apical basolateral polarity

Define cell polarity.

The fundamental ability of a cell to organise its internal components asymmetrically along a specific axis.

In a migrating fibroblast, which cytoskeletal component is responsible for rapid remodeling at the cell's front?

The actin cytoskeleton.

What is the primary role of motor proteins moving along microtubule networks in a polarised cell?

Ensuring cargo, such as vesicles containing proteins or nutrients, reaches the correct cell domain.

What term describes tissue-level polarity often observed in epithelial layers?

Planar cell polarity.

Which epithelial domain faces the lumen or the outside environment?

The apical domain.

Which epithelial domain faces adjacent cells and contains cell-cell junctions?

The lateral domain.

Which epithelial domain faces away from the lumen and contacts the extracellular matrix?

The basal domain.

Where are microfilaments (actin) primarily concentrated in epithelial cells?

At the apical surface, forming the core of microvilli.

What structural feature is located immediately underneath the apical surface microvilli?

The terminal web.

How are microtubules typically arranged within an epithelial cell?

Vertically from the apical end to the basal end.

What is the primary functional role of vertically arranged microtubules in epithelial cells?

Serving as highways for long-distance transport of cargo between cell domains.

To which junctional complexes are intermediate filaments often anchored at the lateral membrane?

Desmosomes.

What is the primary mechanical function of intermediate filaments throughout the cell?

Providing high tensile strength to help the cell sheet resist mechanical stress.

Which junctional complex acts as a barrier to prevent the mixing of proteins and lipids between apical and basolateral membranes?

Tight junctions.

Where are tight junctions specifically located on the lateral membrane?

At the very top of the lateral side.

Which cytoskeletal filaments are anchored by adherens junctions to stabilise connections between neighbours?

Actin filaments.

What historical contribution did Whitman (1878) make to the study of cell fate?

Identified that distinct cytoplasmic domains are differentially partitioned to leech descendants.

What did Conklin (1905) identify in the ascidian oocyte regarding tissue type determination?

Five different cytoplasm types that were differentially inherited by offspring.

In intrinsic cell fate mechanisms, when is the decision about daughter cell identity made?

Inside the mother cell before or during the split.

How do 'localized determinants' lead to different cell fates during division?

Specific molecules concentrate on one side of the mother cell, so only one daughter inherits them.

What is the consequence of an 'asymmetric division plane' on daughter cells?

Daughter cells have different sizes or concentrations of cellular machinery.

In extrinsic cell fate mechanisms, what causes identical daughter cells to differentiate?

Changes in their environment immediately after they are formed.

What extrinsic process involves one cell sending a signal to its sister to suppress a certain fate?

Lateral inhibition.

Why is the lineage of C. elegans described as invariant?

Every worm develops through the exact same pattern of cell division.

In the C. elegans zygote (P₀), which cell type eventually produces sperm and eggs?

Germline stem cells.

What event determines the posterior (tail) end of the C. elegans egg?

The point where the sperm enters the egg.

The division of the P₀ cell in C. elegans results in a large anterior cell and a smaller posterior cell; name the posterior cell.

The P₁ cell.

What does the PAR acronym stand for in developmental biology?

Partitioning defective.

Which specific organelle brought by the sperm triggers the PAR proteins in C. elegans?

The centrosome.

Which kinase is considered the seventh member of the PAR protein group?

Atypical protein kinase C (aPKC or PKC-3).

List the three components that make up the anterior PAR complex (aPARs).

PAR-3, PAR-6, and PKC-3.

List the two primary proteins that make up the posterior PAR complex (pPARs).

PAR-1 and PAR-2.

Which PAR complex promotes somatic cell fates in the developing embryo?

The anterior PAR complex (aPARs).

Which PAR complex promotes germline and internal cell fates?

The posterior PAR complex (pPARs).

How does the centrosome physically clear aPARs from the posterior of the egg?

It causes the actomyosin cortex to contract and flow toward the opposite side.

What allows PAR-2 to move in and bind to the posterior membrane?

The clearance of aPARs from the back creates a blank space for PAR-2 binding.

What is the phenotypic result of PAR mutations on the AB and P₁ daughter cells?

The size and fate differences between them become less pronounced or identical.

Describe the mutual antagonism exerted by PKC-3 on PAR-2.

It phosphorylates PAR-2 to make it 'slippery', causing it to fall off the membrane into the cytoplasm.

Describe the mutual antagonism exerted by PAR-1 on PAR-3.

It phosphorylates PAR-3 to kick it off the posterior membrane.

Which protein is responsible for maintaining the sharp boundary between PAR domains in the middle of the cell?

PAR-5.

What role do microtubules play in the recruitment of posterior proteins?

They recruit PAR-1 and PAR-2 to the posterior cortex.

What mechanism causes the mitotic spindle to displace toward the posterior end in C. elegans?

Pulling forces resulting from interactions between microtubules and the cortex.

The redistribution of PAR proteins and cell fate determinants requires a process based on which two cellular components?

Actin and myosin.

What is a major consequence of the loss of apical-basal cell polarity in epithelial tissues?

Malignancy and the development of advanced tumours.

Which family of scaffolding proteins typically connects the PAR complex to the actin cytoskeleton and cell junctions?

The Amotl family.

How does the deregulation of Amotl2 specifically lead to tumour invasion?

It breaks down polarity, allowing cells to lose connections and move more easily.

How does vesicle trafficking contribute to the maintenance of cell polarity?

By delivering specific materials to the correct domain through secretion and recycling.

In bacteria, what is the role of the ParM and ParR system?

Plasmid segregation.

Which cytoskeletal filament is responsible for vertical highways in epithelial cells?

Microtubules.

How does PAR-1 specifically affect PAR-3 to ensure it stays in the anterior side?

By phosphorylating PAR-3 if it drifts into the posterior, causing it to leave the membrane.