The cell–cell junctions of mammalian testes: II. The lamellar smooth muscle monolayer cells of the peritubular wall are laterally connected by vertical adherens junctions—a novel architectonic cell–cell junction system

Abstract

The testes of sexually mature males of six mammalian species (men, bulls, boars, rats, mice, guinea pigs) have been studied using biochemical as well as light and electron microscopical techniques, in particular immunolocalizations. In these tissues, the peritubular walls represent lamellar encasement structures wrapped around the seminiferous tubules as a bandage system of extracellular matrix layers, alternating with monolayers of very flat polyhedral Blamellar smooth muscle cells^(LSMCs), the number of which varies in different species from 1 to 5 or 6. These LSMCs are complete SMCs containing smooth muscle αactin (SMA), myosin light and heavy chains, α-actinin, tropomyosin, smoothelin, intermediate-sized filament proteins desmin and/or vimentin, filamin, talin, dystrophin, caldesmon, calponin, and protein SM22α, often also cytokeratins 8 and 18. In the monolayers, the LSMCs are connected by adherens junctions (AJs) based on cadherin-11, in some species also with P-cadherin and/or E-cadherin, which are anchored in cytoplasmic plaques containing β-catenin and other armadillo proteins, in some species also striatin family proteins, protein myozap and/or LUMA. The LSMC cytoplasm is rich in myofilament bundles, which in many regions are packed in paracrystalline arrays, as well as in Bdense bodies,^Bfocal adhesions,^and caveolae. In addition to some AJ-like end-on-end contacts, the LSMCs are laterally connected by numerous vertical AJ-like junctions located in variously sized and variously shaped, overlapping (alter super alterum) lamelliform cell protrusions. Consequently, the LSMCs of the peritubular wall monolayers are SMCs sensu stricto which are laterally connected by a novel architectonic system of arrays of vertical AJs located in overlapping cell protrusions. Keywords Seminiferous tubules. Peritubular walls. Desmosomes. Hemidesmosomes. Smooth muscle cells. Adherens junctions (AJs) This research article is dedicated to the memory of Professor Jörg Langowski (Ph.D.) of the German Cancer Research Center who died on May 06, 2017, as a glider pilot in an air accident. As head of the division BBiophysics of Macromolecules,^Jörg has published-inter alia-a series of major contributions in the field of biophysics and molecular biology of cytoskeletal proteins.

Striatin Is Required for Hearing and Affects Inner Hair Cells and Ribbon Synapses

“…Striatin is expressed in diverse cellular and subcellular compartments such as the medium spiny neurons in the striatum (Benoist et al, 2006) and membrane-bound signaling complexes (Lu et al, 2004). Other studies, as well as ours, have shown that striatin is also expressed in junctions between epithelia cells (Breitman et al, 2008;Domke et al, 2014;Franke et al, 2015;Domke and Franke, 2019;Lahav-Ariel et al, 2019). Interestingly, striatin has been shown to be expressed in different types of cell junctions.…”

“…In addition, striatin has been shown to colocalize with β-catenin, a junctional protein, in different tissues (Domke et al, 2014;Franke et al, 2015;Domke and Franke, 2019). However, as our previous studies indicate that in the mammalian cells tested striatin did not bind or colocalize with β-catenin (Breitman et al, 2008) and that in the inner ear β-catenin is barely seen in hair cells (Liu et al, 2016), the possibility that striatin and β-catenin interact was not examined in the current study.…”

“…In another cancer-originating cell line, striatin was found to localize with TJ proteins but not with the AJ protein E-cadherin (Lahav-Ariel et al, 2019). In human colon epithelial sections, mouse testis tissues and lamellar smooth muscle cells striatin colocalizes with the plaque protein P0071 (Domke et al, 2014;Franke et al, 2015;Domke and Franke, 2019). Striatins colocalize with E-cadherin and with plaque proteins, such as β-catenin and P0071, as well as in lateral AJs and in plaques of some forms of tessellate junctions (Franke et al, 2015).…”

The Glucocorticoid Receptor NR3C1 in Testicular Peritubular Cells is Developmentally Regulated and Linked to the Smooth Muscle-Like Cellular Phenotype

“…In situ, these cells and extracellular matrix form the peritubular compartment of the seminiferous tubules. The cells express smooth muscle actin (ACTA2), calponin (CNN1), and other typical cytoskeletal markers, as well as a number of genes for specific extracellular matrix proteins [10]. Accordingly, for example, the extracellular matrix of the peritubular cell wall contains, among others, collagens and elastin (ELN; see images in the Human Protein Atlas; [11]).…”

Development of spermatogonial stem cell niche and immunoexpression of vimentin filaments in the testes of prenatal and postnatal Indian buffalo (Bubalusbubalis)

“…PM cells together with the basement membrane (BM) constitute a physical barrier that provides structural support of the STs [4]. One of the main components of this physical barrier is vimentin [5].…”