Gamete Biology and Development

Gamete Biology

• Ectoderm cells differentiate into tissues like neurons in the brain
• Mesoderm cells become tissues like cardiac muscle
• Endoderm cells form internal organs such as the thyroid
• Pigs and humans have similar primordial germ cell (PGC) development pathways

Mouse Primordial Germ Cells (PGCs)

• Proximal epiblast cells develop into PGCs via extraembryonic signals
• PGCs originate from mesoderm
• PGCs migrate to the gonad around embryonic day 10.5 in mice
• Human and mouse PGCs arise from different progenitor cells

Sex Determination

• Sex determination happens around embryonic day 11.5
• The SRY gene activates in males
• SRY suppresses Dax1 and X-linked genes

Spermatogenesis

• Spermatocytogenesis involves sperm formation through sperm stem cell multiplication
• Differentiated sperm stem cells undergo amplification and differentiation
• Meiosis produces four spermatids from primary spermatocytes, leading to haploid sperm cells
• Post-meiotic sperm cells are transcriptionally inactive
• Post-meiotic sperm acquires motility in the epididymus
• Acrosomal caps form from the Golgi apparatus
• Primordial follicles form

Oogenesis

• Oogenesis involves transcription, translation, and protein accumulation
• mRNA and proteins are essential for sustaining development
• Oocyte maturation, early development, and mRNA and protein storage are crucial aspects of oogenesis

Oocyte Storage and Regulation

• RNA polyadenylation, RNA masking, RNA localization, and antisense RNA, as well as protein phosphorylation, are involved in oocyte storage and regulation.
• Cytoplasmic polyadenylation depends on the length of the Poly-A tail
• Short Poly-A tails prevent translation
• RNA masking prevents translation by binding to ribonucleoproteins
• RNA localization restricts protein production for germline establishment

RNA Localization

• Oocyte polarity determines spatial restriction in protein production
• Germplasm stores RNA and proteins, but mammals lack it
• Protein phosphorylation plays a major role in oocyte maturation, activation, and signaling pathways

Maternal to Zygotic Transition

• Mouse maternal-to-zygotic transition occurs at the 1-2 cell stage
• Pig transition happens at the 4-8 cell stage
• Sheep at the 8-16 cell stage
• Cow transition is at the 8-16 cell stage
• Xenopus occurs at the 4000 cell stage
• In vitro gamete selection is relevant to livestock breeding

In Vitro Fertilization (IVF)

• Oocyte maturation happens at 39 degrees Celsius in 5% CO2 for 24 hours in most species, but can take longer in pigs
• Exogenous gonadotropins used in IVF
• Sperm capacitation can be cryopreserved
• Embryo development to blastocyst stage can be in vitro
• Oocyte collection technique like OPU are used in species like sheep and pigs

Nuclear Transfer (NT)

• Generating a genetic copy of an individual after transferring cell nuclei; using embryonic or somatic cells
• Developmentally related to blastomere stage and species
• Embryo Multiplication can be limited by cell number

Fetal Abnormalities

• Fetal abnormalities such as hydroallantois, extended gestation can result from placental defects
• Other abnormalities involve kidney, brain, cardiovascular, muscle, and skeletal systems

Intracytoplasmic Sperm Injection (ICSI)

• ICSI is part of ART procedures
• Success rates vary between species

Uses of NT

• Cloning
• Production of genetically modified animals
• Preservation of rare breeds of livestock

Human Medicine and Agriculture uses

• Transgenic animals used in biopharmaceuticals, nutraceuticals and xenotransplantation for human diseases, cell transplantation, and gene therapy in human medicine
• In agriculture, transgenic animals are useful in disease research, disease prevention, genetic improvement, genetic preservation of rare breeds, and preserving superior genotypes

Explore the fascinating processes of gamete biology, including cell differentiation of ectoderm, mesoderm, and endoderm tissues. Understand the roles of primordial germ cells in both mice and humans, and learn about sex determination and spermatogenesis. This quiz covers essential concepts in reproductive biology.