Synapsis and Meiotic Recombination in Male Chinese Muntjac (Muntiacus reevesi)

The muntjacs (Muntiacus, Cervidae) have been extensively studied in terms of chromosomal and karyotypic evolution. However, little is known about their meiotic chromosomes particularly the recombination patterns of homologous chromosomes. We used immunostained surface spreads to visualise synaptonemal complexes (SCs), recombination foci and kinetochores with antibodies against marker proteins. As in other mammals pachytene was the longest stage of meiotic prophase. 39.4% of XY bivalents lacked MLH1 foci compared to less than 0.5% of autosomes. The average number of MLH1 foci per pachytene cell in M. reevesi was 29.8. The distribution of MLH1 foci differed from other mammals. On SCs with one focus, the distribution was more even in M. reevesi than in other mammals; for SCs that have two or more MLH1 foci, usually there was a larger peak in the sub-centromere region than other regions on SC in M. reevesi. Additionally, there was a lower level of interference between foci in M. reevesi than in mouse or human. These observations may suggest that the regulation of homologous recombination in M. reevesi is slightly different from other mammals and will improve our understanding of the regulation of meiotic recombination, with respect to recombination frequency and position

SpermatogenesisOnline 1.0:a resource for spermatogenesis based on manual literature curation and genome-wide data mining

Human infertility affects 10–15% of couples, half of which is attributed to the male partner. Abnormal spermatogenesis is a major cause of male infertility. Characterizing the genes involved in spermatogenesis is fundamental to understand the mechanisms underlying this biological process and in developing treatments for male infertility. Although many genes have been implicated in spermatogenesis, no dedicated bioinformatic resource for spermatogenesis is available. We have developed such a database, SpermatogenesisOnline 1.0 (http://mcg.ustc.edu.cn/sdap1/spermgenes/), using manual curation from 30 233 articles published before 1 May 2012. It provides detailed information for 1666 genes reported to participate in spermatogenesis in 37 organisms. Based on the analysis of these genes, we developed an algorithm, Greed AUC Stepwise (GAS) model, which predicted 762 genes to participate in spermatogenesis (GAS probability >0.5) based on genome-wide transcriptional data in Mus musculus testis from the ArrayExpress database. These predicted and experimentally verified genes were annotated, with several identical spermatogenesis-related GO terms being enriched for both classes. Furthermore, protein–protein interaction analysis indicates direct interactions of predicted genes with the experimentally verified ones, which supports the reliability of GAS. The strategy (manual curation and data mining) used to develop SpermatogenesisOnline 1.0 can be easily extended to other biological processes

Self-patterning of human stem cells into post-implantation lineages

Investigating human development is a substantial scientific challenge due to the technical and ethical limitations of working with embryonic samples. In the face of these difficulties, stem cells have provided an alternative to experimentally model inaccessible stages of human development in vitro1,2,3,4,5,6,7,8,9,10,11,12,13. Here we show that human pluripotent stem cells can be triggered to self-organize into three-dimensional structures that recapitulate some key spatiotemporal events of early human post-implantation embryonic development. Our system reproducibly captures spontaneous differentiation and co-development of embryonic epiblast-like and extra-embryonic hypoblast-like lineages, establishes key signalling hubs with secreted modulators and undergoes symmetry breaking-like events. Single-cell transcriptomics confirms differentiation into diverse cell states of the perigastrulating human embryo14,15 without establishing placental cell types, including signatures of post-implantation epiblast, amniotic ectoderm, primitive streak, mesoderm, early extra-embryonic endoderm, as well as initial yolk sac induction. Collectively, our system captures key features of human embryonic development spanning from Carnegie stage16 4–7, offering a reproducible, tractable and scalable experimental platform to understand the basic cellular and molecular mechanisms that underlie human development, including new opportunities to dissect congenital pathologies with high throughput

Distribution of MLH1 foci in each autosomal SC of <i>M. reevesi</i>^*.

<p>*Data from 170 cells.</p>#<p>SCs were numbered arbitrarily based on their length in each cell.</p

Mean MLH1 foci per cell, frequency of autosomal bivalents with 0–4 MLH1 foci, percentage of cells with an MLH1 focus in XY pair of testicular samples of <i>M. reevesi</i>.

<p>Mean MLH1 foci per cell, frequency of autosomal bivalents with 0–4 MLH1 foci, percentage of cells with an MLH1 focus in XY pair of testicular samples of <i>M. reevesi</i>.</p

Average absolute and relative lengths for <i>M. reevesi</i> autosomal SCs.

#<p>SCs were numbered arbitrarily based on their length in each cell.</p

Relationships between autosomal SC length and meiotic recombination frequency in pachytene of male <i>M. reevesi</i> (n = 170).

<p>(A) Correlation between the frequency of XY pair with an MLH1 focus and total autosomal SC length in a cell. The cells have been divided into four groups based on their total autosomal SC length. (B) A positive correlation between the mean number of MLH1 foci and mean length for individual autosomal SCs (Pearson correlation coefficient = 0.99, <i>P</i><0.0001).</p

Distribution of MLH1 foci on autosomal SCs from 170 spermatocytes of Chinese muntjac.

<p>The SCs have been divided into five groups based on length, SCs 1–3, SCs 4–6, SCs 7–13, SCs 14–19, and SCs 20–22. The X-axis represents the positions on the SCs from the centromeric end (left) to the distal telomere (right), the marks on this axis are separated by 0.05 of the mean absolute SC length for each group. The absolute length (micrometer) scale is shown on the bottom of the last figure for each group. The y-axis indicates the frequency of MLH1 foci in each 0.05 SC interval. For each group, in order from top to bottom, the histograms show the results for SCs with different number MLH1 foci, and the overall frequencies. Data were not displayed when the MLH1 foci<100. n is the number of MLH1 foci analysed.</p

Mean distances between two adjacent MLH1 foci in SC groups of different length.

a<p>Significant different , one-way ANOVA, <i>P</i><0.01.</p>b<p>Not included in one-way ANOVA test because <10 observations.</p