Research Summary

Intermediate Fellowship research summary

Recent advances in fluorescent labeling technologies combined with high resolution microscopy have revealed that chromosomes strikingly assume non-random positions in the interphase nucleus. Gene rich chromosomes (human Chromosome 19) are localized towards the center, while gene poor chromosomes (Chromosome 18) are closer to the nuclear periphery of human cells. Such an arrangement is conserved in evolution, strongly suggesting a functional significance. The molecular mechanisms that regulate non-random chromosome positioning patterns are largely unclear. The focus of my laboratory is to address (1) The molecular mechanisms of non-random chromosome positioning and its relationship with transcription (2) Nuclear organization of candidate gene loci and its relationship with gene expression in cancer cells. We are examining these aspects in cancer cells as they are typically aneuploid, with extra copies of chromosomes that significantly destabilize the cancer transcriptome. Therefore cancer cells serve as an invaluable system to address mechanisms of nuclear structure-function relationships. We are using molecular cytogenetic methods such as fluorescence in situ hybridization (FISH), Spectral karyotyping (SKY) along with laser scanning confocal imaging in conjunction with gene expression profiling using microarrays to obtain critical mechanistic insights on molecular mechanisms that regulate nuclear structure-function relationships in cancer cells.

Figure: 1: Nucleolus: Multiple sets of nucleoli are discernible in this confocal image of immunofluorescently stained colon cancer cells (DLD1) probed for nucleolar protein – fibrillarin (green) and counterstained with DAPI (blue).

Figure: 2 & Figure: 3: A representative Spectral Karyotyping (SKY) image of chromosomes from normal human hematopoietic cells. (A) Inverted DAPI stained image of human chromosomes (B) Spectral karyotyping dyes detect 23 pairs of human chromosomes and (C) Pseudocolours showing SKY classification of human chromosomes based on multicolour dye hybridization in (B).