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Infertility in the hyperplasic ovary of freshwater planarians: the role of programmed cell death

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  • Abdel Halim Harrath, Zoology Department College of Science, King Saud University, P. O. Box 2455, Riyadh, 11451, Saudi Arabia, halim.harrath@laposte.net., Unknown
  • Abdelhabib Semlali, Unknown
  • Lamjed Mansour, Unknown
  • Mukhtar Ahmed, Unknown
  • Alexander V Sirotkin, Unknown
  • Suliman Y Al Omar, Unknown
  • Maha Arfah, Unknown
  • Mohamed S Al Anazi, Unknown
  • Ibrahim M Alhazza, Unknown
  • Jens R Nyengaard
  • Saleh Alwasel

Ex-fissiparous planarians produce infertile cocoons or, in very rare cases, cocoons with very low fertility. Here, we describe the features of programmed cell death (PCD) occurring in the hyperplasic ovary of the ex-fissiparous freshwater planarian Dugesia arabica that may explain this infertility. Based on TEM results, we demonstrate a novel extensive co-clustering of cytoplasmic organelles, such as lysosomes and microtubules, and their fusion with autophagosomes during the early stage of oocyte cell death occurring through an autophagic pattern. During a later stage of cell death, the generation of apoptotic vesicles in the cytoplasm can be observed. The immunohistochemical labeling supports the ultrastructural results because it has been shown that the proapoptotic protein bax was more highly expressed in the hyperplasic ovary than in the normal one, whereas the anti-apoptotic protein bcl2 was slightly more highly expressed in the normal ovary compared to the hyperplasic one. TUNEL analysis of the hyperplasic ovary confirmed that the nuclei of the majority of differentiating oocytes were TUNEL-positive, whereas the nuclei of oogonia and young oocytes were TUNEL-negative; in the normal ovary, oocytes are TUNEL-negative. Considering all of these data, we suggest that the cell death mechanism of differentiating oocytes in the hyperplasic ovary of freshwater planarians is one of the most important factors that cause ex-fissiparous planarian infertility. We propose that autophagy precedes apoptosis during oogenesis, whereas apoptotic features can be observed later.

Original languageEnglish
JournalCell and Tissue Research
ISSN0302-766X
DOIs
Publication statusPublished - 9 Aug 2014

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