The Presence of the Y-Chromosome, Not the Absence of the Second X-Chromosome, Alters the mRNA Levels Stored in the Fully Grown XY Mouse Oocyte

Abstract

The oocytes of B6.YTIR sex-reversed female mouse mature in culture but fail to develop after fertilization because of their cytoplasmic defects. To identify the defective components, we compared the gene expression profiles between the fully-grown oocytes of B6.YTIR (XY) females and those of their XX littermates by cDNA microarray. 173 genes were found to be higher and 485 genes were lower in XY oocytes than in XX oocytes by at least 2-fold. We compared the transcript levels of selected genes by RT-PCR in XY and XX oocytes, as well as in XO oocytes missing paternal X-chromosomes. All genes tested showed comparable transcript levels between XX and XO oocytes, indicating that mRNA accumulation is well adjusted in XO oocytes. By contrast, in addition to Y-encoded genes, many genes showed significantly different transcript levels in XY oocytes. We speculate that the presence of the Y-chromosome, rather than the absence of the second X-chromosome, caused dramatic changes in the gene expression profile in the XY fully-grown oocyte.

Bi-directional communication with the cumulus cells is involved in the deficiency of XY oocytes in the components essential for proper second meiotic spindle assembly

“…However, we found that Bmp15 transcript levels were comparable between XY and XX oocytes. Our previous study has shown that many more X-linked genes have equal transcript levels in XX, XO, and XY fully-grown oocytes despite their different gene dosages, suggesting that the storage of mRNAs in fully grown oocytes is well adjusted (Xu et al, 2012). We predict that OSFs other than BMP15 or FGF8 may be deficient in XY oocytes.…”

“…Our previous cDNA-microarray results suggested that gene expression in the XY fully grown oocyte has been altered by a limited supply of glucose or energy source from its neighbouring CCs (Xu et al, 2012). Since the oocyte cannot directly metabolize glucose, its surrounding CCs provide glucose intermediates to the oocyte for energy production (Biggers et al, 1967;Donahue and Stern, 1968).…”

“…This spindle defects can largely be attributed to the XY ooplasm because healthy pups are produced from the nuclei of XY oocytes which have been transferred into enucleated XX oocytes (Obata et al, 2008). To identify the defective cytoplasmic components in the XY oocyte, we compared gene expression profiles in the fullygrown oocytes collected from XX and XY females by cDNAmicroarray (Xu et al, 2012). The results suggested that expression of a couple of genes, in addition to many others, is altered in the XY oocyte in response to a shortage of glucose or energy supply.…”

Melanoma tumors exhibit a variable but distinct metabolic signature

“…Our data are in agreement with literature that virtually all melanocytic tumors are devoid of CAIX and XII. [11,12] Although HIF-1α can be induced by low oxygen levels, many other pathways are now known.…”

Sex Reversal in Non-Human Placental Mammals

“…They generally suffer from the lack of an X chromosome meiotic partner and the presence of a Y chromosome. This leads to meiotic disruption or arrest, decreased oocyte survival, poor preimplantation rates, increased embryonic loss [Villemure et al, 2007;Alton et al, 2008;Xu et al, 2012], and for those that manage to go beyond meiosis, fertility is still greatly reduced as 25% of embryos produced (YY) are non-viable. Clearly, the X * Y females of the 4 taxa manage to bypass the meiotic constraints somehow, but they are still expected to face the high reproductive cost of the YY embryo loss.…”