Discussion Paper 4 Flashcards
How many segments is a drosophila melanogaster embryo divided into?
14
What are the advantages of using drosophila in genomic studies? (4)
- well-sequenced genome
- simple genome with only 4 chromosomes
- fast life cycle/generation time
- genes show a lot of conservation and have functional overlap with mammal genes
The discussion paper examines flies at this stage in their life
Larval stages
What key event occurs during the fly larval stage?
A 2nd wave of neurogenesis
What are the 3 regions of the fly CNS present in the larval stage?
Optic lobe
Mushroom body
Ventral nerve cord
The fly ventral nerve cord innervates…
The thoracic and abdominal segments
What is the specific motor neuron name which is examined in this paper?
RP2
What muscle fiber does RP2 innervate?
Da2
What is the broad overarching question of the paper?
What are the mechanisms that underlie asymmetric cell divisions and cell fate decisions?
The specific scientific objective of this paper is to determine…
The temporal requirement of Notch signaling during RP2/sib cell development
What is the assay in Figure 1?
Immunolabelling for Eve (Even-skipped)
Why did the authors choose to examine Eve for figure 1?
Eve is a marker in GMC cells, which give rise to RP2 and sib cells. RP2 cells stay Eve+, but sib cells become Eve- when they mature (but initially, they are Eve+)
What are the advantages of the Eve assay in figure 1?
- Robust
- Illuminates a pretty simple pathway which mechanism can be addressed
What are some weaknesses of the Eve assay from Figure 1?
Sib cell loses it and you lose track of it, don’t even know if the cell lives or dies
What cell gives rise to the GMC-1 cells?
Type I neuroblast: NB4-2
Previous studies determined that genetic inhibition of (1) signaling causes GMC-1 to divide into two RP2 cells
Notch
Prior to the findings of this paper, it was thought that signaling from this molecule was involved in determining sib cell fate after GMC-1 division
Notch
Describe the previous findings of other studies related to Numb and RP2 specification
Previous studies found that Numb localizes asymmetrically to the basal end of GMCs and is inherited only by the basal daughter cell, and that this promotes RP2 specification because Numb inhibits Notch signaling
How does Numb inhibit Notch signaling?
Promotes endocytosis of Notch, and promotes Notch ubiquitination and degradation
Where is Numb located in the cell?
Along the basal membrane (it is a membrane-associated protein)
What is the overall hypothesis of this paper?
Asymmetric cell division of GMC is mediated by Notch signaling prior to cell division
What is the underlying question of Figure 1?
Is notch signaling required for GMC development prior to cell division?
What is the experimental approach used to address the question of Figure 1?
Use a temperature-sensitive loss-of-function mutation for Notch - they switched the temperature to “non-permissive” at different times prior to cell division (in this figure, E and M refer to Early and Middle)
What is the main takeaway from Figure 1?
When Notch is mutated early on, this results in the most symmetric divisions (get 2 Rp2 cells)
When Notch is mutated in the middle stage, this results in 2 RP2 cells of unequal size - intermediate phenotype