title: Dynamic Hedgehog signalling pathway activity in germline stem cells.
abstract: Although the contribution of Hedgehog (Hh) signalling to stem cell development and oncogenesis is well recognised, its importance for spermatogonial stem cells (SSCs) has not been established. Here we interrogate adult rat SSCs using an established model in which only undifferentiated spermatogonial cells remain in the testis at 15 weeks following irradiation, and spermatogonial differentiation is induced within 4 weeks by gonadotrophin-releasing hormone antagonist (GnRH-ant) administration. Synthesis of Hh pathway components in untreated adult rat testes was compared with that in irradiated testes prior to and after GnRH-ant exposure using in situ hybridization. In adult testes with complete spermatogenesis, the Desert Hedgehog ligand transcript, Dhh, was detected in Sertoli cells, some spermatogonia and in spermatocytes by in situ hybridization. Spermatogenic cells were identified as sites of Hh signalling through detection of transcripts encoding the Hh receptor, Ptc2 transcripts and proteins for the key downstream target of Hh signalling, Gli1 and the Hh transcriptional activator, Gli2. Remarkably, the undifferentiated spermatogonia present in irradiated adult rat testes contained Dhh in addition to Ptc2, Gli1 and Gli2, revealing the potential for an autocrine Hh signalling loop to sustain undifferentiated spermatogonial cells. These transcripts became undetectable by in situ hybridization following GnRH-ant induction of spermatogonial differentiation, however, detection of Gli1 protein in spermatogonia in all groups indicates that Hh signalling is sustained. This is the first evidence of active Hh signalling in mammalian male germline stem cells, as has been documented for some cancer stem cells.
authors.affiliation: Department of Histology and Embryology, Faculty of Medicine, Near East University, Nicosia, Mersin-10, Turkey; Monash Institute of Medical Research, Monash University, Melbourne, VIC, Australia.
authors.forename: Z
authors.initials: Z
authors.lastname: Sahin
authors.forename: A
authors.initials: A
authors.lastname: Szczepny
authors.forename: E A
authors.initials: EA
authors.lastname: McLaughlin
authors.forename: M L
authors.initials: ML
authors.lastname: Meistrich
authors.forename: W
authors.initials: W
authors.lastname: Zhou
authors.forename: I
authors.initials: I
authors.lastname: Ustunel
authors.forename: K L
authors.initials: KL
authors.lastname: Loveland
mesh_terms: D053687:Adult Stem Cells / Q000378:metabolism* / Q000528:radiation effects; D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects / Q000528:radiation effects; D004268:DNA-Binding Proteins / Q000235:genetics; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D053823:Hedgehog Proteins / Q000096:biosynthesis / Q000378:metabolism*; D006727:Hormone Antagonists / Q000494:pharmacology; D051741:Kruppel-Like Transcription Factors / Q000235:genetics; D008297:Male; D000072079:Patched Receptors; D000075722:Promyelocytic Leukemia Zinc Finger Protein; D051381:Rats; D017207:Rats, Sprague-Dawley; D011956:Receptors, Cell Surface / Q000235:genetics; D012708:Sertoli Cells / Q000378:metabolism; D015398:Signal Transduction; D013090:Spermatocytes / Q000378:metabolism; D013091:Spermatogenesis / Q000502:physiology; D013093:Spermatogonia / Q000378:metabolism*; D013737:Testis / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects; D000071676:Zinc Finger Protein GLI1; D000075746:Zinc Finger Protein Gli2
chemical_list: D004268:DNA-Binding Proteins; C556659:Dhh protein, rat; C498521:Gli1 protein, rat; D053823:Hedgehog Proteins; D006727:Hormone Antagonists; D051741:Kruppel-Like Transcription Factors; D000072079:Patched Receptors; D000075722:Promyelocytic Leukemia Zinc Finger Protein; D011956:Receptors, Cell Surface; C534029:ZBTB16 protein, rat; D000071676:Zinc Finger Protein GLI1; D000075746:Zinc Finger Protein Gli2; D007987:Gonadotropin-Releasing Hormone; C062876:cetrorelix
keywords: adult stem cells; spermatogonial stem cells; testicular cancer