Subhra Prakash Hui

Bio: Subhra Prakash Hui is an academic researcher from University of Calcutta. The author has contributed to research in topics: Zebrafish & Regeneration (biology). The author has an hindex of 9, co-authored 17 publications receiving 480 citations. Previous affiliations of Subhra Prakash Hui include Victor Chang Cardiac Research Institute.

Cellular response after crush injury in adult zebrafish spinal cord

Abstract: Zebrafish proves to be an excellent model system to study spinal cord regeneration because it can repair its disengaged axons and replace lost cells after injury, allowing the animal to make functional recovery. We have characterized injury response following crush injury, which is comparable to the mammalian mode of injury. Infiltrations of blood cells during early phases involve macrophages that are important in debris clearance and probably in suppression of inflammatory response. Unlike mammals where secondary injury mechanisms lead to apoptotic death of both neurons and glia, here we observe a beneficial role of apoptotic cell death. Injury-induced proliferation, presence of radial glia cells, and their role as progenitor all contribute to cellular replacement and successful neurogenesis after injury in adult zebrafish. Together with cell replacement phenomenon, there is creation of a permissive environment that includes the absence or clearance of myelin debris, presence of Schwann cells, and absence of inflammatory response.

Genome Wide Expression Profiling during Spinal Cord Regeneration Identifies Comprehensive Cellular Responses in Zebrafish

Abstract: Background Among the vertebrates, teleost and urodele amphibians are capable of regenerating their central nervous system. We have used zebrafish as a model to study spinal cord injury and regeneration. Relatively little is known about the molecular mechanisms underlying spinal cord regeneration and information based on high density oligonucleotide microarray was not available. We have used a high density microarray to profile the temporal transcriptome dynamics during the entire phenomenon.

Regeneration of Zebrafish CNS: Adult Neurogenesis

Abstract: Regeneration in the animal kingdom is one of the most fascinating problems that have allowed scientists to address many issues of fundamental importance in basic biology. However, we came to know that the regenerative capability may vary across different species. Among vertebrates, fish and amphibians are capable of regenerating a variety of complex organs through epimorphosis. Zebrafish is an excellent animal model, which can repair several organs like damaged retina, severed spinal cord, injured brain and heart, and amputated fins. The focus of the present paper is on spinal cord regeneration in adult zebrafish. We intend to discuss our current understanding of the cellular and molecular mechanism(s) that allows formation of proliferating progenitors and controls neurogenesis, which involve changes in epigenetic and transcription programs. Unlike mammals, zebrafish retains radial glia, a nonneuronal cell type in their adult central nervous system. Injury induced proliferation involves radial glia which proliferate, transcribe embryonic genes, and can give rise to new neurons. Recent technological development of exquisite molecular tools in zebrafish, such as cell ablation, lineage analysis, and novel and substantial microarray, together with advancement in stem cell biology, allowed us to investigate how progenitor cells contribute to the generation of appropriate structures and various underlying mechanisms like reprogramming.

Zebrafish FOXP3 is required for the maintenance of immune tolerance.

Abstract: Regulatory T (Treg) cells play a central role in the suppression of excessive immune responses against both self and non-self antigens. The development and function of Treg cells are controlled by a master regulatory gene encoding the forkhead box P3 (FOXP3) protein in mammals. However, little is known regarding the functions of Treg cells and FOXP3 in non-mammalian vertebrates. In this study, we generated mutant zebrafish lacking a functional FOXP3 ortholog, and demonstrated a significant reduction in survival accompanied by a marked increase in inflammatory gene expression, mononuclear cell infiltration, and T cell proliferation in peripheral tissues. Our findings indicate that the zebrafish FOXP3 protein may have an evolutionally conserved role in the control of immune tolerance, illuminating the potential of the zebrafish as a novel model for investigating the development and functions of Treg cells.

Regulatory T Cells

Abstract: Despite the skepticism that once prevailed among immunologists, it is now widely accepted that the normal immune system harbors a T-cell population, called regulatory T cells (Treg cells), specialized for immune suppression. It was first shown that depletion of a T-cell subpopulation from normal rodents produced autoimmune disease. Search for a molecular marker specific for such autoimmune-preventive Treg cells has revealed that the majority, if not all, of them constitutively express the CD25 molecule as depletion of CD25+CD4+ T cells spontaneously evokes autoimmune disease in otherwise normal rodents. The expression of CD25 by Treg cells has made it possible to delineate their developmental pathways, in particular their thymic development, and establish simple in vitro assay for assessing their suppressive activity. The marker and the in vitro assay have helped to identify human Treg cells with similar functional and phenotypic characteristics. Recent efforts have shown that natural Treg cells specifically express the transcription factor Foxp3 and that mutations of the Foxp3 gene produce a variety of immunological diseases in humans and rodents. Specific expression of Foxp3 in natural Treg cells has enabled their functional and developmental characterization by genetic approach. These studies altogether have provided firm evidence for Foxp3+CD25+CD4+ Treg cells as an indispensable cellular constituent of the normal immune system for establishing and maintaining immunologic self-tolerance and immune homeostasis. Treg cells are now within the scope of clinical use to treat immunological diseases and control physiological and pathological immune responses.

Genetic compensation induced by deleterious mutations but not gene knockdowns

Abstract: Cells sense their environment and adapt to it by fine-tuning their transcriptome. Wired into this network of gene expression control are mechanisms to compensate for gene dosage. The increasing use of reverse genetics in zebrafish, and other model systems, has revealed profound differences between the phenotypes caused by genetic mutations and those caused by gene knockdowns at many loci, an observation previously reported in mouse and Arabidopsis. To identify the reasons underlying the phenotypic differences between mutants and knockdowns, we generated mutations in zebrafish egfl7, an endothelial extracellular matrix gene of therapeutic interest, as well as in vegfaa. Here we show that egfl7 mutants do not show any obvious phenotypes while animals injected with egfl7 morpholino (morphants) exhibit severe vascular defects. We further observe that egfl7 mutants are less sensitive than their wild-type siblings to Egfl7 knockdown, arguing against residual protein function in the mutants or significant off-target effects of the morpholinos when used at a moderate dose. Comparing egfl7 mutant and morphant proteomes and transcriptomes, we identify a set of proteins and genes that are upregulated in mutants but not in morphants. Among them are extracellular matrix genes that can rescue egfl7 morphants, indicating that they could be compensating for the loss of Egfl7 function in the phenotypically wild-type egfl7 mutants. Moreover, egfl7 CRISPR interference, which obstructs transcript elongation and causes severe vascular defects, does not cause the upregulation of these genes. Similarly, vegfaa mutants but not morphants show an upregulation of vegfab. Taken together, these data reveal the activation of a compensatory network to buffer against deleterious mutations, which was not observed after translational or transcriptional knockdown.

Astrocyte Reactivity and Reactive Astrogliosis: Costs and Benefits

Abstract: Astrocytes are the most abundant cells in the central nervous system (CNS) that provide nutrients, recycle neurotransmitters, as well as fulfill a wide range of other homeostasis maintaining functions During the past two decades, astrocytes emerged also as increasingly important regulators of neuronal functions including the generation of new nerve cells and structural as well as functional synapse remodeling Reactive gliosis or reactive astrogliosis is a term coined for the morphological and functional changes seen in astroglial cells/astrocytes responding to CNS injury and other neurological diseases Whereas this defensive reaction of astrocytes is conceivably aimed at handling the acute stress, limiting tissue damage, and restoring homeostasis, it may also inhibit adaptive neural plasticity mechanisms underlying recovery of function Understanding the multifaceted roles of astrocytes in the healthy and diseased CNS will undoubtedly contribute to the development of treatment strategies that will, in a context-dependent manner and at appropriate time points, modulate reactive astrogliosis to promote brain repair and reduce the neurological impairment

Animal Tissue Techniques.

Abstract: Clearly, the possibility that Van Peenen's statements are correct exists, but no molecular geneticist would contend that these assertions have been established, in any but a very few cases, which appear at present to be atypical. The educated lavman, for whom this book is intended, will find the author's leaps from the level of the quoted material into sophisticated physical chemistry and back again disconcerting at least, if not completely confusing. It can be said, however, that the authors have assembled an excellent group of illustrations; lecturers in elementary genetics wishing to locate clear illustrations to use as slides would do well to look in this book first.