Polarity in Ciliate Models: From Cilia to Cell Architecture

Abstract

Tetrahymena and Paramecium are highly differentiated unicellular organisms with elaborated cortical patterns showing a regular arrangement of hundreds to thousands of basal bodies in longitudinal rows that extend from the anterior to the posterior region of the cell. Thus both ciliates exhibit a permanent antero–posterior axis and left–right asymmetry. This cell polarity is reflected in the direction of the structures nucleated around each basal body such as the ciliary rootlets. Studies in these ciliates showed that basal bodies assemble two types of cilia, the cortical cilia and the cilia of the oral apparatus, a complex structure specialized in food capture. These two cilia types display structural differences at their tip domain. Basal bodies possessing distinct compositions creating specialized landmarks are also present. Cilia might be expected to express and transmit polarities throughout signaling pathways given their recognized role in signal transduction. This review will focus on how local polarities in basal bodies/cilia are regulated and transmitted through cell division in order to maintain the global polarity and shape of these cells and locally constrain the interpretation of signals by different cilia. We will also discuss ciliates as excellent biological models to study development and morphogenetic mechanisms and their relationship with cilia diversity and function in metazoans.

Mob Family Proteins: Regulatory Partners in Hippo and Hippo-Like Intracellular Signaling Pathways

“…These distinctions raise questions about divergence between unicellular and multicellular eukaryotes, and whether switching between upstream kinases to activate NDR kinases may be particularly important in organizing multicellular structures, such as the fruiting bodies of filamentous fungi (Beier et al, 2016). In this regard, it is striking that the ciliate Tetrahymena appears to have a Mob4 homolog (Soares et al, 2019). To understand the broadly conserved network of Mob functions in Hippo and Hippo-like pathways, it will be valuable to investigate whether ciliates, such as Paramecium and Tetrahymena, have STRIPAK complexes that regulate switching between the ciliate NDR kinase pathways.…”

EGR1 dysregulation defines an inflammatory and leukemic program in cell trajectory of human-aged hematopoietic stem cells (HSC)

“…Sonic hedgehog signaling has been already shown to act on the proliferation of primitive human hematopoietic cells through bone morphogenic protein (BMP) regulation [ 54 ]. TMEM107 also belongs to the transition zone (TZ) ciliary subcompartment is thought to control cilium composition and signaling by facilitating a protein diffusion barrier at the ciliary base [ 55 ], so it could be an interesting candidate potentially implicated in cell polarity [ 56 ] and polarity dysfunction is implicated in dysregulated phenotype of aged HSCs [ 40 ]. Sonic hedgehog signaling plays an important role in the maintenance of symmetric cell division during neurogenesis [ 57 ].…”

Sequence and Properties of Cagein, a Coiled‐Coil Scaffold Protein Linking Basal Bodies in the Polykinetids of the Ciliate Euplotesaediculatus

“…From the clustered basal bodies inside these frameworks emerge closely packed cilia that function together in coordinated patterns of beating, enabling the cells to gather food particles, as well as carry out motile functions such as swimming or creeping on substrates. Cirri and so-called oral membranelles are well-described ciliary organelles of this type (Adoutte and Fleury 1996;Lynn and Corliss 1991;Soares et al 2019).…”

“…Cirri and so‐called oral membranelles are well‐described ciliary organelles of this type (Adoutte and Fleury 1996; Lynn and Corliss 1991; Soares et al. 2019).…”