To mediate chromosome segregation during cell division, the microtubule-based spindle size adapts to changes in cell size and shape, which vary dramatically across species and within a multicellular organism. However, the nature of scaling events and their underlying mechanisms are poorly understood. To elucidate molecular mechanisms, we take advantage of in vitro systems, particularly cytoplasmic extracts prepared from eggs of the frog Xenopus laevis that reconstitute mitotic chromosome condensation and spindle assembly and function in vitro.

To study mechanisms of spindle and nuclear size control, we have utilized a smaller, related frog, Xenopus tropicalis, to investigate interspecies scaling, and extracts prepared from fertilized eggs at different stages of embryogenesis to study size scaling that occurs during early development.

We use phylogenetic comparisons to characterize the key players that define spindle architecture, and are developing the use of other amphibian systems to investigate size control mechanisms at the subcellular, cellular and organism levels.

Our studies aim to reveal underlying principles of spindle assembly and biological size control, as well as the molecular basis of variation that contributes to genomic instability and evolution.

This talk will focus on the nano-scale aspects and include some single molecule experiments our lab is doing.

Rebecca Heald is a cell biologist recognized for her work on cell division and biological size control. In particular, she is known for her use of cytoplasmic extracts prepared from eggs of the African clawed frog Xenopus laevis to study how the mitotic spindle forms and scales to different sizes. Heald graduated from Hamilton College in Clinton, New York with a degree in Chemistry in 1985 and from Harvard Medical School in 1993 with a Ph.D. in Physiology and Biophysics. She was a postdoctoral fellow at the European Molecular Biology Laboratory in Heidelberg, Germany before joining the faculty at the University of California, Berkeley in 1997. She was awarded the NIH Director's Pioneer Award in 2006 and was elected as a fellow of the American Society for cell biology in 2017. Heald is known for postdoctoral mentoring and for promoting diversity and inclusion in the life sciences, and was awarded the Leon K. Henkin Citation for Distinguished Service at UC Berkeley in 2019. She is a member of the National Academy of Sciences.

Berkeley Nanosciences and Nanoengineering Institute

Researchers should cite this work as follows:

• Rebecca W. Heald (2021), "Fun Experiments You Can Only Do With Frogs," https://nanohub.org/resources/35040.

  BibTex | EndNote

1. biology
2. DNA
3. mitotic spindle
4. nano/bio