TY  - JOUR
A1  - Murchison, Elizabeth P.
A1  - Kheradpour, Pouya
A1  - Sachidanandam, Ravi
A1  - Smith, Carly
A1  - Hodges, Emily
A1  - Xuan, Zhenyu
A1  - Kellis, Manolis
A1  - Grützner, Frank
A1  - Stark, Alexander
A1  - Hannon, Gregory J.
T1  - Conservation of small RNA pathways in platypus
Y1  - 2008/06/01 
JF  - Genome Research 
JO  - Genome Research 
SP  - 995 
EP  - 1004 
DO  - 10.1101/gr.073056.107 
VL  - 18 
IS  - 6 
UR  - http://genome.cshlp.org/content/18/6/995.abstract 
N2  - Small RNA pathways play evolutionarily conserved roles in gene regulation and defense from parasitic nucleic acids. The character and expression patterns of small RNAs show conservation throughout animal lineages, but specific animal clades also show variations on these recurring themes, including species-specific small RNAs. The monotremes, with only platypus and four species of echidna as extant members, represent the basal branch of the mammalian lineage. Here, we examine the small RNA pathways of monotremes by deep sequencing of six platypus and echidna tissues. We find that highly conserved microRNA species display their signature tissue-specific expression patterns. In addition, we find a large rapidly evolving cluster of microRNAs on platypus chromosome X1, which is unique to monotremes. Platypus and echidna testes contain a robust Piwi-interacting (piRNA) system, which appears to be participating in ongoing transposon defense. 
ER  -