A step-by-step guide to fragmenting bundled actin filaments.

There has long been conflicting evidence as to how bundled actin filaments, found in cellular structures such as filopodia, are disassembled. In this issue, Chikireddy et al. (https://doi.

Stir it up: The role of actin in mitochondrial mixing during mitosis.

During symmetric cell division, it is important that daughter cells receive not only equal genetic information, but also equal allocations of organelles. Recently, in Nature,Moore et al. (2021) identify three complementary F-actin networks that help ensure proper mixing and distribution of functionally equivalent mitochondria to daughter cells.

F-Actin Cytoskeleton Network Self-Organization Through Competition and Cooperation.

Many fundamental cellular processes such as division, polarization, endocytosis, and motility require the assembly, maintenance, and disassembly of filamentous actin (F-actin) networks at specific locations and times within the cell. The particular function of each network is governed by F-actin organization, size, and density as well as by its dynamics. The distinct characteristics of different F-actin networks are determined through the coordinated actions of specific sets of actin-binding proteins (ABPs).

Mechanism of how augmin directly targets the γ-tubulin ring complex to microtubules.

Microtubules (MTs) must be generated from precise locations to form the structural frameworks required for cell shape and function. MTs are nucleated by the γ-tubulin ring complex (γ-TuRC), but it remains unclear how γ-TuRC gets to the right location. Augmin has been suggested to be a γ-TuRC targeting factor and is required for MT nucleation from preexisting MTs.

XMAP215 is a microtubule nucleation factor that functions synergistically with the γ-tubulin ring complex.

How microtubules (MTs) are generated in the cell is a major question in understanding how the cytoskeleton is assembled. For several decades, γ-tubulin has been accepted as the universal MT nucleator of the cell. Although there is evidence that γ-tubulin complexes are not the sole MT nucleators, identification of other nucleation factors has proven difficult.

Phase Transitioning the Centrosome into a Microtubule Nucleator.

Centrosomes are self-assembling, micron-scale, nonmembrane bound organelles that nucleate microtubules (MTs) and organize the microtubule cytoskeleton of the cell. They orchestrate critical cellular processes such as ciliary-based motility, vesicle trafficking, and cell division. Much is known about the role of the centrosome in these contexts, but we have a less comprehensive understanding of how the centrosome assembles and generates microtubules.

Hedgehog actively maintains adult lung quiescence and regulates repair and regeneration.

Postnatal tissue quiescence is thought to be a default state in the absence of a proliferative stimulus such as injury. Although previous studies have demonstrated that certain embryonic developmental programs are reactivated aberrantly in adult organs to drive repair and regeneration, it is not well understood how quiescence is maintained in organs such as the lung, which displays a remarkably low level of cellular turnover. Here we demonstrate that quiescence in the adult lung is an actively maintained state and is regulated by hedgehog signalling.

Ezh2 represses the basal cell lineage during lung endoderm development.

The development of the lung epithelium is regulated in a stepwise fashion to generate numerous differentiated and stem cell lineages in the adult lung. How these different lineages are generated in a spatially and temporally restricted fashion remains poorly understood, although epigenetic regulation probably plays an important role. We show that the Polycomb repressive complex 2 component Ezh2 is highly expressed in early lung development but is gradually downregulated by late gestation.

Wnt ligand/Frizzled 2 receptor signaling regulates tube shape and branch-point formation in the lung through control of epithelial cell shape.

Changing the morphology of a simple epithelial tube to form a highly ramified branching network requires changes in cell behavior that lead to tissue-wide changes in organ shape. How epithelial cells in branched organs modulate their shape and behavior to promote bending and sculpting of the epithelial sheet is not well understood, and the mechanisms underlying this process remain obscure. We show that the Wnt receptor Frizzled 2 (Fzd2) is required for domain branch formation during the initial establishment of the respiratory tree.

Coordination of heart and lung co-development by a multipotent cardiopulmonary progenitor.

Co-development of the cardiovascular and pulmonary systems is a recent evolutionary adaption to terrestrial life that couples cardiac output with the gas exchange function of the lung. Here we show that the murine pulmonary vasculature develops even in the absence of lung development. We have identified a population of multipotent cardiopulmonary mesoderm progenitors (CPPs) within the posterior pole of the heart that are marked by the expression of Wnt2, Gli1 and Isl1.

Directing lung endoderm differentiation in pluripotent stem cells.

The lung is composed of numerous epithelial lineages that arise from the anterior foregut endoderm. This review discusses how insights into the signaling mechanisms that regulate lung endoderm specification and subsequent differentiation have recently been exploited to direct differentiation of hESCs/iPSCs into expandable lung progenitors.

Identification and characterization of subpopulations of Pax3 and Pax7 expressing cells in developing chick somites and limb buds.

Pax3 and Pax7 are closely related paired-boxed family transcription factors that are known to play important roles in embryonic and adult myogenesis. Previous reports describing the expression of Pax3 and Pax7 transcripts reveal expression in many overlapping domains. In this manuscript, we extend these studies by examining the protein expression profiles for Pax3 and Pax7 in developing chick somites and limbs with cellular resolution.