Decrease in expression of maternal effect gene Mater is associated with maternal ageing in mice

Abstract

Study hypothesis: What factors in mouse oocytes are involved in the ageing-related decline in oocyte quality?

Study finding: The maternal effect gene Mater is involved in ageing-related oocyte quality decline in mice.

What is known already: Premature loss of centromere cohesion is a hallmark of ageing-related oocyte quality decline; the maternal effect gene Mater (maternal antigen that embryos require, also known as Nlrp5) is required for preimplantation embryo development beyond the 2-cell stage, and mRNA expression of Mater decreases with maternal ageing.

Study design, samples/materials, methods: Mater protein expression level in mature oocytes from 7 young (5-8 weeks old) to 7 old mice (41-68 weeks old) was compared by immunoblotting analysis. Wild-type and Mater-null mice were used to examine whether Mater is necessary for maintaining normal centromere cohesion by means of cytogenetic karyotyping, time-lapse confocal microscopy and immunofluorescence staining.

Main results and the role of chance: Mater protein is decreased in mature oocytes from old versus young mice (P = 0.0022). Depletion of Mater from oocytes leads to a reduction in centromere cohesion, manifested by precocious sister chromatid separation, enlargement of sister centromere distance and misalignment of chromosomes in the metaphase plate during meiosis I and II.

Limitations, reasons for caution: This study was conducted in mice. Whether or not the results are applicable to human remains further elucidation. In addition, we were unable to confirm if the strain of mice (C57BL/6XSv129) at the age of 41-68 weeks old has the 'cohesin-loss' phenotype.

Wider implications of the findings: Investigating Mater's functional mechanisms could provide fresh insights into understanding how the ageing-related oocyte quality decline occurs.

Large scale data: N/A.

Study funding and competing interests: This work was supported by the research grant from Chinese NSFC to P.Z. (31071274). We have no conflict of interests to declare.

Keywords: Mater; aneuploidy; cohesion; maternal ageing; oocyte.