DEFINING THE MECHANISM OF POLAR CHROMOSOME CONGRESSION DURING PROMETAPHASE

doctoral thesis

• Title (english): ODREĐIVANJE MEHANIZMA KONGRESIJE POLARNIH KROMOSOMA TIJEKOM PROMETAFAZE
• Author: Isabella Koprivec
• Mentor: Iva Marija Tolić (mentor)
• Committee member: Petar Ozretić (predsjednik povjerenstva)
• Committee member: Biljana Balen (član povjerenstva)
• Granter: University of Zagreb; Faculty of Science; (Department of Biology); Zagreb
• Defense date and country: 2024-10-09, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Biology
• Universal decimal classification (UDC): 576 - Cellular and subcellular biology. Cytology

Abstract

Chromosomes that first attach to the mitotic spindle behind the spindle pole (i.e., polar) are delayed in alignment and prone to segregation errors. Nevertheless, their congression mechanism remains elusive. Using a unique combination of advanced microscopy techniques, I showed that polar chromosomes rely on the pivoting of chromosome-attached astral microtubules around the centrosome to cross the pole. By altering the KIF11/Eg5 activity to reverse, restore, or block spindle elongation, I demonstrated that spindle elongation directs pivoting. I also revealed impaired spindle elongation as a major cause of unalignment for polar chromosomes in hTERT-immortalized retinal pigment epithelial RPE1 cells after TTK/MPS1 kinase inhibition and in the high-grade serous ovarian carcinoma OVSAHO cells. Increasing spindle elongation efficiency by depleting KIF4A rescued unaligned chromosomes in OVSAHO cells, supporting the conclusion that polar chromosomes depend on spindle elongation-driven pivoting to cross the pole and avoid missegregation.

Abstract (english)

Polarni kromosomi stvaraju prvu vezu s diobenim vretenom iza pola te pokazuju sklonost kasnom poravnanju i stvaranju kromosomskih grešaka. Unatoč tome, njihov mehanizam kongresije još uvijek je nerazjašnjen. Koristeći jedinstvenu kombinaciju naprednih mikroskopijskih metoda, predlažem hipotezu da polarni kromosomi prelaze pol zahvaljujući pivotiranju astralnih mikrotubula vezanih za kromosome oko centrosoma. Promjenom aktivnosti KIF11/Eg5 kako bi se narušilo, popravilo ili zaustavilo produljenje diobenog vretena, pokazala sam da produljenje vretena usmjerava pivotiranje. Također, pokazala sam da narušeno produljenje vretena uzrokuje pojavu neporavnanih polarnih kromosoma u hTERT-imortaliziranim retinalnim pigmentnim epitelnim stanicama RPE1 s inhibiranom kinazom TTK/MPS1, kao i u stanicama seroznog raka jajnika visokog stupnja malignosti OVSAHO. Povećanje učinkovitosti produljenja diobenog vretena deplecijom KIF4A spasilo je neporavnane kromosome u stanicama OVSAHO, što podržava hipotezu da polarni kromosomi ovise o pivotiranju vođenom produljenjem vretena kako bi uspješno prešli pol i izbjegli stvaranje grešaka tijekom diobe.

• Keywords: mitosis; prometaphase; chromosome congression; spindle elongation; polar chromosomes; unaligned chromosomes; microtubule pivoting
• Keywords (english): mitoza; prometafaza; kongresija kromosoma; produljenje vretena; polarni kromosomi; neporavnani kromosomi; pivotiranje mikrotubula
• Language: english
• URN:NBN: urn:nbn:hr:217:360022
• Promotion: 2024
• Project: Number: PZS-2019-02-7653; Title: Mehanizmi nastajanja snopova mikrotubula potrebni za sazrijevanje diobenog vretena; Title: Mechanisms of microtubule bundle formation required for spindle maturation; Acronym: SpindleForm; Leader: Iva Marija Tolić; Jurisdiction: Croatia; Funder: Hrvatska zaklada za znanost; Funding stream: Programme Research Cooperability
• Study programme: Title: Doctoral study; Study programme type: university; Study level: postgraduate; Academic / professional title: doktor/doktorica znanosti u području prirodnih znanosti (doktor/doktorica znanosti u području prirodnih znanosti)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2024-12-02 11:58:36