Biology subjects

Singh, R. R.

Publications and source records attributed to Singh, R. R..

3 recordsLinked to original sources

bioRxiv2023

First complete genome characterization of an Indian pigeon pox virus directly from a clinical sample

Avian pox disease is a highly contagious infection caused by pox virus and has serious consequences on avian species with regards to economic and conservation aspects. This viral genus named as Avipox virus (APV) that infects nearly 300 bird species and lack of enough complete genome information creates hindrance to infer this virus biology. Thus in this study, we have revealed the first complete genome of an Indian pigeon pox virus that belongs to the genus APV followed by comparative genomics analysis. The entire genome of present isolate (PPV/Pur-Od-4b/01/Ind) having 280058 bp nucleotide sequences with the GC content 29.51%. The unique feature of this complete genome revealed the presence of 270 open reading frames (ORFs) circumscribed by inverted terminal repeats (ITRs) of 4,689 bp at each end and lack of recombination events. The concatenated amino acid phylogenetic tree deciphered the present isolate closely related with Feral Pigeon pox virus derived from Africa. The molecular markers, such as microsatellites were ubiquitously distributed throughout the genome and more prevalent within the functional genes.

evolutionary biology↗

bioRxiv2023

The Interplay between Mutagenesis and Extrachromosomal DNA Shapes Urothelial Cancer Evolution

Advanced urothelial cancer is a frequently lethal disease characterized by marked genetic heterogeneity. In this study, we investigate the evolution of the genomic signatures caused by endogenous and external mutagenic stimuli and their interplay with complex structural variants. We superimposed mutational signatures and phylogenetic analyses of matched serial tumors from patients with urothelial cancer to define the evolutionary patterns of these processes. We show that APOBEC3-induced mutations are clonal and early, whereas mutational bursts comprising hundreds of late subclonal mutations are induced by chemotherapy. Using a novel genome graph computational paradigm, we observed frequent circular high copy-number amplicons characteristic of extrachromosomal DNA (ecDNA) involving double-minutes, breakage-fusion-bridge, and tyfonas events. We characterized the distinct temporal patterns of APOBEC3 mutations and chemotherapy-induced mutations within ecDNA, gaining new insights into the timing of these events relative to ecDNA biogenesis. Finally, we discovered that most CCND1 amplifications in urothelial cancer arise within circular ecDNA amplicons. These CCND1 ecDNA amplification events persisted and increased in complexity incorporating additional DNA segments potentially contributing selective fitness advantage to the evolution of treatment resistance. Our findings define fundamental mechanisms driving urothelial cancer evolution and have therapeutic implications for treating this disease.

genomics↗

bioRxiv2023

CLN3 deficiency leads to neurological and metabolic perturbations during early development

Juvenile Neuronal Ceroid Lipofuscinosis (or Batten disease) is an autosomal recessive, rare neurodegenerative disorder that affects mainly children above the age of 5 years and is most commonly caused by mutations in the highly conserved CLN3 gene. Here, we generated cln3 morphants and stable mutant lines in zebrafish. Although neither morphant nor mutant cln3 larvae showed any obvious developmental or morphological defects, behavioral phenotyping of the mutant larvae revealed higher basal activity, hyposensitivity to abrupt light changes and hypersensitivity to pro-convulsive drugs. Importantly, in-depth metabolomics and lipidomics analyses revealed significant accumulation of several glycerophosphodiesters (GPDs) and a global decrease of bis(monoacylglycero)phosphate (BMP) species, two classes of molecules previously proposed as potential biomarkers for CLN3 disease based on independent studies in other organisms. We could also demonstrate GPD accumulation in human-induced pluripotent stem cell-derived cerebral organoids carrying a pathogenic variant for CLN3. Our models revealed that GPDs accumulate at very early stages of life in the absence of functional CLN3 and highlight glycerophosphoinositol and BMP as promising biomarker candidates for pre-symptomatic CLN3 disease.

molecular biology↗