sperm

• development of mature gametes = sperm and eggs
• includes processes of mitosis, meiosis, morphogenesis, differentiation

• primordial germ cell
• germ line is separated from somatic cells during the 2nd week post-fertilization
• appear in epiblast of pre-embryo
• appear several weeks before gonad appears
• express TF Oct4

• migrate during 3rd and 4th weeks
• migrate through yolk sac, hindgut, and dorsal mesentery
• arrive at gonadal ridge at week 5
• chemotaxis is one likely mechanism (w/c-kit and SCF)

may become germ cell tumors (teratomas and teratocarcinomas) in ectopic locations

• c-kit is a receptor
• SCF (stem cell factor) is the ligand for c-kit
• cells expressing c-kit and SCF surround PGCs along their migration pathway
• humans with loss of function mutations in c-kit are infertile

a transcription factor expressed by PGCs

required for activating migration of PGCs

after puberty

defect in pigmentation due to mutation in c-kit

• correlation: associated in time and location with migration pathways
• necessary: mutations lead to mice who are sterile, anemic (blood stem cell defects), and have pigmentation defects (neural crest cell defects - migration)
• sufficient: adding SCF to PGCs in vitro rescues cell locomotion defects

testes or ovary - environment exerts profound influence on the subsequent development of the germ cell to enter either oogenesis or spermatogenesis

• RA = signaling molecule, meiosis inducing substance
• Stra8 = TF

spermatogonia (mitosis) primary spermatocytes (meiosis I) secondary spermatocytes (meiosis II) spermatids (spermiogenesis) spermatazoa

• differentiate
• self-renew
• spermatogonia are stem cells

• in close association with male germ line cells through all stages of spermatogenesis
• provide a niche for spermatogenesis
• function to suuport, nourish, and protect male germ line
• synthesize and secrete androgen binding protein (ABP)

• androgen binding protein
• allows sufficient testosterone within seminiferous tubules for spermatogenesis

• in close proximity to Sertoli cells
• outside seminiferous tubule
• somatic cells that produce testosterone

• haploid
• connected via cytoplasmic bridges and share proteins

process of haploid spermatid undergoing morphogenesis into fully formed spermatozoon

• acrosome
• protamine-rich nucleus (protamine is a sperm-specific chromatin)
• mitochondrial midpiece
• flagellar tail

• immotile in the testes
• following ejaculation, sperm undergo capacitation in the female reproductive tract

increase in achondroplasia, Marfan, schizophrenia