Regulation of organelle size and organization during development

Abstract

During early embryogenesis, as cells divide in the developing embryo, the size of intracellular organelles generally decreases to scale with the decrease in overall cell size. Organelle size scaling is thought to be important to establish and maintain proper cellular function, and defective scaling may lead to impaired development and disease. However, how the cell regulates organelle size and organization are largely unanswered questions. In this review, we summarize the process of size scaling at both the cell and organelle levels and discuss recently discovered mechanisms that regulate this process during early embryogenesis. In addition, we describe how some recently developed techniques and Xenopus as an animal model can be used to investigate the underlying mechanisms of size regulation and to uncover the significance of proper organelle size scaling and organization.

Keywords: Cell size; Chromosomes; Development; Nucleus; Organelle size; Spindle; Xenopus.

Figure 1.. Models of cell size control.

Three models have been envisioned to explain cell-size homeostasis. According to the timer model, cells grow for a fixed duration of time before dividing. The adder model posits that cells add a constant volume during the cell cycle. Cells sense the acquisition of a specific threshold size before dividing according to the sizer model. See text for further details. Adapted from [243] under a Creative Commons Attribution-ShareAlike 4.0 International License. Created with BioRender.com.

Figure 2.. Structural elements of the nucleus that influence nuclear size.

LINC, linker of nucleoskeleton and cytoskeleton; MT, microtubule; NE, nuclear envelope; NPC, nuclear pore complex. The nuclear lamina (orange) is composed of lamins and associated proteins. Created with BioRender.com.

Figure 3.. Factors that influence developmental size scaling of the nucleus, spindle, mitotic chromosomes, and ER.

Created with BioRender.com.