Unknown,Transcriptomics,Genomics,Proteomics

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Dosage Compensation of an Aneuploid Genome in Mouse Spermatogenic Cells

ABSTRACT: Autosomal trisomies and monosomies bring serious threats to embryonic development through transcriptional disarray primarily caused by the dosage effect of the aneuploid part of the genome. The present study compared the effect of a mouse viable 30 Mb segmental trisomy on the genome-wide transcriptional profile of somatic (liver) cells and male germ cells. While the 1.6-fold change in expression of triplicated genes reflected the gene dosage in liver cells, the extra copy was almost fully compensated in early pachytene spermatocytes, showing 1.18-fold increase. Allele-specific semi-quantitative evaluation of steady-state mRNA levels of the triplicated Amdhd2 gene revealed silencing evenly distributed among all three copies in these meiotic cells. Although more pronounced, the dosage compensation of trisomic genes was concordant with the incidence of HORMAD2 and Î³H2AX markers of unsynapsed chromatin. The possible explanations include insufficient sensitivity to detect both MSUC markers in the 30 Mb region of the chromosome, or an early silencing effect of another epigenetic factor. Taken together, our results indicate that the meiotic silencing of unsynapsed chromatin is the major but not the only factor driving the dosage compensation of triplicated genes in primary spermatocytes. We compared the global expression profiles in isolated popoulations of meiotic cells and liver cells of Ts43H trisomic males and their t121/D17 euploid siblings.

ORGANISM(S): Mus musculus

SUBMITTER: David Homolka

PROVIDER: E-GEOD-54683 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Balanced constitutional reciprocal translocations are the most common structural chromosomal rearrangements identiï¬ed in man and pigs. Carriers are generally phenotypically normal, but such rearrangements frequently lead to reproductive disorders. In reciprocal translocation heterozygotes, the homologous regions of the normal and derivative chromosomes involved in the rearrangement pair during the prophase of the first meiotic division, thanks to the synaptonemal complex (SC), and form a particular structure called quadrivalent. In some cases, chromosomal regions (within the quadrivalent) remain unsynapsed, especially around the breakpoints, which may trigger meiosis checkpoints leading to spermatogenesis arrest at the pachytene stage. Several hypotheses have been proposed to explain such effects of pairing failure on gametogenesis. The first one is an altered transcription of the genes located on the unpaired segments. Indeed, studies conducted in mice revealed a transcriptional repression of unpaired regions by a specific mechanism called âMeiotic Silencing of Unsynapsed Chromatinâ (MSUC) in individuals with a partial or total spermatogenesis arrest (Turner et al., 2005). If some genes necessary for the proper course of meiosis are located in such unsynapsed genomic regions, MSUC may result in an arrest of the meiotic division. Secondly, associations between the âquadrivalentâ and the XY bivalent which is transcriptionally silenced by a phenomenon known as meiotic sex chromosome inactivation (MSCI, (Turner, 2007) were also observed in individuals with altered semen parameters (azoospermic or oligospemic) (Oliver-Bonet et al., 2005; Sciurano et al., 2007a, 2012). Such an association could result in a partial reactivation of the XY body (XYB) leading to the expression of some genes located on the X chromosome (Lifschytz and Lindsley, 1972), or result in the spreading of the XYB inactivation towards the autosomal segments attached to the XYB, without reactivation of the latter (Jaafar et al., 1993). Beyond the potential spermatogenesis failure mentioned above, reciprocal translocations are systematically responsible for the production of genetically unbalanced gametes. Here we report the detailed analysis of the whole meiotic process (from spermatocytes to spermatozoa) in the case of a constitutional balanced reciprocal translocation responsible for severe oligoasthenoteratospermia. Total RNA was extracted in 3 replicates from testicular biopsies control animals, from testicular biopsy of an oligospermic boar and from testicular biopsy of a severe oligo-astheno-teratospermic boar carrier of the trcp(1;14) reciprocal translocation.

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Dosage Compensation of an Aneuploid Genome in Mouse Spermatogenic Cells

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