Aswathy Sebastian

Dr. Aswathy Sebastian

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Research Focus & Metrics

Academic Career Length

17Years (2010-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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21 June 2015 in Neural Development
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DZDONGHUA ZOU
DONGHUA ZOU
CMColleen McSweeney
Colleen McSweeney
ASAswathy Sebastian
Aswathy Sebastian
DRDerrick James Reynolds
Derrick James Reynolds
FDFengping Dong
Fengping Dong
YMYingwei Mao
Yingwei Mao
Nonsense mediated mRNA decay (NMD) is an RNA surveillance mechanism that controls RNA stability and ensures the speedy degradation of erroneous and unnecessary transcripts. This mechanism depends on several core factors in the exon junction complex (EJC), eIF4A3, RBM8a, Magoh, and BTZ, as well as peripheral factors to distinguish premature stop codons (PTCs) from normal stop codons in transcripts. Recently, emerging evidence has indicated that NMD factors are associated with neurodevelopmental disorders such as autism spectrum disorder (ASD) and intellectual disability (ID). However, the mechanism in which these factors control embryonic brain development is not clear. We found that RBM8a is critical for proliferation and differentiation in cortical neural progenitor cells (NPCs). RBM8a is highly expressed in the subventricular zone (SVZ) of the early embryonic cortex, suggesting that RBM8a may play a role in regulating NPCs. RBM8a overexpression stimulates embryonic NPC proliferation and suppresses neuronal differentiation. Conversely, knockdown of RBM8a in the neocortex reduces NPC proliferation and promotes premature neuronal differentiation. Moreover, overexpression of RBM8a suppresses cell cycle exit and keeps cortical NPCs in a proliferative state. To uncover the underlying mechanisms of this phenotype, genome-wide RNAseq was used to identify potential downstream genes of RBM8a in the brain, which have been implicated in autism and neurodevelopmental disorders. Interestingly, autism and schizophrenia risk genes are highly represented in downstream transcripts of RBM8a. In addition, RBM8a regulates multiple alternative splicing genes and NMD targets that are implicated in ASD. Taken together, this data suggests a novel role of RBM8a in the regulation of neurodevelopment. Our studies provide some insight into causes of mental illnesses and will facilitate the development of new therapeutic strategies for neurodevelopmental illnesses.

11 July 2016 in BMC Microbiology
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KMKilaza Mwaikono
Kilaza Mwaikono
SMSolomon Maina
Solomon Maina
ASAswathy Sebastian
Aswathy Sebastian
MSMegan Schilling
Megan Schilling
VKVivek Kapur
Vivek Kapur
PGPaul Gwakisa
Paul Gwakisa
Multiple types of solid waste in developing countries is disposed of together in dumpsites where there is interaction between humans, animals and the bacteria in the waste. To study the bacteria at the dumpsite and the associated risks, previous studies have focused on culturable, leaving behind a great number of unculturable bacteria. This study focuses on a more comprehensive approach to study bacteria at the dumpsite. Since the site comprised of unsorted wastes, a qualitative survey was first performed to identify the variety of solid waste as this has influence on the microbial composition. Thus, domestic (Dom), biomedical (Biom), river sludge (Riv), and fecal material of pigs scavenging on the dumpsite (FecD) were sampled. Total DNA was extracted from 78 samples and the v4-16S rRNA amplicons was characterized using an Illumina MiSeq platform. A total of 8,469,294 sequences passed quality control. Catchall analysis predicted a mean of 8243 species per sample. Diversity was high with an average InvSimpson index of 44.21 ± 1.44. A total of 35 phyla were detected and the predominant were Firmicutes (38 %), Proteobacteria (35 %), Bacteroidetes (13 %) and Actinobacteria (3 %). Overall 76,862 OTUs were detected, however, only 20 % were found more than 10 times. The predominant OTUs were Acinetobacter (12.1 %), Clostridium sensu stricto (4.8 %), Proteinclasticum and Lactobacillus both at (3.4 %), Enterococcus (2.9 %) and Escherichia/Shigella (1.7 %). Indicator analysis (P ≤ 0.05, indicator value ≥ 70) shows that Halomonas, Idiomarina, Tisierella and Proteiniclasticum were associated with Biom; Enterococcus, Bifidobacteria, and Clostridium sensu stricto with FecD and Flavobacteria, Lysobacter and Commamonas to Riv. Acinetobacter and Clostridium sensu stricto were found in 62 % and 49 % of all samples, respectively, at the relative abundance of 1 %. None of OTUs was found across all samples. This study provides a comprehensive report on the abundance and diversity bacteria in municipal dumpsite. The species richness reported here shows the complexity of this man-made ecosystem and calls for further research to assess for a link between human diseases and the dumpsite. This would provide insight into proper disposal of the waste, as well as, limit the risks to human health associated with the dumpsite.

1 November 2020 in International Journal of Systematic and Evolutionary Microbiology
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MSMohit Kumar Saini
Mohit Kumar Saini
WCWeng ChihChe
Weng ChihChe
NSNathan Soulier
Nathan Soulier
ASAswathy Sebastian
Aswathy Sebastian
IAIstvan Albert
Istvan Albert
MTMarcus Tank
Marcus Tank
A novel thermophilic phototrophic purple sulphur bacterium was isolated from microbial mats (56 °C) at Nakabusa hot springs, Nagano prefecture, Japan. Cells were motile, rod-shaped, stain Gram-negative and stored sulphur globules intracellularly. Bacteriochlorophyll a and carotenoids of the normal spirilloxanthin series were the major pigments. Dense liquid cultures were red in colour. Strain No.7T was able to grow photoautotrophically using sulfide, thiosulfate, sulfite and hydrogen (in the presence of sulfide) as electron donors and bicarbonate as the sole carbon source. Optimum growth occurred under anaerobic conditions in the light at 50 °C (range, 40–56 °C) and pH 7.2 (range, pH 7–8). Major fatty acids were C16 : 0 (46.8 %), C16 : 1 ω7c (19.9 %), C18 : 1 ω7c (21.1 %), C14 : 0 (4.6 %) and C18 : 0 (2.4 %). The polar lipid profile showed phosphatidylglycerol and unidentified aminophospholipids to be the major lipids. The only quinone detected was ubiquinone-8. 16S rRNA gene sequence comparisons indicated that the novel bacterium is only distantly related to Thermochromatium tepidum with a nucleotide identity of 90.4 %. The phylogenetic analysis supported the high novelty of strain No.7T with a long-branching phylogenetic position within the Chromatiaceae next to Thermochromatium tepidum . The genome comprised a circular chromosome of 2.99 Mbp (2 989 870 bp), included no plasmids and had a DNA G+C content of 61.2 mol%. Polyphasic taxonomic analyses of the isolate suggested strain No.7T is a novel genus within the Chromatiaceae . The proposed genus name of the second truly thermophilic purple sulphur bacterium is Caldichromatium gen. nov. with the type species Caldichromatium japonicum sp. nov. (DSM 110881=JCM 39101).

1 October 2021 in Journal of Hazardous Materials
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YLYishan Lin
Yishan Lin
JGJessica A. Grembi
Jessica A. Grembi
SGSara S. Goots
Sara S. Goots
ASAswathy Sebastian
Aswathy Sebastian
IAIstván Albert
István Albert
RBRachel Brennan
Rachel Brennan

23 December 2021 in Genes
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LGLalitha Gopalan
Lalitha Gopalan
ASAswathy Sebastian
Aswathy Sebastian
CPCraig A. Praul
Craig A. Praul
IAIstvan Albert
Istvan Albert
RRRamesh Ramachandran
Ramesh Ramachandran
Ovarian cancer is the most lethal gynecological malignancy in women. Metformin intake is associated with a reduced incidence of ovarian cancer and increased overall survival rate. We determined the effect of metformin on sphere formation, extracellular matrix invasion, and transcriptome profile of ovarian cancer cells (COVCAR) isolated from ascites of chickens that naturally developed ovarian cancer. We found that metformin treatment significantly decreased sphere formation and invasiveness of COVCAR cells. RNA-Seq data analysis revealed 0, 4, 365 differentially expressed genes in cells treated with 0.5, 1, 2 mM metformin, respectively compared to controls. Transcriptomic and ingenuity pathway analysis (IPA) revealed significant downregulation of MMP7, AICDA, GDPD2, APOC3, APOA1 and predicted inhibition of upstream regulators NFKB, STAT3, TP53 that are involved in epithelial–mesenchymal transition, DNA repair, and lipid metabolism. The analysis revealed significant upregulation of RASD2, IHH, CRABP-1 and predicted activation of upstream regulators VEGF and E2F1 that are associated with angiogenesis and cell cycle. Causal network analysis revealed novel pathways suggesting predicted inhibition of ovarian cancer through master regulator ASCL1 and dataset genes DCX, SEMA6B, HEY2, and KCNIP2. In summary, advanced pathway analysis in IPA revealed novel target genes, upstream regulators, and pathways affected by metformin treatment of COVCAR cells.

31 December 2021 in Microorganisms
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MSMohit Kumar Saini
Mohit Kumar Saini
SYShohei Yoshida
Shohei Yoshida
ASAswathy Sebastian
Aswathy Sebastian
EHEri Hara
Eri Hara
HTHideyuki Tamaki
Hideyuki Tamaki
DBDonald A. Bryant
Donald A. Bryant
Strain MS-P2T was isolated from microbial mats associated with Mushroom Spring, an alkaline siliceous hot spring in Yellowstone National Park, WY, USA. The isolate grows chemoheterotrophically by oxygen-dependent respiration, and light stimulates photoheterotrophic growth under strictly oxic conditions. Strain MS-P2T synthesizes bacteriochlorophyll a and the carotenoid spirilloxanthin. However, photoautotrophic growth did not occur under oxic or anoxic conditions, suggesting that this strain should be classified as an aerobic anoxygenic phototrophic bacterium. Strain MS-P2T cells are motile, curved rods about 0.5 to 1.0 μm wide and 1.0 to 1.5 μm long. The optimum growth temperature is 45–50 °C, and the optimum pH for growth is circum-neutral (pH 7.0–7.5). Sequence analysis of the 16S rRNA gene revealed that strain MS-P2T is closely related to Elioraea species, members of the class Alphaproteobacteria, with a sequence identity of 96.58 to 98%. The genome of strain MS-P2T is a single circular DNA molecule of 3,367,643 bp with a mol% guanine-plus-cytosine content of 70.6%. Based on phylogenetic, physiological, biochemical, and genomic characteristics, we propose this bacteriochlorophyll a-containing isolate is a new species belonging to the genus Elioraea, with the suggested name Elioraeatepida. The type-strain is strain MS-P2T (= JCM33060T = ATCC TSD-174T).