• Himanshu Mishra

      Articles written in Journal of Biosciences

    • Classification and expression analyses of homeobox genes from Dictyostelium discoideum

      Himanshu Mishra Shweta Saran

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      Homeobox genes are compared between genomes in an attempt to understand the evolution of animal development. The ability of the protist, Dictyostelium discoideum, to shift between uni- and multicellularity makes this group ideal for studying the genetic changes that may have occurred during this transition. We present here the first genome-wide classification and comparative genomic analysis of the 14 homeobox genes present in D. discoideum. Based on the structural alignment of the homeodomains, they can be broadly divided into TALE and non-TALE classes. When individual homeobox genes were compared with members of known class or family, we could further classify them into 3 groups, namely, TALE, OTHER and NOVEL classes, but no HOX family was found. The 5 members of TALE class could be further divided into PBX, PKNOX, IRX and CUP families; 4 homeobox genes classified as NOVEL did not show any similarity to any known homeobox genes; while the remaining 5 were classified as OTHERS as they did show certain degree of similarity to few known homeobox genes. No unique RNA expression pattern during development of D. discoideum emerged for members of an individual group. Putative promoter analysis revealed binding sites for few homeobox transcription factors among many probable factors.

    • Deletion of Dictyostelium discoideum Sir2A impairs cell proliferation and inhibits autophagy


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      Sirtuins are a family of deacetylases (Class III histone deacetylases) with evolutionarily conserved functions in cellularmetabolism and chromatin regulation. Out of the seven human Sirtuins, the function of Sirt2 is the least understood. Thepurpose of the present study was to investigate the role of Sir2A, a homolog of human Sirt2 in Dictyostelium discoideum(Dd), a lower eukaryote. We created both overexpressing and deletion strains of Ddsir2A to analyse its functions. Weobserved sir2A mRNA expression throughout development and the transcript was present in the prespore/spore region ofmulticellular structures developed. They show a preference towards prestalk/stalk pathway when co-developed with wildtypecells during chimera formation. Deletion strain showed a multi-tipped phenotype, decrease in cell proliferation andinhibition of autophagy. In conclusion, our results show low cAMP levels, reduced cell-adhesion, weak cell migration andimpaired autophagy to be responsible for the phenotype shown by the null cells. This study provides new insights into thefunctions of Ddsir2A.

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