Animal Science 434 Development of the Pituitary Gland Reproductive Physiology Infundibulum Brain Rathke’s Pouch Lec 5: Embryogenesis of the Pituitary and Sexual Development Stomodeum Germ Cell Migration

Migration from endoderm through mesoderm.

Migration begins by the 4 week of gestation in cow and human.

Fetal Kidneys

• Pronephros » regresses • Mesonephros » portions of reproductive tract • Metenephros » Adult kindney and urinary ducts

In birds the migration is via the blood stream.

Development of Mesenephros and Metenephros Development of Mesenephros and Metenephros

Early Development Flash Movie

http://www.ansci.wisc.edu/jjp1/as434/powerpoint/fa08/early_dev.swf

Requires the free flash player which can be downloaded from: www.adobe.com Jost Experiments Sex Determination: The Jost Paradigm

Mesonephric Ducts Chromosomal Sex Paramesonephric Ducts (Wolffian Ducts) (Mullerian Ducts)

Gonadal Sex

Testis Ovary Epididymis Phenotypic Sex Oviduct VaEsp Didefierens Sedmyimnail Uterus Vesiscles

Sex Determination: The Jost Paradigm Chromosomal Sex

Chromosomal Sex Chromosomal Sex • Single Pair of sex chromosomes Gonadal Sex » mammals, some but not all vertebrates • Sex is environmentally determined Gonadal Sex Hormonal Sex » sea worms, fish, reptiles Multiple sex chromosomes Phenotypic Sex • » invertebrates, insects, reptiles Phenotypic Sex Brain and/or Behavioral Sex • Haplodiploidy » bees, spiders

Chromosomal Sex Chromosomal Sex

A. Drosophila A. Drosophila • Sex depends on the number of X chromosomes • Sex depends on the number of X chromosomes – X or XY or XO = Male – X or XY or XO = Male – XX or XXX or XXY = Female – XX or XXX or XXY = Female

B. Human (mammals) • XY or XXY or XXYY or XXXY = Male (testis) • XX or XXX = Female (ovary) • XO = Female with incomplete ovarian development • XXY or XXYY or XXXY or XXXXY = testis but impaired sperm production Chromosomal Sex Human X and Y Chromosomes A. Drosophila • Sex depends on the number of X chromosomes – X or XY or XO = Male – XX or XXX or XXY = Female

B. Human (mammals) X • XY or XXY or XXYY or XXXY = Male (testis) • XX or XXX = Female (ovary) • XO = Female with incomplete ovarian development • XXY or XXYY or XXXY or XXXXY = testis but impaired sperm production Y C. Conclusion • The gene that controls testicular differentiation is on the Y chromosome in mammals.

The Y Chromosome The Y Chromosome Cont. A. Region coding for testicular development • Short arm of Y chromosome B. Other genes on the Y chromosome –H-Y Antigen » Spermatogenesis « no longer believed to be involved » androgen production » long bone growth –SRY « Codes for a DNA binding protein « acts as a transcription factor « Causes • primary sex chord (seminiferous tubule) development • Development of Sertoli Cells • Anti-Mullerian Hormone production by Sertoli Cells « absence of SRY • 2nd sex chords (egg nests) develop

SRY and Birds Gonadal Sex

• Birds » females ZW, males ZZ » W chromosome determines sex » SRY is found on the Z chromosome !

• SRY is not the only sex determining gene in animals XY Male Testis Determining Factor Testicular Development (SRY gene product) Mesonephric Duct Mesonephric Tubules Testes develop (Wolffian Duct)

Rete Tubules

Mullerian Duct Tunica Undifferentiated Albuginea Sex Chords

Mesonephric Tubules Primary Sex Chords in Fetal Testis Rete Tubules Pre-Sertoli

Wolffian Duct

Mullerian Duct Primary, Epithelial or Medullary Sex Chords Tunica • Primordial germ cells Gonocyte Albuginea (gonocytes) • Pre-Sertoli Cells

XY Male Testis Determining Factor Hormonal Sex (SRY gene product)

Testes develop

Sertoli cells secrete anti-mullerian hormone (AMH)

AMH causes leydig cells to differentiate

Testosterone

Development of male duct system Efferent Ducts Rete Tubules Wolffian Duct Cells (Vas Efferentia)

Nucleus Epididymis T Testis T TR

Vas Seminiferous Deferens Tubules Tunica Albuginea

XY Male Testis Determining Factor (SRY gene product) Vas efferentia

Testes develop

Sertoli cells secrete anti-mullerian hormone (AMH)

AMH causes leydig Degeneration of cells to differentiate Mullerian duct

Testosterone

Development of male duct system

Female Development Ovarian Development XX Female No TDF Testes Determining Factor Regressing Tubules Mullerian Ovaries Develop Duct Primary or Epithelial Sex Chords No No AMH Testosterone Future Ovarian Mullerian ducts become Cortex Wolffian Ducts the oviducts, uterus, cervix and part of the vagina Wolffian Regress Duct Regressing Regressing Tubules Tubules Primordial Follicles Mullerian Mullerian Duct Duct Regressing Epithelial Regressing Sex Chords Epithelial Sex Chords

Future Ovarian Future Ovarian Cortex Cortex Regressing Regressing Secondary or Wolffian Wolffian Cortical Sex Duct Duct Chords (egg nests)

Primordial 2nd Sex Chords in Fetal Ovary Follicles

Mullerian Duct Ovarian Medulla

Ovarian Regressing Cortex Wolffian Duct

Development of the Uterus, Cervix Fused Mullerian Duct and Vagina

Mullerian Duct

Hymen Reproductive tract develops outside the peritoneum! Broad Ligament Development (transverse anterior section)

Ovary

Regressing Wolffian Duct

Mullerian Duct

(Posterior Transverse Section) Ovary Genital Fold (Future Broad Ligament)

Regressing Wolffian Duct Regressing Mullerian Wolffian Duct Duct Mullerian Duct

Testis Determining Factor (SRY gene product) No TDF Phenotypic Sex XY Male XX Female

Testes develop Ovaries Develop

Sertoli cells secrete No No AMH anti-mullerian hormone (AMH) Testosterone

AMH causes leydig Degeneration of cells to differentiate Mullerian duct Degeneration of Mullerian ducts Wolffian duct become the oviducts, uterus, cervix Testosterone and part of the vagina

Development of male duct system XY Male Testis Determining Factor XY Male Testis Determining Factor (SRY gene product) (SRY gene product)

Testes develop Testes develop

Sertoli cells secrete Sertoli cells secrete anti-mullerian hormone (AMH) anti-mullerian hormone (AMH)

AMH causes leydig Degeneration of AMH causes leydig Degeneration of cells to differentiate Mullerian Duct cells to differentiate Mullerian Duct

Testosterone Testosterone Dihydrotestosterone

Development of penis Development of male Development of male scrotum and accessory duct system duct system sex glands

Wolffian Duct Cells Accessory Sex Glands* and External Genitalia Cells

Nucleus Nucleus

T T Testis T TR Testis T D DR 5α - Reductase

*Prostate, Cowper’s Gland