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Results for “incomplete lineage sorting”

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60 records · Page 4Linked to original sources
PubMed2006

Mitochondrial cytochrome b sequence variation and phylogenetics of the highly specialized Schizothoracine fishes (Teleostei: Cyprinidae) in the Qinghai-Tibet plateau.

The complete 1140 bp mitochondrial cytochrome b sequences were obtained from 39 individuals representing five species of all four genera of highly specialized schizothoracine fishes distributed in the Qinghai-Tibet plateau. Sequence variation of the cytochrome b gene was surveyed among the 39 individuals as well as three primitive schizothoracines and one outgroup. Phylogenetic analysis suggested that the group assignment based on 1140 bp of the cytochrome b sequence is obviously different from previous assignments, and the highly specialized schizothoracine fishes (Schizopygopsis pylzovi, Gymnocypris przewalskii, G. eckloni, Chuanchia labiosa, and Platypharodon extremus) form a monophyletic group that is sister to the clade formed by the primitive schizothoracine fishes (Schizothorax prenanti, S. pseudaksaiensis, and S. argentatus). The haplotypes of Schizopygopsis pylzovi and G. przewalskii were paraphyletic based on cytochrome b data, which most likely reflected incomplete sorting of mitochondrial DNA lineages. The diploid chromosome numbers of Schizothoracinae were considered in phylogenetic analysis and provided a clear pattern of relationships. Molecular dating estimated for highly specialized schizothoracine fishes suggested that the highly specialized schizothoracine fishes diverged in the late Miocene Pliocene to Pleistocene (4.5 x 10(4)-4.05 x 10(6 ) years BP). The relationship between the cladogenesis of highly specialized schizothoracine fishes and geographical events of the Qinghai-Tibet plateau is discussed.

Animals↗
PubMed1996

Identification of stromal cell products that interact with pre-B cells.

Our understanding of lympho-hematopoietic microenvironments is incomplete, and a new cloning strategy was developed to identify molecules that bind to B lineage lymphocyte precursors. A cell sorting procedure was used for initial enrichment of cDNAs from stromal cell mRNA that contained signal sequences and were therefore likely to encode transmembrane or secreted proteins. A second step involved expression of the library as soluble Ig fusion proteins. Finally, pools representing these proteins were screened for the ability to recognize pre-B cells. This approach resulted in the cloning of biglycan, syndecan 4, collagen type I, clusterin, matrix glycoprotein sc1, osteonectin, and one unknown molecule (designated SIM). The full-length cDNA of SIM revealed that it is a type I transmembrane protein, and its intracellular domain has weak homology with myosin heavy chain and related proteins. Staining of established cell lines and freshly isolated hematopoietic cells with the Ig fusion proteins revealed distinct patterns of reactivity and differential dependence on divalent cations. Biglycan-, sc1-, and SIM-Ig fusion proteins selectively increased interleukin 7-dependent proliferation of pre-B cells. Overexpression of the entire SIM protein affected the morphology of 293T cells, while expression of just the extracellular portion was without effect. Thus, a series of stromal cell surface molecules has been identified that interact with blood cell precursors. Three of them promoted the survival and/or proliferation of pre-B cells in culture, and all merit further study in relation to lympho-hematopoiesis.

Amino Acid Sequence↗
PubMed1997

Leptin stimulates the proliferation of murine myelocytic and primitive hematopoietic progenitor cells.

Leptin, the product of obese gene, was originally identified as a factor regulating body-weight homeostasis and energy balance. The present study has shown that leptin acts on murine hematopoiesis in vitro. In the culture of bone marrow cells (BMC) of normal mice, leptin induced only granulocyte-macrophage (GM) colony formation in a dose-dependent manner, and no other types of colonies were detected even in the presence of erythropoietin (Epo). Leptin also induced GM colony formation from BMC of db/db mutant mice whose leptin receptors were incomplete, but the responsiveness was significantly reduced. The effect of leptin on GM colony formation from BMC of normal mice was also observed in serum-free culture, and comparable with that of GM-colony-stimulating factor (CSF ). Although leptin alone supported few colonies from BMC of 5-fluorouracil (5-FU)-treated mice in serum-free culture, remarkable synergism between leptin and stem cell factor (SCF ) was obtained in the colony formation. The addition of leptin to SCF enhanced the SCF-dependent GM colony formation and induced the generation of a number of multilineage colonies in the presence of Epo. When lineage (Lin)-Sca-1(+) cells sorted from BMC of 5-FU-treated mice were incubated in serum-free culture, leptin synergized with SCF in the formation of blast cell colonies, which efficiently produced secondary colonies including a large proportion of multilineage colonies in the replating experiment. In serum-free cultures of clone-sorted Lin-c-Kit+Sca-1(+) and Lin-c-Kit+Sca-1(-) cells, although synergism of leptin and SCF was observed in the colony formation from both cells, leptin alone induced the colony formation from Lin-c-Kit+Sca-1(-), but not Lin-c-Kit+Sca-1(+) cells. These results have shown that leptin stimulates the proliferation of murine myelocytic progenitor cells and synergizes with SCF in the proliferation of primitive hematopoietic progenitors in vitro.

Animals↗
PubMed2004

Maternal and paternal lineages in cross-breeding bovine species. Has wisent a hybrid origin?

The tribe Bovini comprises cattle and cattle-like species. Reconstructions of their phylogeny have so far been incomplete and have yielded conflicting conclusions about the relationship of American bison and wisent (European bison). We have compared the sequences of three mitochondrial and two Y-chromosomal DNA segments. Mitochondrial DNA indicates that four distinct maternal lineages diverged after an early split-off of the buffalo species, leading to (1) taurine cattle and zebu, (2) wisent, (3) American bison and yak, and (4) banteng, gaur, and gayal, respectively. At a higher level, lineages (1) and (2) and lineages (3) and (4) are probably associated. In contrast, Y-chromosomal sequences indicate a close association of American and European bison, which is in agreement with their morphological similarity, complete fertility of hybrid offspring, and amplified fragment length polymorphism (AFLP) fingerprints of nuclear DNA. One explanation for the anomalous divergence of the mitochondrial DNA from the two bison species is lineage sorting, which implies that two distinct mitochondrial lineages coexisted in the bison-yak branch until the recent divergence of American bison and wisent. Alternatively, the wisent may have emerged by species hybridization initiated by introgression of bison bulls in another ancestral species. This "transpatric" mode of species formation would be consistent with the recent appearance of the wisent in the fossil record without clearly identifiable ancestors.

Animals↗
PubMed1987

Unusual immunoglobulin DNA sequences from the nonexpressed chromosome of mouse normal B lymphocytes: implications for allelic exclusion and the DNA rearrangement process.

Allelic exclusion of immunoglobulin gene products results in the expression of only one of two possible alleles in normal B lineage cells. Attempts to define the role of heavy chain gene rearrangements in this process have revealed the nonexpressed allele to be rarely in its germline context, but rather incompletely rearranged (D/J rearrangements) or completely rearranged (V/D/J rearrangements) and in a context that cannot be expressed as a protein. Nearly all DNA sequences of heavy chain genes from the nonexpressed allele have originated from plasmacytomas, virus-induced pre-B leukemias, and hybridomas--all clonal cell lines perhaps altered by the neoplastic process. In this communication, we present the first examples of isolation and DNA sequence analysis of heavy chain gene rearrangements from the nonexpressed allele of normal B lymphocytes. Splenic B lymphocytes from allotype heterozygous (BALB/c X C57BL/6J)F1 mice expressing the BALB/c IgD allotype were detected with a monoclonal antibody, H10-4.22, to the BALB/c delta chain genetic marker and were isolated with a FACS (fluorescence-activated cell sorter). lambda phage clones containing the JH gene region from the sorted cells were isolated, and those containing sequences derived from the C57BL/6J nonexpressed chromosome were identified by a restriction fragment length polymorphism. DNA sequences of seven rearranged clones from the nonexpressed allele are presented. Five of these rearrangements have unexpected compositions. Four of the five clones contain V/D/J rearrangements with no obvious impediments to expression generated by the rearrangements. The novel variable region gene in one of these V/D/J rearrangements is a member of a newly described VH gene family. The fifth clone has a 3.5 kb deletion removing all of the JH gene segments. The remaining two clones contain D/J rearrangements that are typical of the initial stage of variable region assembly. These findings suggest that the mechanisms that generate nontranslatable heavy chains do not exclusively account for allelic exclusion. Rather, several different mechanisms may contribute to the establishment of allelic exclusion in normal B lymphocytes.

Alleles↗
PubMed1998

Flow cytometric analysis of recombinant human osteogenic protein-1 (BMP-7) responsive subpopulations from fetal rat calvaria based on intracellular osteopontin content.

The bone morphogenetic proteins (BMPs) are characterized by their ability to induce both chondrogenic and osteogenic differentiation of mesenchymal cells in vivo and in vitro. Primary cultures of fetal rat calvarial cells contain a broad spectrum of osteogenic cells at various stages of differentiation, but the responsive subpopulations are incompletely characterized. To identify responsive cells in osteogenic cell differentiation, we have treated fetal rat calvarial cells with recombinant osteogenic protein-1 and used flow cytometric analyses of intracellular osteopontin, and of cartilage and bone nodule formation, to evaluate the effects. When administered as a single dose at confluence, osteogenic protein-1 stimulated bone nodule formation in fetal rat calvarial cultures in dose-dependently way. To determine the response of osteogenic subpopulations at two discrete stages of differentiation, fetal rat calvaria cells were cultured for 2 days (proliferative stage) or 12 days (early mineralization stage) and treated with 100 ng/ml recombinant osteogenic protein-1 for 12 h before analysis by flow cytometry. Flow cytometry analyses of cell suspensions revealed that osteogenic protein-1 increased the total protein content of cells, and selectively increased the mean expression of osteopontin and the size and granularity of osteopontin expressing cells, particularly at day 12, consistent with a stimulation of osteogenic differentiation and matrix formation. Pulse administration of 100 ng/ml osteogenic protein-1 to sorted, osteopontin-negative subpopulations enriched for stem cells reduced by more than four-fold the number and size of bone nodules while promoting chondrogenesis and adipogenesis. In contrast, a pulse administration of osteogenic protein-1 to more differentiated, large osteopontin-positive cells increased bone nodule formation two-fold. Continuous administration of 100 ng/ml osteogenic protein-1 to the large osteopontin-positive and small osteopontin-negative cell populations obliterated bone nodule formation and promoted chondrogenesis. We conclude that pulse administration of osteogenic protein-1 promotes osteogenic differentiation of cells committed to the osteogenic lineage, whereas undifferentiated periosteal cells are induced to differentiate along the chondrogenic pathway. In contrast, continuous exposure to osteogenic protein-1 promotes chondrogenesis in populations of committed osteogenic cells and in undifferentiated periosteal cells.

Adipocytes↗