Organelles of sperm
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Transcript of Organelles of sperm
Organelles of Sperm
BY SHAHROKH PAKTINAT
Introduction
Differentiation of germ cells
Oocyte
Spermatozoon
Structure of Mammalian Spermatozoon
Sperm head & Sperm tail or flagellum
Rodent → hook-shaped or falciform
Ungulate, carnivore & primate → spatula-shaped or spatulate
Major distinction: centrosomes
Sperm Head
Nucleus (DNA & Protamines)
Reduced nuclear envelope (removed NPC)
Perinuclear theca or perinuclear matrix:
Subacrosomal layer
Equatorial segment (folded-over complex of PT, IAM & OAM)
Postacrosomal sheath (harbor SOAF)
Sperm Head
Sperm Flagellum
9+2 arrangement of microtubules
9 Outer dense fibers
4 major Segments (innermost and external structures):
Connecting piece: 9 segmented columns, capitulum, basal plate
Midpiece: mitochondrial sheath, mtDNA
Principal piece: annulus, fibrous sheath
End piece: axonemal doublets, outer dense fibers
Spermiogenesis
Extensive remodeling process
Biogenesis of accessory structures:
Acrosome
Amalgamation of cytosol
PT
Axoneme
Head shaping and hypercondensation
Centrosome reduction
Mitochondria rejection
NE reduction
Spermiogenesis
Recycle of organelles and proteins
Ubiquitin-dependent proteolysis (26 S proteasome)
E1, E2, E3 & E4
Monoubiquitin regeneration
Known substrates:
H2A & H3
Mitochondrial membrane protein prohibitin
Nucleolar ribonucleoproteins, NPC proteins, nucleoporins
Spermiogenesis
Transient structures & molecules:
Transitional proteins (TP1 & TP2)
Pro-acrosomal granules
Caudal manchette
Chromatid body
Residual body & Cytoplasmic droplet (CD)
Sperm Transport
Liquefaction
Chemotaxis (guanylate cyclase, ANP, P91& formylated N-peptides) → granulosa cell
Capacitation (2-4h in vitro): hyperactivation & acrosome reaction
Cholesterol removal
Expression of mannose binding site & progesterone receptor
Phosphorylation of tyrosine residues
Calcium influx
ROS
Changes of Sperm Head During Fertilization
ZP glycoproteins → ZP1, ZP2 & ZP3
ZP3 → before AR
ZP2 → after AR
Acrosome reaction (proacrosin)
P hormone & P-binding protein
Receptors of P: PR1 (Ca), PR2 (PTk) & PR3 (Cl & GABA) → infertility
Zona penetration → ubiquitin-proteasome system
Equatorial acrosome → equatorin
Changes of Organelles During Fertilization
Surface membranes → lost
PT → dissolved for oocyte activation
Smooth NE → replaced by maternally derived NE
Protamines → degraded & replaced by oocyte-derived histones
Zygotic centrosome → maternal centrosomal proteins + sperm-contributed centriole
Mitochondria, axoneme, accessory structures → degraded
Sperm Incorporation in Ooplasm, Oocyte Activation & Zygotic Development
Incorporation of plasma membranes → adhesion molecules & receptors
In mouse: α6β1 integrin receptors & ADAM proteins (fertilin β & cyritestin) & CD9
Direct contact of equatorial & postacrosomal segments with ooplasm
Transmission of SOAF into ooplasm → oocyte activation
PLC-zeta → calcium oscillation-inducing component of SOAF
Other PT proteins → oocyte activation & early stages of pronuclear development
Candidate Molecules Involved in the Sperm-Oocyte Fusion
Sperm Incorporation in Ooplasm, Oocyte Activation & Zygotic Development
Reversal of histone-protamine exchange
Replacement of NPC-free NE by de novo formed NE
Sperm contributed mRNAs → translated or maternal mRNA silencing
Sperm proximal centriole + oocyte pericentriolar material → zygotic centrosome
Sperm mitochondria → degraded by ooplasmic proteasomes
Ubiquitin label → spermatogenesis
Oocyte glutathione
Other sperm accessory structures
Importance of Centrosome in Fertilization
Incomplete centrosomes → arrest in fertilization → infertility
Absence or anomaly → Immotile or non-progressive sperms
vasectomy → anti-centriole antibodies
Ultrastructure & Pathology of Human Spermatozoa
Thanks for Your Attention