Stem cell chicken and egg debate moves to unlikely arena: ...(he support cells said Voog. By contrast...)

Their study also explores the molecular basis of stem cell/niche interactions. "SSCs in the testis look similar to hub cells," explained Jones. "Both cell types express many of the same proteins." The team experimentally decreased levels of one of those a sticky surface protein called DE-cadherin that likely allows stem cells to latch on to the support hub but only in somatic stem cells. When they did so, DE-cadherin expression on hub cells also decreased, providing further circumstantial support for the idea that hub cells emerge from SSCs.

"Stem cell biology is a fast-moving field and insights from model organisms like Drosophila provide great insight into how stem cell behavior is regulated," said Voog. "The architecture of the fruit fly testis makes it an ideal system to address questions about what regulates stem cell interactions within the niche."

Jones agrees, noting that spermatogenesis is also a great system to manipulate experimentally. "Spermatogenesis is less complex than stem cell systems that give rise to multiple cell types, such as blood stem cells," she said. "Only one cell type emerges from the processspermso if something goes wrong with the system it is readily apparent: you won't form any sperm."

According to Jones, mammalian stem cell niches are not so well characterized. Although their whereabouts in tissues like brain or bone marrow is known, how niche compartments relate to their respective neural or blood stem cell charges is an open question.

Issues raised by this study will have to be addressed in humans before good stem cells are exploited or bad ones are eradicated. Will stem cells transplanted in proposed regeneration therapies establish their own support crew or will a "niche transplant" be required to maintain them?

Or, do so-called cancer stem cells, which are thought t
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