A Lineage-Specific Centromeric Satellite Sequence in the Genus Trifolium

We report the molecular structure, genomic organization, chromosomal distribution and evolutionary dynamics of TrR350, a satellite DNA isolated from the forage legume white clover (Trifolium repens L.; 2n = 4 x = 32). The basic repeating unit is an A+T rich 350 bp Hin dIII fragment with a complex dimeric structure consisting of an internal direct repeat of 156 bp packed between unrelated flanking sequences. Each 156 bp repeat has a conserved 24 bp motif repeating at two places. Most of the 24 bp short repeating units enclose a pentanucleotide CAAAA motif, presumed to be involved in breakage-reunion mechanism of tandemly repeating arrays. The dimers share high sequence homology among themselves while monomers within dimers show significant sequence divergence. Genomic Southern hybridization and/or fluorescence in situ hybridization (FISH) on 17 Trifolium species/subspecies revealed that it is a lineage-specific repeat confined to several species within the section Lotoidea originating in the Mediterranean region. The uniform length of the basic repeating unit and the centromeric localization in most of the species harbouring it reflects its extensive conservation in the lineage. However, the Hin dIII restriction profile in seven species also indicated independent evolution of this repeat.     

Mendelian segregation of normal CAG trinucleotide repeat alleles at three autosomal loci

Segregation ratio distortion (SRD) with preferential transmission of expanded CAG alleles has been reported in Machado-Joseph disease (MJD/SCA3), spinocerebellar ataxia type I (SCA1), and dentatorubral-pallidoluysian atrophy (DRPLA). We have examined the transmission frequencies of alleles in normal heterozygotes at these disease loci in 377 pairs of twins and their parents and find no evidence for SRD.     

Provisionally unique autosomal recessive chondrodysplasia punctata syndrome

Stippled epiphyses occur in several monogenie, teratogenic, or aneuploidy syndromes. We describe two sibs with a provisionally unique chondrodysplasia punctata syndrome, who have, in addition to stippled epiphyses, minor facial anomalies, short stature, and ocular colobomata. Inheritance of this condition is likely autosomal recessive. © 1993 Wiley-Liss, Inc.     

Molecular diversification of tandemly organized DNA sequences and heterochromatic chromosome regions in some triticeae species

The subtelomeric heterochromatin of rye (Secale cereale) chromosomes makes up 12–18% of the genome and consists largely of a small number of tandemly organized DNA sequence families. The genomic organization, chromosomal locations and the structural organization of monomer units of the major DNA sequences from these regions were investigated and compared in other Triticeae species from the generaSecale, Agropyron, Dasypyrum, Triticum andHordeum. Southern hybridization and polymerase chain reaction analysis established that all studied species preserve the tandem type of sequence organization but the copy number is altered drastically between species. In the pSc200 family, a fraction of the tandem arrays is present with a head-to-head orientation of dimers inS. cereale andS. montanum. Members of the same family are more heterogeneous and present as head-to-head monomers in theDasypyrum species andA. cristatum. In situ hybridization demonstrates different organization of the sequence families in the various species: pSc200 and pSc250 are concentrated in major blocks at the ends of most rye chromosome arms, whereas they are more dispersed and in smaller blocks inDasypyrum andAgropyron indicating that accumulation is not simply due to the sequence itself. In contrast to rye,D. villosum has large blocks of only pSc200 whereasD. breviaristatum shows greater amplification of pSc250. These data indicate that each repetitive family is an independent unit of evolution, and suggest that the twoDasypyrum species are not closely related. The data are discussed in terms of existing evolutionary models for repetitive DNA sequences. The contribution of random events, through molecular drive and selection, to the evolution of heterochromatic regions is considered.accepted for publication by S. Mizuno     

Characterization of the termini of linear plasmids from Nectria haematococca and their use in construction of an autonomously replicating transformation vector

Summary The mitochondria of isolate FS37 from Nectria haematococca mating population I (Fusarium solani f. sp. cucurbitae) contain two linear plasmids, pFSCI and pFSC2, of 9.2 and 8.3 kbp, respectively. Evidence for a protein blocking the 5 termini of these plasmids was obtained from exonuclease digestion experiments. A single protein band with an apparent M_r of 80 K was labeled when the DNA-protein complex of either plasmid was reacted with [¹²⁵I] Bolton-Hunter reagent and then digested with DNase I. DNA sequence analysis of the termini of both plasmids revealed long inverted repeats of 1,211 by (pFSC1) and 1,027bp (pFSC2). No sequence similarity was found between the terminal inverted repeats (TIRs) of pFSC1 and pFSC2, nor was any similarity identified between the TIRs of the these plasmids and sequences of TIRs from other linear DNAs. A restriction fragment containing the TIR of pFSCI conferred autonomous replication when incorporated into an integrative transformation vector of Ustilago maydis.     

成都汉族群体五个短串联重复序列基因频率及其种属特异性研究

目的对成都汉族群体5个短串联重复序列（short tandem repeat，STR）基因座的等位基因频率及其种属特异性进行研究，探讨其在法医学中的应用价值。方法用PCR扩增、非变性聚丙烯酰胺凝胶电泳、硝酸银染色方法，对100名成都汉族无血缘关系健康个体的5个STR基因座的等位基因频率及其种属特异性进行研究。结果D18S979、D11S2014、D18S548、D1S1667和GATA164F07在成都汉族群体中等位基因个数分别为6、5、5、7、6；基因型个数分别为12、11、13、19、14；基因型分布符合Hardy-Weinberg平衡定律。通过种属特异性分析发现5个STR基因座中，猴在D18S979、D11S2014和D1S1667基因座均检测出扩增产物，但未在人类基因座分型区内；D18S979位点人类分型区内可检测到牛、狗、鳝鱼有扩增产物，猪、鸭、鼠、兔有微弱扩增产物；D18S548位点人类分型区内只检测到牛有微弱扩增产物；D1S1667位点人类分型区内检测到狗、羊、鳝鱼有扩增产物；GATA164F07位点人类分型区内只检测到狗有微弱扩增产物；泥鳅、鸡、豚鼠在5个基因座均未检测到扩增产物。结论5个短串联重复序列中D18S979、D18S548、D1S1667和GATA164F07在成都汉族群体中具有较好的遗传多态性，D11S2014、D18S548和GATA164F07具有较好的种属特异性，在法医学个人识别和亲子鉴定中有应用价值。     

Silver STR Ⅲ系统基因座中等位基因在葡萄胎基因组中的分布及其意义

目的研究S ilver STR(Ⅲ系统3个基因座中各等位基因在葡萄胎基因组中的分布及潜在意义。方法对应用多重PCR和变性聚丙烯酰胺凝胶电泳技术鉴别出的39例遗传物质完全来自父方的完全性葡萄胎进行分析,统计S ilverSTR(Ⅲ系统3个基因座中各等位基因的出现率。结果在39例葡萄胎中,S ilver STR(Ⅲ系统的D16S539座位出现6个等位基因,D7S820座位出现5个等位基因,D13S317座位出现7个等位基因;D16S539座位中等位基因14出现率显著高于人群(P<0.05),D7S820座位中等位基因9出现率显著低于人群(P<0.01),其余各等位基因出现率与人群基因频率无显著差异;D16S539、D7S820和D13S317基因座位杂合度分别为0.1795,0.1282和0.1538;其中可追踪的23例良性葡萄胎中,D16S539出现6个等位基因,D7S820出现4个等位基因,D13S317出现7个等位基因;可追踪的7例侵袭性葡萄胎中,D7S820出现5个等位基因,D16S539与D13S317均出现4个等位基因,其中D16S539和D13S317座位的等位基因9出现率高于良性葡萄胎(P<0.01和P<0.05)。结论葡萄胎D16S539、D7S820和D13S317基因座位等位基因杂合度远低于人群杂合度;葡萄胎具有侵袭性与D16S539和D13S317座位的等位基因9出现率具有相关性。     

A case report of a de novo tandem duplication (5p) (p14 → pter)

The case described in this paper represents on the basis of cytogenetic evidence, the first reported example of a de novo tandem dup (5p)(p14----pter). Clinical changes were minimal, unlike previously described cases in which more complex structural chromosomal changes were involved and a phenotype was provisionally attributed to dup (5p)(p14----pter). The duplicated segment of minimal effect identified in this case involved more than five eighths of 5p. It is proposed that there is a localised critical segment elsewhere on the short arm of chromosome 5 (p11-p13), which when duplicated is of greater significance in terms of clinical effects.     

An Enterobacter cloacae toxin able to generate oxidative stress and to provoke dose-dependent lysis of leukocytes

We investigated an Enterobacter cloacae strain exhibiting high hemolytic and leukotoxic activity. Monomeric and polymeric forms of the toxin showed similar effects on blood cells, although the polymer was more active than the monomer. Fluorescence microscopy revealed that both forms of the FITC-labeled toxin interacted with leukocytes, principally with neutrophils. Prelytic concentrations of polymeric and monomeric toxin significantly increased the production of reactive oxygen species (ROS) in neutrophils. Conversely, lytic concentrations of both toxin forms showed an increase followed by a decrease of ROS due to neutrophil damage. Monocytes did not show oxidative stress at all the toxin concentrations assayed. The toxin-neutrophil interaction at prelytic concentrations of toxin-stimulated ROS production and led to oxidative stress with subsequent cell death by apoptosis. However, high concentrations of E. cloacae toxin damaged leukocytes, producing lysis before the trigger of apoptosis, which suggests that the toxic effect is concentration dependent. The inhibition of oxidative stress observed with genistein and chloroquine suggests a potential involvement of the tyrosine kinase and nitric oxide synthesis pathways in E. cloacae toxin-mediated elevation of ROS.     

Effects of calcium channel blockade on intestinal fluid secretion: sites of action

Most intestinal secretagogues, including cholera toxin, evoke fluid secretion in part by activating the enteric nervous system (ENS). The enterotoxins that, due to size, cannot pass the intestinal epithelial lining have been proposed to activate the ENS via the release of amines/peptides from the intestinal endocrine cells. It has been shown that calcium channel blockers of the L-type attenuate intestinal fluid secretion. This study was performed on rat jejunal segments to elucidate where calcium channel antagonists interact with the secretory nervous reflex(es) of the ENS. In vivo, net fluid transport, transmural potential difference (PD) and luminal release of serotonin from the enterochromaffin cells were monitored before and after exposing the intestinal mucosa to cholera toxin (20 μg/mL) or the calcium ionophore A23187 (0.5 mm ). In vitro, the effects of transmural electrical field stimulation (EFS) on short circuit current (SCC) was investigated using the Ussing chamber method. Cholera toxin and A23187 evoked a net fluid secretion, an increased PD and an augmented luminal release of 5-HT. These effects were markedly attenuated by giving the calcium channel blocker nifedipine i.v. (5.75 μmol kg^?1 body wt). On the other hand, nifedipine (0.02 mm ) had no significant effect on the increased SCC caused by EFS in vitro. The results obtained in the in vivo experiments suggest that the nifedipine markedly attenuates the initial event in cholera toxin- and A23187-induced secretion, the release of amines and probably also of peptides from the intestinal endocrine cells. The in vitro experiments seem to exclude an effect of the calcium channel blockade on the efferent part of the secretory nervous reflex.