عنوان

Characterization and Mapping of Meiotic Mutants in C. elegans

Number

TL53727

.Language of Text, Soundtrack etc

انگلیسی

Title Proper

Characterization and Mapping of Meiotic Mutants in C. elegans

General Material Designation

[Thesis]

First Statement of Responsibility

Tabassum, Muhammad

Subsequent Statement of Responsibility

Zetka, Monique

Name of Publisher, Distributor, etc.

McGill University (Canada)

Date of Publication, Distribution, etc.

2019

Text of Note

139 p.

Dissertation or thesis details and type of degree

M.S.

Body granting the degree

McGill University (Canada)

Text preceding or following the note

2019

Text of Note

Meiosis is a specialized cell division program during which a reduction in the genetic content from diploid progenitor cells leads to the formation of haploid gametes, which contain only one copy of each chromosome. This process is crucial for sexual reproduction, where the fusion of two complementing haploid gametes restores diploidy in the resulting zygote. Critical to the production of euploid gametes is the segregation of homologous chromosomes to opposing poles of the cell during meiosis I. This process is carefully choreographed, and requires coordination of three key steps: pairing, synapsis and recombination. Using immunohistochemical analysis, the landmark prophase I substages were examined in the nematode C. elegans, a powerful model organism for the study of meiosis. Process-centred phenotypic profiling of eight previously isolated putative meiotic alleles was performed in the Zetka Laboratory in a bid to decrypt their meiotic roles. Genetic mapping was performed in parallel, which enabled a comparison of these alleles with previously known meiotic genes. Analysis of vv63, vv36 and vv100 mutants revealed elevated levels of embryonic lethality and incidence of males, together with the presence of univalents at diakinesis, indicating that these mutants are defective in crossover formation. vv67 mutants displayed increased embryonic lethality and an extended transition zone, indicative of a cell cycle delay. However, diakinesis oocytes were virtually indistinguishable from wild type, raising the possibility that the major defect responsible for embryonic lethality in this mutant lies downstream of prophase I. vv58 and vv35 mutants exhibited defects in chromosome morphology at the transition zone, with an aberrant axis morphology at pachytene typical of synapsis defective mutants, corroborated by the aberrant SYP-1 staining in the mutant germlines. Furthermore, the lack of bivalent formation together with the presence of DNA fragments in diakinesis oocytes was suggestive of defects in double strand break (DSB) repair in these mutant alleles. vv95 mutants appeared to be proficient in pairing and synapsis, with chromosome morphology at each substage of prophase I indistinguishable from wild type as well. However, a closer examination with the highly conserved recombinase RAD-51 revealed major defects in DSB regulation and/or DSB resolution. Analysis of vv70 mutants revealed anomalies at each substage of prophase I, accompanied by aberrant chromosome morphologies and a complete lack of bivalent formation. The major defect in vv70 was revealed to be a failure in introducing programmed DSBs during prophase I. The vv70 mutation may therefore affect a novel meiotic gene, which intriguingly, could be involved in both recombination initiation and chromosome morphogenesis. Collectively, the mutant alleles characterized in this study exhibited anomalies in all major prophase I processes and provide a valuable resource for the further study of meiosis.

Subject Term

Biology

Subject Term

Cellular biology

Subject Term

Genetics

Tabassum, Muhammad

Zetka, Monique

McGill University (Canada)

Electronic name

p

[Thesis]

276903

a

Y