Primordial germ cells

Stem cell biology

1. P RIMORDIAL GERM CELLS P.PARANI SANKAR | 3rd B.sc Biotechnology | A8UBT028

2. I NTRODUCTION Primordial germ cells (PGCs) are the precursors of the gametes. They are unipotent and differentiate into sperm and gametes. PGCs in culture give rise to Pluripotent embryonic stem cells. PGCs in are extensively studied in models like drosophila , zebra fish , mice but human are not studied well due to ethical issues .

3. SEX DIFFERENTATION The sex chromosomes in the somatic cells of the genital ridges determine which type of gonad the ridge becomes. In females: Differentiates PGCs Oogonia 9th week Oogonia gets arrested at diplotene stage in meiosis 1. In the male , after reaching the developing the testis , PGCs are usually termed Gonocytes . Gonocytes enter mitotic arrest and stay quiescent till birth.

4. DIFFERENTIATION OF PGCs

5. M ORPHOLOGY PGCs are generally Spherical and larger in size , Large nucleus with marked nuclear membrane. D iameter .10 to 20µm. M orphological modifications of PGCs depending on the 2 phases: Separation and migration phase Colonization phase .

6. O RIGIN In mammals the primordial germ cells have extra gonadal origin. Alkaline phosphate enzyme is used as a Marker to determine the location and migration of these cells. In human embryo, PGCs originate in the endodermal epithelium of the yolk sac in the vicinity of the allantoic stalk. Germplasm PGC recognised Sperm Ovum Embryo Gametes Early embryonic stage PGC Inside embryo

7. T RANSPORTATION OF PGCs P GC originate outside , they move to reach gonads. T hey transported int o two types , By Blood stream in chick embryo By Amoeboid movement in human embryo

8. MIGRATON Begins to migrate from yolk sac in the 4th week and reach gonads by 5th week in mammals. Controlled through two separate ligand receptor , chemo attractant signalling interactions.

9. P GCs IN DIFFERENT ANIMALS FISHES: PGC ENDODERM

10. B IRDS AND REPTILES P GC ENDODERM Extra embryonic part of the blastoderm Anterior to the head region of the embryo

11. THANK YOU “THINK GLOBALLY , ACT LOCALLY”