Developmental Biology and Fertilization Lecture Review

A comprehensive 50-card vocabulary study set covering fertilization mechanisms, cell adhesion, tissue induction, major developmental signaling pathways, stem cell factors, and gametogenesis.

Sea urchin sperm chemotaxis

Mediation by sperm-activating peptides (such as Resact) that bind to a sperm-membrane receptor guanylyl cyclase, increasing intracellular cGMP levels, opening calcium channels, and stimulating mitochondrial respiration and flagellar motility.

Cumulus oophorus acrosome reaction

The initiation of the mammalian acrosome reaction at the level of the cumulus oophorus matrix (via progesterone and/or cumulus components) before reaching the zona pellucida, though it classically peaks at the zona pellucida (ZP3).

Izumo

A protein expressed on the sperm cell membrane (specifically localized to the equatorial segment after the acrosome reaction) that binds to its egg receptor, Juno.

ZP2 cleavage

A reaction catalyzed by ovastacin (a cortical granule metalloprotease) released upon fertilization, which clips ZP2 to prevent subsequent sperm binding and acts as a block to polyspermy.

Mammalian egg state at sperm entry

The developmental stage of the mammalian female gamete when sperm entry occurs, arrested at metaphase of Meiosis II.

Sea urchin egg polar bodies

Structures that are not generated post-entry because sea urchin eggs complete all of meiosis before spawning and are already mature haploid eggs at fertilization.

Sea urchin acrosome reaction components

A process involving exocytosis of the acrosomal vesicle, influx of $Ca^{2+}$ and $Na^+$ ions, efflux of $H^+$ ions (raising intracellular pH), and the exposure/polymerization of bindin.

Fast block to polyspermy in sea urchins

A polyspermy prevention mechanism achieved via a transient influx of sodium ions ($Na^+$) that depolarizes the egg cell membrane from a negative to a positive resting potential.

Resact receptor

A receptor guanylyl cyclase located on the flagellar membrane of the sperm that recognizes the sperm-activating peptide Resact.

Sperm-activating proteins

Peptides that lead to elevated intracellular cGMP, opening of $Ca^{2+}$ channels, enhanced sperm motility, and metabolic activation (chemotaxis).

Bindin receptors

Receptors expressed on the sea urchin egg vitelline envelope, specifically identified as the species-specific receptor protein EBR1.

Bindin-coated beads agglutination

An experimental assay where beads specifically agglutinate with eggs of the same species, demonstrating species-specific fertilization barriers.

Phospholipase C activation in sea urchins

An enzymatic process that cleaves $PIP_2$ into $IP_3$ and DAG, triggering the release of stored $Ca^{2+}$ from the endoplasmic reticulum to produce the fertilization calcium wave.

Egg fertilization consequences

Events triggered by fertilization that include metabolic activation, completion/resumption of meiosis, fusion of male and female pronuclei (syngamy), and initiation of embryonic cleavage cycles.

Lack of functional dynein

A defect that causes immotile sperm flagella and cilia (associated with conditions like Primary Ciliary Dyskinesia), resulting in male infertility.

Gamete stage at fertilization

The taxonomic-dependent nuclear maturity stage of the female gamete at fertilization, which can be a mature haploid egg (e.g., sea urchins) or a secondary oocyte arrested in meiosis (e.g., mammals).

$Ca^{2+}$ in egg activation

The universal second messenger that triggers egg activation, cortical granule exocytosis, and cell cycle resumption.

Differential Adhesion Hypothesis (DAH)

A hypothesis stating that differences in intercellular adhesion and cortical surface tension dictate that cells with higher cohesive strength internalize relative to those with lower surface tension.

Anoikis

A specialized form of programmed cell death (apoptosis) induced when anchorage-dependent cells lose contact with the extracellular matrix (ECM) or neighboring cells.

Epithelial-mesenchymal transition (EMT)

A cellular transformation in which epithelial cells lose apical-basal polarity and cell-cell adhesions (e.g., downregulating E-cadherin), remodel their basement membrane, and acquire migratory mesenchymal characteristics.

Amphibian eye induction genes

Master control and transcription factor genes involved in amphibian eye development, including Pax6, Otx2, Sox2, and Six3.

Lens induction

The process by which the lens is induced in the head ectoderm through instructive signaling originating from the optic vesicle.

Epithelial-mesenchymal trans-species transplants

Experiments proving that while the inducing tissue determines the regional specificity of the response, the responding tissue dictates what specific structural components are formed according to its own genomic repertoire.

Saunders' regional specificity experiments

Experimental studies demonstrating that the Apical Ectodermal Ridge (AER) and the underlying progress zone mesenchyme maintain limb outgrowth and proximal-distal patterning.

Bone Morphogenetic Protein (BMP)

A member of the $TGF\text{-}\beta$ superfamily of paracrine factors that regulate dorsal-ventral axis formation, epidermal specification, and programmed cell death.

Frizzled

The transmembrane Wnt receptor that acts alongside coreceptors like LRP5/6 to mediate canonical signaling.

Absence of Wnt signal

A pathway state in which $\beta\text{-catenin}$ is bound by a destruction complex (Axin, APC, GSK3, CK1), phosphorylated, and targeted for proteasomal degradation.

Planar Cell Polarity (PCP) pathway

A non-canonical Wnt signaling pathway that regulates cytoskeletal dynamics, cell polarization, and convergent extension via Rho/Rac/JNK cascades independently of $\beta\text{-catenin}$.

Notum

An enzyme that acts as a Wnt deacylase, inhibiting Wnt signaling by removing its palmitoleoyl group.

Canonical Wnt receptor configuration

A cell-surface receptor complex comprising Frizzled and LRP5/6.

Loss of Wnt4 effects

Developmental defects including disrupted kidney development, disrupted female sex determination (mammalian ovary differentiation), and disrupted mammary gland branching.

Hedgehog pathway molecules

The signaling components Sonic Hedgehog (Shh), the transmembrane receptor Patched (Ptch), the signal transducer Smoothened (Smo), and downstream Gli transcription factors.

Absence of Hedgehog signal

A state in which Patched constitutively inhibits Smoothened, causing full-length Gli to be phosphorylated and cleaved into a transcriptional repressor ($GliR$).

Primary cilium in Hedgehog signaling

The vertebrate organelle where Sonic hedgehog signaling components are primarily concentrated and upon which the pathway depends.

Juxtacrine non-molecules

Paracrine factors such as FGF, Wnt, and BMP that do not act via juxtacrine mechanisms because they do not require direct membrane contact.

Juxtacrine differential expression

The process utilizing direct cell-to-cell contact and lateral inhibition mechanisms (like Delta-Notch) to create sharp binary cell-fate boundaries irrespective of simple long-range gradients.

Notch signaling mechanism

A signaling pathway relying on direct physical contact between a transmembrane ligand (Delta/Jagged) and the Notch receptor, triggering sequential proteolytic cleavage by ADAM proteases and $\gamma\text{-secretase}$ to release the Notch intracellular domain (NICD).

Notch pathway molecules

The core signaling factors Delta, Jagged, Notch, Presenilin ($\gamma\text{-secretase}$ complex), and CSL (RBP-J) transcription factors.

Active BMP transcriptional complex

A transcriptional complex formed by phosphorylated receptor-regulated Smads (R-Smads: Smad1/5/8) complexing with the co-mediator Smad4.

Thanatophoric dysplasia cause

Gain-of-function mutations in Fibroblast Growth Factor Receptor 3 (FGFR3) that result in constitutive receptor activation and inhibited endochondral ossification (severe dwarfism).

Heparan sulfate proteoglycans (HSPGs)

Molecules that bind morphogens (such as FGFs, Wnts, and Hh) to immobilize/stabilize them, shape extracellular concentration gradients, and facilitate receptor presentation.

Cytonemes

Specialized, ultra-long, actin-based filopodial projections that transport morphogens directly between distant cells.

Factors affecting paracrine diffusion

Extracellular matrix composition, binding affinity to HSPGs, rates of endocytosis/degradation, and molecular mass/size.

Yamanaka factors

The canonical genes used for induced pluripotent stem (iPS) cell reprogramming: Oct4, Sox2, Klf4, and c-Myc (OSKM).

SRY gene chromosome location

The specific cytogenetic position of the SRY gene on the short arm of the Y chromosome, designated as $Yp11.2$.

Chromosomal crossing over

The exchange of corresponding segments of genetic material between homologous non-sister chromatids during Prophase I of meiosis (specifically pachytene), generating genetic recombination.

Primordial germ cells (PGCs)

Cells that originate outside the gonads in extraembryonic tissues (or early endoderm/mesoderm depending on the organism) and undergo active migration to populate the genital ridges.

Retinoic acid (RA) in gametogenesis

A signaling factor that controls the onset of meiosis by initiating meiosis in embryonic ovaries and preventing it prematurely in male fetal testes via degrading enzymes like Cyp26b1.

$IP_3$ signaling capability

The binding of $IP_3$ to $IP_3\text{-gated}$ calcium channels on the endoplasmic reticulum membrane to release stored intracellular $Ca^{2+}$ into the cytoplasm.

Centrosomes from 3 sperms

The introduction of 3 centrosomes into a single egg following polyspermic entry by 3 mammalian sperm, disrupting the bipolar mitotic spindle and causing catastrophic multipolar divisions and embryonic lethality.