Imaging cytoplasmic lipid droplets in vivo with fluorescent perilipin 2 and perilipin 3 knock-in zebrafish

Abstract

Cytoplasmic lipid droplets are highly dynamic storage organelles that are critical for cellular lipid homeostasis. While the molecular details of lipid droplet dynamics are a very active area of investigation, this work has been primarily performed in cultured cells. Taking advantage of the powerful transgenic and in vivo imaging opportunities available in zebrafish, we built a suite of tools to study lipid droplets in real-time from the subcellular to the whole organism level. Fluorescently tagging the lipid-droplet-associated proteins, perilipin 2 and perilipin 3, in the endogenous loci permits visualization of lipid droplets in the intestine, liver, and adipose tissue. Using these tools, we found that perilipin 3 is rapidly loaded on intestinal lipid droplets following a high-fat meal and later replaced by perilipin 2. These powerful new tools will facilitate studies on the role of lipid droplets in different tissues, under different genetic and physiological manipulations, and in a variety of human disease models.

Structural insights into perilipin 3 membrane association in response to diacylglycerol accumulation

“…PLIN3 is unique in that it is stable and not degraded in the absence of LDs. This allows PLIN3 to translocate from the cytoplasm to sites of early LD formation, where it acts as a marker for the biogenesis of early LDs [10,[28][29][30][31][32][33].…”

“…For example, PLIN1 is the major PLIN that binds to mature LDs in adipocytes, while PLIN2 and PLIN5 reside on mature LDs in liver and muscle cells, respectively [27]. In contrast, PLIN3 displays near ubiquitous expression and binds to early LDs as they bud from the ER, but is later displaced by other PLINs as LDs grow and mature [10, 28]. PLIN3 is unique in that it is stable and not degraded in the absence of LDs.…”

A fluorescent perilipin 2 knock-in mouse model visualizes lipid droplets in the developing and adult brain

“…Existing staining-free approaches comprise specific microscopy techniques, such as Raman microscopy (Yu et al, 2014) or transgenic LD reporters (Targett-Adams et al, 2003), and a few transgenic invertebrate model organisms, such as C.elegans (Liu et al, 2014) and Drosophila (Beller et al, 2010). A very recent addition to the LD imaging toolbox is two LD reporter zebrafish models with fluorescently tagged endogenous Plin2 (Lumaquin et al, 2021) and Plin2/Plin3 (Wilson et al, 2021). However, a mammalian LD reporter model has been missing to this date.…”

Progress and perspectives: fluorescent to long-lived emissive multifunctional probes for intracellular sensing and imaging

“…Lipid droplets (LDs) are hydrophobic organelles that control several intracellular processes like metabolism, lipid storage and membrane formation. 83 However, the misregulation of the functions of LDs leads to several disorders like obesity, fatty liver diseases and diabetes. The cellular microenvironments also play a crucial role in governing the functions of LDs.…”