Abstract
In just ten years, tens of millions of vultures have vanished from the Indian subcontinent. Since the early 1990s, white-backed (Gyps bengalensis), long-billed (G. indicus), and slender-billed (G. tenuirostris) vulture populations have dropped by over 95%. In Europe, it was clear that human persecution eradicated bearded and griffon vultures from some countries (reintroduction and protection efforts are now restoring populations). But in India, where it is illegal to kill wildlife and the bird is valued for its ecological role, their unprecedented decline was puzzling. Dead birds found in India, Pakistan, and Nepal had extensive visceral gout (a buildup of uric acid crystals in the internal organs associated with renal failure). The birds often appeared sick and lethargic, some showed prolonged severe neck drooping, before collapsing—sometimes from their perches.
Highlights
Because uncontrolled cell division is so dangerous for an organism, the well-behaved cell must know when to divide, and—crucially—when not to
A cell in such a temporary, nondividing state is said to be “quiescent.” Signals that send a cell into quiescence include loss of contact with the underlying surface, too much contact with neighboring cells, and not receiving specific growth factors from the surroundings
The reversibility of quiescence contrasts with the cell cycle arrest induced by inhibition of cyclin-dependent kinase (CDK), a key regulatory protein
Summary
Because uncontrolled cell division is so dangerous for an organism, the well-behaved cell must know when to divide, and—crucially—when not to. After 20 days, there were over 100 genes whose change in expression linked them to quiescence These included those that regulate metabolism and cell division, as might be expected, and genes that suppress the transition to two other cell fates— differentiation and programmed death. The expression of these genes (along with many others) was increased, indicating the active nature of the quiescent state. The identification of different quiescent states, induced by the three different signals, may lead to a better understanding of context-specific control of cell growth during development and repair, in muscle, but perhaps in other tissues as well.
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