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#acrosome

3 public questions tagged with this topic.

Fertilization in mammals-l

Structure containing enzymes for egg penetration:

Sperm head contains specialized organelle housing hydrolytic enzymes for egg investment penetration. Derived from Golgi, acrosome forms cap over nucleus filled with hyaluronidase digesting cumulus hyaluronic acid, acrosin serine protease and acid hydrolases cleaving zona glycoproteins. Calcium-triggered fusion of outer acrosomal membrane with plasma membrane during acrosome reaction releases enzymes focally at sperm-egg interface, creating path through zona. Inner acrosomal membrane retained displays secondary binding proteins. Therefore acrosome provides essential enzymatic toolkit for breaching maternal investments surrounding oocyte, reaching plasmalemma, permitting membrane merger, activation and zygote formation.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 7: Acrosomal enzymes and penetration of cumulus and zona investments.

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Fertilization in mammals-l

Acrosome originates from:

Acrosome is Golgi-derived cap-shaped secretory vesicle forming anterior to spermatid nucleus during spermiogenesis. Golgi stacks contribute proacrosomal granules that coalesce into single granule attaching to nuclear envelope, expanding over half nuclear surface. Containing hyaluronidase acrosin and acid hydrolases similar to lysosomal enzymes, organelle functionally analogous to lysosome but specialized for fertilization. Acrosome formation requires Hrb, GOPC and pick1 genes; defects cause globozoospermia with round heads lacking acrosome resulting in infertility due to inability to penetrate zona pellucida, access oolemma, trigger fusion and activate oocyte for development.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 19: Golgi origin of acrosome and globozoospermia defects in humans.

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Fertilization in mammals-iv

Acrosomal vesicle originates from:

Acrosome is large secretory vesicle capping anterior half of sperm nucleus, formed during spermiogenesis from Golgi apparatus of developing spermatid. Golgi cisternae generate proacrosomic vesicles containing hydrolytic enzymes that coalesce into single acroblast near nucleus then flatten over it, under manoeuvre of acroplaxome. Contents include acid hydrolases typical of lysosome-like organelle but origin is Golgi, not mitochondria, lysosomes or endoplasmic reticulum. Enzyme sorting involves mannose-6-phosphate-like pathways; disruption of Golgi trafficking proteins such as Pick1 results in globozoospermia lacking acrosome, confirming Golgi ancestry essential for male fertility.

Ref: Toshimori K, Reproductive Medicine and Biology: Golgi origin of acrosome and acrosome biogenesis in mammalian spermiogenesis.

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