Cell-to Cell Communication + Gametogenesis

4 basic Processes by which multicellular organisms grown

Proliferation, Specialization, Interaction, Movement

Cell Environment _________

impacts differentiation

3 Components of Cell-Cell Communication

Signal, Receptor, mechanism to transport signal to rest of cell

Induction (Def + Key Components)

change of behavior in physiology, morphology, or behavior of a group of cells

inducer, responder, competence

Instructive vs Permissive

Instructive: leads to new gene expression in responder → specification

Permissive: responding tissue is already specified but req appropriate environment for expression

Sequential vs Reciprocal Induction

Sequential: induced cell releases signal that influences another cell

Reciprocal induction: cell 1 influences cell 2, cell 2 influences cell 3, and cell 3 goes back and influences cell 1

Mesenchyme cells are often ______ of epithelia leading to ________

inducers; epithelial differentiation

Juxtacrine vs Paracrine

Juxtacrine: cell membrane proteins interact w/ receptor protein on adjacent cell surfaces

Paracrine: releases proteins that diffuse over small distance to induce changes in neighboring cell

Four Major Paracrine Molecule Families

Fibroblast Growth Factor

Hedgehog

Wingless

TGF Beta

JAKSTAT

Ligand brings receptors together → JAK phosphorylates STAT → STAT dimer goes directly to the nucleus (fewer steps)

Paracrine factors importance and speed

• maintaining differentiating by releasing txn factor important for maintaining cell state

• fast or slow

Autocrine signaling

Same cell makes ligand and receptor

Paracrine Loop

Interactions with neighboring cell stimulates differentiation

PAX6

transcription factor, that must expressed in head ectoderm to respond to optic vesicle and form eye (competence)

BMP 4

paracrine molecule secreted from optic vesicle, needed for retinal formation

RTK Pathway

Ligand binding causes receptor dimerization and autophosphorylation, which triggers a multi-step intracellular phosphorylation cascade to regulate genes

Hedgehog Pathway

In the absence of ligand the pathway is actively repressed, and ligand binding relieves that repression to allow transcription.

Wnt/β-catenin

Ligand binding prevents β-catenin degradation so it can accumulate and enter the nucleus to activate genes.

TGF-β/SMAD

Ligand binding phosphorylates SMADs, which form complexes and move to the nucleus to control transcription

Gametogenesis

Biochemical/structural changes that cause Primordial Germ Cells to become gametes

Spermatocytogensis definition and location

sperm stay connected in bridges thoughout genesis and drop cytoplasm at the end (residual bodies)

• seminiferous tubules

Acrosomal Rxn

Acrosome derived from golgi body contains enzyme that digest egg ECM

• acrosomal vesical fuses with sperm cell membrane and extends process into vitelline layer

Bindin

on acrosomal process mediates species specific binding to egg

Blocking Polyspermy

egg resting potential rises from Na+ Influx

cortical granules fuse to membrane to from a fertilization envelope

Oogenesis

primordial follicle → primary →secondary → antral → preovulatory

Egg Cytoplasmic Contributin

Nutritive proteins, Ribosomes and tRNA, Messenger RNA, Morphogenic factors, Protective chemicals

Sea Urchin attracting sperm

Sea Urchin Jelly Coat releases SAPS (Sperm Activation Peptides) Induce a calcium gradient that chemotactically attracts sperm

Vertebrate Egg at the Time of Fertilization

Polarized into animal and vegetal poles

Enclosed by one or more cellular envelopes

A secondary oocyte arrested in metaphase II

Possesses typical cellular organelles, including secretory vesicles (cortical granules) near plasma membrane

Fertilizable and capable of cleaving

Metabolically repressed

**global transcription only occurs for a short period after cleavage

Capacitation

• occurs in female reproductive tract

• removes seminal proteins so sperm head can bind to ZP

Sperm binds to ____ in _____ via ____

GlcNAC in ZP3 using Galtase