有丝分裂过程中染色体的精确分离对于维持细胞内基因组的稳定性至关重要，染色体错误分离会导致基因组不稳定性及染色体非整倍性，基因组不稳定性会引起多种人类疾病，包括出生缺陷，衰老，以及各种肿瘤。
我的实验室致力于研究细胞周期过程中调控染色体遗传和完整性的分子机制，主要聚焦于理解纺锤体组装检验点和姐妹染色体黏连这两个在细胞分裂过程中维持染色体正确分离的细胞体系和过程。
通过结合多学科的研究手段，我的实验室已经在染色体分离及基因组稳定性维持的分子机制领域做出了多项重要的原创性贡献。未来，我们将继续在这一领域进行探索。
The cohesin ring topologically entraps both sister chromatids, thereby establishing sister-chromatid cohesion. The mechanism of cohesion establishment during DNA replication is not understood. The current evidence suggests that cohesin and NIPBL interact with both DDK-modified MCM2–7 and replisome components bound to the active CMG replicative helicase. The former interaction is specific to metazoans whereas the latter is conserved from yeast to human. We will in vitro reconstitute both interactions with human cohesin, NIPBL, PDS5B, ESCO2 (the cohesin acetyltransferase), sororin, MCM2–7, DDK, and replisome components, and dissect these interactions using standard pulldown and crosslinking/mass spectrometry methods. We will determine the structures of the MCM–ESCO2, MCM–cohesin–NIPBL, replisome–cohesin–NIPBL, and endogenous cohesive cohesin–DNA complexes with cryo-EM. Establishing molecular details of the cohesin–replisome interactions will enable the design of separation-of-function replisome mutants that support DNA replication but not cohesion. We will examine the phenotypes of key mutants in human cells using a depletion-complementation strategy and established replication and cohesion assays. These biochemical, structural, and functional analyses will reveal how cohesive cohesin holds two sister chromatids and how cohesion establishment is coupled to DNA replication.
The diploid human genome consists of 6 billion nucleotides, which are assembled into 22 pairs of autosomes and 2 sex chromosomes. Chromosomes in a single human diploid cell, if linearly stitched together, span a length of more than 2 meters. They need to be folded to be housed in the cell nucleus with a diameter of about 10 µm. Chromosome folding occurs in a dynamic, structured way that regulates gene expression, and DNA replication and repair.
There are about 200 cell types in the human body. All have the same genome. It is the selective expression of specific subsets of genes in pluripotent stem cells that determines the cell fate. We hypothesize that dynamic 3D genome organization makes and breaks long-range interactions between distal DNA elements, including promoters and enhancers. As such, it shapes the gene expression landscape of the genome in response to developmental cues, thereby impacting cell fate decisions. Consistent with this hypothesis, we have recently shown that deletion of the cohesin subunit gene STAG2 in the nervous system causes delayed differentiation of the oligodendrocyte lineage, hypomyelination, and neurological defects.
We will further test this hypothesis using brain organoids derived from hESCs as the model system. We have successfully cultured human cerebral organoids from hESCs that have the expected cell types (e.g. neural progenitors, neurons, and oligodendrocytes) and tissue patterning (e.g. neural rosettes). In the future, we hope to establish the mechanism by which cohesin-mediated 3D genome organization regulates gene expression and cell fate decisions.
