Discovery of the youngest sex chromosomes reveals first case of convergent co-option of ancestral autosomes in turtles.

Most turtle species possess temperature-dependent sex determination (TSD), but genotypic sex determination (GSD) has evolved multiple times independently from the TSD ancestral condition. GSD in animals typically involves sex chromosomes, yet the sex chromosome system of only 9 out of 18 known GSD turtles has been characterized. Here, we combine comparative genome hybridization (CGH) and BAC clone fluorescent in situ hybridization (BAC FISH) to identify a macro-chromosome XX/XY system in the GSD wood turtle Glyptemys insculpta (GIN), the youngest known sex chromosomes in chelonians (8-20 My old). Comparative analyses show that GIN-X/Y is homologous to chromosome 4 of Chrysemys picta (CPI) painted turtles, chromosome 5 of Gallus gallus chicken, and thus to the X/Y sex chromosomes of Siebenrockiella crassicollis black marsh turtles. We tentatively assign the gene content of the mapped BACs from CPI chromosome 4 (CPI-4) to GIN-X/Y. Chromosomal rearrangements were detected in G. insculpta sex chromosome pair that co-localize with the male-specific region of GIN-Y and encompass a gene involved in sexual development (Wt1-a putative master gene in TSD turtles). Such inversions may have mediated the divergence of G. insculpta sex chromosome pair and facilitated GSD evolution in this turtle. Our results illuminate the structure, origin, and evolution of sex chromosomes in G. insculpta and reveal the first case of convergent co-option of an autosomal pair as sex chromosomes within chelonians.

A systematic review and meta-analysis of the effects of respiratory muscle training on pulmonary function in tetraplegia.

STUDY DESIGN: Systematic reviewObjectives:To determine the effect of respiratory muscle training (RMT) on pulmonary function in tetraplegia. METHODS: A comprehensive search of the research literature included MEDLINE, EMBASE, CINAHL, ISI Web of Science, PubMed, the relevant Cochrane and clinical trials registers and hand-searching the reference lists of appropriate papers. There was no language restriction. All randomised controlled trials that involved RMT vs. control were considered for inclusion. Two reviewers independently selected articles for inclusion, evaluated the methodological quality and extracted data. Additional information was sought from the authors when necessary. RESULTS: Eleven studies (212 participants) were included. A significant benefit of RMT was revealed for five outcomes: vital capacity (mean difference (95% confidence interval))=0.41(0.17-0.64) l, maximal inspiratory pressure=10.66(3.59, 17.72) cmH2O, maximal expiratory pressure=10.31(2.80-17.82) cmH2O, maximum voluntary ventilation=17.51(5.20, 29.81) l min(-1) and inspiratory capacity=0.35 (0.05, 0.65) l. No effect was found for total lung capacity, peak expiratory flow rate, functional residual capacity, residual volume, expiratory reserve volume or forced expiratory volume in 1 second. CONCLUSION: RMT increases respiratory strength, function and endurance during the period of training. Further research is needed to determine optimum dosages and duration of effect. This article is based in part on a Cochrane review published in the Cochrane Database of Systematic Reviews (CDSR) 2013, DOI:10.1002/14651858.CD008507.pub2. Cochrane reviews are regularly updated as new evidence emerges and in response to feedback, and the CDSR should be consulted for the most recent version of the review.