Espermátida: Diferenzas entre revisións

{{en tradución}}

[[Ficheiro: Germinal_epithelium_testicle.svg|miniatura|''Epitelio xerminal do [[testículo]].''<br>1: [[lámina basal]]<br>2: [[espermatogonia]]<br>3: [[espermatocito]] primario<br>4: espermatocito secundario<br>5: espermátida<br>6: espermátida madura<br>7: [[célula de Sertoli]]<br>8: [[unión hermética]] ([[barreira hematotesticular]])]]

[[Ficheiro:Gray1150.png|miniatura|Sección transversal dun [[túbulo seminífero]] dun testículo de [[rata]] (× 250).]]

 

No testículo, as espermátidas están conectadas unhas con outras por material citoplásmico e teñen material citoplásmico supérfluo aredor dos [[núcleo celular|núcleos]].

 

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The spermatids begin to grow a living thread, develop a thickened mid-piece where the [[mitochondria]] become localised, and form an [[acrosome]]. Spermatid DNA also undergoes packaging, becoming highly condensed. The DNA is packaged firstly with specific nuclear basic proteins, which are subsequently replaced with [[protamines]] during spermatid elongation. The resultant tightly packed [[chromatin]] is transcriptionally inactive.

 

In 2016 scientists at [[Nanjing Medical University]] claimed they had produced cells resembling mouse spermatids artificially from [[stem cells]]. They injected these spermatids into mouse eggs and produced pups.<ref name="Nature">{{cite journal|last1=Cyranoski|first1=David|title=Researchers claim to have made artificial mouse sperm in a dish|journal=Nature|date=25 February 2016|doi=10.1038/nature.2016.19453|s2cid=87014225|url=http://www.nature.com/news/researchers-claim-to-have-made-artificial-mouse-sperm-in-a-dish-1.19453|access-date=4 March 2016}}</ref>

 

As postmeiotic [[germ cell]]s develop to mature [[sperm]] they progressively lose the ability to repair [[DNA damage (naturally occurring)|DNA damage]] that may then accumulate and be transmitted to the [[zygote]] and ultimately the embryo.<ref name="pmid18282746">{{cite journal |vauthors=Marchetti F, Wyrobek AJ |title=DNA repair decline during mouse spermiogenesis results in the accumulation of heritable DNA damage |journal=DNA Repair (Amst.) |volume=7 |issue=4 |pages=572–81 |year=2008 |pmid=18282746 |doi=10.1016/j.dnarep.2007.12.011 |url=https://digital.library.unt.edu/ark:/67531/metadc895292/}}</ref> In particular, the [[DNA repair|repair of DNA]] double-strand breaks by the [[non-homologous end joining]] pathway, although present in round spermatids, appears to be lost as they develop into elongated spermatids.<ref name="pmid26694360">{{cite journal |vauthors=Ahmed EA, Scherthan H, de Rooij DG |title=DNA Double Strand Break Response and Limited Repair Capacity in Mouse Elongated Spermatids |journal=Int J Mol Sci |volume=16 |issue=12 |pages=29923–35 |year=2015 |pmid=26694360 |pmc=4691157 |doi=10.3390/ijms161226214 |doi-access=free }}</ref>

 

== Notas ==

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