3. RecapitulationRecapitulation
Work on role ofWork on role of EstrogenEstrogen in spermatogenesisin spermatogenesis
initiated ininitiated in 19911991 and continues to dateand continues to date
TamoxifenTamoxifen, an antiestrogen (, an antiestrogen (SERMSERM) was used to) was used to
block ER in rats. (block ER in rats. (19911991))
Estradiol valerateEstradiol valerate was used to activatewas used to activate ERER in ratsin rats
((19961996))
Estradiol
5. Estrogen ReceptorsEstrogen Receptors
Estrogen receptor alpha (Estrogen receptor alpha (ESR1ESR1))
was demonstrated in testes andwas demonstrated in testes and
sperm of rat.sperm of rat. ((G Sethi Aaberwal PhD).G Sethi Aaberwal PhD).
Estrogen receptor beta (Estrogen receptor beta (ESR2ESR2))
was demonstrated in rat testes.was demonstrated in rat testes.
((S Pathak PhDS Pathak PhD).). ESR2ESR2
ESR1
6. Tamoxifen and EmbryogenesisTamoxifen and Embryogenesis
Our studies withOur studies with tamoxifentamoxifen in male rats havein male rats have
demonstrated that exposure to thisdemonstrated that exposure to this SERMSERM
compromised early mitotic divisions incompromised early mitotic divisions in 2-42-4 cell stagecell stage
embryos sired by treated males, that led toembryos sired by treated males, that led to
preimplantation losses (preimplantation losses (PILPIL). (). (N Balasinor PhD; P Parte PhD)N Balasinor PhD; P Parte PhD)
Our studies withOur studies with tamoxifentamoxifen in male rats have furtherin male rats have further
shown that exposure to thisshown that exposure to this SERMSERM also compromisedalso compromised
development of implanted (development of implanted (9-11d9-11d) embryos sired by) embryos sired by
treated males, that led to postimplantation lossestreated males, that led to postimplantation losses
((POLPOL). (). (S D’Souza PhD; N Kedia-Mokashi PhD)S D’Souza PhD; N Kedia-Mokashi PhD)
ESR1-OHESR1-OH--TamTam
7. Mitosis and MeiosisMitosis and Meiosis
Our studies withOur studies with tamoxifentamoxifen in male rats have shownin male rats have shown
that exposure to thisthat exposure to this SERMSERM allows spermatogenesisallows spermatogenesis
to proceed to stageto proceed to stage VIIVII seminiferous tubules.seminiferous tubules.
((M Aleem PhD; V Padwal MScM Aleem PhD; V Padwal MSc))
Our studies withOur studies with E2E2 in male rats too have shown thatin male rats too have shown that
exposure to this hormone allows spermatogenesis toexposure to this hormone allows spermatogenesis to
proceed to stageproceed to stage VIIVII tubules.tubules.
((J Choudhari MSc, MSc; P Das-Gupta MScJ Choudhari MSc, MSc; P Das-Gupta MSc))
E2E2 is a known mitogen. Observations suggest thatis a known mitogen. Observations suggest that ERER
dependent transcription could be important for celldependent transcription could be important for cell
divisiondivision during germ cellduring germ cell mitosismitosis and for chromosomeand for chromosome
segregationssegregations inin meiosismeiosis..
ESR1/2-E2
8. Chromatin CondensationChromatin Condensation
TamoxifenTamoxifen ((SERMSERM) affects) affects condensationcondensation ofof chromatinchromatin ((looseloose
packagingpackaging) in elongating spermatids dependent upon) in elongating spermatids dependent upon
transcription factors intranscription factors in androgenandrogen-dependent stage-dependent stage VIIVII roundround
spermatids. This could be the cause of PIL. (spermatids. This could be the cause of PIL. (M Aleem PhDM Aleem PhD))
TamoxifenTamoxifen induced intratesticularinduced intratesticular testosteronetestosterone deficiency coulddeficiency could
be reducingbe reducing ARAR dependent transcription in Sertoli cells,dependent transcription in Sertoli cells,
necessary for providing factors for germ cellnecessary for providing factors for germ cell differentiationdifferentiation
program. (program. (P Parte PhDP Parte PhD))
E2E2 also adversely affectsalso adversely affects chromatin condensationchromatin condensation ((tighttight
packagingpackaging). (). (M Aleem PhDM Aleem PhD))
E2E2 induced intratesticular deficits ofinduced intratesticular deficits of TT could be partlycould be partly
responsible for adverse effects. But elevation ofresponsible for adverse effects. But elevation of intratesticularintratesticular
E2E2 suggests additionalsuggests additional ERER-dependent effects. (-dependent effects. (R D’Souza PhDR D’Souza PhD))
testosterone
9. Postimplantation LossPostimplantation Loss (POL)(POL)
ExpertsExperts were of the opinion thatwere of the opinion that tamoxifentamoxifen treatment wastreatment was
embryotoxic. Observed postimplantation losses were due toembryotoxic. Observed postimplantation losses were due to
Dominant Lethal MutationsDominant Lethal Mutations..
Alternative HypothesisAlternative Hypothesis:: We proposed thatWe proposed that tamoxifentamoxifen being anbeing an
antiestrogenantiestrogen, could have caused, could have caused epigeneticepigenetic modifications inmodifications in
spermatid genesspermatid genes required for implantation & epigeneticrequired for implantation & epigenetic
remodelling of the genome for organogenesis/remodelling of the genome for organogenesis/embryogenesisembryogenesis..
Our studies confirmed thatOur studies confirmed that tamoxifentamoxifen treatment causedtreatment caused
epigeneticepigenetic modification ofmodification of EREERE-dependent,-dependent, Igf2 imprintedIgf2 imprinted genegene
viavia ERbetaERbeta//Dnmt1Dnmt1 during spermatogenesis. Reduced expressionduring spermatogenesis. Reduced expression
of Igf2 from the paternal copy of Igf2 Imprinted gene inof Igf2 from the paternal copy of Igf2 Imprinted gene in
embryos led toembryos led to POLPOL..
((S Pathak PhD; N Kedia-Mokashi PhD; N Balasinor PhDS Pathak PhD; N Kedia-Mokashi PhD; N Balasinor PhD))
ESR2-E2
10. SpermiationSpermiation
Our studies withOur studies with E2E2 in male rat have shown that exposure toin male rat have shown that exposure to
this hormone lowersthis hormone lowers intratesticular testosteroneintratesticular testosterone, raises, raises
intratesticularintratesticular E2E2, concomitant with, concomitant with spermiation failurespermiation failure..
((R D’ SouzaR D’ Souza))
Electron microscopic and confocal studies detected anElectron microscopic and confocal studies detected an absenceabsence
ofof tubulobulbar complextubulobulbar complex inin step 19step 19 spermatids involved inspermatids involved in
spermiation. (spermiation. (R D’Souza PhD; S D’Souza PhD; S Sonawane MScR D’Souza PhD; S D’Souza PhD; S Sonawane MSc))
Arp2/3Arp2/3 complex critical forcomplex critical for de novode novo polymerization of actinpolymerization of actin
during tubulobulbar complex formation was affected.during tubulobulbar complex formation was affected.
((R D’Souza PhDR D’Souza PhD).).
IntratesticularIntratesticular levels oflevels of TT andand E2E2 determine thedetermine the disengagementdisengagement
of matured spermatids from Sertoli cells (Spermiation).of matured spermatids from Sertoli cells (Spermiation).
((R Upadhyay PhDR Upadhyay PhD))
ESR1/2
11. ConclusionsConclusions
TT andand E2E2, acting in, acting in concertconcert, determine the, determine the
mitotic and meiotic germ cell divisions,mitotic and meiotic germ cell divisions,
nuclear chromatin condensation,nuclear chromatin condensation,
spermiation, through cognate testicularspermiation, through cognate testicular
receptorsreceptors, during spermatogenesis., during spermatogenesis.
PILPIL andand POLPOL of embryos sired by males areof embryos sired by males are
linked tolinked to qualitativequalitative differentiation ofdifferentiation of
spermatids.spermatids.
AR-T
12. Novel PerspectiveNovel Perspective
Bisphenol ABisphenol A is anis an endocrine disruptorendocrine disruptor which binds towhich binds to
constitutionallyconstitutionally activeactive Estrogen receptor gammaEstrogen receptor gamma
((ERR3ERR3)/estrogen related receptor, without deactivation)/estrogen related receptor, without deactivation
ERR3ERR3 is anis an OrphanOrphan receptor, has no known physiological ligandreceptor, has no known physiological ligand
It activatesIt activates Dnmt1Dnmt1 expression by binding toexpression by binding to EREERE in promoterin promoter
ERR3ERR3 interferesinterferes with ER-mediated estrogen responsewith ER-mediated estrogen response
ERR3ERR3 sharesshares target genes, co-regulators, promoters withtarget genes, co-regulators, promoters with ERER
TamoxifenTamoxifen binds tobinds to ERR3ERR3 andand deactivatesdeactivates itit
Does ERR3Does ERR3 figurefigure in the process ofin the process of SpermatogenesisSpermatogenesis??
estrogen receptor gammaestrogen receptor gamma
13. Novel PerspectiveNovel Perspective
Aurora Kinases A/B/C are a set of enzymes involved inAurora Kinases A/B/C are a set of enzymes involved in
mitotic/meiotic cell divisions/chromosome segregationsmitotic/meiotic cell divisions/chromosome segregations
Aurora A localizes to centrosomes for spindle formationAurora A localizes to centrosomes for spindle formation
Aurora B localizes to kinetochores for chromosome segregationAurora B localizes to kinetochores for chromosome segregation
Aurora C localizes to centromeres for meioticAurora C localizes to centromeres for meiotic
metaphase1/cytokinesis in male/preimplantation embryosmetaphase1/cytokinesis in male/preimplantation embryos
E2E2, mitogen, completes spermatogenesis in hpg mice till stage, mitogen, completes spermatogenesis in hpg mice till stage
VII tubules (Ebling et al Endocrinology 141, 2000).VII tubules (Ebling et al Endocrinology 141, 2000).
4hydroxy4hydroxy tamoxifentamoxifen increases weight of rat testes (Gill-increases weight of rat testes (Gill-
Sharma et al Contraception 63, 2001)Sharma et al Contraception 63, 2001)
Do AUKs figure in mechanism via whichDo AUKs figure in mechanism via which E2E2 facilitatesfacilitates
quantitativequantitative spermatogenesisspermatogenesis??
