Biology subjects

Hua, L. L.

Publications and source records attributed to Hua, L. L..

4 recordsLinked to original sources

bioRxiv2026

Mitotic chromosomes are mechanically connected by chromatin-based interchromosome linkers

The spatial organization of chromosomes is crucial for gene regulation and genome stability. Metaphase chromosomes appear physically discrete from one another in conventional chromosome preparations. However, interchromosomal connections, or "linkers", have been observed among mitotic chromosomes, and may play important roles in coordinated chromosome movements and genome stability. We use micropipette-based isolation and manipulation to analyze interchromosome linkers between mammalian mitotic chromosomes. Pulling an isolated chromosome reveals that thin linkers connect them; CREST staining indicates their locations to be at centromeres. The linkers display linear elasticity and have a length-doubling force of approximately 300 pN, comparable to the length-doubling force of an entire metaphase chromosome. Enzymatic treatments demonstrate that the linkers are disrupted by DNase, but not by RNase, protease, or microtubule polymerization (spindle fiber) inhibitors, indicating that linker connectivity is based on DNA. Immunofluorescence experiments indicate that histones and topo II are on the linkers, with topo II organized into discrete foci spaced by approximately 0.4 Mbp. After prolonged metaphase arrest using spindle inhibitors isolated genomes do not display interchromosome linkers. Finally, experiments on intact cells show that interchromosome linkers containing CENP-B can be observed between mitotic chromosomes, indicating they are not an artifact of genome isolation.

genomics↗

bioRxiv2025

Steady-state epithelial apical flatness is characterized by MLCK morphodynamics and asynchronous Ca2+ oscillations, but not underlying ECM geometry

The canonical simple epithelium is a flat sheet-like tissue of horizontally packed cells. While the basal surface is delineated by the basement membrane of extracellular matrix (ECM), little is known about how a flat apical surface is maintained, or if apical/basal dynamics are coordinated. The current study tests the role of the apical domain, to define mechanisms involved in maintaining a flat apical geometry in an epithelium. When the basal geometry is modulated, Madin-Darby Canine Kidney (MDCK) cells adjust their morphology to maintain an overall apical flatness of the confluent layer. Pharmacological and transgenic disruption of non-muscle myosin ATPase, and MLCK activity results in an uneven apical structure, and overall loss of the flat geometry typical of a confluent epithelium. Surprisingly, transgenic experimentation showed that forces maintaining individual MDCK cell flatness are cell-autonomous. Finally, Ca2+ imaging reveals an asynchronous calcium flux across a confluent epithelium, suggesting a myosin II-mediated mechanism for maintaining a flat apical architecture. Our results highlight that apical/basal cellular surfaces may not be tightly coordinated, but rather independently regulated. This study provides a new paradigm for how apical flatness is regulated at steady state. Impact StatementO_LIHow surface flatness of an epithelium is established and maintained is unknown; the data reveal that apical flatness is controlled independently from basement membrane geometry, and require balancing of myosin II morphodynamics. C_LI

cell biology↗

bioRxiv2025

Higher frequency of homologous chromosome pairing in human adult aortic endothelial cells

We previously demonstrated that homologous chromosomes are spatially segregated, or antipaired, in neonatal human endothelial cells at metaphase/anaphase, which may help prevent abnormal recombination. However, it is unclear if this antipairing persists in adult endothelial cells. To test whether the antipairing, or one homolog per nuclear hemisphere motif, is conserved in adult endothelial cells, we examined human aortic endothelial cells at metaphase. Using ImmunoFISH and high-resolution confocal microscopy to visualize the chromosomes and centrosomes, we found that small homologous chromosomes 13, 15, 17, 19, 21, 22, and the sex chromosomes, XY, exhibit a loss of spatial segregation in human adult aortic endothelial cells. In addition, fewer adult endothelial cells showed segregation for the larger chromosomes 1, 4, and XX, as compared to neonatal endothelial cells. Notably, we observed a higher frequency of abnormal pairing in both small and large chromosomes in adult aortic endothelial cells as compared to neonatal umbilical vein endothelial cells. These findings suggest that mechanisms governing chromosome antipairing may decline with aortic endothelial cell age. Summary StatementA higher frequency of homologous chromosome pairing is observed in human adult aortic endothelial cells as compared to neonatal umbilical vein endothelial cells.

cell biology↗

bioRxiv2023

Ipsilateral restriction of chromosome movement along a centrosome, and apical-basal axis during the cell cycle

Little is known about how distance between homologous chromosomes are controlled during the cell cycle. Here, we show that the distribution of centromere components display two discrete clusters placed to either side of the centrosome and apical/basal axis from prophase to G1 interphase. 4-Dimensional live cell imaging analysis of centromere and centrosome tracking reveals that centromeres oscillate largely within one cluster, but do not cross over to the other cluster. We propose a model of an axis-dependent ipsilateral restriction of chromosome oscillations throughout mitosis.

cell biology↗