DjPiwi-1, a member of the PAZ-Piwi gene family, defines a subpopulation of planarian stem cells.
Planarian regeneration, based upon totipotent stem cells, the neoblasts, provides a unique opportunity to study in vivo the molecular program that defines a stem cell. In this study, we report the identification of DjPiwi-1, a planarian homologue of Drosophila Piwi. Expression analysis showed that DjPiwi-1 transcripts are preferentially accumulated in small cells distributed along the midline of the dorsal parenchyma. DjPiwi-1 transcripts were not detectable after X-ray irradiation by whole mount in situ hybridization. Real time reverse transcriptase polymerase chain reaction analysis confirmed the significant reduction of DjPiwi-1 expression after X-ray treatment. However, the presence of residual DjPiwi-1 transcription suggests that, although the majority of DjPiwi-1-positive cells can be neoblasts, this gene is also expressed in differentiating/differentiated cells. During regeneration DjPiwi-1-positive cells reorganize along the midline of the stump and no accumulation of hybridization signal was observed either in the blastema area or in the parenchymal region beneath the blastema. DjPiwi-1-positive cells, as well as the DjMCM2-expressing neoblasts located along the midline and those spread all over the parenchyma, showed a lower tolerance to X-ray with respect to the DjMCM2-expressing neoblasts distributed along the lateral lines of the parenchyma. Taken together, these findings suggest the presence of different neoblast subpopulations in planarians.
Dipartimento di Morfologia Umana e Biologia Applicata, Università di Pisa, Pisa, Italy.
Leonardo
L
Rossi
Alessandra
A
Salvetti
Annalisa
A
Lena
Renata
R
Batistoni
Paolo
P
Deri
Claudio
C
Pugliesi
Elena
E
Loreti
Vittorio
V
Gremigni
D000595:Amino Acid Sequence; D000818:Animals; D002470:Cell Survival / Q000528:radiation effects; D017124:Conserved Sequence; D020224:Expressed Sequence Tags; D017238:Genes, Helminth; D015801:Helminth Proteins; D017403:In Situ Hybridization; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D010932:Planarians / Q000033:anatomy & histology / Q000235:genetics* / Q000502:physiology* / Q000648:ultrastructure; D017434:Protein Structure, Tertiary; D034622:RNA Interference; D012038:Regeneration / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D013234:Stem Cells / Q000378:metabolism / Q000502:physiology* / Q000648:ultrastructure; D014158:Transcription, Genetic; D014965:X-Rays
D015801:Helminth Proteins