Family expansion and gene rearrangements contributed to the functional specialization of PRDM genes in vertebrates.
BACKGROUND
Progressive diversification of paralogs after gene expansion is essential to increase their functional specialization. However, mode and tempo of this divergence remain mostly unclear. Here we report the comparative analysis of PRDM genes, a family of putative transcriptional regulators involved in human tumorigenesis.


RESULTS
Our analysis assessed that the PRDM genes originated in metazoans, expanded in vertebrates and further duplicated in primates. We experimentally showed that fast-evolving paralogs are poorly expressed, and that the most recent duplicates, such as primate-specific PRDM7, acquire tissue-specificity. PRDM7 underwent major structural rearrangements that decreased the number of encoded Zn-Fingers and modified gene splicing. Through internal duplication and activation of a non-canonical splice site (GC-AG), PRDM7 can acquire a novel intron. We also detected an alternative isoform that can retain the intron in the mature transcript and that is predominantly expressed in human melanocytes.


CONCLUSIONS
Our findings show that (a) molecular evolution of paralogs correlates with their expression pattern; (b) gene diversification is obtained through massive genomic rearrangements; and (c) splicing modification contributes to the functional specialization of novel genes.
Fumasoni
Irene
I
Department of Experimental Oncology, European Institute of Oncology, IFOM-IEO Campus, Via Adamello 16, 20139 Milan, Italy. irene.fumasoni@ifom-ieo-campus.it
Meani
Natalia
N
Rambaldi
Davide
D
Scafetta
Gaia
G
Alcalay
Myriam
M
Ciccarelli
Francesca D
FD
D000595:Amino Acid Sequence; D000818:Animals; D017931:DNA Primers; D019143:Evolution, Molecular; D020440:Gene Duplication; D005786:Gene Expression Regulation; D015321:Gene Rearrangement; D006801:Humans; D005810:Multigene Family; D010802:Phylogeny; D012097:Repressor Proteins / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D013045:Species Specificity; D014157:Transcription Factors / Q000235:genetics*; D014714:Vertebrates / Q000235:genetics*
D017931:DNA Primers; D012097:Repressor Proteins; D014157:Transcription Factors