Aparellament i sinapsi en oòcits humans

Abstract

Aneuploidy is the major cause of human miscarriages. These anomalies are mainly caused by errors produced during female gametogenesis. In mammals, gametogenesis presents a sexual dimorphism: while in the males, this is a continuous process that starts at puberty and it is carried on during most of the adult life-span, in the females it starts during fetal life, it is blocked before completion before birth and it is not resumed until sexual maturity is achieved. Thus, due to the difficult sample collection, although its major implication in human aneuploidy etiology, most of the studies performed uses male samples. During gametogenesis, cells undergoes meiosis which reduces the genome to haploidy thanks to a single replication of the DNA followed by two rounds of cell divisions. This way species diploidy is maintained after fertilization. During the first meiotic division, homologue chromosomes pair and exchange material between them. These processes are thought to be crucial for the progress of the meiotic division. In this thesis dissertation a complete analysis of the pairing process in human oocytes as well as the relationship between pairing and recombination in humans is presented. Our results, obtained both in euploid and aneuploid oocytes, show homologues pairing process is an extremely efficient process, leading to a very low error rate. This is significantly lower than the frequency of unbalanced oocytes or aneupoid embryos found in humans, suggesting that other processes, as recombination, may be involved in the production of unbalanced oocytes. This study also reports the existence of important differences between human and mouse meiosis that would promote the search of another animal model in order to study particular aspects of human reproduction. Moreover, in this thesis dissertation a new human oocyte culture technique is described. In our opinion, this technique may enable the study in deep of the human female meiotic prophase in a near future.

Date of Award	14 Jul 2005
Original language	Undefined/Unknown
Supervisor	Josep Egozcue Cuixart (Director) & Montserrat García Caldés (Director)