Biology subjects

Nayak, G.

Publications and source records attributed to Nayak, G..

6 recordsLinked to original sources

bioRxiv2025

Turning blood to brain cells: a plasma mediated reprograming model

The lack of effective stem cell protocols for generating personalized neurovascular niches poses a critical challenge in precision medicine. While iPSC-based methods are explored, their clinical use is hindered by high costs, long timelines, and cancer risks. Recent advancements in plasma-driven differentiation, using circulating monocytes, offer a promising solution as they can be reprogrammed into neuron-like, endothelial-like, and hematopoietic cells without genetic manipulation, by inducing growth factors mediated transdifferentiation. Vasculature is integral to neurodevelopment, with early blood supply transitioning from the perineural to intrinsic vascular plexus, driven by neuro-hematovascular signaling. The choroid plexus selectively transports proteins and growth factors from blood to CSF, supporting neural proliferation and differentiation. Building on these insights, we leveraged the innate reprograming potential of blood-derived cells to generate neuro-hematovascular niches using a novel PITTRep methodology, devoid of transgene and growth factor mediated transdifferentiation opening new avenues for regenerative and investigative neurovascular studies.

cell biology↗

bioRxiv2025

Methionine sulfoxide reductase B3 antioxidant activity is indispensable for mouse inner ear cuticular plate structure and hair bundle integrity

Methionine sulfoxide reductases (MSR) are enzymes responsible for catalyzing the reduction of methionine-sulfoxides. We previously demonstrated that variants in human MSRB3, a member of the MSR family, are associated with profound autosomal recessive prelingual non-syndromic hearing loss DFNB74. To better understand the role of MSRB3 in the auditory pathway, we generated a complete MsrB3 gene knock-out mouse model of human DFNB74 deafness. The MsrB3 deficient mouse showed profound hearing loss by postnatal day 16 (P16), which was accompanied by hair cell morphological abnormalities including altered stereocilia bundle shape and cuticular plate degeneration followed by hair cell apoptotic death. Although the absence of MSRB3 primarily affected the actin cytoskeleton, rootlets were present, and the expression and localization of major F-actin stereocilia-core proteins were unaltered. Biochemical assays demonstrated that wild-type MSRB3, but not MSRB3 harboring p.Cys89Gly, the same variant reported for human deafness DFNB74, can repolymerize oxidized actin. Consistent with these in vitro data, we observed a decreased ratio of reduced/total actin in the inner ears of Msrb3 knock-out mice. These data suggest a protective role of MSRB3 in the maintenance and maturation of stereocilia and hair cells, a conserved mechanism aimed at maintaining actin redox dynamics in these sensory cells.

genetics↗

bioRxiv2024

Building neurovascular tissue from autologous blood for modeling brain-activity

There are no faithful individualized stem cell-based bioengineered neuro-vascularized models that can recapitulate the physiological hemodynamic phenomenon of neuro-vascular coupling (NVC)-the principal behind BOLD (blood oxygen level-dependent) signal in functional neuroimaging, thereby dissuading the research in exploring the brain activity-based investigative studies in neurological/neurosensory diseases. This encouraged us to establish a preclinical optoacoustic (Hb/dHb hemoglobin/deoxyhemoglobin) imaging-competent in vitro neuro-vascularized model by employing a novel cellular reprograming PITTRep (Plasma Induced Transcriptomics/ epi-Transcriptomics Reprograming) approach. The current reprograming approach is based on coaxing autologous blood components to ecto-mesodermal lineage intermediates that can subsequently self-pattern into neurovascular tissue by harnessing the hemorheological properties of RBCs. The nature of blood flow is non-Newtonian and is a function of RBC concentration /haematocrit when they flow through the regions of low shear rates as seen in cerebral microcirculation. The current reprograming approach is a modification of our previous cellular reprograming approach that employed a Newtonian plasma fluid. The autologous blood-derived neurovascular tissue is free from exogenous genetic modification, external growth factors, and induced pluripotent stem cell (iPSC) derivation. This model uniquely integrates functional vasculature and neurogenesis. The current reprogramming approach resulted (in part) serendipitously while testing a potential (yet completely unexplored) hypothesis of haemodynamic reprograming by leveraging the fluid mechanic feature of blood erythrocytes as seen in thrombus formation during cerebral ischemic stroke, that is characterized by physiologically intriguing yet clinically meaningful neurological recovery (neuroplasticity) during an early time window. The current study attempted to induce "a post stroke-like model" of adult neurogenesis with functional synaptogenesis by instructing autologous blood components into thrombus formation through incorporation of erythrocytes in varying concentrations. We tried to instruct adult neurogenesis and neuroplasticity (a relatively non-resilient phenomenon under in vitro conditions) by co-induction of a neuro-vascular niche (NVN). These NVNs are marked by dendrites, synapses, astrogliosis, microglia activation, and growth factor signaling, thus phenocopying molecular and cellular aspects of post-stroke recovery window. The induction of neuro-vascularized niches and functional neuro-vascular coupling (NVC) was characterized by confocal microscopy, scanning electron microscopy, proteomic profiling, and Hb/dHb spectra based optoacoustic imaging. The blood thrombus formation was checked by rotational thromboelastometry (ROTEM), and switching of adult-to-embryonic hemoglobin was confirmed by routine hemoglobin typing. We also attempted to establish patient-specific neuro-vascularized niches from autologous blood of sensorineural hearing loss (SNHL) patients. The individualized neovascularised tissues are intended to be employed for investigating deregulated synaptic plasticity/ long term potentiation underlying poor auditory comprehension outcomes in school going kids suffering from SNHL that greatly compromises their academic performance and socio-behavioural-cognitive development. The attendant multiomics of patient-specific NVNs may have potential implications in developing stem-cell based therapies for neurosensory and cerebrovascular diseases.

neuroscience↗

bioRxiv2019

Adaptive thermogenesis in mice requires adipocyte light-sensing via Opsin 3

Almost all life forms can decode light information for adaptive advantage. Examples include the visual system, where photoreceptor signals are interpreted as images, and the circadian system, where light entrains a physiological clock. Here we describe a local, non-visual light response in mice that employs encephalopsin (OPN3, a 480 nm, blue light responsive opsin) to regulate the function of adipocytes. Germ line null and adipocyte-specific conditional null mice show a deficit in thermogenesis that is phenocopied in mice under blue-light deficient conditions. We show that blue light stimulation of adipocytes activates hormone sensitive lipase, the rate limiting enzyme in the lipolysis pathway, and that this is OPN3-dependent. Opn3 adipocyte conditional null mice also use reduced levels of fat mass when fasted and cold exposed further suggesting a lipolysis deficit. These data suggest the hypothesis that in mice, a local, OPN3-dependent light response in adipocytes is a mechanism for regulation of energy homeostasis.

physiology↗

bioRxiv2019

Fetal stage melanopsin (OPN4) and GNAQ (Gαq) signaling regulates vascular development of the eye

Maturation of sensory systems in mammals is regulated by appropriate sensory stimulation. Developmental refinement of the eye and visual system is regulated by light and visual stimulation. One compelling example is that fetal mouse pups deprived of light exhibit altered vascular development in their eyes. Previous work demonstrated that light activation of the photopigment melanopsin (Opn4), an atypical opsin expressed in intrinsically photosensitive retinal ganglion cells (ipRGCs), is crucial to normal vascular development. This suggested the unusual hypothesis that vascular development of the eye was regulated by ipRGC responses in the fetal eye by light that traveled through the body wall of the mother. Here, we test the requirement of OPN4 during fetal stages using genetic approaches. The G-protein GNAQ (Gq) is a candidate mediator of melanopsin signaling. We show that ipRGC-specific deletion of Gnaq phenocopies both hyaloid and retinal vascular development of the Opn4 null mouse. Furthermore, GNAQ gain-of-function in Opn4-expressing cells only during late gestation was sufficient to reverse the consequences for vascular development of either dark rearing or Opn4 loss-of-function. We conclude that melanopsin-dependent signaling in the fetal mouse eye is necessary and sufficient for vascular maturation.

developmental biology↗

bioRxiv2018

An adipocyte light-Opsin 3 pathway regulates the circadian clock and energy balance.

Almost all life forms can detect and decode light information for adaptive advantage. Examples include the visual system, where photoreceptor signals are processed into virtual images, and the circadian system, where light entrains a physiological clock. Here we describe a pathway in mice that employs encephalopsin (OPN3, a 480 nm light responsive opsin) to mediate light responses in murine adipocytes. The adipocyte light-OPN3 pathway regulates neonatal growth in mice and is required for at least three important functions including (1) photoentrainment of a local circadian clock, (2) extracellular matrix deposition, and (3) regulation of mitochondrial content and the proportion of \"brite\" adipocytes. Furthermore, we show that the light-OPN3 pathway is required for normal levels of uncoupling protein 1 (UCP1) in white and brown adipose tissue. Consequently, neonatal Opn3 germ-line and adipocyte-conditional null mice show a reduced ability to maintain their body temperature under cold stress. This was also observed in wild-type mice deprived of blue light. We hypothesize that the adipocyte light-OPN3 pathway provides a dynamically responsive, circadian clock-integrated mechanism for regulating adipocyte function and in turn directing metabolism to thermogenesis rather than anabolism. These data indicate an important role for peripheral light sensing in mammals and may have broad implications for human health given the unnatural lighting conditions in which we live.

physiology↗