Biomedical subjects

Swati Banerjee

Publications and source records attributed to Swati Banerjee.

5 recordsLinked to original sources

PubMed2026

A complete genome for the common marmoset.

The common marmoset is a New World monkey widely used to study primate evolution and human disease. We present a telomere-to-telomere (T2T) reference assembly for the species, plus three near-T2T haplotypes. These resolve previously inaccessible regions, including the centromeres, sex chromosomes, subterminal satellites, acrocentric chromosomes, and the major histocompatibility complex (MHC). We find marmoset centromeres carry dimeric alpha satellites with chromosomal specificity, flanked by inactive layers interpreted as ancestral centromere remnants. We assemble gene-poor, satellite-rich short arms of the acrocentrics and find that most can harbor rDNA and all share pseudo-homolog regions (PHRs). PHR-sharing chromosomes also share closely related centromeric satellites, consistent with a model of ongoing rDNA-facilitated recombinational exchange between heterologous chromosomes. We further identify over 500 marmoset-lineage-specific transcribed genes with previously unknown transcript models or expansions. These resources, along with a preliminary pangenome, improve the utility of the marmoset as a model organism and address gaps in primate genome evolution.

Animals↗

PubMed2006

Axonal ensheathment and septate junction formation in the peripheral nervous system of Drosophila.

Axonal insulation is critical for efficient action potential propagation and normal functioning of the nervous system. In Drosophila, the underlying basis of nerve ensheathment is the axonal insulation by glial cells and the establishment of septate junctions (SJs) between glial cell membranes. However, the details of the cellular and molecular mechanisms underlying axonal insulation and SJ formation are still obscure. Here, we report the characterization of axonal insulation in the Drosophila peripheral nervous system (PNS). Targeted expression of tau-green fluorescent protein in the glial cells and ultrastructural analysis of the peripheral nerves allowed us to visualize the glial ensheathment of axons. We show that individual or a group of axons are ensheathed by inner glial processes, which in turn are ensheathed by the outer perineurial glial cells. SJs are formed between the inner and outer glial membranes. We also show that Neurexin IV, Contactin, and Neuroglian are coexpressed in the peripheral glial membranes and that these proteins exist as a complex in the Drosophila nervous system. Mutations in neurexin IV, contactin, and neuroglian result in the disruption of blood-nerve barrier function in the PNS, and ultrastructural analyses of the mutant embryonic peripheral nerves show loss of glial SJs. Interestingly, the murine homologs of Neurexin IV, Contactin, and Neuroglian are expressed at the paranodal SJs and play a key role in axon-glial interactions of myelinated axons. Together, our data suggest that the molecular machinery underlying axonal insulation and axon-glial interactions may be conserved across species.

Animals↗

PubMed2006

Organization and function of septate junctions: an evolutionary perspective.

In most cell types, distinct forms of intercellular junctions have been visualized at the ultrastructural level. Among these, the septate junctions are thought to seal the neighboring cells and thus to function as the paracellular barriers. The most extensively studied form of septate junctions, referred to as the pleated septate junctions, is ultrastructurally distinct with an electron-dense ladder-like arrangement of transverse septa present in invertebrates as well as vertebrates. In invertebrates, such as the fruit fly Drosophila melanogaster, septate junctions are present in all ectodermally derived epithelia, imaginal discs, and the nervous system. In vertebrates, septate junctions are present in the myelinated nerves at the paranodal interface between the myelin loops and the axonal membrane. In this review, we present an evolutionary perspective of septate junctions, especially their initial identification across phyla, and discuss many common features of their morphology, molecular organization, and functional similarities in invertebrates and vertebrates.

Animals↗

PubMed2004

Drosophila contactin, a homolog of vertebrate contactin, is required for septate junction organization and paracellular barrier function.

Septate junctions (SJs) in epithelial and neuronal cells play an important role in the formation and maintenance of charge and size selective barriers. They form the basis for the ensheathment of nerve fibers in Drosophila and for the attachment of myelin loops to axonal surface in vertebrates. The cell-adhesion molecules NRX IV/Caspr/Paranodin (NCP1), contactin and Neurofascin-155 (NF-155) are all present at the vertebrate axo-glial SJs. Mutational analyses have shown that vertebrate NCP1 and its Drosophila homolog, Neurexin IV (NRX IV) are required for the formation of SJs. In this study, we report the genetic, molecular and biochemical characterization of the Drosophila homolog of vertebrate contactin, CONT. Ultrastructural and dye-exclusion analyses of Cont mutant embryos show that CONT is required for organization of SJs and paracellular barrier function. We show that CONT, Neuroglian (NRG) (Drosophila homolog of NF-155) and NRX IV are interdependent for their SJ localization and these proteins form a tripartite complex. Hence, our data provide evidence that the organization of SJs is dependent on the interactions between these highly conserved cell-adhesion molecules.

Animals↗

PubMed2003

Seroreactivity of 31 kDa and 41 kDa mycobacterial secretory proteins isolated from culture filtrate in extra pulmonary tuberculosis.

Despite rapid advances in molecular genetics for detection of mycobacteria, it is clear that interest in serodiagnosis remains high, especially for those situations in which a specimen may not contain the infecting agent in particular in extrapulmonary tuberculosis. Immune response to excretory-secretory (ES) proteins of Mycobacterium tuberculosis (M.tb) has been of diagnostic interest in tuberculosis. In earlier study from our laboratory, a secretory protein M.tb ES-31 has been shown to have diagnostic potential in pulmonary tuberculosis. Further, another M.tb H37Ra ES protein (ES-41) was isolated and purified by trichloroacetic acid solubilization followed by Fast Performance Liquid Chromatography (FPLC). These two protein fractions viz ES-31 and ES-41 secreted by M.tb H37 Ra bacilli were employed in stick indirect penicillinase ELISA to study seroreactivity in extra pulmonary tuberculosis namely tuberculous lymphadenopathy, tuberculous meningitis, abdominal tuberculosis and bone & joint tuberculosis. While using ES-31 antigen 88% (22/25) of tuberculous lymphadenopathy and 90% (9/10) of tuberculous meningitis cases showed positive reaction for tuberculous IgG antibody, ES-41 showed 80% positivity in both groups. In abdominal and bone & joint tuberculosis cases, ES-41 antigen showed better sensitivity of 81.5% (22/27) and 84.6% (22/26) respectively in IgG antibody detection compared to 70% (19/27) and 69.2% (18/26) shown by ES-31. This study is of interest that different antigen protein fractions of M.tb exhibit differential seroreactivity, as ES-31 protein showed good potential in detecting tuberculous IgG antibodies in tuberculous lymphadenopathy (TBLN) & tuberculous meningitis (TBM), while ES-41 in abdominal and bone & joint tuberculosis cases.

Antibodies, Bacterial↗