Poly(ADP-ribose) controls DE-cadherin-dependent stem cell maintenance and oocyte localization

Area of Science:

• Developmental Biology
• Cellular Biology
• Molecular Biology

Background:

• Poly(ADP-ribose) (pADPr) is a dynamic post-translational modification rapidly synthesized and degraded during the cell cycle.
• Heterogeneous nuclear ribonucleoproteins (hnRNPs) are involved in various RNA processing events, including mRNA transport and translation.
• Germline stem cells (GSCs) in Drosophila are maintained in a niche that regulates their self-renewal and differentiation.

Purpose of the Study:

• To investigate the role of pADPr and hnRNPs in regulating GSC maintenance and oogenesis in Drosophila.
• To elucidate the molecular mechanism by which pADPr-hnRNP interactions affect stem cell behavior and oocyte polarity.

Main Methods:

• Analysis of pADPr levels and Hrp38 protein association in Drosophila ovaries.
• Investigation of Hrp38 binding to DE-cadherin mRNA using techniques like RNA immunoprecipitation.
• Assessment of DE-cadherin translation levels and GSC behavior under conditions of altered pADPr metabolism or Hrp38 function.

Main Results:

• The association of pADPr with Hrp38 disrupts Hrp38 binding to the 5'-untranslated region of DE-cadherin mRNA.
• This disruption leads to diminished DE-cadherin translation, causing GSCs to exit their niche and differentiate.
• Impaired pADPr degradation or Hrp38 function results in reduced DE-cadherin levels, GSC loss, and oocyte mislocalization.

Conclusions:

• Hrp38, an hnRNP, plays a critical role in GSC maintenance and oocyte polarity in Drosophila.
• The dynamic association of pADPr with Hrp38 modulates DE-cadherin translation, thereby controlling GSC self-renewal.
• These findings highlight a novel regulatory mechanism involving post-translational modification and RNA-binding proteins in stem cell biology and development.