AC - C.ELEGANS PAR GENES AND A-P AXIS DEVELOPMENT Flashcards
How do c.elegans have the ability to produce both egg and sperm?
They are hermaphrodites
How is the distribution of PAR proteins described before fertilisation in an embryo?
Before fertilisation PAR proteins are equally distributed
What happens when the sperm enters?
- Fertilisation will occur
- Causing a change in the layout/arrangement of proteins in the embryo
- Polarisation is determined
- Initiates A&P axis development
- Also begins the process of asymmetry in cells
How are the anterior + posterior determined?
The sperm determines the posterior site via entry.
What structure enters alongside the sperm ?
A centrosome enters with the sperm and generates a network of microtubules (actin-dense)
How are the 2 cells formed?
The spindles at metaphase contract asymmetrically to produce ABcell (Anterior) and P1 cell (small posterior cell)
What genes are maternally expressed?
PAR genes are maternally expressed
How were PAR genes discovered?
PAR genes were initially discovered when scientists studied mutant embryos which produced symmetrical cells after cell division
What is the arrangement of PAR genes before fertilisation?
PAR 3 and 6 are bound to the membrane wall via lipid binding domain.
PAR 2 is bound to the kinase, PKC-3 which phosphorylates it. Due to this, It is unable to bind to the membrane with PAR 3 + 6.
How does PAR2 bind to the membrane wall after fertilisation?
After fertilisation, PAR 2 binds to the sperms microtubule aster, which protects it from the phosphorylating kinase PKC-3.
PAR 2 is now able to bind to the local membrane (Posterior region) with Microtubule aster.
What does PAR 2 do once its bound to the membrane wall?
PAR 2 recruits PAR 1 (a Kinase) which phosphorylates PAR3.
The phosphorylation of PAR 3 removes it from the cell wall. PAR 3 + 6 relocate to the anterior region.
PAR 2 and 1 will be highly recruited at the microtubule aster site in the posterior domain
What maternal component system in which the distribution of different proteins drives A+P development in early cell division?
The arrangement of maternally expressed PAR genes causes the asymmetry in cell division, ultimately distinguishing the Anterior-Posterior development in early nematode embryos.
