A diminished zone, devoid of CENP-B

protein, along the centrosome axis in human cells.

Presenter: Marcos Peech

Co-Presenter(s):
Christian Casas, Lisa Hua

Presenter Status: Undergraduate student

Academic Year: 22-23

Semester: Spring

Faculty Mentor: Lisa Hua

Department: Biology

Funding Source/Sponsor: LSAMP

Other Funding Source/Program: NSF, CSUPERB, KORET, MESA Genentech

Screenshot URL: https://drive.google.com/uc?id=1wpZ3ZOESLlT7ob_jq9ergWFWCLVpRsni

Abstract:
It was recently discovered that homologous chromosomes are spatially segregated, or anti-paired, during mitosis in human cells (Hua and Mikawa, 2018). The spatial separation of homologous chromosomes form a haploid (1n) chromosome set on either side of the centrosome axis (Hua and Mikawa, 2018). This organization has been proposed to prevent homologous chromosome pairing in somatic cells, which can lead to abnormal recombination or gene misregulation (Koeman et al, 2008; Hua and Mikawa, 2018). However, the underlying mechanisms remain elusive. Recent data in the lab has shown the presence of a diminished zone devoid of centromeric DNA sequences of alpha satellite and cenpb box, along the centrosome axis in human cells at metaphase (Cai et al, https://www.biorxiv.org/content/10.1101/2023.03.27.534352v1). To test whether the diminished zone can also be visualized with a centromeric protein marker, we employed high resolution confocal microscopy, and immunofluorescence to the Centromeric protein B (CENP-B) , and γ-tubulin to visualize the centrosome axis for human metaphase cells. CENP-B has been shown to bind to the cenp-b box in human cells (Kuznetsova, Tanaka et al, 2001). Our data reveals that the diminished zone is also devoid of CENP-B positive staining, coincident with the boundary between two chromosome sets. Volume analysis of DNA staining along the diminished zone of CENP-B shows approximate equal halves. These results are consistent with prior results for the diminished zone that is devoid of DNA satellite staining. Taken together, the data suggest that the diminished zone is devoid of CENP-B protein and DNA satellite sequences, and may represent the boundary between the haploid chromosome sets. Our findings will contribute to a new model for understanding chromosome organization in human cells and its implications in disease.