Identification of mediator complex 26 (Crsp7) gametologs on platypus X1 and Y5 sex chromosomes: a candidate testis-determining gene in monotremes?

The basal lineage of monotremes features an extraordinarily complex sex chromosome system which has provided novel insights into the evolution of mammalian sex chromosomes. Recently, sequence information from autosomes, X chromosomes, and XY-shared pseudoautosomal regions has become available. However, no gene has so far been described on any of the Y chromosome-specific regions. We analyzed sequences derived from Y-specific BAC clones to identify genes with potentially male-specific function. Here, we report the identification and characterization of the mediator complex protein gametologs on platypus Y5 (Crspy). We also identified the X-chromosomal copy which unexpectedly maps to X1 (Crspx). Sequence comparison shows extensive divergence between the X and Y copy, but we found no significant positive selection on either gametolog. Expression analysis shows widespread expression of Crspx. Crspy is expressed exclusively in males with particularly strong expression in testis and kidney. Reporter gene assays to investigate whether Crspx/y can act on the recently discovered mouse Sox9 testis-specific enhancer element did reveal a modest effect together with mouse Sox9 + Sf1, but showed overall no significant upregulation of the reporter gene. This is the first report of a differentiated functional male-specific gene on platypus Y chromosomes, providing new insights into sex chromosome evolution and a candidate gene for male-specific function in monotremes.

Comparison of the Asleep-Awake-Asleep Technique and Monitored Anesthesia Care During Awake Craniotomy: A Systematic Review and Meta-analysis.

Awake craniotomy (AC) is the preferred surgical option for intractable epilepsy and resection of tumors adjacent to or within eloquent cortical areas. Monitored anesthesia care (MAC) or an asleep-awake-asleep (SAS) technique is most widely used during AC. We used a random-effects modeled meta-analysis to synthesize the most recent evidence to determine whether MAC or SAS is safer and more effective for AC. We included randomized controlled trials and observational studies that explored the incidence of AC failure, duration of surgery, and hospital length of stay in adult patients undergoing AC. Eighteen studies were included in the final analysis. MAC was associated with a lower risk of AC failure when compared with SAS (global pooled proportion MAC vs. SAS 1% vs. 4%; odds ratio [ORs]: 0.28; 95% confidence interval [CI]: 0.11-0.71; P=0.007) and shorter surgical procedure time (global pooled mean MAC vs. SAS 224.44 vs. 327.94 min; mean difference, -48.76 min; 95% CI: -61.55 to -35.97; P<0.00001). SAS was associated with fewer intraoperative seizures (global pooled proportion MAC vs. SAS 10% vs. 4%; OR: 2.38; 95% CI: 1.05-5.39; P=0.04). There were no differences in intraoperative nausea and vomiting between the techniques (global pooled proportion MAC vs. SAS: 4% vs. 8%; OR: 0.86; 95% CI: 0.30-2.45; P=0.78). Length of stay was shorter in the MAC group (MAC vs. SAS 3.96 vs. 6.75 days; mean difference, -1.30; 95% CI: -2.69 to 0.10; P=0.07). In summary, MAC was associated with lower AC failure rates and shorter procedure time compared with SAS, whereas SAS was associated with a lower incidence of intraoperative seizures. However, there was a high risk of bias and other limitations in the studies included in this review, so the superiority of 1 technique over the other needs to be confirmed in larger randomized studies.

Chloroplastic photorespiratory bypass increases photosynthesis and biomass production in Arabidopsis thaliana.

We introduced the Escherichia coli glycolate catabolic pathway into Arabidopsis thaliana chloroplasts to reduce the loss of fixed carbon and nitrogen that occurs in C(3) plants when phosphoglycolate, an inevitable by-product of photosynthesis, is recycled by photorespiration. Using step-wise nuclear transformation with five chloroplast-targeted bacterial genes encoding glycolate dehydrogenase, glyoxylate carboligase and tartronic semialdehyde reductase, we generated plants in which chloroplastic glycolate is converted directly to glycerate. This reduces, but does not eliminate, flux of photorespiratory metabolites through peroxisomes and mitochondria. Transgenic plants grew faster, produced more shoot and root biomass, and contained more soluble sugars, reflecting reduced photorespiration and enhanced photosynthesis that correlated with an increased chloroplastic CO(2) concentration in the vicinity of ribulose-1,5-bisphosphate carboxylase/oxygenase. These effects are evident after overexpression of the three subunits of glycolate dehydrogenase, but enhanced by introducing the complete bacterial glycolate catabolic pathway. Diverting chloroplastic glycolate from photorespiration may improve the productivity of crops with C(3) photosynthesis.

Characterizing the mouse ES cell transcriptome with Illumina sequencing.

Large datasets generated by Illumina sequencing are ideally suited to transcriptome characterization. We generated 3,052,501 27-mer reads from F1 mouse embryonic stem (ES) cell cDNA. Using the ELAND alignment tool, 74.5% of reads matched sequenced mouse resources, <1% were contaminants, and 3.7% failed quality control. Of the reads, 21.6% did not match mouse sequences using ELAND, but most of them were successfully aligned with mouse mRNAs using MegaBLAST. We conclude that most of the reads in the dataset are derived from mouse transcripts. A total of 14,434 mouse RefSeq genes were represented by at least 1 read. A Pearson correlation coefficient of 0.7 between Illumina sequencing and Illumina array expression data suggested similar results for both technologies. A weak 3' bias of reads was found. Reads from genes with low expression had lower GC content than the corresponding RefSeq genes, indicating a GC bias. Biases were confirmed with further Illumina read datasets generated with cDNA from mouse brain and from mutagen-treated F1 ES cells. We calculated relative expression values, because transcript length and read number were correlated. In the absence of signal saturation or background noise, we believe that short-read sequencing technologies will have a major impact on gene expression studies in the near future.

Mitochondrial glycolate oxidation contributes to photorespiration in higher plants.

The oxidation of glycolate to glyoxylate is an important reaction step in photorespiration. Land plants and charophycean green algae oxidize glycolate in the peroxisome using oxygen as a co-factor, whereas chlorophycean green algae use a mitochondrial glycolate dehydrogenase (GDH) with organic co-factors. Previous analyses revealed the existence of a GDH in the mitochondria of Arabidopsis thaliana (AtGDH). In this study, the contribution of AtGDH to photorespiration was characterized. Both RNA abundance and mitochondrial GDH activity were up-regulated under photorespiratory growth conditions. Labelling experiments indicated that glycolate oxidation in mitochondrial extracts is coupled to CO(2) release. This effect could be enhanced by adding co-factors for aminotransferases, but is inhibited by the addition of glycine. T-DNA insertion lines for AtGDH show a drastic reduction in mitochondrial GDH activity and CO(2) release from glycolate. Furthermore, photorespiration is reduced in these mutant lines compared with the wild type, as revealed by determination of the post-illumination CO(2) burst and the glycine/serine ratio under photorespiratory growth conditions. The data show that mitochondrial glycolate oxidation contributes to photorespiration in higher plants. This indicates the conservation of chlorophycean photorespiration in streptophytes despite the evolution of leaf-type peroxisomes.