CSB329H1 Lecture 4: Lecture 4 Part 2
9 May 2018
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Lecture 4(b): Stem Cell Divison
Asymmetric Cell Division:
• Neuronal stem cells undergo asymmetric cell division during embryonic development
giving rise to:
o Ganglion mother cell (GMC) and an undifferentiated self-renewed neural stem cell
ð NSC delaminates from neuronal ectodermal cells
o Polarity of first embryonic neuroblast is
inherited from the original epithelial cells
ð NSC undergoes repeated self-renewing
asymmetric cell division to give rise to ganglion mother cells (GMC)
o GMC further divides and differentiates to give rise to neuronal cells and glial cells
*note: asymmetric cellular division is mediated by polarity cues promoting this event
Polarity Complexes:
• Epithelial cell shave three main polarity complexes (apical-basal polarity)
a) Crumbs Complex
§ Crumb/ protein associated with Lin-7 (Pals1)/
Pals1-associated right junction (PatJ)
b) Par-Complex.
§ Par3/ Partition deficient-6/ Atypical-protein Kinase C
c) Scribble Complex
§ Scribble/ Disc large/ Lethal giant larva
Drosophila Embryogenesis:
1. Par-Complex:
o Baz, Par6 and aPKC [blue line] localized
asymmetrically at the apical cortex
2. Recruitment:
o Par-complex recruits an adaptor protein, inscuteable (Insc) [green line]
§ Insc will in turn recruit the Pins/Mud/G
a
i complex [orange line]
ð Insc bridges the Par-complex to spindle orientation molecules
o Mud – spindle orientation in asymmetric cell division bind to microtubules and
enhance microtubule polymerization
o Partners of Inscuteable (Pins) – asymmetric cell division and mitotic spindle orientation
§ Function to have mitotic spindles in an apical-to-basal direction
ð If a defect existed and mitotic spindles are rotating 90° - we will have asymmetric division
within the plane of the epithelial – we want them to have a polarized exit (out of epithelial)
Document Summary
Asymmetric cell division: giving rise to: neuronal stem cells undergo asymmetric cell division during embryonic development, ganglion mother cell (gmc) and an undifferentiated self-renewed neural stem cell. Nsc delaminates from neuronal ectodermal cells: polarity of first embryonic neuroblast is inherited from the original epithelial cells. Nsc undergoes repeated self-renewing asymmetric cell division to give rise to ganglion mother cells (gmc: gmc further divides and differentiates to give rise to neuronal cells and glial cells. *note: asymmetric cellular division is mediated by polarity cues promoting this event. Polarity complexes: epithelial cell shave three main polarity complexes (apical-basal polarity, crumbs complex. Par3/ partition deficient-6/ atypical-protein kinase c: par-complex, scribble complex. Drosophila embryogenesis: par-complex, baz, par6 and apkc [blue line] localized asymmetrically at the apical cortex, recruitment, par-complex recruits an adaptor protein, inscuteable (insc) [green line] Insc will in turn recruit the pins/mud/gai complex [orange line]
