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BIOL 130 (305)

Reproductive System

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BIOL 130
Barry Mc Clinchey

Reproductive System Integrated with urinary system development relies upon mesonephric ducts (Wolffian ducts) Wolffian form vas deferens and epididymis in males closed system Mullerian Mullerian ducts - paramesonephric ducts that arise alongside mesonephric ducts derived from surface epithelium form oviducts/uterus of female **Embryos are IDENTICAL until week 6  after this, genetic sex is expressed** PRIMORDIAL GERM CELLS – PGC arise very early in development, distinct from gonad position - endodermal, highly motile (large filopodia) - proliferate as they migrate to the gonadal ridge Migration: - c-Kit receptor (migration along genital ridge) c-kit - B-1 integrin B-1 integrin - SDF-1/ CXCR4 (migration into genital ridge) SDF-1/CXCR4 Survival/Proliferation: - SCF/c-KIT (survival) SCF - Pin-1 (increase cell cycle rate  inc. proliferation) Pin-1 - SDF/CXCR4 (survival) PGC’s are not required for testes, but ARE required for ovaries GERM CELL FATES mitotic arrest XY PGC’s in testes will have MITOTIC arrest until puberty XX PGC’s in testes will die after mitosis resumes at puberty XY PGC’s in ovaries will have MEOTIC arrest until puberty meiotic arrest **XY PGC’s in ovaries may survive after meosis resumes** Reproductive System CENTRAL DOGMA OF SEX DEVELOPMENT genetic sex  gonadal sex  phenotypic sex (no gonads  phenotypically female) Genetic Sex determination: depends on Y chromosome sry, TDF locus of sry gene  codes for TDF (TF) (testes-determining factor) downstream targets of TDF not yet id’d sry expression is necessary but not sufficient for: testis development (not ovaries) sperm (not oocytes) sertoli cells (not follicle granulosa cells) leydig cells (not theca cells) peritubular tunica (not stromal tunica) other important genes – Sox9 – mutations cause XY females Sox9 DaxI, Wnt4 – duplications cause XY females DaxI, Wnt4 Phenotypic Sex: (Genital ducts determined by gonads present) testis present  Wolffian ducts remain (testosterone effect) testosterone Mullerian ducts regress (MIS effect) MIS (Mullerian inhibiting substance) grafting experiments: remove testes early  only Mullerian ducts are present late  both sets present and incomplete (more Mullerian than Wolffian) add testes unilaterally  same side Wolffian present opposite side ½ present (testosterone operates over small distances only)  same side Mullerian gone opposite side FULLY present (MIF operates over small dist. also) add testosterone bead  Wolffian present
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