organelles of sperm
DESCRIPTION
These slides concentrate mostly on cellular organelles existing in human sperm cell.TRANSCRIPT
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