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PubMed2004

Brain size and encephalization in early to Mid-Pleistocene Homo.

Important changes in the brain have occurred during the course of human evolution. Both absolute and relative size increases can be documented for species of Homo, culminating in the appearance of modern humans. One species that is particularly well-represented by fossil crania is Homo erectus. The mean capacity for 30 individuals is 973 cm(3). Within this group there is substantial variation, but brain size increases slightly in specimens from later time periods. Other Middle Pleistocene crania differ from those of Homo erectus. Characters of the facial skeleton, vault, and cranial base suggest that fossils from sites such as Arago Cave in France, the Sima de los Huesos in Spain, Bodo in Ethiopia, Broken Hill in Zambia, and perhaps Dali in China belong to the taxon Homo heidelbergensis. Ten of these mid-Quaternary hominins have brains averaging 1,206 cm(3) in volume, and many fall beyond the limits of size predicted for Homo erectus of equivalent age. When orbit height is used to construct an index of relative brain size, it is apparent that the (significant) increase in volume documented for the Middle Pleistocene individuals is not simply a consequence of larger body mass. Encephalization quotient values confirm this finding. These changes in absolute and relative brain size can be taken as further corroborative evidence for a speciation event, in which Homo erectus produced a daughter lineage. It is probable that Homo heidelbergensis originated in Africa or western Eurasia and then ranged widely across the Old World. Archaeological traces indicate that these populations differed in their technology and behavior from earlier hominins.

Animals↗
PubMed1990

How do societies and "corporate" groups delimit themselves? A puzzle common to social and medical anthropology.

Classic anthropological theories define the first but neglect the second condition of social life. When they assume that the universal effect of the incest taboo is the opening of the consanguinial groups to the others, to exchange, they do not explain the closure of their sphere of reciprocity, i.e., the delimitation of the society. Hence the question: How, by which means, are stateless societies delimited or do they delimit themselves? Among the Senoufo of Ivory Coast (Nafara), one of the main acts of male initiation ceremonies--to the Poro, which is the very basis of the Senoufo's ethnic identity--is a ritual intercourse between the neophytes and their symbolic mother who has just given birth to them. This rite materializes the initiatic axiom: Senoufo men reproduce themselves by incest. In this case, the prescription of ritual incest is a means by which the society "closes" the field of reciprocity "opened" by the prohibition of actual incest. The return of the forbidden--at the heart of the institution which reproduces its identity--is the basic principle of the ritual delimitation of this society. Despite appearances, the delimitation of the so-called "corporate groups"--for example, an African lineage--is neither more "natural" nor more jural than that of the society which contains them. The limits of these groups are traced and retraced notably in the course of traditional "therapies" and by means of etiological entities which share several common, distinctive properties. (1) They cannot operate outside of the group delimited by them. (2) They are polyvalent and their effects are permutable from one group-member to another. (3) They act periodically: they have to dismantle the group periodically from the inside in order to be able to delimit it constantly from the outside. This phenomenon of spatio-temporal inversion (inside-outside; periodic-continuous), observable in any process of ritual delimitation, deserves our attention insofar as its closer analysis could lead us to rethink our present theories of ritual.

Ceremonial Behavior↗
PubMed2004

The mitochondrial DNA of land plants: peculiarities in phylogenetic perspective.

Land plants exhibit a significant evolutionary plasticity in their mitochondrial DNA (mtDNA), which contrasts with the more conservative evolution of their chloroplast genomes. Frequent genomic rearrangements, the incorporation of foreign DNA from the nuclear and chloroplast genomes, an ongoing transfer of genes to the nucleus in recent evolutionary times and the disruption of gene continuity in introns or exons are the hallmarks of plant mtDNA, at least in flowering plants. Peculiarities of gene expression, most notably RNA editing and trans-splicing, are significantly more pronounced in land plant mitochondria than in chloroplasts. At the same time, mtDNA is generally the most slowly evolving of the three plant cell genomes on the sequence level, with unique exceptions in only some plant lineages. The slow sequence evolution and a variable occurrence of introns in plant mtDNA provide an attractive reservoir of phylogenetic information to trace the phylogeny of older land plant clades, which is as yet not fully resolved. This review attempts to summarize the unique aspects of land plant mitochondrial evolution from a phylogenetic perspective.

DNA, Mitochondrial↗
PubMed2004

Epigenetic reprogramming during early development in mammals.

Epigenetic modifications serve as an extension of the information content by which the underlying genetic code may be interpreted. These modifications mark genomic regions and act as heritable and stable instructions for the specification of chromatin organisation and structure that dictate transcriptional states. In mammals, DNA methylation and the modification of histones account for the major epigenetic alterations. Two cycles of DNA methylation reprogramming have been characterised. During germ cell development, epigenetic reprogramming of DNA methylation resets parent-of-origin based genomic imprints and restores totipotency to gametes. On fertilisation, the second cycle is triggered resulting in an asymmetric difference between parental genomes. Further epigenetic asymmetry is evident in the establishment of the first two lineages at the blastocyst stage. This differentiative event sets the epigenetic characteristics of the lineages as derivatives of the inner cell mass (somatic) and trophectoderm (extra-embryonic). It is the erasure and subsequent re-tracing of the epigenetic checkpoints that pose the most serious obstacles to somatic nuclear transfer. Elaboration of the mechanisms of these interactions will be invaluable in our fundamental understanding of biological processes and in achieving substantial therapeutic advances.

Animals↗
PubMed1999

Colorectal adenoma and cancer divergence. Evidence of multilineage progression.

Colorectal cancer progression involves changes in phenotype and genotype. Although usually illustrated as a linear process, more complex underlying pathways have not been excluded. The object of this paper is to apply modern quantitative principles of molecular evolution to multistep tumor progression. To reconstruct progression lineages, the genotypes of two adjacent adenoma-cancer pairs were determined by serial dilution and polymerase chain reaction at 28-30 microsatellite (MS) loci and then traced back to their most recent common ancestor. The tumors were mismatch repair deficient, and therefore relatively large numbers of MS mutations should accumulate during progression. As expected, the MS genotypes were similar (correlation coefficients >0.9) between different parts of the same adenoma or cancer, but very different (correlation coefficients <0. 2) between unrelated metachronous adenoma-cancer pairs. Unexpectedly, the genotypes of the adjacent adenoma-cancer pairs were also very different (correlation coefficients of 0.30 and 0.36), consistent with early adenoma-cancer divergence rather than direct linear progression. More than 60% of the divisions occurred after this early adenoma-cancer divergence. Therefore, the tumor phylogenies were not consistent with sequential stepwise selection along a single most "fit" and frequent lineage from adenoma to cancer. Instead, one effective early progression strategy creates and maintains multiple evolving candidate lineages, which are subsequently selected for terminal clonal expansion.

Adenoma↗
PubMed2002

Novel approaches for identifying genes regulating lymphocyte development and function.

The draft sequence of the human and mouse genomes provides an unparalleled opportunity for understanding the genetic control of immune-cell development. Strategies can begin with a gene sequence and pursue a putative immune-system function by employing mRNA-expression profiling or creating gene knockouts in embryonic stem cells. The latter can be produced by utilising the Cre/Lox system, a tetracycline operon, a gene-trap method or chemical mutagenesis. Alternatively, mutant phenotypes (derived using the mutagen ethylnitrosourea) can be traced back to gene sequences.

Animals↗
PubMed2005

Progenitor analysis of primitive erythropoiesis generated from in vitro culture of embryonic stem cells.

OBJECTIVE: A variety of hematopoietic lineage cells have been produced from embryonic stem (ES) cells, but their differentiation processes have not been elucidated well, especially from the point of view of progenitor analysis. In this study, we utilized our coculture system, in which ES-derived Flk-1+ cells differentiated into TER-119+ primitive erythroid (EryP) cells on OP9 cells, and looked for progenitors in primitive erythropoiesis. MATERIALS AND METHODS: We studied the kinetics of TER-119+ erythroblast generation from Flk-1+ cells by monitoring the expression of TER-119, CD41, VE-cadherin, CD34, and c-kit antigens. Multicolor analysis was performed to detect CD41+TER-119+ cells and the stained cells were sorted to examine their morphology and EryP-producing potential in colony formation. RESULTS: Kinetic studies showed that the CD41+ population appeared early in the coculture and its expression pattern implied a role as an immediate progenitor of TER-119+ EryP cells. Multicolor analysis and colony-formation study supported this notion. Other progenitor markers such as VE-cadherin, CD34, and c-kit did not seem to define an immediate progenitor of EryP cells. One interesting observation is the detection of unique populations, CD41dim and CD41bright, detectable after 48 hours of the coculture. Majority of the CD41dim population progressed to the EryP lineage, whereas the CD41bright population seemingly advanced on a pathway distinct from the CD41dim population. CONCLUSIONS: CD41 expression was a useful marker to trace hematopoietic progenitors in ES-derived differentiation system. In particular, the CD41dim but not CD41bright population could serve as immediate precursors of EryP cells.

Animals↗
PubMedDate not supplied

Breast cancer genetics: family history, heterogeneity, molecular genetic diagnosis, and genetic counselling.

Between 5% and 10% of breast cancer cases can be traced to primary genetic factors. Before the discovery of the BRCA1 and BRCA2 genes, if a first-degree relative in direct genetic lineage had hereditary breast cancer or hereditary breast-ovarian cancer syndrome, the best estimate of family members' genetic risk for breast cancer was 50%. Now the lifetime cancer destiny of a patient who carries a BRCA1 or BRCA2 germ line mutation can be determined with an extraordinary degree of precision. However, a major concern facing clinicians is how to use this powerful genetic knowledge without harming the patient. This presentation focuses on the need for (a) compilation of a detailed family history of cancer of all anatomic sites; (b) understanding of the natural history of hereditary breast cancer and its heterogeneous forms and the pathobiology of hereditary breast cancer; and (c) preparation for performance of genetic counseling that is based on the results of DNA sequencing to detect genes related to cancer susceptibility. The discussion addresses the advantages of this molecular genetic movement, which include the abilities (a) to predict who is and who is not at inordinately high risk for cancer; (b) to provide opportunities for highly targeted disease surveillance and management; (c) to give patients the information they need to make appropriate long-term decisions about matters such as procreation; and (d) to give genetic counselors the information they need to appreciate the emotions patients may encounter, such as fear, anxiety, and apprehension, and the ordeal of being subjected to discrimination by insurance companies and employers.

Adult↗
PubMed1994

Phylogeny and evolution of the auks (subfamily Alcinae) based on mitochondrial DNA sequences.

The genetic divergence and phylogeny of the auks was assessed by mitochondrial DNA sequence comparisons in a study using 19 of the 22 auk species and two outgroup representatives. We compared more than 500 nucleotides from each of two mitochondrial genes encoding 12S rRNA and the NADH dehydrogenase subunit 6. Divergence times were estimated from transversional substitutions. The dovekie (Alle alle) is related to the razorbill (Alca torda) and the murres (Uria spp). Furthermore, the Xantus's murrelet (Synthliboramphus hypoleucus) and the ancient (Synthliboramphus antiquus) and Japanese murrelets (Synthliboramphus wumizusume) are genetically distinct members of the same main lineage, whereas brachyramphine and synthliboramphine murrelets are not closely related. An early adaptive radiation of six main species groups of auks seems to trace back to Middle Miocene. Later speciation probably involved ecological differentiations and geographical isolations.

Animals↗
PubMed2005

Tracing the hemangioblast during embryogenesis: developmental relationships between endothelial and hematopoietic cells.

We review here the development of the hematopoietic system and its relationship to the endothelium, with a special focus on the characterisation of the hemangioblast, the putative ancestor for endothelial cells and hematopoietic cells. Using the avian model, we have traced in vivo the progeny of embryonic endothelial cells and shown that aortic-born hematopoietic cells (known to generate the definitive hematopoietic lineage) derive from endothelial cells in the floor of the aorta. During this process, endothelial cells undergo a switch from endothelial cells to hematopoietic cells characterised by a downgrading of endothelial cell-specific genes and the parallel upgrading of hematopoietic cell-specific genes. Using a similar approach, we have shown that generation of hematopoietic cells from endothelial cells also takes place during mouse embryonic development. We have thoroughly characterised the dynamics of key molecules (several of which we have cloned) specifically expressed by the yolk sac or aortic hemangioblast. The yolk sac hemangioblast is characterized by the specific expression of SCL/Tal-1 and Lmo2, whereas the aortic hemangioblast expresses Runx-1 (a runt domain transcription factor). Finally, we have demonstrated the existence of a new site for hematopoiesis, namely the allantois. Using quail/chick grafts, we show that this embryonic appendage autonomously produces endothelial cells and hematopoietic cells, these latter being endowed with the attributes of the definitive hematopoietic lineage.

Animals↗
PubMed1993

Leukemia-associated marker combinations in acute leukemia suitable for detection of minimal residual disease.

In the absence of truly leukemia-specific antigen, antigen combinations were identified in leukemia cells that are absent or extremely rare among normal hemopoietic cells. Some of the studied combinations related to the simultaneous surface and cytoplasmic marker expression, others, expressed mainly on cell surface membrane, represented atypical or aberrant combinations. Comparing membrane (m) and cytoplasmic (c) antigen expression (followed in 23 acute leukemia cases), we observed that CD3 could be detected in cytoplasm in the majority of T-ALL cells, while was absent on cell surface membrane where simultaneous expression of more immature T cell markers, such as CD7 and CD5, could be detected. Combination of mCD7/cCD3 could be regarded as a suitable marker of individual T-ALL cells. In cases of B-precursors of acute leukemia cells, leukemia-related combination of mCD19/cCD22 was found, which could characterize a single leukemia cell. The cells in one of 11 AML followed cases were positive for CD13 in cytoplasm, but not on cell surface membrane, where CD33 and other myeloid antigens were expressed. The cells in another two AML cases were positive for CD11 in cytoplasm but not on cell surface membrane, where CD13 or CD33 were expressed. Again, marker combinations of mCD33/cCD13 and mCD13 or mCD33/cCD11, respectively, represent a leukemia-related feature, suitable for tracing single leukemia cells in double immunofluorescence. Acute leukemia defined by the coexpression on most blast cells of antigens classically attributed to different lineages (referred as atypical/aberrant marker combinations) remains a rare event. We isolated a series of 27 (12%) such cases of 225 acute leukemia patients whose cells were immunophenotyped at diagnosis. Myeloid markers were present in T-ALL of two cases, T and B markers were coexpressed in 13 cases, markers of B and myeloid lineage were associated in one case, and T cell and myeloid antigens were found in 10 AML cases; in one AML case (M3 according to FAB classification) an aberrant nuclear coexpression of TdT was observed. In one case of the last group an interesting antigen combination of CD4/CD34 present in AML with monocytic differentiation was observed. When 5 patients with leukemia-associated (aberrant) markers were again analyzed at relapse, the relevant antigen combinations were retained in all of them. In summary, 44 of 50 cases (88%) from our acute leukemia series studied for leukemia-associated antigen combination, both with surface membrane and cytoplasmic marker combinations and those with aberrant markers coexpression allow the detection of minimal residual disease.

Adult↗
PubMed2000

Developmental fates of larval tissues after metamorphosis in the ascidian, Halocynthia roretzi. II. Origin of endodermal tissues of the juvenile.

Cell lineages during ascidian embryogenesis are invariant. Developmental fates of larval mesodermal cells after metamorphosis are also invariant with regard to cell type of descendants. The present study traced developmental fates of larval endodermal cells after metamorphosis in Halocynthia roretzi by labeling each endodermal precursor blastomere of larval endoderm. Larval endodermal cells gave rise to various endodermal organs of juveniles: endostyle, branchial sac, peribranchial epithelium, digestive organs, peripharyngeal band, and dorsal tubercle. The boundaries between clones descended from early blastomeres did not correspond to the boundaries between adult endodermal organs. Although there is a regular projection from cleavage stage and larval stage to juvenile stage, this varies to some extent between individuals. This indicates that ascidian development is not entirely deterministic. We composed a fate map of adult endodermal organs in larval endoderm based on a statistical analysis of many individual cases. Interestingly, the topographic position of each prospective region in the fate map was similar to that of the adult organ, indicating that marked rearrangement of the positions of endodermal cells does not occur during metamorphosis. These findings suggest that fate specification in endoderm cells during metamorphosis is likely to be a position-dependent rather than a deterministic and lineage-based process.

Animals↗
PubMed2006

High-resolution mtDNA studies of the Indian population: implications for palaeolithic settlement of the Indian subcontinent.

The population of the Indian subcontinent represents a very complex social and cultural structure. Occupying a geographically central position for the early modern human migrations, indications are that the founder group that migrated out of East Africa also reached India. In the present study we used the twin strategy of mapping the whole mitochondrial DNA (mtDNA) using the standard 14 restriction enzymes, and sequencing the non-transcribed HVSI region, to derive maximum maternal lineages from a sample of non-tribal Indians. The essential features of the reduced median network of the two datasets were the same. Both showed two demographic expansions of two major haplogroups, 'M' and 'N'. The reduced median network was drawn with inputs from other studies on the Indian population, and correlated with data from other ethnic populations. The coalescence time of expansions and genetic diversity were estimated. A reduced median network was also drawn combining data from studies on Africans, Southeast Asians and West-Eurasians, tracing the migration of 'M' from East Africa to India. A time estimate of the migration of major mtDNA haplogroups from Africa was attempted. The comparison of a set of Indian maternal lineages belonging to different geographical regions of the country, with other populations revealed the in-situ differentiation and antiquity of the Indian population. Our analysis places the 'southern route' migration as the source of haplogroup 'M'. Multiple migrations might have brought the other major haplogroups, 'N' and 'R', found in our sample to India. Archaeological evidence of modern humans in the subcontinent supports this mtDNA study.

Cluster Analysis↗
PubMed2002

Regulator-driven functional diversification of protein phosphatase-1 in eukaryotic evolution.

We have used the (nearly) completed eukaryotic genome sequences to trace the evolution of thirteen families of established vertebrate regulators of type-1 protein phosphatases (PP1). Two of these families are present in all lineages of the eukaryotic crown and therefore qualify as candidate primordial regulators that determined the surface of PP1. The set of regulators of PP1 has continued to expand ever since, often in response to functional innovations in different eukaryotic lineages. In particular, the development of metazoan multicellularity was accompanied by an explosive increase in the number of regulators of PP1. The further increase in the functional diversity of PP1 in the vertebrate lineage was mainly achieved by the duplication of genes for regulatory subunits and by the conversion of already existing proteins into regulators of PP1. Unexpectedly, our analysis has also enabled us to classify nine poorly characterized proteins as likely regulators of PP1.

Animals↗
PubMed2004

The evolution of host plant manipulation by insects: molecular and ecological evidence from gall-forming aphids on Pistacia.

One of the most striking characteristics of gall-forming insects is the variability in gall position, morphology, and complexity. Our knowledge of the driving forces behind the evolutionary divergence of gall types is limited. Natural enemies, competition, and behavioral constraints might be involved. We present a cladogram, based on sequences of COI and COII (1952bp), of mitochondrial DNA for the evolution of 14 species of gall-forming aphids (Fordinae). These insects induce five gall types with remarkable morphological variation on Pistacia spp. hosts. The parsimony cladogram divides the Fordinae into three lineages, Fordini and Baizongiini, and a third (new) sister group including the previously Fordini member, Smynthurodes betae (West). We then use ecological data to trace and explain the evolution of gall morphology. The aphids seem to have evolved gradually towards better ability to manipulate their host plant, induce stronger sinks, and gain higher reproductive success. We suggest that the ancestral gall type was a simple, open, "pea"-sized gall located on the leaflet midvein. Some Fordini and S. betae evolved a two-gall life cycle, inducing a new gall type on the leaflet margin. The Baizongiini improved the manipulation of their host by inducing larger galls near the midvein, with stronger sinks supporting thousands of aphids. Similar gall types are induced at similar sites on different Pistacia hosts suggesting control of the aphids on gall morphology and frequent host shifts. Thus, even extreme specialization (specific gall and host) is flexible.

Animals↗
PubMedDate not supplied

Evolutionary redeployment of a biosynthetic module: expression of eye pigment genes vermilion, cinnabar, and white in butterfly wing development.

Ommochromes are common among insects as visual pigments; however, in some insect lineages ommochromes have evolved novel functions such as integument coloration and tryptophan secretion. One role of ommochromes, as butterfly wing pigments, can apparently be traced to a single origin in the family Nymphalidae. The synthesis and storage of ommochrome pigments is a complex process that requires the concerted activity of multiple enzyme and transporter molecules. To help understand how this subcellular process appeared in a novel context during evolution, we explored aspects of ommochrome pigment development in the wings of the nymphalid butterfly Vanessa cardui. Using chromatography and radiolabeled precursor incorporation studies we identified the ommochrome xanthommatin as a V. cardui wing pigment. We cloned fragments of two ommochrome enzyme genes, vermilion and cinnabar, and an ommochrome precursor transporter gene, white, and found that these genes were transcribed in wing tissue at relatively high levels during wing scale development. Unexpectedly, however, the spatial patterns of transcription were not associated in a simple way with adult pigment patterns. Although our results suggest that the evolution of ommochrome synthesis in butterfly wings likely arose in part through novel regulation of vermilion, cinnabar, and white transcription, they also point to a complex relationship between transcriptional prepatterns and pigment synthesis in V. cardui.

Amino Acid Sequence↗
PubMed1991

Cell lineage analysis of the gynoecium of maize using the transposable element Ac.

The maize gynoecium develops from a primordium comprising two distinct cell lineages: an epidermal LI and a subepidermal LII lineage. We have analyzed somatic gynoecial sectors marked with red flavonoid pigments by excision of Ac from the P locus. Somatic sector analysis indicates the epidermal lineage starts as a single cell layer at the base of the ovary and thickens into several cell layers, presumably by periclinal divisions, near the silk attachment point. The silk attachment point appears to be mainly an epidermal outgrowth of two of three fused carpels and presumably the silk contains only LI, or mostly LI, with only traces of subepidermal LII cells. The third carpel, covering the germinal face of the kernel, retains a multicellular LII and unicellular LI organization but fails to contribute substantially to stylar outgrowth. Ac transpositions in subepidermal somatic sectors are transmitted to the archesporial cell lineage. Ac transpositions that occur in epidermal sectors are not transmitted to offspring. These results demonstrate that the female megasporocyte is derived from subepidermal (LII) cells.

Clone Cells↗
PubMed1999

Bone marrow as a potential source of hepatic oval cells.

Bone marrow stem cells develop into hematopoietic and mesenchymal lineages but have not been known to participate in production of hepatocytes, biliary cells, or oval cells during liver regeneration. Cross-sex or cross-strain bone marrow and whole liver transplantation were used to trace the origin of the repopulating liver cells. Transplanted rats were treated with 2-acetylaminofluorene, to block hepatocyte proliferation, and then hepatic injury, to induce oval cell proliferation. Markers for Y chromosome, dipeptidyl peptidase IV enzyme, and L21-6 antigen were used to identify liver cells of bone marrow origin. From these cells, a proportion of the regenerated hepatic cells were shown to be donor-derived. Thus, a stem cell associated with the bone marrow has epithelial cell lineage capability.

2-Acetylaminofluorene↗