Use of Xenopus cell-free extracts to study size regulation of subcellular structures

Abstract

Striking size variations are prominent throughout biology, at the organismal, cellular, and subcellular levels. Important fundamental questions concern organelle size regulation and how organelle size is regulated relative to cell size, also known as scaling. Uncovering mechanisms of organelle size regulation will inform the functional significance of size as well as the implications of misregulated size, for instance in the case of nuclear enlargement in cancer. Xenopus egg and embryo extracts are powerful cell-free systems that have been utilized extensively for mechanistic and functional studies of various organelles and subcellular structures. The open biochemical nature of the extract permits facile manipulation of its composition, and in recent years extract approaches have illuminated mechanisms of organelle size regulation. This review largely focuses on in vitro Xenopus studies that have identified regulators of nuclear and spindle size. We also discuss potential relationships between size scaling of the nucleus and spindle, size regulation of other subcellular structures, and extract experiments that have clarified developmental timing mechanisms. We conclude by offering some future prospects, notably the integration of Xenopus extract with microfluidic technology.

Elucidating nuclear size control in the Xenopus model system

“…Proper morphology of intracellular organelles is a precisely regulated cellular feature important for organellar function. The sizes of organelles, including the nucleus and mitotic spindle, generally positively scale with cell size to maintain a proper organelle-to-cytoplasmic volume ratio ( Wuhr et al, 2008 ; Levy & Heald, 2012 ; Jevtic et al, 2015 ; Jevtic et al, 2016 ). Dysregulation of this ratio and organelle morphology affects normal cell, tissue, and organismal physiology and is linked to diseases.…”