Chr.Organization: 15, 16, and G2 D. Zone

Presenter: Samantha Smedshammer

Co-Presenter(s):
Demitri Shami

Presenter Status: Undergraduate student

Academic Year: 22-23

Semester: Spring

Faculty Mentor: Lisa Hua

Department: Biology

Funding Source/Sponsor: Koret Scholars Program

Abstract:
It was recently found that homologous chromosomes are spatially segregated during mitosis in human neonatal endothelial cells (Hua and Mikawa 2018). Individual homologous chromosomes of a pair were found to be segregated, or antipaired, along the centrosome axis, resulting in one complete haploid (1n) chromosome set on either side (Hua and Mikawa 2018). Loss of the haploid set, or antipairing, organization has been correlated with carcinogenesis (Hua and Mikawa 2018; Koeman et al 2008). The underlying mechanisms and persistence of haploid set organization throughout development remains unclear. Recent data from our lab has revealed a diminished zone, devoid of interchromosomal linkage components of DNA satellite sequences and the CENP-B protein along the centrosome axis between two chromosome groups at metaphase (Cai et al, https://www.biorxiv.org/content/ 10.1101/2023.03.27.534352v1). To investigate whether a diminished zone is present at other cell cycle stages, we performed 3D cell analysis of human endothelial cells stained with DNA fluorescent probes for satellite sequences at G2 interphase. Ɣ-tubulin immunofluorescence was used to visualize the centrosomes, a subcellular organelle in the cell. Employing four different approaches using nuclear axes (long/short), apical-basal axes, center of the nuclear volume, and the angle between centrosomes, our 3D analysis did not reveal a diminished zone at G2 interphase. The data suggests that a diminished zone may not be identifiable at G2 interphase. To test whether the antipairing organization present in neonatal endothelial cells persists into adulthood, we employed high resolution confocal microscopy, and chromosome painting to visualize chromosomes 15 and 16 in adult human endothelial cells. Our preliminary data shows that homologous chromosomes 15, and 16 both display a loss of antipairing, and show abnormal pairing. This data suggests that the antipairing mechanism present in neonatal cells may be lost in an adult cell line. Although future analysis for other chromosomes is necessary. Findings of our project will provide the necessary groundwork for future studies for understanding chromosome organization in human endothelial cells. These studies will contribute to our knowledge for fundamental cell biology with implications in human disease.