F, Yang Y, Jin Y - Nat Commun (2016)

Each variable cassette preceded by a promoter in sDscam.(a) A schematic diagram of the expression of variable cassettes in M. martensii sDscamβ6. Symbols used are the same as in Fig. 1. Potential promoter elements (PPE) are shown as green circles. (b) Analysis of sDscam variable cassette promoter in the reporter assays. A portion of the sequence immediately preceding a given variable cassette was cloned into a luciferase reporter construct and subsequently transfected into Drosophila S2 cells. The luciferase vector containing the Drosophila Dscam2 promoter or intronic sequence of sDscamβ6 served as positive and negative controls, respectively. Schematic diagrams of mutants with the indicated sizes are depicted on the left. The deleted PPEs are shown as dashed circles. Data are expressed as a percentage of the mean±s.d. from three independent experiments. *P<0.05, **P<0.01 and ***P<0.001 (Student's t-test, two-tailed); NS, not significant.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4835542&req=5

f4: Each variable cassette preceded by a promoter in sDscam.(a) A schematic diagram of the expression of variable cassettes in M. martensii sDscamβ6. Symbols used are the same as in Fig. 1. Potential promoter elements (PPE) are shown as green circles. (b) Analysis of sDscam variable cassette promoter in the reporter assays. A portion of the sequence immediately preceding a given variable cassette was cloned into a luciferase reporter construct and subsequently transfected into Drosophila S2 cells. The luciferase vector containing the Drosophila Dscam2 promoter or intronic sequence of sDscamβ6 served as positive and negative controls, respectively. Schematic diagrams of mutants with the indicated sizes are depicted on the left. The deleted PPEs are shown as dashed circles. Data are expressed as a percentage of the mean±s.d. from three independent experiments. *P<0.05, **P<0.01 and ***P<0.001 (Student's t-test, two-tailed); NS, not significant.
Mentions: To clarify the mechanisms by which isoforms were generated and regulated from a single sDscam gene locus, it was ascertained whether the sDscam genes applied a similar strategy to that in vertebrate Pcdhs, with the alternative use of a separate promoter upstream of each first exon of a variable region1920. In Pcdhs, each first exon is preceded by a promoter and produces a transcript in which the first exon is spliced to common exons. To determine whether each sDscam variable cassette has its own promoter, sequences immediately upstream of the transcription start site of each variable region in sDscamα and six sDscamβ genes were examined. A rich array of potential promoter elements (PPEs) was predicted to be located upstream of the 5′ end of each variable region (Fig. 4a; Supplementary Fig. 9). Therefore our data suggest that each variable cassette is generally preceded by a given promoter.

Bottom Line: Furthermore, extraordinary isoform diversity has been generated through a combination of alternating promoter and alternative splicing.These sDscams have a high sequence similarity with Drosophila Dscam1, and share striking organizational resemblance to the 5' variable regions of vertebrate clustered Pcdhs.Hence, our findings have important implications for understanding the functional similarities between Drosophila Dscam1 and vertebrate Pcdhs, and may provide further mechanistic insights into the regulation of isoform diversity.

View Article: PubMed Central - PubMed

Affiliation: Institute of Biochemistry, Innovation Center for Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang ZJ310058, China.

ABSTRACT
Drosophila Dscam1 (Down Syndrome Cell Adhesion Molecules) and vertebrate clustered protocadherins (Pcdhs) are two classic examples of the extraordinary isoform diversity from a single genomic locus. Dscam1 encodes 38,016 distinct isoforms via mutually exclusive splicing in D. melanogaster, while the vertebrate clustered Pcdhs utilize alternative promoters to generate isoform diversity. Here we reveal a shortened Dscam gene family with tandemly arrayed 5' cassettes in Chelicerata. These cassette repeats generally comprise two or four exons, corresponding to variable Immunoglobulin 7 (Ig7) or Ig7-8 domains of Drosophila Dscam1. Furthermore, extraordinary isoform diversity has been generated through a combination of alternating promoter and alternative splicing. These sDscams have a high sequence similarity with Drosophila Dscam1, and share striking organizational resemblance to the 5' variable regions of vertebrate clustered Pcdhs. Hence, our findings have important implications for understanding the functional similarities between Drosophila Dscam1 and vertebrate Pcdhs, and may provide further mechanistic insights into the regulation of isoform diversity.

No MeSH data available.


Related in: MedlinePlus