Large-scale clustering of CAGE tag expression data.
BACKGROUND
Recent analyses have suggested that many genes possess multiple transcription start sites (TSSs) that are differentially utilized in different tissues and cell lines. We have identified a huge number of TSSs mapped onto the mouse genome using the cap analysis of gene expression (CAGE) method. The standard hierarchical clustering algorithm, which gives us easily understandable graphical tree images, has difficulties in processing such huge amounts of TSS data and a better method to calculate and display the results is needed.


RESULTS
We use a combination of hierarchical and non-hierarchical clustering to cluster expression profiles of TSSs based on a large amount of CAGE data to profit from the best of both methods. We processed the genome-wide expression data, including 159,075 TSSs derived from 127 RNA samples of various organs of mouse, and succeeded in categorizing them into 70-100 clusters. The clusters exhibited intriguing biological features: a cluster supergroup with a ubiquitous expression profile, tissue-specific patterns, a distinct distribution of non-coding RNA and functional TSS groups.


CONCLUSIONS
Our approach succeeded in greatly reducing the calculation cost, and is an appropriate solution for analyzing large-scale TSS usage data.
Shimokawa
Kazuro
K
Genome Exploration Research Group, RIKEN Genomic Sciences Center, RIKEN Yokohama Institute, Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa, Japan. kazsi@gsc.riken.jp
Okamura-Oho
Yuko
Y
Kurita
Takio
T
Frith
Martin C
MC
Kawai
Jun
J
Carninci
Piero
P
Hayashizaki
Yoshihide
Y
D000465:Algorithms; D000818:Animals; D002874:Chromosome Mapping / Q000379:methods*; D020224:Expressed Sequence Tags; D020869:Gene Expression Profiling / Q000379:methods*; D051379:Mice; D005810:Multigene Family / Q000235:genetics*; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods*; D017422:Sequence Analysis, DNA / Q000379:methods*; D014157:Transcription Factors / Q000235:genetics*
D014157:Transcription Factors