New research from the Cabernard Lab on cell fusion was recently published in Communications Biology. Authors of the paper include Bharath Sunchu and Nicole Lee, former postdoctoral researcher and former lab technician in the Cabernard lab, respectively; Carlos Segura and Jenny Taylor, current UW MCB graduate student and current postdoctoral researcher in the Cabernard lab, respectively; and UW Biology Associate Professor Clemens Cabernard. Congratulations to all!

When two cells fuse with each other, they mix their cytoplasm, organelles and chromosomes in a shared cell body. Cell-cell fusion occurs during fertilization, when an egg cell fuses with a sperm cell, during muscle formation or in the liver. It has been found that the first division of the fertilized zygote in insects, arthropods and mice separates the chromosomes from the egg and the sperm by forming two spindles – one spindle is attaching and separating the sperm chromosomes, the other spindle is the egg chromosomes. Similarly, when somatic cells fuse in culture, the resulting hybrid cells usually form two spindles compartmentalizing and separating the different chromosome sets. How hybrid cells distinguish and separate chromosomes from different cell types is an open question in cell and developmental biology. 

To learn more about the underlying mechanisms, Nicole Lee and Bharath Sunchu, a former lab technician and a former postdoc in the Cabernard lab, artificially fused fly neural stem cells with differentiated brain cells in the intact fly brain. They then used live cell imaging to characterize the hybrid cell’s behavior. Nicole and Bharath found that Neural stem cell/brain cell hybrid cells also formed two separate spindles, one of which attached to the stem cell chromosomes, the other to the differentiated brain cell chromosomes. Careful characterization of spindle and chromosome dynamics revealed that these hybrid cells use nuclear envelopes to compartmentalize the two different chromosome sets. Nicole and Bharath did not find a special chromosome recognition marker but based on their genetic experiments, they proposed that the physical separation of the two chromosome sets is also co-dependent on the stem cells ability to form one active microtubule organizing center (MTOC) in interphase. This MTOC is attached to the stem cell’s chromosomes only. How neural stem cells form only one active MTOC and how it is connected to chromatin in interphase is actively being investigated by Carlos Segura and Jenny Taylor, a current MCB graduate student and postdoc in the lab. Carlos and Jenny also  contributed to the cell fusion study.

Read the full paper in Nature.