Asymmetric cell division

Question 1

What is asymmetric cell division?

Answer 1

When two cells after division have both a different cell fate and an asymmetric inheritance of cellular components.

Question 2

Two mechanisms that ensure the maintenance of a constant number of stem cells.

Answer 2

Symmetric self-renewal, where the SC produces two SCs, and asymmetric renewal, where the SC produces one SC and one differentiated progenitor cell. The balance is maintained through signaling from the SC niche.

Question 3

List 3 cell types which undergo asymmetric cell division in mammals.

Answer 3

Hematopoietic cells (B and T cells), neural SCs, epidermal SCs

Question 4

Give an example of ACD in an invertebrate model.

Answer 4

The budding of yeast (S. cerevisiae) is intrinsically asymmetric. The asymmetric inheritance is actomyosin dependent. The actin cytoskeleton and myosin proteins transport molecules towards bud.
Another example is C. elegans, where the first division of the zygotes is already asymmetric. The symmetry is broken by the entry of the sperm cell, leading to reorganization of the cytoskeleton and asymmetric spindle displacement.
In Drosophila melanogaster, 3 rounds of ACD generate the different cell types of the Sensory Organ Precursor (SOP).