BioEssays 10/2020

Frequent independent origins of environmental sex determination (ESD) are assumed within amniotes. However, the phylogenetic distribution of sex-determining modes suggests that ESD is likely very ancient and may be homologous across ESD groups. Sex chromosomes are demonstrated to be old and stable in endothermic (mammals and birds) and many ectothermic (non-avian reptiles) lineages, but they are mostly non-homologous between individual amniote lineages. The phylogenetic pattern may be explained by ancestral ESD with multiple transitions to later evolutionary stable genotypic sex determination. It is pointed out here that amniote ESD shares several key aspects with sequential hermaphroditism of fishes such as a lack of sex differences in genomes, biased population sex ratios, and potentially also molecular mechanism related to general stress responses. Here, it is speculated that ESD evolves via a heterochronic shift of the sensitive period of sex change from the adult to the embryonic stage in a hermaphroditic amniote ancestor. Also see the video abstract here https://youtu.be/q2mjtlCefu4 .     

Cellular architecture of the lamina propria of human seminiferous tubules

Summary The lamina propria of human seminiferous tubules is composed of 5 to 7 cellular layers separated by laminae of extracellular connective-tissue components. By means of immunocytochemical methods the different nature of the cellular layers could be defined for the first time. Based on the light-microscopic demonstration of both desmin-like and vimentin-like immunoreactivity in the inner 3 to 4 layers of the lamina propria, these cells can be identified as myofibroblasts. The outermost one or two cellular layers, on the contrary, only show a vimentin-like immunoreactivity indicating the pure fibroblastic nature of these cells. Therefore, the outermost cellular layers are suggested to be derivatives of the interstitium. In cases of disturbed spermatogenesis, the lamina propria is frequently considerably thickened by an increase in the extracellular matrix components between the cellular layers. Whereas the ultrastructural localization of laminin-, collagen type-IV- and fibronectin-like immunoreactivity remains unaffected in the thickened lamina propria, the desmin-like immunoreactive cells of the inner layers strongly decrease in number and staining intensity. Most probably, the myofibro-blasts lose their myoid characteristics to participate in the secretion of increased amounts of extracellular matrix components, which in turn presumably block the mediation of the lamina propria between the interstitium and the germinal epithelium. It is still unclear whether the thickened lamina propria provokes the disturbance of spermatogenesis or vice versa.     

Albumin evolution in polyploid species of the genusXenopus

Electrophoresis of serum from 21 Xenopus species and subspecies reveals variable numbers of albumin bands. The diploid X. tropicalis has one albumin, while the tetraploid species (laevis, borealis, muelleri, clivii, fraseri, epitropicalis) have two. The octoploid species (amieti, boumbaensis, wittei, vestitus, andrei) have two to three bands, and the dodecaploid X. ruwenzoriensis has three. The molecular weight of the Xenopus albumins varies from 68 kd (in the tropicalis group) to 74 kd. The subspecies of X. laevis possess two albumins of different molecular weights (70 and 74 kd), whereas most species have only 70-kd albumins. Peptide maps have been obtained from albumin electromorphs by limited proteolysis in sodium dodecyl sulfate (SDS) gels, using S. aureus V8 protease. The peptide patterns produced by electromorphs from the same tetraploid Xenopus species generally differ from each other, suggesting that the two albumin genes contain a substantial amount of structural differences. In addition, the peptide maps are diagnostic for most tetraploid species and for some subspecies of X. laevis as well. Proteolysis of albumins from most octoploid and dodecaploid species results in patterns which are very similar to the ones produced by the electromorphs from X. fraseri. The albumins of X. vestitus differ from those of the other octoploid species. X. andrei possesses two fraseri-type and one vestitus-type albumin, which indicates that it probably originated by allopolyploidy.     

Localization of substance P-like immunoreactive fibers in the thoracic spinal cord of guinea pig

Summary A dorsal-horn fiber system is revealed in the thoracic spinal cord of guinea pig by means of substance P immunocytochemistry. This system has repeated craniocaudal and/or caudo-cranial extensions and possesses five main components: (1) a superficial network, situated beneath the dorsolateral surface of the spinal cord. This network is connected with the dorsal root fibers and the accumulations of substance P-like immunoreactive (SP-LI) fibers in the Lissauer's tract; (2) an accumulation of SP-LI fibers in the Lissauer's tract at the border of the dorsal horn; (3) two collateral SP-LI fascicles (one lateral and one medial) emerging from the SP-LI fiber accumulation in the Lissauer's tract; (4) a transversal fascicle running through laminae III–V, and (5) an SP-LI network in the region of the lateral spinal cord nucleus. These components of the dorsal-horn fiber system show widespread connections with ipsi-and contralateral spinal cord areas, connecting them in cranio-caudal and/or caudo-cranial directions. The SP-LI dorsal-horn system has close relationship with groups of preganglionic sympathetic cells in the intermediate zone of the spinal cord, respective with the vegetative network of this zone. It is suggested that some fibers of the dorsal-horn system that originate from dorsal-root ganglia may represent primary sensory or visceral afferents. It is likely that the dorsal-horn fiber system and the vegetative network of the thoracic spinal cord may represent the morphological basis for the integration of (1) the central and peripheral vegetative nervous systems, and (2) the somatic and vegetative nervous system.     

Acetylcholinesterase activity and type C synapses in the hypoglossal,facial and spinal-cord motor nuclei of rats

Summary Using the electron-microscope technique of Lewis and Shute, we studied the localization of the acetylcholinesterase (AChE) activity in the hypoglossal, facial and spinal-cord motor nuclei of rats. The technique used selectively detects synapses with subsynaptic cisterns (type C synapses) as well as heavy deposits of reaction products in the rough endoplasmic reticulum, in fragments of the nuclear envelope, in some Golgi zones and on parts of the pericaryal plasma membrane, the axolemma and the dendritic membrane. In C synapses, AChE activity was located in the synaptie cleft and on the membrane of presynaptic boutons. Some C synapses exhibited distinct synaptic specialization in the form of multiple active zones. These zones were characterized by dense presynaptic projections, short dilations of the synaptic cleft, and postsynaptic densities localized between the postsynaptic membrane and the outer membrane of the subsynaptic cistern. Within the postsynaptic densities, rows of rod- or channel-like structures were observed. The subsynaptic cisterns were continuous with the positive rough endoplasmic reticulum. The results are discussed in terms of the possible role of C synapses in the regulation of AChE synthesis in postsynaptic cholinergic neurons and/or in the regulation of AChE release into the extracellular space as well as in the establishment of new synaptic contacts.In honour of Prof. P. van Duijn     

Polymeric derivatives of plant growth regulators: synthesis and properties

The polymeric formulations of plant growth regulators (PGRs) are high molecular weight systems in which the PGR unit is attached to the polymeric chain by a hydrolysable chemical bond. These polymeric derivatives (esters, ethers, or else) of PGRs are characterised by the ability to release the active compound (PGR) from their solutions (mainly aqueous) in certain conditions. The release of the PGR can be controlled by external factors (pH, temperature, enzymes, solution concentration), and inherent properties of the whole macrosystem chemical structure, such as the type of the hydrolysable bond between PGR unit and the main polymeric chain, the structure of the polymer chain (e.g. molecular weight, level of hydrophilicity, and the content of hydrophobic groups, macromolecular conformation in solution etc.). These controlled (slow) release PGRs display certain advantages over conventional PGR formulations due to their prolonged action, improved efficiency (e.g. wide range of effective concentrations) greater safety to non-target organisms and the applicators. In addition the ability of altering the solubility level and modifying the aplication form is of considerable interest. The biological activity efficiency of polymeric PGRs has been documented and the relation of this efficiency to the PGR unit hydrolytic release ability has been mentioned. Slow release polymeric PGRs are considered to solve certain problems in agriculture.Abbreviations PGR plant growth regulator - C(S)RF controlled (slow) release form - PD polymeric derivative - ACC 1-amino-cyclopropane-1-carboxylic acid - NAA 1-naphthylacetic acid - 2,4-D 2,4-dichlorophenoxyacetic acid - IAA indole-3-acetic acid - BAP N⁶-benzylaminopurine - ABA abscisic acid - GA gibberellin - LMW low molecular weight - HMW high molecular weight     

Two recessive mutations with maternal effect upon colour and cleavage ofXenopus l. laevis eggs

Summary Pale eggs and partial cleavage are two mutations with a maternal effect that are found in the same family ofXenopus l. laevis. The pale eggs have animal hemispheres of a yellow to beige colour and give rise to normally pigmented tadpoles and frogs. The cells of pale embryos contain fewer melanosomes than those of controls. The partial cleavage eggs are characterized by an abnormality of cleavage visible from the eight-cell stage onwards, by abnormal yolk platelet distribution and abnormal cytological features. Cleaved, syncytial and uncleaved areas are observed in these eggs, which are lethal at the blastula stage.     

The postnatal development of the hypoglossal nucleus in the rat]

Using light and electron microscopy the neurons, glial cells and capillaries in hypoglossal nucleus of the rats have been examined up to 20 days after birth. The neuronal nuclei are usually situated ecentrically. The mitochondria and extensively developed Golgi-zones occupy the perinuclear region. The microtubules and lysosomes become more numerous with aging. At the earliest periods rough endoplasmic reticulum (ER) occupies the neuronal periphery, whereas after 14th day it is extended to the perinuclear region also. The ER forms elongated and concentric lamellated bodies and subsurface cisternae. At this time nucleolus like bodies are also numerous in the cytoplasm. After 4th and 6th days the extensive growth of dendrites, containing many cell organelles, and axons rich in microtubules are observed. Only at the birthday do neurons contain glycogen deposit. After 1st day the glycogen leaves the pericaryon, but it persists a long time in the neuronal processes. The symmetrical and asymmetrical contacts are characteristic for the examined period. The axo-somatic and axo-dendritic synapses are more abundant, but "double synapses" are also established. More synaptic boutons possess besides synaptic vesicles dense-core vesicles at the earlier periods. The quantity of asymmetric synapses increases with differentiation. Extensive cell degeneration has been established between 8 and 18th days. At 4 and 6 days the glial cells penetrate from subependymal layer and they have satellite neuronal position. This is more pronounced between 14 and 18 days when the oligodendrocytes are more numerous and active. At the same time fibrous astrocyte like cells are appeared. Microglial cells were not observed. Capillary differentiation, expressed by changes of the endothelial cells, pericytes and connective tissue cells, continues after birth also.     

Functional characterization of human myosin-binding protein C3 variants associated with hypertrophic cardiomyopathy reveals exon-specific cardiac phenotypes in zebrafish model

Myosin-binding protein C 3 (MYBPC3) variants are the most common cause of hypertrophic cardiomyopathy (HCM). HCM is a complex cardiac disorder due to its significant genetic and clinical heterogeneity. MYBPC3 variants genotype–phenotype associations remain poorly understood. We investigated the impact of two novel human MYBPC3 splice-site variants: V1: c.654+2_654+4dupTGG targeting exon 5 using morpholino MOe5i5; and V2: c.772+1G>A targeting exon 6 using MOe6i6; located within C1 domain of cMyBP-C protein, known to be critical in regulating sarcomere structure and contractility. Zebrafish MOe5i5 and MOe6i6 morphants recapitulated typical characteristics of human HCM with cardiac phenotypes of varying severity, including reduced cardiomyocyte count, thickened ventricular myocardial wall, a drastic reduction in heart rate, stroke volume, and cardiac output. Analysis of all cardiac morphological and functional parameters demonstrated that V2 cardiac phenotype was more severe than V1. Coinjection with synthetic human MYBPC3 messenger RNA (mRNA) partially rescued disparate cardiac phenotypes in each zebrafish morphant. While human MYBPC3 mRNA partially restored the decreased heart rate in V1 morphants and displayed increased percentages of ejection fraction, fractional shortening, and area change, it failed to revert the V1 ventricular myocardial thickness. These results suggest a possible V1 impact on cardiac contractility. In contrast, attempts to rescue V2 morphants only restored the ventricular myocardial wall hypertrophy phenotype but had no significant effect on impaired heart rate, suggesting a potential V2 impact on the cardiac structure. Our study provides evidence of an association between MYBPC3 exon-specific cardiac phenotypes in the zebrafish model providing important insights into how these genetic variants contribute to HCM disease.     

An N-terminal, 830 residues intrinsically disordered region of the cytoskeleton-regulatory protein supervillin contains Myosin II- and F-actin-binding sites

Supervillin, the largest member of the villin/gelsolin family, is a cytoskeleton regulating, peripheral membrane protein. Supervillin increases cell motility and promotes invasive activity in tumors. Major cytoskeletal interactors, including filamentous actin and myosin II, bind within the unique supervillin amino terminus, amino acids 1–830. The structural features of this key region of the supervillin polypeptide are unknown. Here, we utilize circular dichroism and bioinformatics sequence analysis to demonstrate that the N-terminal part of supervillin forms an extended intrinsically disordered region (IDR). Our combined data indicate that the N-terminus of human and bovine supervillin sequences (positions 1–830) represents an IDR, which is the largest IDR known to date in the villin/gelsolin family. Moreover, this result suggests a potentially novel mechanism of regulation of myosin II and F-actin via the intrinsically disordered N-terminal region of hub protein supervillin.