Morphological Maturation Research Articles

Investigation of the functions of n-3 very-long-chain PUFAs in skin using in vivo Atlantic salmon and in vitro human and fish skin models.

The purpose of this study was to investigate the effect of dietary n-3 very-long-chain PUFA (n-3 VLC-PUFA) on the maturation and development of skin tissue in juvenile Atlantic salmon (Salmo salar) in vivo, as well as their effects on skin keratocyte and human skin fibroblast cell migration in vitro. Atlantic salmon were fed different dietary levels of n-3 VLC-PUFA from an initial weight of 6 g to a final weight of 11 g. Changes in skin morphology were analysed at two time points during the experiment, and the effects on skin tissue fatty acid composition were determined. Additionally, in vitro experiments using human dermal fibroblasts and primary Atlantic salmon keratocytes were conducted to investigate the effect of VLC-PUFA on the migration capacity of the cells. The results demonstrated that increased dietary levels of n-3 VLC-PUFA led to an increased epidermis thickness and more rapid scale maturation in Atlantic salmon skin in vivo, leading to a more mature skin morphology, and possibly more robust skin, at an earlier life stage. Additionally, human skin fibroblasts and salmon skin keratocytes supplemented with n-3 VLC-PUFA in vitro showed more rapid migration, indicating potentially beneficial effects of VLC-PUFA in wound healing. In conclusion, VLC-PUFA may have beneficial effects on skin tissue development, function and integrity.

Gene transcriptional expression of cortical thinning during childhood and adolescence.

The cognitive and behavioral development of children and adolescents is closely related to the maturation of brain morphology. Although the trajectory of brain development has been depicted in detail, the underlying biological mechanism of normal cortical morphological development in childhood and adolescence remains unclear. By combining the Allen Human Brain Atlas dataset with two single-site magnetic resonance imaging data including 427 and 733 subjects from China and the United States, respectively, we performed partial least squares regression and enrichment analysis to explore the relationship between the gene transcriptional expression and the development of cortical thickness in childhood and adolescence. We found that the spatial model of normal cortical thinning during childhood and adolescence is associated with genes expressed predominantly in astrocytes, microglia, excitatory and inhibitory neurons. Top cortical development-related genes are enriched for energy-related and DNA-related terms and are associated with psychological and cognitive disorders. Interestingly, there is a great deal of similarity between the findings derived from the two single-site datasets. This fills the gap between early cortical development and transcriptomes, which promotes an integrative understanding of the potential biological neural mechanisms.

Comparative genomics identified TLR-dependent fine tuning of the dendritic cell immune response by melatonin

Abstract Melatonin, a neuro hormone, has been shown to activate human monocytes and induce their cytotoxic properties in addition to the production of IL-1, IL-6, and TNF-α. The molecular mechanisms involved in melatonin and dendritic cell interactions are largely unknown. In this study, we performed a comprehensive RNA sequencing (RNA-seq)-based analysis of monocyte-derived human dendritic cells across different melatonin stimulations. We profiled gene expression changes among naïve DCs along with DCs generated with melatonin (MDCs) and DCs matured with melatonin (DCMs). We found that melatonin significantly promoted the morphological maturation of MDCs and increased the expression of DC-related surface markers. Furthermore, MDCs increased the general immune response by promoting the secretion of IL-12, IL-6 and IFN-γ cytokines and enhancing the proliferation of TH cells, while DCM did not. Genome-wide comparative transcriptomic profiling showed that the expression of 7417 genes was significantly upregulated, and 3325 genes were significantly downregulated in MDCs. We observed the spatiotemporal activity of TLR 2-, 4-, 6- and 8-specific genes in MDCs. Interestingly, we found that the expression of TLR 10-specific signaling genes was significantly higher in DCMs. Further in vitro validation showed that along with TLRs, the upregulation of IRAK, GRB2, CREB and TNFRSF was significantly associated with MDCs. Overall, we found that during the differentiation of dendritic cells, the presence of melatonin generates a unique population of dendritic cells with activated TLR4 signaling. DCs generated through this unique culture process may act as good candidates for immunomodulation during cancer and inflammation. Supported by grants fromDST-SERB, GOI (CRG/2019/001296)

AKAP1 Regulates Mitochondrial Dynamics during the Fatty-Acid-Promoted Maturation of Human-Induced Pluripotent Stem Cell-Derived Cardiomyocytes as Indicated by Proteomics Sequencing.

Human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) are cells with promising applications. However, their immaturity has restricted their use in cell therapy, disease modeling, and other studies. Therefore, the current study focused on inducing the maturation of CMs. We supplemented hiPSC-CMs with fatty acids (FAs) to promote their phenotypic maturity. Proteomic sequencing was performed to identify regulators critical for promoting the maturation of hiPSC-CMs. AKAP1 was found to be significantly increased in FA-treated hiPSC-CMs, and the results were verified. Therefore, we inhibited AKAP1 expression in the FA-treated cells and analyzed the outcomes. FA supplementation promoted the morphological and functional maturation of the hiPSC-CMs, which was accompanied by the development of a mitochondrial network. Proteomic analysis results revealed that AKAP1 expression was significantly higher in FA-treated hiPSC-CMs than in control cells. In addition, increased phosphorylation of the mitochondrial dynamin Drp1 and an increased mitochondrial fusion rate were found in FA-treated hiPSC-CMs. After AKAP1 was knocked down, the level of DRP1 phosphorylation in the cell was decreased, and the mitochondrial fusion rate was reduced. FA supplementation effectively promoted the maturation of hiPSC-CMs, and in these cells, AKAP1 regulated mitochondrial dynamics, possibly playing a significant role.

Disturbances in Switching between Canonical and Non-Canonical Wnt Signaling Characterize Developing and Postnatal Kidneys of Dab1-/- (yotari) Mice.

This study aims to determine the protein expression patterns of acetylated α-tubulin, inversin, dishevelled-1, Wnt5a/b, and β-catenin in developing (E13.5 and E15.5) and early postnatal (P4 and P14) kidneys of Dab1-/- (yotari) mice, their role in regulating the Wnt signaling pathway, and the possible relation to congenital anomalies of kidney and urinary tract (CAKUT). The analysis of target protein co-expression, observed in the renal vesicles/immature glomeruli, ampullae/collecting ducts, convoluted tubules, metanephric mesenchyme of developing kidneys, but proximal convoluted tubules, distal convoluted tubules and glomeruli of postnatal kidneys, was performed using double immunofluorescence and semi-quantitative methods. The overall expression of acetylated α-tubulin and inversin during normal kidney development increases with higher expression in yotari mice as the kidney acquires mature morphology. An increase in β-catenin and cytosolic DVL-1 levels, indicating a switch from non-canonical to canonical Wnt signaling, is found in the postnatal kidney of yotari mice. In contrast, healthy mouse kidney expresses inversin and Wnt5a/b in the postnatal period, thus activating non-canonical Wnt signaling. Target protein expression patterns in kidney development and the early postnatal period observed in this study could indicate that switching between canonical and non-canonical Wnt signaling is crucial for normal nephrogenesis, while the defective Dab1 gene product in yotari mice may promote CAKUT due to interfering with this process.

Skin-dependent morphological and molecular maturation of specialized mechanosensory neurons (S34.005)

<h3>Objective:</h3> Identification of the developmental steps leading to somatosensory neuron development. <h3>Background:</h3> Our sense of touch is essential for life and relies on Low-Threshold Mechanoreceptors (LTMRs). LTMR subtypes characterized by early embryonic expression of Ntrk2 (TrkB) and Ret exhibit distinct properties depending on the skin region they innervate - hairy skin or glabrous(hairless) skin. In glabrous skin, TrkB+ and Ret+ LTMRs form Meissner corpuscles, while in hairy skin they form longitudinal lanceolate endings around hair follicles. These morphological features reflect the physiological properties and specialized functions of these neurons. The developmental steps leading to glabrous and hairy skin LTMR properties are largely unknown, in particular whether they are genetically pre-specified or whether interactions with different target skin regions define their unique features. <h3>Design/Methods:</h3> Sparse genetic labeling experiments demonstrate that morphological specialization of glabrous- and hairy paw skin-innervating TrkB+ and Ret+ LTMRs arise at nearly identical times during postnatal development. Interestingly, we find that individual neurons that terminate along the border of glabrous and hairy skin, termed “border neurons”, exhibit branches that form both lanceolate endings and Meissner corpuscle endings. Additionally, transcriptomic profiling and RNAscope experiments show that neonatal glabrous skin-and hairy skin-innervating TrkB+ and Ret+ neurons are transcriptionally similar, although distinct from other DRG neuron types. Lastly, using mouse mutants that have either ectopic glabrous skin or ectopic hairy skin we find that neurons that innervate ectopic skin regions of these mutants form ending types (either lanceolate or Meissner corpuscle endings) in accordance with the ectopic skin type. <h3>Results:</h3> These findings support a model in which embryonic TrkB+ and Ret+ LTMRs are able to form either Meissner corpuscle or lanceolate endings, and that the skin target region differentially instructs morphological maturation of these LTMR types. <h3>Conclusions:</h3> This model implies that neuronal identity in the peripheral nervous system is flexibly determined by target tissue. <b>Disclosure:</b> Dr. Koutsioumpa has nothing to disclose. Dr. Santiago has nothing to disclose. Miss Jacobs has nothing to disclose. Dr. Lehnert has received personal compensation for serving as an employee of Flagship Pioneering. Dr. Ginty has nothing to disclose.

Cephalometric Evaluation of Cervical Vertebral Column Morphology and Cervical Vertebral Maturation in Subjects with Vertical and Horizontal Growth Pattern

Cephalometric Evaluation of Cervical Vertebral Column Morphology and Cervical Vertebral Maturation in Subjects with Vertical and Horizontal Growth Pattern

Role of Graphene Oxide in Bacterial Cellulose-Gelatin Hydrogels for Wound Dressing Applications.

Biopolymer-based hydrogels have several advantages, including robust mechanical tunability, high biocompatibility, and excellent optical properties. These hydrogels can be ideal wound dressing materials and advantageous to repair and regenerate skin wounds. In this work, we prepared composite hydrogels by blending gelatin and graphene oxide-functionalized bacterial cellulose (GO-f-BC) with tetraethyl orthosilicate (TEOS). The hydrogels were characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), atomic force microscope (AFM), and water contact angle analyses to explore functional groups and their interactions, surface morphology, and wetting behavior, respectively. The swelling, biodegradation, and water retention were tested to respond to the biofluid. Maximum swelling was exhibited by GBG-1 (0.01 mg GO amount) in all media (aqueous = 1902.83%, PBS = 1546.63%, and electrolyte = 1367.32%). All hydrogels were hemocompatible, as their hemolysis was less than 0.5%, and blood coagulation time decreased as the hydrogel concentration and GO amount increased under in vitro standard conditions. These hydrogels exhibited unusual antimicrobial activities against Gram-positive and Gram-negative bacterial strains. The cell viability and proliferation were increased with an increased GO amount, and maximum values were found for GBG-4 (0.04 mg GO amount) against fibroblast (3T3) cell lines. The mature and well-adhered cell morphology of 3T3 cells was found for all hydrogel samples. Based on all findings, these hydrogels would be a potential wound dressing skin material for wound healing applications.

Nuclear Translocation Triggered at the Onset of Hearing in Cochlear Inner Hair Cells of Rats and Mice

PurposeNuclear position is precisely orchestrated during cell division, migration, and maturation of cells and tissues. Here we report a previously unrecognized, programmed movement of the nucleus in rat and mouse cochlear inner hair cells (IHCs) coinciding with the functional maturation of inner hair cells around the onset of hearing.MethodsWe measured hair cell length and nuclear position from confocal scans of immunofluorescence-labeled hair cells from whole-mount cochlear preparations throughout post-natal development.ResultsIn early post-natal days, the IHC experiences a period of sustained growth, during which the nucleus sits at the very basal pole of the cell, far from the apically located mechano-transducing stereocilia, but close to where synapses with primary afferent and efferent neurons are forming. After IHCs reach their final length, the nucleus moves to occupy a new position half-way along the length of the cell. Nuclear translocation begins in the middle turn, completes throughout the cochlea within 2–3 days, and coincides with the emergence of endolymphatic potential, the acquisition of big-conductance potassium channels (BK), and the onset of acoustic hearing. IHCs cultured in-vitro without endolymphatic potential (EP) do not grow, do not express BK, and do not experience nuclear movement. IHCs cultured in high K+ solutions (to simulate EP) grow but do not experience nuclear movement or acquire BK channels.ConclusionNuclear migration at the onset of hearing is a key step in the morphological maturation of IHCs. Whether this plays a role in functional maturation remains to be explored.

How do the skin barrier and microbiome adapt to the extra-uterine environment after birth? Implications for the clinical practice.

The multiple protective functions of the skin derive from the interactions between epithelial skin and immune cells as well as the commensal microbiota. Developed in the last trimester of intra-uterine life, the skin barrier adapts dynamically after birth. Specific differences in the structure and physiology have been disclosed between infant and adult skin. The stratum corneum of infants is thinner and structured by thicker corneocytes with a more anisotropic surface in comparison to adult skin. Lower levels of the natural moisturizing factor and its constituents, together with the increased protease activity in the epidermis result in dry baby skin and ongoing adaptation of the desquamation to the extra-uterine environment. Infant epidermis is characterized by an accelerated proliferation rate and clinically competent permeability barrier in term neonates, despite the higher baseline values of transepidermal water loss in infants. The skin surface of newborns is less acidic, which could increase susceptibility to diaper and atopic dermatitis. Immediately after birth, skin is colonized by commensal bacteria-a process dependent on the mode of delivery and of major importance for the maturation of the immune system. Skin bacterial diversity and dysbiosis have been related to different pathology such as atopic and seborrheic dermatitis. This paper focuses on the ongoing structural, functional and biochemical adaptation of the human skin barrier after birth. We discuss the interactions on the 'skin barrier/ microbiota/ immune system' axis and their role in the development of competent functional integrity of the epidermal barrier.

Blue Photons from Broad-Spectrum LEDs Control Growth, Morphology, and Coloration of Indoor Hydroponic Red-Leaf Lettuce

For indoor crop production, blue + red light-emitting diodes (LEDs) have high photosynthetic efficacy but create pink or purple hues unsuitable for workers to inspect crops. Adding green light to blue + red light forms a broad spectrum (white light), which is created by: phosphor-converted blue LEDs that cast photons with longer wavelengths, or a combination of blue, green, and red LEDs. A broad spectrum typically has a lower energy efficiency than dichromatic blue + red light but increases color rendering and creates a visually pleasing work environment. Lettuce growth depends on the interactions of blue and green light, but it is not clear how phosphor-converted broad spectra, with or without supplemental blue and red light, influence crop growth and quality. We grew red-leaf lettuce 'Rouxai' in an indoor deep-flow hydroponic system at 22 °C air temperature and ambient CO2. Upon germination, plants received six LED treatments delivering different blue fractions (from 7% to 35%) but the same total photon flux density (400 to 799 nm) of 180 μmol·m-2·s-1 under a 20 h photoperiod. The six LED treatments were: (1) warm white (WW180); (2) mint white (MW180); (3) MW100 + blue10 + red70; (4) blue20 + green60 + red100; (5) MW100 + blue50 + red30; and (6) blue60 + green60 + red60. Subscripts denote photon flux densities in μmol·m-2·s-1. Treatments 3 and 4 had similar blue, green, and red photon flux densities, as did treatments 5 and 6. At the harvest of mature plants, lettuce biomass, morphology, and color were similar under WW180 and MW180, which had different green and red fractions but similar blue fractions. As the blue fraction in broad spectra increased, shoot fresh mass, shoot dry mass, leaf number, leaf size, and plant diameter generally decreased and red leaf coloration intensified. Compared to blue + green + red LEDs, white LEDs supplemented with blue + red LEDs had similar effects on lettuce when they delivered similar blue, green, and red photon flux densities. We conclude that the blue photon flux density in broad spectra predominantly controls lettuce biomass, morphology, and coloration.

Moderate Copper Deprivation during Gestation and Lactation Affects Dentate Gyrus and Hippocampal Maturation in Immature Male Rats

The hippocampal formation (HF) is involved in higher brain functions including learning and declarative memory. The possibility that dietary copper has a role in the morphological development, and therefore the function of the HF, has received little attention. A rat model of tiered copper deficiency, initiated during gestation, was employed to determine the susceptibility of the HF, regions of which develop postnatally, to copper deficiency. At postnatal 23, pups whose dams had received either 1.8 or 1.4 mg Cu/kg diet during both gestation and lactation, compared with offspring of a group that had received 4.3 mg Cu/kg diet during both periods had, significantly more cell nuclei in the infrapyrimidal arm of the dentate gyrus. Offspring of rats fed 1.4 mg Cu/kg diet, but not those fed 1.8 mg/kg, compared with those fed 4.3 mg/kg, exhibited smaller, shorter, and narrower cell nuclei in the infrapyrimidal and suprapyrimidal arms of the dentate gyrus and smaller cell nuclei in region CA3c of the hippocampus. A fourth group (gestation, 1.8 mg Cu/kg diet; lactation, 0.9 mg Cu/kg diet) exhibited alterations less marked than those exhibited by the group fed 1.4 mg Cu/kg diet. All alterations in the groups fed low copper diets were consistent with slowed cell nuclear maturation. The findings indicate that copper is required for maturation of the dentate gyrus and hippocampus. Also, copper supplied at or below 1.8 mg/kg is insufficient for morphological maturation of the dentate gyrus and hippocampus. Because the HF is important for higher brain functions, further research is needed to determine whether the copper deficiency-induced alterations in dentate gyrus and hippocampus development are transient or permanent.

Oligodendrocyte-lineage cell exocytosis and L-type prostaglandin D synthase promote oligodendrocyte development and myelination.

In the developing central nervous system, oligodendrocyte precursor cells (OPCs) differentiate into oligodendrocytes, which form myelin around axons. Oligodendrocytes and myelin are essential for the function of the central nervous system, as evidenced by the severe neurological symptoms that arise in demyelinating diseases such as multiple sclerosis and leukodystrophy. Although many cell-intrinsic mechanisms that regulate oligodendrocyte development and myelination have been reported, it remains unclear whether interactions among oligodendrocyte-lineage cells (OPCs and oligodendrocytes) affect oligodendrocyte development and myelination. Here, we show that blocking vesicle-associated membrane protein (VAMP) 1/2/3-dependent exocytosis from oligodendrocyte-lineage cells impairs oligodendrocyte development, myelination, and motor behavior in mice. Adding oligodendrocyte-lineage cell-secreted molecules to secretion-deficient OPC cultures partially restores the morphological maturation of oligodendrocytes. Moreover, we identified L-type prostaglandin D synthase as an oligodendrocyte-lineage cell-secreted protein that promotes oligodendrocyte development and myelination in vivo. These findings reveal a novel autocrine/paracrine loop model for the regulation of oligodendrocyte and myelin development.

Mechanical loading is required for initiation of extracellular matrix deposition at the developing murine myotendinous junction

The myotendinous junction (MTJ) contributes to the generation of motion by connecting muscle to tendon. At the adult MTJ, a specialized extracellular matrix (ECM) is thought to contribute to the mechanical integrity of the muscle-tendon interface, but the factors that influence MTJ formation during mammalian development are unclear. Here, we combined 3D imaging and proteomics with murine models in which muscle contractility and patterning are disrupted to resolve morphological and compositional changes in the ECM during MTJ development. We found that MTJ-specific ECM deposition can be initiated via static loading due to growth; however, it required cyclic loading to develop a mature morphology. Furthermore, the MTJ can mature without the tendon terminating into cartilage. Based on these results, we describe a model wherein MTJ development depends on mechanical loading but not insertion into an enthesis.

Multiomics approach to profiling Sertoli cell maturation during development of the spermatogonial stem cell niche.

Spermatogonial stem cells (SSCs) are the basis of spermatogenesis, a complex process supported by a specialized microenvironment, called the SSC niche. Postnatal development of SSCs is characterized by distinct metabolic transitions from prepubertal to adult stages. An understanding of the niche factors that regulate these maturational events is critical for the clinical application of SSCs in fertility preservation. To investigate the niche maturation events that take place during SSC maturation, we combined different '-omics' technologies. Serial single cell RNA sequencing analysis revealed changes in the transcriptomes indicative of niche maturation that was initiated at 11 years of age in humans and at 8 weeks of age in pigs, as evident by Monocle analysis of Sertoli cells and peritubular myoid cell (PMC) development in humans and Sertoli cell analysis in pigs. Morphological niche maturation was associated with lipid droplet accumulation, a characteristic that was conserved between species. Lipidomic profiling revealed an increase in triglycerides and a decrease in sphingolipids with Sertoli cell maturation in the pig model. Quantitative (phospho-) proteomics analysis detected the activation of distinct pathways with porcine Sertoli cell maturation. We show here that the main aspects of niche maturation coincide with the morphological maturation of SSCs, which is followed by their metabolic maturation. The main aspects are also conserved between the species and can be predicted by changes in the niche lipidome. Overall, this knowledge is pivotal to establishing cell/tissue-based biomarkers that could gauge stem cell maturation to facilitate laboratory techniques that allow for SSC transplantation for restoration of fertility.

Morphological study of the postnatal hippocampal development in the TRPV1 knockout mice

ABSTRACT Transient receptor potential vanilloid 1 (TRPV1) is a non-selective cation channel with polymodal sensory function. TRPV1 links to fever, while, according to previous studies on TRPV1 knock-out (KO) mice, the role of the channel in the generation of febrile seizure is debated. In the hippocampal formation, functional TRPV1 channels are expressed by Cajal-Retzius cells, which have a role in guidance of migrating neurons during development. Despite the developmental aspects of febrile seizure as well as of Cajal-Retzius cells, no information is available about the hippocampal development in TRPV1 KO mouse. Therefore, in the present work postnatal development of the hippocampal formation was studied in TRPV1 KO mice. Several morphological characteristics including neuronal positioning and maturation, synaptogenesis and myelination were examined with light microscopy following immunohistochemical detection of protein markers of various neurons, synapses, and myelination. Regarding the cytoarchitectonics, neuronal migration, morphological, and neurochemical maturation, no substantial difference could be detected between TRPV1 KO and wild-type control mice. Our data indicate that synapse formation and myelination occur similarly in TRPV1 KO and in control animals. We have found slightly, but not significantly larger numbers of persisting Cajal-Retzius cells in the KO mice than in controls. Our result strengthens previous suggestion concerning the role of TRPV1 channel in the postnatal apoptotic cell death of Cajal-Retzius cells. However, the fact that the hippocampus of KO mice lacks major developmental abnormalities supports the use of TRPV1 KO in various animal models of diseases and pathological conditions.

Enhanced podocyte differentiation and changing drug toxicity sensitivity through pressure-controlled mechanical filtration stress on a glomerulus-on-a-chip.

Podocytes, localized in the glomerulus, are a prognostic factor of proteinuria in kidney disease and are exposed to distinct physiological stimuli from basal to apical filtration flow. Research studies on drug discovery and disease modeling for glomerulopathy have developed a glomerulus-on-a-chip and studied podocyte mechanobiology to realize alternative methods to animal experiments. However, the effect of filtration stimulus on podocytes has remained unclear. Herein, we report the successful development of a user-friendly filtration culture device and system that can precisely control the filtration flow using air pressure control by incorporating a commercially available culture insert. It allows mouse podocytes to be cultured under filtration conditions for three days with a guarantee of maintaining the integrity of the podocyte layer. Using our system, this study demonstrated that podocyte damage caused by hyperfiltration resulting from glomerular hypertension, a common pathophysiology of many glomerulopathies, was successfully recapitulated and that filtration stimulus promotes the maturation of podocytes in terms of their morphology and gene expression. Furthermore, we demonstrated that filtration stimulus induced different drug responsiveness in podocytes than those seen under static conditions, and that the difference in drug responsiveness was dependent on the pharmacological mechanism. Overall, this study has revealed differentiating and pharmacodynamic properties of filtration stimulus and brings new insights into the research field of podocyte mechanobiology towards the realization of glomerulus-on-a-chip.

Development of the Hair Cells of the Human Cochlea: A Scanning Electron Microscopic Study.

In the mammalian auditory system, the cochlea is the first to attain structural and functional maturity. Although ultrastructural details of the developing cochlea of lower animals have been elucidated in the last few decades, comprehensive studies on human cochlea are lacking. In the present investigation we studied the development and maturation of the hair cells of ten human fetal cochlea from gestational weeks (GW) 12 to 37 by scanning electron microscopy. We observed undifferentiated hair cells possessing numerous surface projections and long kinocilium during GW 14. At GW16, the primitive hair cells were arranged in one inner and four outer rows and had globular apices indicating the initiation of stereocilia formation. By GW 22, the globular apices were replaced by linear stereocilia and occasional kinocillia. Mature hair cells with sterocilia were observed in the basal turn at 30th week of gestation. At GW 37, the stereocilia were arranged in a typical "V" shaped pattern at the middle and apical coil, while the stereocilia of the basal turn were shorter in length resembling the adult cochlea. The inner hair cells were long and slender while outer hair cells were pear shaped, kinocilium were absent and the tunnel of Corti were well formed. It is concluded that in human, the morphological maturation of the hair cells starts in the basal turn around GW 22 and continues till 37th week in the apical turn indicating that early maturation of the cochlea may have a role on development of the higher auditory pathway connections.

Mutations in the transcriptional regulator MeCP2 severely impact key cellular and molecular signatures of human astrocytes during maturation

Mutations in the MECP2 gene underlie a spectrum of neurodevelopmental disorders, most commonly Rett syndrome (RTT). We ask whether MECP2 mutations interfere with human astrocyte developmental maturation, thereby affecting their ability to support neurons. Using human-based models, we show that RTT-causing MECP2 mutations greatly impact the key role of astrocytes in regulating overall brain bioenergetics and that these metabolic aberrations are likely mediated by dysfunctional mitochondria. During post-natal maturation, astrocytes rely on neurons to induce their complex stellate morphology and transcriptional changes. While MECP2 mutations cause cell-intrinsic aberrations in the astrocyte transcriptional landscape, surprisingly, they do not affect the neuron-induced astrocyte gene expression. Notably, however, astrocytes are unable to develop complex mature morphology due to cell- and non-cell-autonomous aberrations caused by MECP2 mutations. Thus, MECP2 mutations critically impact key cellular and molecular features of human astrocytes and, hence, their ability to interact and support the structural and functional maturation of neurons.

Density and temperature controlled fluid extraction in a bacterial biofilm is determined by poly-γ-glutamic acid production

A hallmark of microbial biofilms is the self-production of an extracellular molecular matrix that encases the resident cells. The matrix provides protection from the environment, while spatial heterogeneity of gene expression influences the structural morphology and colony spreading dynamics. Bacillus subtilis is a model bacterial system used to uncover the regulatory pathways and key building blocks required for biofilm growth and development. In this work, we report on the emergence of a highly active population of bacteria during the early stages of biofilm formation, facilitated by the extraction of fluid from the underlying agar substrate. We trace the origin of this fluid extraction to the production of poly-γ-glutamic acid (PGA). The flagella-dependent activity develops behind a moving front of fluid that propagates from the boundary of the biofilm towards the interior. The extent of fluid proliferation is controlled by the presence of extracellular polysaccharides (EPS). We also find that PGA production is positively correlated with higher temperatures, resulting in high-temperature mature biofilm morphologies that are distinct from the rugose colony biofilm architecture typically associated with B. subtilis. Although previous reports have suggested that PGA production does not play a major role in biofilm morphology in the undomesticated isolate NCIB 3610, our results suggest that this strain produces distinct biofilm matrices in response to environmental conditions.