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PubMed2001

Otx1 null mutant mice show partial segregation of sensory epithelia comparable to lamprey ears.

We investigated the development of inner ear innervation in Otx1 null mutants, which lack a horizontal canal, between embryonic day 12 (E12) and postnatal day 7 (P7) with DiI and immunostaining for acetylated tubulin. Comparable to control animals, horizontal crista-like fibers were found to cross over the utricle in Otx1 null mice. In mutants these fibers extend toward an area near the endolymphatic duct, not to a horizontal crista. Most Otx1 null mutants had a small patch of sensory hair cells at this position. Measurement of the area of the utricular macula suggested it to be enlarged in Otx1 null mutants. We suggest that parts of the horizontal canal crista remain incorporated in the utricular sensory epithelium in Otx1 null mutants. Other parts of the horizontal crista appear to be variably segregated to form the isolated patch of hair cells identifiable by the unique fiber trajectory as representing the horizontal canal crista. Comparison with lamprey ear innervation reveals similarities in the pattern of innervation with the dorsal macula, a sensory patch of unknown function. SEM data confirm that all foramina are less constricted in Otx1 null mutants. We propose that Otx1 is not directly involved in sensory hair cell formation of the horizontal canal but affects the segregation of the horizontal canal crista from the utricle. It also affects constriction of the two main foramina in the ear, but not their initial formation. Otx1 is thus causally related to horizontal canal morphogenesis as well as morphogenesis of these foramina.

Animals↗
PubMed1998

The RHC21 gene of budding yeast, a homologue of the fission yeast rad21+ gene, is essential for chromosome segregation.

The Saccharomyces cerevisiae gene RHC21 is a homologue of the fission yeast rad21+ gene, which affects the sensitivity of cells to gamma-irradiation and is essential for cell growth in S. pombe. Disruption of the RHC21 gene showed that it is also essential in S. cerevisiae. To examine its function in cell growth further, we have isolated temperature-sensitive mutants for the RHC21 gene and characterized one of them, termed rhc21-sk16. When this mutant was incubated at 36 degrees C, the percentage of large-budded cells was increased. Most of the large-budded cells had aberrant nuclear structures, such as unequally extended nuclear DNA with incompletely elongated spindles across the mother-daughter neck or only in a mother cell. Furthermore, a circular minichromosome is more unstable in the mutant than in the wild-type, even at 25 degrees C. Flow cytometry showed that the bulk of DNA replication takes place normally at the restrictive temperature in the mutant. These results indicated that the RHC21 gene is required for proper segregation of the chromosomes. In addition, we found that the mutant is sensitive not only to UV radiation and gamma-rays but also to the antimicrotubule agent nocodazole at 25 degrees C. This suggests that the RHC21 gene is involved in the microtubule function. We discuss how the RHC21 gene product may be involved in chromosome segregation and microtubule function.

Cell Cycle Proteins↗
PubMed1998

T-DNA mediated disruption of essential gametophytic genes in Arabidopsis is unexpectedly rare and cannot be inferred from segregation distortion alone.

Many genes are thought to be expressed during the haploid phase in plants, however, very few haploid-specific genes have been isolated so far. T-DNA insertion mutagenesis is a powerful tool for generating mutations that affect gametophyte viability and function, as disruption of a gene essential for these processes should lead to a defect in the transmission of the gametes. Mutants can therefore be screened on the basis of segregation distortion for a reporter resistance gene contained in the T-DNA. We have screened the Versailles collection of Arabidopsis transformants for 1:1 KanR:KanS segregation after selfing, focussing on gametophyte mutations which show normal transmission through one gametophyte and cause lethality or dysfunction of the other. Only 1.3% (207) of the 16,000 lines screened were scored as good candidates. Thorough genetic analysis of 38 putative T-DNA transmission defect lines (Ttd) identified 8 defective gametophyte mutants, which all showed 0 to 1% T-DNA transmission through the pollen. During the screen, we observed a high background of low-penetrance mutations, often affecting the function of both gametophytes, and many lines which were likely to carry chromosomal rearrangements. The reasons for the small number of retained lines (all male gametophytic) are discussed, as well as the finding that, for most of them, residual T-DNA transmission is obtained through the affected gametophyte.

Arabidopsis↗
PubMed2002

Vitiligo: complex segregation and linkage disequilibrium analyses with respect to microsatellite loci spanning the HLA.

Familial clustering and linkage disequilibrium studies suggest that genetic factors predispose to vitiligo, although a clear transmission pattern and cosegregation of vitiligo with specific mutations have not been demonstrated. We collected pedigree data on vitiligo from a set of 56 multigeneration families belonging to the Paisa community from Antioquia, Colombia, with the goal of applying the unified model of complex segregation and linkage disequilibrium analyses to test the hypotheses of the existence of a major gene predisposing to vitiligo and that allelic or haplotype polymorphisms of microsatellite loci at 6p21.3-21.4 spanning HLA (D6S276, D6S265, D6S273, and D6S291) are associated with this predisposition. Minimum sibship sample size to discriminate dominant and recessive inheritance models was largely accomplished. Between the 15 models of complex segregation used, the one that best fitted the data was that of a major dominant gene and the existence of strong environmental effects acting on the recessive genotype. The penetrance and risk estimations discriminated two sets of vitiligo patients: those with early onset of vitiligo cosegregating with a dominant mode of inheritance without environmental effects, and those with late onset of vitiligo cosegregating with the recessive genotype and being influenced by environmental effects. After establishing the normal distribution of allelic frequencies and performing multiple comparisons correction, the linkage disequilibrium analysis suggested that a major genetic factor could be located at 6p21.3-21.4, because we detected significant case-control differences for allele 122 at D6S265 ( Pc=0.0264) and significant linkage disequilibrium between loci D6S276 and D6S273 in the cases but not in the controls. We cannot explain these results as a consequence of evolutionary forces or as genetic stratification acting differentially on cases and controls, because there was neither deviation from the Hardy-Weinberg expectations nor genetic subdivision between cases and controls, as theta; (non-biased F(ST)) was not significantly different from 0.

Female↗
PubMed2002

Complex segregation analysis of hypospadias.

Hypospadias, when the urethra opens on the ventral side of the penis, is a common malformation seen in about 3 per 1000 male births. It is considered a complex disorder with both genetic and environmental factors involved in the pathogenesis. Low birth weight is known to be an important risk factor for hypospadias, but several observations speak in favour of genetic factors as well. In order to delineate the relative contribution of the genetic factors behind hypospadias, we performed a complex segregation analysis of 2005 pedigrees in Sweden. The probands were ascertained through the departments of paediatric surgery and departments of plastic surgery and urology in Sweden where boys with hypospadias undergo surgery. In 7% of the ascertained families one or more additional cases of hypospadias were present. The complex segregation analysis showed a heritability of 0.99 and evidence for multifactorial inheritance. The results suggest that hypospadias might be due to monogenic effects in a small proportion of the families, but that there is a multifactorial cause for the majority of the cases.

Alleles↗
PubMed1996

Complex segregation analysis of non-myoclonic idiopathic generalized epilepsy in families ascertained from probands affected with idiopathic epilepsy with tonic-clonic seizures in Antioquia, Colombia.

In an attempt to identify the possible role of major genes, multifactorial inheritance, and cohort effects in the susceptibility to idiopathic epilepsy with generalized tonic-clonic seizures of the awakening type (GTCS), complex segregation analysis was performed in 196 nuclear families ascertained through affected probands with idiopathic epilepsy with GTCS belonging to the Paisa community of Antioquia (Colombia). Models postulating no transmission, single major locus (dominant and recessive) only, and multifactorial component only, were rejected. Since the codominant single major locus model could not be rejected and models that assign no major locus to transmission, no polygenic component to transmission, and no transmission of the major effect were rejected, complex segregation analysis suggested that a major autosomal codominant allele together with a multifactorial component (mixed model) best explained clustering of idiopathic epilepsy with GTCS in families of the Paisa community. The deficit of transmission of heterozygotes (0.17) is compatible with the existence of epistasis acting on a major gene whose frequency was estimated to be 0.0211. Its transmission variance accounts for 81% of the susceptibility to idiopathic epilepsy with GTCS. The complementary variance (19%) is due to the polygenic component.

Alleles↗
PubMed2002

Root cooperation in a clonal plant: connected strawberries segregate roots.

The ability to selectively avoid competition with members of the same clone should be highly advantageous but has not been demonstrated in plants. We found that physical connection between plants in a clone of the wild strawberry Fragaria chiloensis induced them to segregate their roots, significantly increasing clonal performance. Such increase in performance was not found when plants were grown in containers that artificially divided their rooting zones. There was no effect of connection in a different clone of F. chiloensis with a lower degree of carbon transport between connected plants, suggesting that the mechanism for root segregation depended upon transport of a signal through the strawberry runners. We suggest that clonal integration allows some clones to coordinate below-ground resource foraging with other clone members, thus exhibiting a type of root cooperation.

Biomass↗
PubMed2006

Polycyclic aromatic hydrocarbons in bulk PM2.5 and size-segregated aerosol particle samples measured in an urban environment.

To analyze polycyclic aromatic hydrocarbons (PAHs) at an urban site in Seoul, South Korea, 24-hr ambient air PM2.5 samples were collected during five intensive sampling periods between November 1998 and December 1999. To determine the PAH size distribution, 3-day size-segregated aerosol samples were also collected in December 1999. Concentrations of the 16 PAHs in the PM2.5 particles ranged from 3.9 to 119.9 ng m(-3) with a mean of 24.3 ng m(-3). An exceptionally high concentration of PAHs( approximately 120 ng m(-3)) observed during a haze event in December 1999 was likely influenced more by diesel vehicle exhaust than by gasoline exhaust, as well as air stagnation, as evidenced by the low carbon monoxide/elemental carbon (CO/EC) ratio of 205 found in this study and results reported by previous studies. The total PAHs associated with the size-segregated particles showed unimodal distributions. Compared to the unimodal size distributions of PAHs with modal peaks at < 0.12 microm measured in highway tunnels in Los Angeles (Venkataraman and Friedlander, 1994), four- to six-ring PAHs in our study had unimodal size distributions, peaking at the larger size range of 0.28-0.53 microm, suggesting the coagulation of freshly emitted ultrafine particles during transport to the sampling site. Further, the fraction of PAHs associated with coarse particles(> 1.8 microm) increased as the molecular weight of the PAHs decreased due to volatilization of fine particles followed by condensation onto coarse particles.

Aerosols↗
PubMed2007

Genotyping of phenotypically defined cells in neoplasia: enhanced immunoFISH via tyramide signal amplification (TSA) segregates immunophenotypically-defined cell populations for gated genotyping.

Molecular morphologic tools exist for simultaneously visualizing immunophenotype and genotype of tumors, but are frequently hampered by a delicate balance between removing sufficient amount of the protein blocking full access of the probe to hybridize to target nucleic acids while still preserving sufficient target antigen for immunophenotyping. The result is often suboptimal, with either insufficiently visualized gene deletions and amplifications due to masking protein, or overdigestion of the protein target. Our purpose was to design and validate a gated genotyping assay that enables optimal and concomitant detection of both gene and protein. Using the proliferating endothelial cell compartment within gliomas organized in a tissue microarray (TMA), we tested the hypothesis that tyramide signal amplification (TSA) with deposition of a fluorochrome could be used during immunophenotyping, permitting sufficient protein digestion while insuring probe accessibility to nucleic acid target. The method was successfully validated using a TMA containing 38 glioma cases previously genotyped for EGFR amplification. CD31 positive endothelial cells were segregated via TSA-based Alexa-Fluor 647 immunofluorescence for analysis of EGFR amplification of the gliomas organized in the TMA. Enhanced immunoFISH (TSA) successfully segregates immunophenotypically-defined cell populations for gated genotyping.

ErbB Receptors↗
PubMed2006

Residential segregation and Latino, black and white mortality in New York City.

Although racial segregation is associated with health status, few studies have examined this relationship among Latinos. We examined the effect of race/ethnic group concentration of Latinos, blacks and whites on all-cause mortality rates within a highly segregated metropolitan area, New York City (NYC). We linked NYC mortality records from 1999 and 2000 with the 2000 U.S. Census data by zip code area. Age-adjusted mortality rates by race/ethnic concentration were calculated. Linear regression was used to determine the association between population characteristics and mortality. Blacks living in predominantly black areas had lower all-cause mortality rates than blacks living in other areas regardless of gender (1616/100,000 vs. 2014/100,000 for men; 1032/100,000 vs. 1362/100,000 for women). Amongst whites, those living in predominantly white areas had the lowest mortality rates. Latinos living in predominantly Latino areas had lower mortality rates than those in predominantly black areas (1187/100,000 vs.1950/100,000 for men; 760/100,000 vs. 779/100,000 for women). After adjustment for socioeconomic conditions, whites, older blacks, and young Latino men experienced decreasing mortality rates when living in areas with increasing similar race/ethnic concentrations. Increasing residential concentration of blacks is independently associated with lower mortality in older blacks; similarly, increasing residential concentration of Latinos and whites is associated with lower mortality in young Latino men and whites, respectively.

Adult↗
PubMed1985

Segregation of electroreceptive and mechanoreceptive lateral line afferents in the hindbrain of chondrostean fishes.

The anterior lateral line nerve (ALLN) in the chondrostean fishes (sturgeon and paddlefishes) consists of both fibers innervating ampullary electroreceptors and fibers innervating the mechanoreceptive neuromasts of the cephalic lateral line system. The fibers of the posterior lateral line nerve (PLLN) innervate only mechanoreceptive neuromasts on the body trunk. The ALLN enters the medulla via dorsal and ventral roots; the dorsal root projects to the dorsal octavolateralis nucleus (DON), whereas the ventral root and the PLLN project principally to the medial octavolateralis nucleus (MON). Previous studies in elasmobranchs have demonstrated that fibers of the dorsal root of the ALLN convey electrosensory information, and fibers of the ventral root are concerned with mechanoreceptive information. Electrophysiological and neuroanatomical methods are employed in this study in order to determine if there exists a similar segregation of electroreceptive and mechanoreceptive lateral line afferents within the chondrostean medulla. In specimens of shovelnose, Scaphirhynchus platorynchus, and Atlantic sturgeon, Acipenser oxyrhynchus, and paddlefish, Polyodon spathula, evoked potentials recorded from the hindbrain and elicited by electric fields reached maximum amplitude within the DON and decreased in amplitude through the cerebellar crest. Evoked potentials elicited by stimulation of the posterior lateral line nerve achieved maximum amplitude within the MON. Single and multiple unit recordings revealed that units within the DON responded only to electric field stimulation, whereas units recorded in the MON responded only to mechanical stimulation. Horseradish peroxidase implanted beneath isolated patches of ampullae in Polyodon revealed fibers innervating electroreceptors projecting to the DON via the dorsal root of the ALLN. These results demonstrate a segregation of electroreceptive and mechanoreceptive lateral line afferent fibers in the chondrostean hindbrain, similar to that seen in elasmobranchs. This supports the contention that the electrosensory systems of elasmobranchs and chondrosteans are homologous, and are derived from the common ancestor of elasmobranch and actinopterygian fishes.

Animals↗
PubMed1990

Evidence for spontaneous segregation phenomena in mixed micelles of gangliosides.

A light scattering study of the effect of mixing in aqueous solution two gangliosides, GM2 and GT1b, having different hydrophilic headgroups and similar lipid moieties is presented. Mixed micelle formation with spatial segregation of one ganglioside with respect to the other was observed. It is also shown that segregation is a spontaneous phenomenon which is explainable only in terms of simple geometrical arguments, that is by the fact that the large headgroup of GT1b provides the lipidic core of the aggregate with a better shielding from water in the highly curved regions than the smaller headgroup of GM2 can do. This finding may be of help in understanding the behaviour of gangliosides in artificial and natural membranes.

Carbohydrate Sequence↗
PubMed1984

Combined analysis of genetic segregation and linkage under an oligogenic model.

For traits with incomplete penetrance, simultaneous segregation analysis and linkage analysis may offer increased information. Since the numerical properties of the mixed model are a drawback in this more complicated analysis, a second locus is substituted for the polygenic component yielding a simpler and more tractable oligogenic model. While less realistic, the simpler model is not easily discriminated from the mixed model, particularly when used on affection data rather than quantitative traits. Calculations for combined linkage and segregation analysis are described for nuclear families with pointers to account for sampling scheme.

Computers↗
PubMed1984

Dynamics of the actin microfilament system in the Tubifex egg during ooplasmic segregation.

Following the second polar body formation (PBF), the Tubifex egg undergoes ooplasmic segregation consisting of two steps, i.e., centrifugal migration of membranous organelles forming a subcortical ooplasmic layer and then movements of these organelles along the egg surface. The present investigation was undertaken to examine the microfilament organization in eggs during these ooplasmic rearrangements. Microfilaments throughout the egg are identified as actin by their reversible heavy meromyosin binding. Before the second PBF, a distinct network of actin filaments is present in the endoplasmic region. It is disorganized during the second PBF; short actin filaments are caused to aggregate with membranous organelles. Following the second PBF, similar short filaments become localized in the subcortical layer but not in the underlying yolky region. However, it is not until 50-60 min after the second PBF that an elaborate actin network is established in the subcortical layer. The cortex contains a sheet-like lattice of actin filaments. It is thickest around the animal pole, and tapes toward the equator of the egg. At about 90 min after the second PBF, this polarized distribution of cortical filaments becomes more pronounced as the result of their movements. Chronologically, subcortical actin network formation and cortical reorganization correspond to the later portion of the first step and the earlier portion of the second step of ooplasmic segregation, respectively. These findings are discussed in terms of ooplasmic movements and rearrangements.

Actins↗
PubMed1987

Sea urchin actin gene linkages determined by genetic segregation.

Genetic linkage between the actin genes of Strongylocentrotus purpuratus was investigated by observing the segregation of restriction fragment length polymorphisms (RFLPs). Specific RFLPs of actin gene pairs CyI/CyIIa and CyIIIa/CyIIIb always cosegregated, confirming the linkage groups CyI-CyIIa-CyIIb previously previously determined by molecular cloning. In contrast, RFLPs of actin genes CyI/CyIIa, CyIIIa/CyIIIb, and M all segregated at random with respect to one another. This demonstrates that the known actin gene clusters CyI-CyIIa-CyIIb, CyIIIa-CyIIIb, and the M actin gene are not closely linked.

Actins↗
PubMed1990

Segregation of oral from aboral ectoderm precursors is completed at fifth cleavage in the embryogenesis of Strongylocentrotus purpuratus.

A specific set of founder cells uniquely gives rise to the oral and aboral ectoderms in the regularly developing sea urchin Strongylocentrotus purpuratus. We showed earlier that the polar No and Na (animal oral and animal aboral) blastomeres are specified by third cleavage, while the respective oral and aboral lineage contributions of the left and right NL (animal lateral) blastomeres have not yet segregated from one another at third cleavage. Here we demonstrate by iontophoretic injection of lysyl rhodamine dextran lineage tracer that segregation of oral vs aboral cell fates in the lineages of the NL blastomeres has still not occurred by fourth cleavage, but at fifth cleavage there arise from the NL sublineages founder cells whose progeny contribute exclusively to the aboral ectoderm. The sister cells of these fifth cleavage blastomeres are founder cells that contribute exclusively to oral structures. The aboral ectoderm tracts to which NL derivatives give rise occupy lateral regions of the anterior aboral ectoderm, while the oral structures deriving from the NL blastomeres are the lateral sectors of the ciliated bands. The cells of the ciliated bands do not express aboral ectoderm markers and are considered to constitute the border of the oral region. With these new findings we complete our knowledge of the origins, identities, and fates of the 11 founder cells, the progeny of which exclusively give rise to the aboral ectoderm, and of the 5 founder cells, the progeny of which exclusively produce the oral ectoderm and its derivatives.

Animals↗
PubMed1990

Neuronal lineages in chimeric mouse forebrain are segregated between compartments and in the rostrocaudal and radial planes.

On the basis of neuronal phenotypes and the mode of development of the mammalian forebrain, the cerebral cortex can be subdivided into deep versus superficial layers, and the striatum into patch versus matrix compartments. Interspecific chimeric Mus musculus----Mus caroli mice were used to determine the contribution of lineage to cellular position within these forebrain compartments. Statistical analysis revealed evidence of both spatial and compartmental lineage segregation. A significant difference in genotype ratio depending on chimeric specimen was observed between areas (regardless of compartment) that were separated by greater than 300 microns in the rostrocaudal plane. Differences were observed between early-born (striatal patch and deep cortex) versus late-born (striatal matrix and superficial cortex) neurons, but not between neurons of cortex as a whole versus neurons of striatum as a whole. The difference between early- and late-born neurons was primarily due to the difference between deep and superficial cortical neurons. On a finer scale of analysis, differences in genotype ratios were seen between radially aligned deep versus superficial cortical compartments, in both the neuronal and glial populations. This evidence is consistent with an early positional and compartmental segregation of forebrain progenitor cells.

Analysis of Variance↗
PubMed1983

X chromosome-induced reversion of chromosome segregation in mouse/Chinese hamster somatic cell hybrids. Cellular recognition of native and foreign X chromosomes.

The direction of chromosome loss in two sets of mouse-Chinese hamster hybrids was compared with the direction of segregation of the same hybrids, to which an additional X chromosome derived from either of the mouse sarcoma lines MethAa, MethAs, or CMS4, was introduced at the time of the fusion. The addition of the X chromosome was carried out by substituting in place of the Chinese hamster parent a mouse X containing microcell hybrid of the latter. It was found that the addition of an X chromosome reverses the direction of chromosome segregation, but it can do so only if the mouse parent in the hybridization is different from the line from which the X originated. The possible reasons for recognition by the cells of a native and a foreign X are discussed. The existence of a multigene family on the X chromosome, involved in this recognition, is proposed.

Animals↗