The evolutionary conserved proteins CEP90, FOPNL, and OFD1 recruit centriolar distal appendage proteins to initiate their assembly

The function of the ATG8 in the cilia and cortical microtubule maintenance of Euplotes amieti

Autophagy regulates the formation of primary cilia, which in turn affects autophagy. The relationship between autophagy and cilia is known to be bidirectional although the specific mechanisms involved have yet to be elucidated. In this study, we found for the first time that ATG8 protein localizes in the basal body of the dorsal kineties and the base of the ventral cirri in Euplotes amieti. ATG8 protein maintains the structural integrity of cilia and plays a role in the construction of the cortical ciliature and microtubule cytoskeleton associated with cilia. ATG8 gene interference leads to the degradation of IFT88, the transport protein in cilia, thus inhibiting the generation of cilia, and affecting the swing of cilia. This influences the swimming speed and cilia pattern, leading to death in Euplotes amieti.

PIBF1 regulates trophoblast syncytialization and promotes cardiovascular development

Proper placental development in early pregnancy ensures a positive outcome later on. The developmental relationship between the placenta and embryonic organs, such as the heart, is crucial for a normal pregnancy. However, the mechanism through which the placenta influences the development of embryonic organs remains unclear. Trophoblasts fuse to form multinucleated syncytiotrophoblasts (SynT), which primarily make up the placental materno-fetal interface. We discovered that endogenous progesterone immunomodulatory binding factor 1 (PIBF1) is vital for trophoblast differentiation and fusion into SynT in humans and mice. PIBF1 facilitates communication between SynT and adjacent vascular cells, promoting vascular network development in the primary placenta. This process affected the early development of the embryonic cardiovascular system in mice. Moreover, in vitro experiments showed that PIBF1 promotes the development of cardiovascular characteristics in heart organoids. Our findings show how SynTs organize the barrier and imply their possible roles in supporting embryogenesis, including cardiovascular development. SynT-derived factors and SynT within the placenta may play critical roles in ensuring proper organogenesis of other organs in the embryo.

Proteomic profiling of centrosomes across multiple mammalian cell and tissue types by an affinity capture method

Centrosomes are the major microtubule-organizing centers in animals and play fundamental roles in many cellular processes. Understanding how their composition varies across diverse cell types and how it is altered in disease are major unresolved questions, yet currently available centrosome isolation protocols are cumbersome and time-consuming, and they lack scalability. Here, we report the development of centrosome affinity capture (CAPture)-mass spectrometry (MS), a powerful one-step purification method to obtain high-resolution centrosome proteomes from mammalian cells. Utilizing a synthetic peptide derived from CCDC61 protein, CAPture specifically isolates intact centrosomes. Importantly, as a bead-based affinity method, it enables rapid sample processing and multiplexing unlike conventional approaches. Our study demonstrates the power of CAPture-MS to elucidate cell-type-dependent heterogeneity in centrosome composition, dissect hierarchical interactions, and identify previously unknown centrosome components. Overall, CAPture-MS represents a transformative tool to unveil temporal, regulatory, cell-type- and tissue-specific changes in centrosome proteomes in health and disease.

Control of centrosome distal appendages assembly and disassembly

Centrosomes are microtubule organizing centers involved in chromosome segregation, spindle orientation, cell motility and cilia formation. In recent years, they have also emerged as key modulators of asymmetric cell division. Centrosomes are composed of two centrioles that initiate duplication in S phase. The conservative nature of centriole duplication means that the two centrioles of a G1 cell are of different ages. They are also structurally different as only the older centriole carry appendages, an assembly of a subset of proteins primarily required for cilia formation. In a growing tissue, the non-motile, primary cilium acts as a mechano- and sensory organelle that influences cell behavior via modulation of signaling pathways. Here, we discuss the most recent findings about distal appendage composition and function, as well as cell cycle-specific regulation and their implications in various diseases.

[Closer to the native architecture of the cell using Cryo-ExM]

Most cellular imaging techniques, such as light or electron microscopy, require that the biological sample is first fixed by chemical cross-linking agents. This necessary step is also known to damage molecular nanostructures or even sub-cellular organization. To overcome this problem, another fixation approach was invented more than 40 years ago, which consists in cryo-fixing biological samples, thus allowing to preserve their native state. However, this method has been scarcely used in light microscopy due to the complexity of its implementation. In this review, we present a recently developed super-resolution method called expansion microscopy, which, when coupled with cryo-fixation, allows to visualize at a nanometric resolution the cell architecture as close as possible to its native state.

Single-molecule localization microscopy reveals the ultrastructural constitution of distal appendages in expanded mammalian centrioles

Distal appendages (DAPs) are vital in cilia formation, mediating vesicular and ciliary docking to the plasma membrane during early ciliogenesis. Although numerous DAP proteins arranging a nine-fold symmetry have been studied using superresolution microscopy analyses, the extensive ultrastructural understanding of the DAP structure developing from the centriole wall remains elusive owing to insufficient resolution. Here, we proposed a pragmatic imaging strategy for two-color single-molecule localization microscopy of expanded mammalian DAP. Importantly, our imaging workflow enables us to push the resolution limit of a light microscope well close to a molecular level, thus achieving an unprecedented mapping resolution inside intact cells. Upon this workflow, we unravel the ultra-resolved higher-order protein complexes of the DAP and its associated proteins. Intriguingly, our images show that C2CD3, microtubule triplet, MNR, CEP90, OFD1, and ODF2 jointly constitute a unique molecular configuration at the DAP base. Moreover, our finding suggests that ODF2 plays an auxiliary role in coordinating and maintaining DAP nine-fold symmetry. Together, we develop an organelle-based drift correction protocol and a two-color solution with minimum crosstalk, allowing a robust localization microscopy imaging of expanded DAP structures deep into the gel-specimen composites.

Structure and function of distal and subdistal appendages of the mother centriole

Centrosomes are composed of centrioles surrounded by pericentriolar material. The two centrioles in G1 phase are distinguished by the localization of their appendages in the distal and subdistal regions; the centriole possessing both types of appendage is older and referred to as the mother centriole, whereas the other centriole lacking appendages is the daughter centriole. Both distal and subdistal appendages in vertebrate cells consist of multiple proteins assembled in a hierarchical manner. Distal appendages function mainly in the initial process of ciliogenesis, and subdistal appendages are involved in microtubule anchoring, mitotic spindle regulation and maintenance of ciliary signaling. Mutations in genes encoding components of both appendage types are implicated in ciliopathies and developmental defects. In this Review, we discuss recent advances in knowledge regarding the composition and assembly of centriolar appendages, as well as their roles in development and disease.

Human SFI1 and Centrin form a complex critical for centriole architecture and ciliogenesis

Over the course of evolution, the centrosome function has been conserved in most eukaryotes, but its core architecture has evolved differently in some clades, with the presence of centrioles in humans and a spindle pole body (SPB) in yeast. Similarly, the composition of these two core elements has diverged, with the exception of Centrin and SFI1, which form a complex in yeast to initiate SPB duplication. However, it remains unclear whether this complex exists at centrioles and whether its function has been conserved. Here, using expansion microscopy, we demonstrate that human SFI1 is a centriolar protein that associates with a pool of Centrin at the distal end of the centriole. We also find that both proteins are recruited early during procentriole assembly and that depletion of SFI1 results in the loss of the distal pool of Centrin, without altering centriole duplication. Instead, we show that SFI1/Centrin complex is essential for centriolar architecture, CEP164 distribution, and CP110 removal during ciliogenesis. Together, our work reveals a conserved SFI1/Centrin module displaying divergent functions between mammals and yeast.