Ubc9 regulates mitosis and cell survival during zebrafish development

SUMOylation is a post-translational modification that affects many proteins. It requires enzymes like Ubc9, an E2 conjugating enzyme. Ubc9 is conserved across species and is involved in cell cycle regulation. Previous studies in yeast, nematodes, fruit flies, and mice show Ubc9's role in nuclear structure and chromosome segregation. However, its function during vertebrate development remains unclear. Zebrafish embryos offer a model to study Ubc9's role in vivo. This paper investigates Ubc9's function in zebrafish development. It addresses a gap in understanding how Ubc9 affects organogenesis in vertebrates. The study explores whether Ubc9 is essential for mitosis and cell survival in developing tissues.

This study aims to examine Ubc9's role in zebrafish development. It focuses on mitosis and cell survival during organogenesis. The authors use zebrafish embryos to model Ubc9 function in vertebrates. They investigate whether Ubc9 is required for G2/M transition. The study also explores how Ubc9 deficiency affects cell cycle progression. The researchers compare dominant-negative Ubc9 effects with antisense knockdown. They assess apoptosis and cell cycle markers in affected tissues. The goal is to determine Ubc9's in vivo necessity during vertebrate development.

The study uses zebrafish embryos to assess Ubc9 function. Researchers employ a dominant-negative Ubc9 construct. They also use antisense oligonucleotides to knock down zygotic ubc9. Apoptosis is detected using TUNEL staining and caspase activity. Mitotic markers are used to assess cell cycle progression. 5-Bromo-2'-deoxyuridine incorporation tracks S-phase cells. FACS analysis measures DNA content in affected tissues. The study compares morphological and developmental outcomes between groups.

Dominant-negative Ubc9 causes widespread apoptosis in embryos. Antisense knockdown leads to specific defects in cranial cartilage and eyes. Affected cartilage elements are normal in size but contain fewer cells. Mitotic markers show fewer chondrocyte precursors in mitosis. S-phase cell proportion remains unchanged in these tissues. FACS analysis reveals increased 4n and 8n DNA content in affected cells. Cells lacking Ubc9 may bypass mitosis without undergoing apoptosis. These cells continue DNA replication and developmental programs.

The study shows Ubc9 is required for G2/M transition in zebrafish embryos. Ubc9 deficiency leads to mitotic failure without necessarily causing apoptosis. Cells may continue DNA replication and developmental programs. Failed mitosis results in cells with higher DNA content. The findings suggest Ubc9's role in vertebrate organogenesis. The data support Ubc9's in vivo necessity during development. The study does not claim Ubc9 is essential for all cell functions. It highlights Ubc9's specific role in mitotic progression.