Gene expression profiling of U12-type spliceosome mutant Drosophila reveals widespread changes in metabolic pathways.
BACKGROUND
The U12-type spliceosome is responsible for the removal of a subset of introns from eukaryotic mRNAs. U12-type introns are spliced less efficiently than normal U2-type introns, which suggests a rate-limiting role in gene expression. The Drosophila genome contains about 20 U12-type introns, many of them in essential genes, and the U12-type spliceosome has previously been shown to be essential in the fly.


RESULTS
We have used a Drosophila line with a P-element insertion in U6atac snRNA, an essential component of the U12-type spliceosome, to investigate the impact of U12-type introns on gene expression at the organismal level during fly development. This line exhibits progressive accumulation of unspliced U12-type introns during larval development and the death of larvae at the third instar stage. Surprisingly, microarray and RT-PCR analyses revealed that most genes containing U12-type introns showed only mild perturbations in the splicing of U12-type introns. In contrast, we detected widespread downstream effects on genes that do not contain U12-type introns, with genes related to various metabolic pathways constituting the largest group.


CONCLUSIONS
U12-type intron-containing genes exhibited variable gene-specific responses to the splicing defect, with some genes showing up- or downregulation, while most did not change significantly. The observed residual U12-type splicing activity could be explained with the mutant U6atac allele having a low level of catalytic activity. Detailed analysis of all genes suggested that a defect in the splicing of the U12-type intron of the mitochondrial prohibitin gene may be the primary cause of the various downstream effects detected in the microarray analysis.
Pessa
Heli K J
HK
Institute of Biotechnology, University of Helsinki, Helsinki, Finland.
Greco
Dario
D
Kvist
Jouni
J
Wahlström
Gudrun
G
Heino
Tapio I
TI
Auvinen
Petri
P
Frilander
Mikko J
MJ
D000818:Animals; D004330:Drosophila / Q000235:genetics*; D020869:Gene Expression Profiling; D007438:Introns; D009154:Mutation; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017381:Spliceosomes