How Do Testicles Know When To Stop Making More Sperm?

Every time someone ejaculates , it produces millions of spermatozoon . But the average brace of testicles produces billions of sperm cells over an entire lifetime . Why do n’t they produce all of their sperm in one go ? Answer : Because testicles have a complicated process to avoid run out of sperm and endangering next natality .

Sperm cells are derived from stem cells , that are tuck deep inside the testes . When these stem cells part , they have a pick : They can become another couplet of stem electric cell that will remain inside the testes . Or they can become a pair of more specialized cellular phone , that start out down the road to becoming spermatozoan .

Testes need to keep these choices cautiously balanced if their owners are to remain fertile : if too many cells exchange , the organs ’ reserve of stem cellular telephone could vanish , leaving them ineffectual to make new sperm . But if too few change , spermatozoan counting would fall , as the testes fill with stem cells .

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When it ’s time to make new sperm , the eubstance issue a pulse of retinoic superman , a chemical derive from Vitamin A , into the ballock . All of the stalk cells get the signal at the same meter . But only some of them make the shift to becoming spermatozoon . According to new work on mice by Kanako Ikami and her colleagues at the National Institute for Basic Biology in Japan , this differentiation is the result of a single difference inside the cells .

When Ikami seem closely at the genes these cells were using , she found they fell into two distinct groups : One chemical group made a protein with a shape that retinoic acid could tail with , the other did not .

The cells that could bind retinoic acid went on to become sperm , the cellular telephone that remained deliberately blind to the signal kept producing more stem cells . When she forced the “ unsighted ” cells to make the docking protein and exposed them to retinoic Zen , those cubicle shifted onto the sperm - making way of life . All of the stem jail cell within the bollock are perfectly open of induce sperm — but one little switch keeps them from doing it all at once .

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