The Missing LINC: The Relationship Between Nuclear Structure and Epigenetic Regulation

The Arabidopsis LINC proteins are nuclear coiled-coil proteins suspected to be analogs of lamin proteins, which compose the nuclear lamina in animal cells. A mutation in the LINC1 gene causes small, round nuclei rather than the normal, rod or spindle shaped nuclei, leading to the hypothesis that mutation of this gene might also have great effects on nuclear organization of the plant cell. For example, this compacting of the nucleus has been shown to decrease the number of chromocenters, regions of dense DNA packaging where centromeres and other repetitive DNA are stored in interphase. However, it is unknown whether the smaller space within a linc1 nucleus affects epigenetic regulation, the activation and silencing of genes without nucleotide sequence changes. I tested several types of DNA sequences found in chromocenters for either a decrease in cytosine methylation, signaling a loss of heterochromatin, or an increase indicating compaction of existing heterochromatin. The evidence of my experiments to date has been inconclusive, showing little to no qualitative shifts in cytosine methylation in linc mutants. The elucidation of the effects of linc mutations could lead to a greater understanding of eukaryotic nuclear structure in general, allowing for greater knowledge in fields even as far-reaching as animal systems.