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Published online: 18 February 2009 | doi:10.1038/nchina.2009.25

Cellular development: Selective demise

Jane Qiu

Introduction

© (2009) Elsevier

Cells degrade damaged proteins through autophagy, a catabolic process that helps maintain the quality of cellular products during development. Hong Zhang at the National Institute of Biological Sciences in Beijing and co-workers¹ have found autophagy to be responsible for keeping somatic cells free from P granules, a specialized type of protein aggregate that should only appear in germ cells during embryogenesis.

The researchers scanned the genome of mutant Caenorhabditis elegans embryos and compared the genetic makeup of those with an accumulation of P granules (see bottom images; P granules marked in green) in somatic cells to normal embryos (see top images). They found that embryos with an accumulation of P granules in somatic cells all had several genes inactivated that express autophagy proteins, such as LGG-1 and Atg-18. The result suggests that autophagy is important for preventing the formation of P granules in somatic cells.

The researchers performed a second genetic screen on mutant embryos without P granules in somatic cells. They found the embryos — including those with igg-1 and atg-18 inactivated — all carried a genetic locus, known as sepa-1, which helps suppress the formation of P granules in somatic cells. Loss-of-function mutation in sepa-1 resulted in the re-accumulation of P granules in somatic cells.

Biochemical studies show that Sepa-1 proteins interact directly with PGL-3, a protein component of P granules, and with Atg8. Zhang and co-workers propose that Sepa-1 proteins may function as a bridging molecule in mediating the specific recognition and degradation of P granule components by autophagy.

The authors of this work are from:
National Institute of Biological Sciences, Beijing, China; Graduate Programme, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China; National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.

Reference

1. Zhang, Y. et al. SEPA-1 mediates the specific recognition and degradation of P granule components by autophagy in C. elegans. Cell 136, 308–321 (2009).  | Article | PubMed |