A new β-globin gene from the zebrafish, β E1 , and its pattern of transcription during embryogenesis

In a search for novel, developmentally regulated genes we screened randomly picked cDNA clones, obtained from zebrafish mRNA, by in situ hybridization with digoxigenin-labelled riboprobes. Out of 150 clones tested, 1 codes for a new beta-globin gene and is expressed during embryogenesis. Here we describe its pattern of expression and its use as a marker for early zebrafish erythropoiesis.     

银鲫原肠胚差异表达基因的筛选

胚胎发育是基因组中各个基因在时间和空间上选择性表达的结果。为了鉴定参与鱼类早期胚胎发育和胚层分化的调控因了,分别构建了银鲫(Carassiusauratusgibelio)原肠胚和成熟卵子的SMARTcDNA文库,并采用差异筛选的方法,从银鲫原肠胚SMARTcDNA文库中筛选不同于成熟卵子的差异表达基因。通过菌斑和PCR产物的两轮斑点杂交,从大约1500个克隆中筛选出131个阳性克隆,从中选择58个克隆测序并将测得的序列进行了数据库比对分析,结果显示这些差异表达基因大部分为参与转录和翻译的调控因子和核糖体蛋白以及一些在胚胎早期大量表达的参与脂类代谢的脂蛋白和一些未知的新基因。接着采用RTPCR技术,对其中6个基因在胚胎发育不同阶段的表达特征进行了分析,进一步证实这些基因在胚胎发育过程中存在表达差异;研究还从分析的基因中揭示出4类不同的表达模式。通过本研究,已筛选出一批在银鲫胚胎发育早期开始表达的调控基因,为开展鱼类胚胎发育早期表达基因的功能研究奠定了前期工作基础。       

Identification and Characterization of Neuron-Specific and Developmentally Regulated Gene Transcripts in the Chick Embryo Spinal Cord

Clones corresponding to neuron-specific and developmentally regulated messenger RNA species in the chick have been isolated from a complementary DNA library prepared using polyadenylated RNA from 7-day embryonic spinal cord. The library was initially screened by differential complementary DNA hybridization procedures for clones identifying polyadenylated RNAs present in embryonic spinal cord but absent from or at low abundance in liver tissue. A high proportion of selected recombinant plasmids were found to identify different RNA species which, although present in 14-day embryonic spinal cord, could not be detected in a corresponding region of the developing chick CNS that is devoid of neuronal cell bodies, the optic nerve. The neuron-specific assignment of these mRNAs within the developing neuroectoderm was confirmed using bulk-isolated neuronal and glial-enriched cell fractions from 7-day embryonic spinal cord. In addition, several distinctive patterns of developmentally regulated expression of neuron-specific messenger RNA species have been observed in the chick spinal cord. The studies lay a foundation for detailed examination of the regional and temporal distribution and control of neuronal gene expression in the chick spinal cord during embryogenesis.     

Molecular and genetic analysis of an embryonic gene, DC 8, from Daucus carota L

Summary To understand the morphogenetic and physiological processes occurring during plant embryogenesis, we isolated cDNA clones homologous to genes preferentially expressed during somatic embryogenesis. One of these cDNA clones detected an embryo-specific mRNA species with a corresponding protein of 66 kDa. The expression pattern of the mRNA is similar between somatic and zygotic embryos of carrots. To characterize the gene encoding this mRNA, we isolated the corresponding genomic clones. Molecular analysis of the DNA from several haploid and diploid carrots showed that the mRNA was encoded by a single copy gene, named DC 8. DNA sequence analysis showed that the gene consisted of three exons and coded for a hydrophilic protein with a central region composed of 17 repeats. At the NH₂-terminus no typical signal sequence was found. Immunocytochemical analysis localized the protein primarily in the vacuoles and protein bodies of zygotic embryos; the cytoplasm showed some antibody staining. The protein was also found in cell walls of endosperm tissue. The amount of DC 8 protein was too low for it to be categorized as a seed storage protein; its role in embryogenesis remains to be determined.     

Characterization and application of soybean YACs to molecular cytogenetics

Yeast artificial chromosomes (YACs) are widely used in the physical analysis of complex genomes. In addition to their value in chromosome walking for map-based cloning, YACs represent excellent probes for chromosome mapping using fluorescence in situ hybridization (FISH). We have screened such a library for low-copy-number clones by hybridization to total genomic DNA. Four clones were chosen for chromosome tagging based upon their low or moderate signal. By using degenerate oligonucleotide-primed PCR (DOP-PCR), we were able to use relatively small amounts of soybean YAC DNA, isolated directly by preparative pulsed-field gel electrophoresis, as FISH probes for both metaphase chromosome spreads and interphase nuclei. FISH chromosomal analysis using the three of the clones as probes resulted in relatively simple hybridization patterns consistent with a single homologous locus or two homoeologous loci. The fourth YAC probe resulted in a diffuse hybridization pattern with signal on all metaphase chromosomes. We conclude that YACs represent a valuable source of probes for chromosomal analysis in soybean.     

The expression and genomic organization of randomly selected cloned Drosophila melanogaster genes

A lambda recombinant DNA library containing Drosophila melanogaster nuclear DNA inserts was screened with cDNA made from oocyte and gastrula poly(A)+ RNA. 124 clones were isolated which represented sequences complementary to a distribution of abundancies of their RNAs. The clone set was then used as probes to identify those whose RNA abundancies changed during embryonic development. The vast majority of clones showed little difference during development. Four different clones were identified whose poly(A)+ RNAs were quantitatively regulated; two were oocyte-specific, and two were embryonic-specific. 44 clones were chosen for in situ hybridization to salivary gland polytene chromosomes. The location and distribution of their sites are described. A class of clones, identified by in situ hybridization to the nucleolus, is further described. These clones contain a scrambled array of ribosomal intervening sequences.     

Some somatic sequences are absent or exceedingly rare in Xenopus oocyte RNA

A variety of Xenopus laevis cDNA clones derived from somatic cell RNAs were hybridized to oocyte pA⁺ RNA separated on Northern gels. We were unable to detect oocyte pA⁺ sequences complementary to three undefined tadpole cDNA clones. With one of these clones, a complex pattern of bands appears during embryogenesis. With the other two clones, a single band appears. Two additional tadpole clones hybridize to both oocyte and tadpole RNA, but yield a more complex RNA pattern from embryos than from oocytes. One of these additional tadpole clones has complementarity to actin DNA, suggesting that the additional RNA band which appears during embryogenesis is α-actin mRNA (E. A. Sturgess, J. E. M. Ballantine, H. R. Woodland, P. R. Mohun, C. D. Lane, and G. J. Dimitriadis, 1980, J. Embryol. Exp. Morphol.58, 303–320). We have also failed to detect hybridization to oocyte pA⁺ RNA with one vitellogenin and three adult globin cDNA clones. Reconstruction experiments with purified globin mRNA from anemic adult blood cells set the lower level of sensitivity for globin mRNA at one part in 10⁶. The data suggest that some Xenopus mRNA sequences are absent or very rare in the oocyte pA⁺ RNA population.     

AIV血凝素亚型同步检测基因芯片技术研究

对流感病毒14个血凝素亚型的基因芯片检测技术进行了初步研究。通过RT-PCR克隆禽流感病毒血凝素基因片段,获得重组质粒。从重组质粒扩增大约500bp的DNA片段,浓缩后点到氨基化玻璃载体上,制成芯片。待检病毒样品用TRIzolLS提取RNA,反转录过程中用Cy5标记样品cDNAs。将标记样品与芯片杂交,扫描芯片上待检样品与芯片上捕捉探针的结合位点,杂交信号与预期设想一致。结果显示,DNA芯片技术可以提供一种有效的AIV血凝素亚型鉴别诊断方法。     

Analysis of pericentromeric chromosome 21 specific YAC clones by FISH: Identification of new markers for molecular-cytogenetic application

Fluorescence in situ hybridization (FISH) of chromosome 21 specific yeast artificial chromosome (YAC) clones after Alu-PCR (polymerase chain reaction) amplification has been used to find new region-specific DNA probes for the heterochromatic region of chromosome 21. Six overlapping YAC clones from a pericentromeric contig map (region 21cen-21q11) were analyzed. Four YAC clones were characterized as hybridizing to several chromosomal locations. They are, therefore, either chimeric or shared by different chromosomes. Two of them containing alphoid satellite DNA, are localized at the centromeric regions of chromosomes 13 and 21 (clone 243A11), and on 13cen, 21cen and 1q3 (clone 781G5); the two others are localized at both 21q11 and 13q2 (clone 759D3), and at 18p (clone 770B3). Two YACs were strongly specific for chromosome 21q11 only (clones 124A7 and 881D2). These YACs were used effectively as probes for identifications of chromosome 21 during metaphase and interphase analysis of 12 individuals, including three families with Down syndrome offspring, and 6 amniocyte samples. The location of YAC clones on 21q11 close to the centromeric region allows the application of these clones as molecular probes for the analysis of marker chromosomes with partial deletions of the long arm as well as for pre- and postnatal diagnosis of trisomy 21 when alphoid or more distal region-specific DNA probes are uninformative. Overlapping YAC clones covering human chromosome 21q may be systematically used to detect a set of band-specific DNA probes for molecular-cytogenetic application.