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#sperm development

6 public questions tagged with this topic.

Regeneration -ll

Actin polymerization in sperm cells occurs primarily during:

Actin polymerization in sperm is temporally restricted to acrosomal reaction. G-actin monomers stored bound to profilin in sperm head rapidly assemble into F-actin bundle forming slender acrosomal process that extends bindin to reach vitelline envelope. Calcium influx and pH rise activate actin nucleation via formin and depolymerization of capping proteins, generating force to protrude process through egg jelly remnants. Cytochalasin B or latrunculin blocking polymerization prevents process formation and fertilization fails. Cortical reaction involves secretory exocytosis in egg, fertilization cone actin polymerization occurs in egg cortex during sperm incorporation, and slow block relies on envelope hardening rather than actin assembly.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 7: Actin polymerization driving acrosomal process extension in sea urchin sperm.

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Fertilization in mammals-l

Sperm maturation from spermatids to spermatozoa is known as:

Round haploid spermatids produced after meiosis undergo dramatic morphological transformation called spermiogenesis without further division, converting into streamlined spermatozoa. Process includes formation of acrosome from Golgi vesicles, replacement of histones with transition proteins then protamines condensing nucleus, axoneme assembly forming flagellum, mitochondrial aggregation around midpiece forming helical sheath for ATP production, and removal of residual cytoplasm as residual bodies phagocytosed by Sertoli cells. Spermiogenesis yields functional gamete with motility apparatus, compact genome ready for fertilization but not yet capacitated for zona interaction, hyperactivation and fusion competence.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 19: Spermiogenesis – morphologic transformation of spermatids to spermatozoa.

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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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