During cell division in fruit flies’ sensory organ precursor cells, microtubules draw endosomes with the Sara protein on their surface to the central spindle. There, Sara is phosphorylated, causing the endosomes to detach from the spindle and travel to one side of the mother cell, with most of them moving into the daughter cell known as pIIa, where microtubule disassembly is greater. That cell divides again to form the outer shaft and socket of a hair on the fly’s back, while its sibling, pIIb, gives rise to the hair’s inner sheath and neuron. Without Sara, hair formation is compromised.THE SCIENTIST STAFF
S. Loubéry et al., “Sara phosphorylation state controls the dispatch of endosomes from the central spindle during asymmetric division,” Nat Commun, 8:15285, 2017.
Central to normal development are steps in which stem or progenitor cells divide asymmetrically to form daughters with different fates. But what determines these divergent paths? A recent study by Marcos Gonzalez-Gaitan and colleagues at the University of Geneva found that phosphorylation is key to preferentially directing certain cellular vesicles called endosomes to one of the daughter cells, enabling asymmetric division.
To study asymmetrical cell division, many researchers look to the sensory organ precursor cells (SOPs) that form hairs on the backs of fruit flies in a series of three cell-division steps. First, an SOP divides asymmetrically into cells known as pIIa and pIIb. The pIIa cell then divides again to form an outer hair cell and a socket, while pIIb divides twice more, ultimately producing a neuron and its sheath.
Gonzalez-Gaitan’s group had previously found that while most endosomes are split evenly between the two daughter cells during asymmetric cell division, those that contain signaling molecules Notch and Delta and have a surface protein called Sara mainly end up in pIIa. Prior to that, the Sara endosomes are ferried along microtubules to a structure in ...
