Loss of ATRX in Chondrocytes Has Minimal Effects on Skeletal Development

BACKGROUND:Mutations in the human ATRX gene cause developmental defects, including skeletal deformities and dwarfism. ATRX encodes a chromatin remodeling protein, however the role of ATRX in skeletal development is currently unknown. METHODOLOGY/PRINCIPAL FINDINGS:We induced Atrx deletion in mouse cartilage using the Cre-loxP system, with Cre expression driven by the collagen II (Col2a1) promoter. Growth rate, body size and weight, and long bone length did not differ in Atrx(Col2cre) mice compared to control littermates. Histological analyses of the growth plate did not reveal any differences between control and mutant mice. Expression patterns of Sox9, a transcription factor required for cartilage morphogenesis, and p57, a marker of cell cycle arrest and hypertrophic chondrocyte differentiation, was unaffected. However, loss of ATRX in cartilage led to a delay in the ossification of the hips in some mice. We also observed hindlimb polydactily in one out of 61 mutants. CONCLUSIONS/SIGNIFICANCE:These findings indicate that ATRX is not directly required for development or growth of cartilage in the mouse, suggesting that the short stature in ATR-X patients is caused by defects in cartilage-extrinsic mechanisms

A New Eusuchian Crocodyliform with Novel Cranial Integument and Its Significance for the Origin and Evolution of Crocodylia

Crocodyliforms were one of the most successful groups of Mesozoic tetrapods, radiating into terrestrial, semiaquatic and marine environments, while occupying numerous trophic niches, including carnivorous, insectivorous, herbivorous, and piscivorous species. Among these taxa were the enigmatic, poorly represented flat-headed crocodyliforms from the late Cretaceous of northern Africa. Here we report a new, giant crocodyliform from the early Late Cretaceous (Cenomanian) Kem Kem Formation of Morocco. Represented by a partial braincase, the taxon has an extremely long, flat skull with large jaw and craniocervical muscles. The skull roof is ridged and ornamented with a broad, rough boss surrounded by significant vascular impressions, likely forming an integumentary structure unique among crocodyliforms. Size estimates using endocranial volume indicate the specimen was very large. The taxon possesses robust laterosphenoids with laterally oriented capitate processes and isolated epipterygoids, features allying it with derived eusuchians. Phylogenetic analysis finds the taxon to be a derived eusuchian and sister taxon to Aegyptosuchus, a poorly understood, early Late Cretaceous taxon from the Bahariya formation. This clade forms the sister clade of crown-group Crocodylia, making these taxa the earliest eusuchian crocodyliforms known from Africa. These results shift phylogenetic and biogeographical hypotheses on the origin of modern crocodylians towards the circum-Tethyean region and provide important new data on eusuchian morphology and evolution

Transgene Expression Is Associated with Copy Number and Cytomegalovirus Promoter Methylation in Transgenic Pigs

Transgenic animals have been used for years to study gene function, produce important proteins, and generate models for the study of human diseases. However, inheritance and expression instability of the transgene in transgenic animals is a major limitation. Copy number and promoter methylation are known to regulate gene expression, but no report has systematically examined their effect on transgene expression. In the study, we generated two transgenic pigs by somatic cell nuclear transfer (SCNT) that express green fluorescent protein (GFP) driven by cytomegalovirus (CMV). Absolute quantitative real-time PCR and bisulfite sequencing were performed to determine transgene copy number and promoter methylation level. The correlation of transgene expression with copy number and promoter methylation was analyzed in individual development, fibroblast cells, various tissues, and offspring of the transgenic pigs. Our results demonstrate that transgene expression is associated with copy number and CMV promoter methylation in transgenic pigs

Epigenetic Signatures Associated with Different Levels of Differentiation Potential in Human Stem Cells

BACKGROUND: The therapeutic use of multipotent stem cells depends on their differentiation potential, which has been shown to be variable for different populations. These differences are likely to be the result of key changes in their epigenetic profiles. METHODOLOGY/PRINCIPAL FINDINGS: to address this issue, we have investigated the levels of epigenetic regulation in well characterized populations of pluripotent embryonic stem cells (ESC) and multipotent adult stem cells (ASC) at the trancriptome, methylome, histone modification and microRNA levels. Differences in gene expression profiles allowed classification of stem cells into three separate populations including ESC, multipotent adult progenitor cells (MAPC) and mesenchymal stromal cells (MSC). The analysis of the PcG repressive marks, histone modifications and gene promoter methylation of differentiation and pluripotency genes demonstrated that stem cell populations with a wider differentiation potential (ESC and MAPC) showed stronger representation of epigenetic repressive marks in differentiation genes and that this epigenetic signature was progressively lost with restriction of stem cell potential. Our analysis of microRNA established specific microRNA signatures suggesting specific microRNAs involved in regulation of pluripotent and differentiation genes. CONCLUSIONS/SIGNIFICANCE: Our study leads us to propose a model where the level of epigenetic regulation, as a combination of DNA methylation and histone modification marks, at differentiation genes defines degrees of differentiation potential from progenitor and multipotent stem cells to pluripotent stem cells

Historical Isolation versus Recent Long-Distance Connections between Europe and Africa in Bifid Toadflaxes (Linaria sect. Versicolores)

Background: Due to its complex, dynamic and well-known paleogeography, the Mediterranean region provides an ideal framework to study the colonization history of plant lineages. The genus Linaria has its diversity centre in the Mediterranean region, both in Europe and Africa. The last land connection between both continental plates occurred during the Messinian Salinity Crisis, in the late Miocene (5.96 to 5.33 Ma). Methodology/Principal Findings: We analyzed the colonization history of Linaria sect. Versicolores (bifid toadflaxes), which includes c. 22 species distributed across the Mediterranean, including Europe and Africa. Two cpDNA regions (rpl32-trnL UAG and trnK-matK) were sequenced from 66 samples of Linaria. We conducted phylogenetic, dating, biogeographic and phylogeographic analyses to reconstruct colonization patterns in space and time. Four major clades were found: two of them exclusively contain Iberian samples, while the other two include northern African samples together with some European samples. The bifid toadflaxes have been split in African and European clades since the late Miocene, and most lineage and speciation differentiation occurred during the Pliocene and Quaternary. We have strongly inferred four events of post-Messinian colonization following long-distance dispersal from northern Africa to the Iberian Peninsula, Sicily and Greece. Conclusions/Significance: The current distribution of Linaria sect. Versicolores lineages is explained by both ancien

Lunar samples record an impact 4.2 billion years ago that may have formed the Serenitatis Basin

Impact cratering on the Moon and the derived size-frequency distribution functions of lunar impact craters are used to determine the ages of unsampled planetary surfaces across the Solar System. Radiometric dating of lunar samples provides an absolute age baseline, however, crater-chronology functions for the Moon remain poorly constrained for ages beyond 3.9 billion years. Here we present U–Pb geochronology of phosphate minerals within shocked lunar norites of a boulder from the Apollo 17 Station 8. These minerals record an older impact event around 4.2 billion years ago, and a younger disturbance at around 0.5 billion years ago. Based on nanoscale observations using atom probe tomography, lunar cratering records, and impact simulations, we ascribe the older event to the formation of the large Serenitatis Basin and the younger possibly to that of the Dawes crater. This suggests the Serenitatis Basin formed unrelated to or in the early stages of a protracted Late Heavy Bombardment

Geographic Distribution, Habitat, Reproduction, and Conservation Status of Crocodilians in the Americas

The chapter gives an introductory overview on the biology of the 11 species of crocodilians inhabiting the Americas. Geographical distribution is broadly discussed in the light of biogeographical and evolutionary origins. As a broad generalization, crocodilians are morphologically, genetically, and ecologically conservative and show a high dispersal ability, which together complicate the delimitation of species boundaries. Furthermore, distinct clades of crocodilians are a result of environmental selection for different adaptive characteristics. Gene flow occurs between clades, but distinct morphological varieties are sometimes a result of environmental filters. Thus, many taxa of crocodilians can be considered ecological species. Reproductive characteristics, such as nest-site choice and female reproductive output, influence reproductive success and thus population trends, so we discuss reproductive and habitat characteristics in the light of conservation genetics. Finally, the status of crocodilians is discussed both in terms of past hunting pressure and current conservation and management initiatives. In general, crocodilians can look after themselves if they have sufficient habitat, but some species are critically endangered by hunting, even though much of their original habitat remains intact. Conservation actions must be applied locally, taking into account threats and dispersal between source and sink populations. Given the difficulty of studying the dispersal of crocodilians by direct observation in most places in Latin America, the definition of effective management units will depend on genetic studies that can be linked to economic or conservation goals

Defective iron uptake and globin synthesis by erythroid cells in the anemia of the Belgrade laboratory rat

Erythroid cell iron uptake and globin synthesis were studied in the anemia of the Belgrade Laboratory rat (gene symbol, b), an autosomal recessive trait characterized by hypochromia and hyperferrinemia. Reticulocyte protein and globin synthesis, as measured in vitro by the incorporation of 3H-L-leucine, were significantly diminished in b/b animals, although no major imbalance between alpha-and beta-chain production was observed in b/b reticulocytes. The incorporation in vitro of 3H-L-methionine into marrow cell globin demonstrated no difference between b/b animals and +/? control animals in the proportion of alpha-to beta-chain production. The transfer of iron from plasma to reticulocytes, as measured in vitro by the uptake of 59Fe, was significantly decreased in b/b animals; Sephadex G 200 chromatography of b/b red cell lysates did not reveal the accumulation of 59Fe in nonhemoglobin fractions found when heme synthesis was inhibited with isoniazid. The magnitude of the reticulocyte iron-uptake defect was greater than the reticulocyte globin-synthesis defect, suggesting that the former is the primary lesion.</jats:p

Defective iron uptake and globin synthesis by erythroid cells in the anemia of the Belgrade laboratory rat

Abstract Erythroid cell iron uptake and globin synthesis were studied in the anemia of the Belgrade Laboratory rat (gene symbol, b), an autosomal recessive trait characterized by hypochromia and hyperferrinemia. Reticulocyte protein and globin synthesis, as measured in vitro by the incorporation of 3H-L-leucine, were significantly diminished in b/b animals, although no major imbalance between alpha-and beta-chain production was observed in b/b reticulocytes. The incorporation in vitro of 3H-L-methionine into marrow cell globin demonstrated no difference between b/b animals and +/? control animals in the proportion of alpha-to beta-chain production. The transfer of iron from plasma to reticulocytes, as measured in vitro by the uptake of 59Fe, was significantly decreased in b/b animals; Sephadex G 200 chromatography of b/b red cell lysates did not reveal the accumulation of 59Fe in nonhemoglobin fractions found when heme synthesis was inhibited with isoniazid. The magnitude of the reticulocyte iron-uptake defect was greater than the reticulocyte globin-synthesis defect, suggesting that the former is the primary lesion.</jats:p