Lecture 15: Polarity

Thirty flashcards covering cell polarity, Par proteins, asymmetry in model organisms, and the relationship between polarity loss and disease (cancer).

According to the lecture, what does cell polarity generate that allows for a diverse array of functions?

A wide variety of forms

Which component of the cytoskeleton is identified as being key to cell polarity?

Actin

In the historical perspective of cell fate determination, what did Whitman ($1878$) discover about cytoplasmic domains in leech descendants?

They are differentially partitioned and reflected in different cell lineages

How many different cytoplasm types did Conklin ($1905$) identify in the ascidina oocyte?

$$5$$

What is the intrinsic route for generating cell fate diversity?

Polar mother cells divide and daughters inherit different components

What are the two model organisms mentioned for studying cell fate because they are transparent and have fixed somatic cell numbers?

C. elegans and Drosophila

What are the partitioning defective genes discovered in genetic screens of asymmetric division called?

par genes

In par mutants, what happens to the size and fate differences between daughter cells AB and P1?

They are less pronounced, and in extreme cases, the two cells are identical

How many members are in the Par protein group, and what is the seventh atypical member?

There are $7$ members, and the seventh is atypical protein kinase C (aPKC)

Which specific Par protein is the only one not conserved in other metazoans besides the worm?

Par2

What defines the posterior pole and the axis of polarity following fertilization?

The sperm entry point

What does the sperm deliver to the embryo that helps define polarity?

A microtubule organizing centre (MTOC)

Which Par proteins and associated molecule accumulate at the anterior cortex?

Par3, Par6, aPKC, and Cdc42

Which proteins are localized to the posterior cortex in the C. elegans embryo?

Par1, Par2, and LGL

What is the role of Par5 in the establishment of polarity?

It maintains the boundary between the anterior and posterior domains

What biochemical process is key in the feedback loops that allow the poles to be defined?

Phosphorylation

In immunofluorescence staining (Side-on view), what colors are used to mark apical, junctional, and basolateral markers?

Apical marker in blue, junctional marker in red, and basolateral marker in green

What are the adhesive molecules that hold cells together and are vital for epithelium maintenance?

Cadherins

Transcellular transport of which molecule is cited as a primary example of the need for cell polarity?

Glucose

What type of transporter uses the high concentration of sodium outside the cell to drive glucose into the cell?

Glucose-sodium symporter

Which network within the cell is responsible for sorting and delivering newly made proteins to the apical domain?

The trans-Golgi net (TGN)

Why is polarity required in bacteria regarding extra DNA?

For plasmid segregation

What is ParM and what is its function in bacteria?

An actin-related cytoskeletal protein that assembles into a fibre to push plasmids to opposite ends of the cell

Where do the majority of human cancers originate?

They are epithelial in origin

What property is gained by advanced tumors when cell polarity is lost?

Invasive and malignant properties

What type of proteins are the Amotl family?

Scaffold proteins

According to experimental data, what do Amotl proteins integrate besides apical polarity and junctional formation?

The actin cytoskeleton

What happens to Par3 and Crb3 proteins when AmotL2 is overexpressed?

They are sequestered to intracellular large vesicles in the wrong subcellular location

What is the effect of p60 AmotL2 on tumor intravasation?

It promotes tumor intravasation and growth

Maintaining the boundary between different domains prevents what problematic event for epithelial cells?

Pathogens entering the body or materials being delivered to the wrong domain