Extant xenarthrans (armadillos, anteaters and sloths) are among the most derived placental mammals ever evolved. South America was the cradle of their evolutionary history. During the Tertiary, ...xenarthrans experienced an extraordinary radiation, whereas South America remained isolated from other continents. The 13 living genera are relics of this earlier diversification and represent one of the four major clades of placental mammals. Sequences of the three independent protein-coding nuclear markers alpha2B adrenergic receptor (ADRA2B), breast cancer susceptibility (BRCA1), and von Willebrand Factor (VWF) were determined for 12 of the 13 living xenarthran genera. Comparative evolutionary dynamics of these nuclear exons using a likelihood framework revealed contrasting patterns of molecular evolution. All codon positions of BRCA1 were shown to evolve in a strikingly similar manner, and third codon positions appeared less saturated within placentals than those of ADRA2B and VWF. Maximum likelihood and Bayesian phylogenetic analyses of a 47 placental taxa data set rooted by three marsupial outgroups resolved the phylogeny of Xenarthra with some evidence for two radiation events in armadillos and provided a strongly supported picture of placental interordinal relationships. This topology was fully compatible with recent studies, dividing placentals into the Southern Hemisphere clades Afrotheria and Xenarthra and a monophyletic Northern Hemisphere clade (Boreoeutheria) composed of Laurasiatheria and Euarchontoglires. Partitioned likelihood statistical tests of the position of the root, under different character partition schemes, identified three almost equally likely hypotheses for early placental divergences: a basal Afrotheria, an Afrotheria + Xenarthra clade, or a basal Xenarthra (Epitheria hypothesis). We took advantage of the extensive sampling realized within Xenarthra to assess its impact on the location of the root on the placental tree. By resampling taxa within Xenarthra, the conservative Shimodaira-Hasegawa likelihood-based test of alternative topologies was shown to be sensitive to both character and taxon sampling.
Abstract Purpose To evaluate testicular function in men with previously acquired undescended testes (AUDT) in whom spontaneous descent was awaited until puberty followed by orchiopexy in case of ...nondescent. Methods Andrological evaluation including paternity, scrotal ultrasound, reproductive hormones, and semen analysis was performed in three groups: men with AUDT, healthy controls, and men with previously congenital undescended testes (CUDT). Results In comparison with controls, men with AUDT more often had significantly abnormal testicular consistency, smaller testes, lower sperm concentration, and less motile sperm. Except for more often a normal testicular consistency in men with AUDT, no differences were found between men with AUDT and men with CUDT. Also, no differences were found between men with AUDT which had spontaneously descended and men who underwent orchiopexy. Conclusions Fertility potential in men with AUDT is compromised in comparison with healthy controls, but comparable with men with CUDT. This suggests that congenital and acquired UDT share the same etiology. No significant difference was found between men who had spontaneous descent and men needing orchiopexy. However, fertility potential is unknown for men after immediate surgery at diagnosis, and this should be a subject for future studies.
To obtain an inventory of all human genes that code for α-crystallin–related small heat shock proteins (sHsps), the databases available from the public International Human Genome Sequencing ...Consortium (IHGSC) and the private Celera human genome project were exhaustively searched. Using the human Hsp27 protein sequence as a query in the protein databases, which are derived from the predicted genes in the human genome, 10 sHsp-like proteins were retrieved, including Hsp27 itself. Repeating the search procedure with all 10 proteins and with a variety of more distantly related animal sHsps, no further human sHsps were detected, as was the case when searches were performed at deoxyribonucleic acid level. The 10 retrieved proteins comprised the 9 earlier recognized human sHsps (Hsp27/HspB1, HspB2, HspB3, αA-crystallin/HspB4, αB-crystallin/HspB5, Hsp20/HspB6, cvHsp/HspB7, H11/HspB8, and HspB9) and a sperm tail protein known since 1993 as outer dense fiber protein 1 (ODF1). Although this latter protein probably serves a structural role and has a high cysteine content (14%), it clearly contains an α-crystallin domain that is characteristic for sHsps. ODF1 can as such be designated as HspB10. The expression of all 10 human sHsp genes was confirmed by expressed sequence tag (EST) searches. For Hsp27/HspB1, 2 retropseudogenes were detected. The HspB1–10 genes are dispersed over 9 chromosomes, reflecting their ancient origin. Two of the genes (HspB3 and HspB9) are intronless, and the others have 1 or 2 introns at various positions. The transcripts of several sHsp genes, notably HspB7, display low levels of alternative splicing, as supported by EST evidence, which may result in minor amounts of isoforms at the protein level.
Prion protein (PrP) sequences are until now available for only six of the 18 orders of placental mammals. A broader comparison of mammalian prions might help to understand the enigmatic functional ...and pathogenic properties of this protein. We therefore determined PrP coding sequences in 26 mammalian species to include all placental orders and major subordinal groups. Glycosylation sites, cysteines forming a disulfide bridge, and a hydrophobic transmembrane region are perfectly conserved. Also, the sequences responsible for secondary structure elements, for N- and C-terminal processing of the precursor protein, and for attachment of the glycosyl-phosphatidylinositol membrane anchor are well conserved. The N-terminal region of PrP generally contains five or six repeats of the sequence P(Q/H)GGG(G/-)WGQ, but alleles with two, four, and seven repeats were observed in some species. This suggests, together with the pattern of amino acid replacements in these repeats, the regular occurrence of repeat expansion and contraction. Histidines implicated in copper ion binding and a proline involved in 4-hydroxylation are lacking in some species, which questions their importance for normal functioning of cellular PrP. The finding in certain species of two or seven repeats, and of amino acid substitutions that have been related to human prion diseases, challenges the relevance of such mutations for prion pathology. The gene tree deduced from the PrP sequences largely agrees with the species tree, indicating that no major deviations occurred in the evolution of the prion gene in different placental lineages. In one species, the anteater, a prion pseudogene was present in addition to the active gene.
Molecular phylogenies challenge the view that bats belong to the superordinal group Archonta, which also includes primates, tree shrews, and flying lemurs. Some molecular studies also challenge ...microbat monophyly and instead support an alliance between megabats and representative rhinolophoid microbats from the families Rhinolophidae (horseshoe bats, Old World leaf-nosed bats) and Megadermatidae (false vampire bats). Another molecular study ostensibly contradicts these results and supports traditional microbat monophyly, inclusive of representative rhinolophoids from the family Nycteridae (slit-faced bats). Resolution of the microbat paraphyly/monophyly issue is essential for reconstructing the temporal sequence and deployment of morphological character state changes associated with flight and echolocation in bats. If microbats are paraphyletic, then laryngeal echolocation either evolved more than once in different microbats or was lost in megabats after evolving in the ancestor of all living bats. To examine these issues, we used a 7.1-kb nuclear data set for nine outgroups and twenty bats, including representatives of all rhinolophoid families. Phylogenetic analyses and statistical tests rejected both Archonta and microbat monophyly. Instead, bats are in the superorder Laurasiatheria and microbats are paraphyletic. Further, the superfamily Rhinolophoidea is polyphyletic. The rhinolophoid families Rhinolophidae and Megadermatidae belong to the suborder Yinpterochiroptera along with rhinopomatids and megabats. The rhinolophoid family Nycteridae belongs to the suborder Yangochiroptera along with vespertilionoids, noctilionoids, and emballonuroids. These results resolve the apparent conflict between previous molecular studies that sampled different rhinolophoid families. An important implication of rhinolophoid polyphyly is independent evolution of key anatomical innovations associated with the nasal-emission of echolocation pulses.
Phosphorylation modulates the functioning of αB-crystallin as a molecular chaperone. We here explore the role of phosphorylation in the nuclear import and cellular localization of αB-crystallin in ...HeLa cells. Inhibition of nuclear export demonstrated that phosphorylation of αB-crystallin is required for import into the nucleus. As revealed by mutant analysis, phosphorylation at Ser-59 is crucial for nuclear import, and phosphorylation at Ser-45 is required for speckle localization. Co-immunoprecipitation experiments suggested that the import of αB-crystallin is possibly regulated by its phosphorylation-dependent interaction with the survival motor neuron (SMN) protein, an important factor in small nuclear ribonucleoprotein nuclear import and assembly. This interaction was supported by co-localization of endogenous phosphorylated αB-crystallin with SMN in nuclear structures. The cardiomyopathy-causing αB-crystallin mutant R120G was found to be excessively phosphorylated, which disturbed SMN interaction and nuclear import, and resulted in the formation of cytoplasmic inclusions. Like for other protein aggregation disorders, hyperphosphorylation appears as an important aspect of the pathogenicity of αB-crystallin R120G.
AlphaB-crystallin is a small heat-shock protein in which three serine residues (positions 19, 45, and 59) can be phosphorylated under various conditions. We describe here the interaction of ...alphaB-crystallin with FBX4, an F-box-containing protein that is a component of the ubiquitin-protein isopeptide ligase SCF (SKP1/CUL1/F-box). The interaction with FBX4 was enhanced by mimicking phosphorylation of alphaB-crystallin at both Ser-19 and Ser-45 (S19D/S45D), but not at other combinations. Ser-19 and Ser-45 are preferentially phosphorylated during the mitotic phase of the cell cycle. Also alphaB-crystallin R120G, a mutant found to co-segregate with a desmin-related myopathy, displayed increased interaction with FBX4. Both alphaB-crystallin S19D/S45D and R120G specifically translocated FBX4 to the detergent-insoluble fraction and stimulated the ubiquitination of one or a few yet unknown proteins. These findings implicate the involvement of alphaB-crystallin in the ubiquitin/proteasome pathway in a phosphorylation- and cell cycle-dependent manner and may provide new insights into the alphaB-crystallin-induced aggregation in desmin-related myopathy.
The order Insectivora, including living taxa (lipotyphlans) and archaic fossil forms, is central to the question of higher-level relationships among placental mammals. Beginning with Huxley, it has ...been argued that insectivores retain many primitive features and are closer to the ancestral stock of mammals than are other living groups. Nevertheless, cladistic analysis suggests that living insectivores, at least, are united by derived anatomical features. Here we analyse DNA sequences from three mitochondrial genes and two nuclear genes to examine relationships of insectivores to other mammals. The representative insectivores are not monophyletic in any of our analyses. Rather, golden moles are included in a clade that contains hyraxes, manatees, elephants, elephant shrews and aardvarks. Members of this group are of presumed African origin. This implies that there was an extensive African radiation from a single common ancestor that gave rise to ecologically divergent adaptive types. 12S ribosomal RNA transversions suggest that the base of this radiation occurred during Africa's window of isolation in the Cretaceous period before land connections were developed with Europe in the early Cenozoic era.
Various mammalian small heat-shock proteins (sHSPs) can interact with one another to form large polydisperse assemblies. In muscle cells, HSPB2/MKBP (myotonic dystrophy protein kinase-binding ...protein) and HSPB3 have been shown to form an independent complex. To date, the biochemical properties of this complex have not been thoroughly characterized. In this study, we show that recombinant HSPB2 and HSPB3 can be successfully purified from
Escherichia coli cells co-expressing both proteins. Nanoelectrospray ionization mass spectrometry and sedimentation velocity analytical ultracentrifugation analysis showed that HSPB2/B3 forms a series of well defined hetero-oligomers, consisting of 4, 8, 12, 16, 20 and 24 subunits, each maintaining a strict 3:1 HSPB2/HSPB3 subunit ratio. These complexes are thermally stable up to 40 °C, as determined by far-UV circular dichroism spectroscopy. Surprisingly, HSPB2/B3 exerted a poor chaperone-like and thermoprotective activity, which is likely related to the low surface hydrophobicity, as revealed by its interaction with the hydrophobic probe 1-anilino-8-naphthalenesulfonic acid. Co-immunoprecipitation experiments demonstrated that the HSPB2/B3 oligomer cannot interact with HSP20, HSP27 or αB-crystallin, whereas the homomeric form of HSPB2, thus not in complex with HSPB3, could associate efficiently with HSP20. Taken altogether, this study provides evidence that, despite the high level of sequence homology within the sHSP family the biochemical properties of the HSPB2/B3 complex are distinctly different from those of other sHSPs, indicating that the HSPB2/B3 assembly is likely to possess cellular functions other than those of its family members.
For more than a century, living insectivore-like mammals have been viewed as little removed from the ancestral mammalian stock based on their retention of numerous primitive characteristics. This ...circumstance has made “insectivores” a group of special interest in the study of mammalian evolution.
Wagner (1855) included hedgehogs, moles, shrews, solenodons, golden moles, tenrecs, flying lemurs, tree shrews, and elephant shrews in Insectivora. Subsequently, morphologists excluded flying lemurs, tree shrews, and elephant shrews from Insectivora and placed these taxa in the orders Dermoptera, Scandentia, and Macroscelidea, respectively. The remaining insectivores constitute Lipotyphla, which is monophyletic based on morphology. In contrast, molecular data suggest that lipotyphlans are polyphyletic, with golden moles and tenrecs placed in their own order (Afrosoricida) in the superordinal group Afrotheria. Studies based on nuclear genes support the monophyly of the remaining lipotyphlans (=Eulipotyphla) whereas mitochondrial genome studies dissociate hedgehogs from moles and place the former as the first offshoot on the placental tree. One shortcoming of previous molecular studies investigating lipotyphlan relationships is limited taxonomic sampling. Here, we evaluate lipotyphlan relationships using the largest and taxonomically most diverse data set yet assembled for Lipotyphla. Our results provide convincing support for both lipotyphlan diphyly and the monophyly of Eulipotyphla. More surprisingly, we find strong evidence for a sister-group relationship between shrews and hedgehogs to the exclusion of moles.
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