The DNA sequence of human chromosome 21.

Chromosome 21 is the smallest human autosome. An extra copy of chromosome 21 causes Down syndrome, the most frequent genetic cause of significant mental retardation, which affects up to 1 in 700 live births. Several anonymous loci for monogenic disorders and predispositions for common complex disorders have also been mapped to this chromosome, and loss of heterozygosity has been observed in regions associated with solid tumours. Here we report the sequence and gene catalogue of the long arm of chromosome 21. We have sequenced 33,546,361 base pairs (bp) of DNA with very high accuracy, the largest contig being 25,491,867 bp. Only three small clone gaps and seven sequencing gaps remain, comprising about 100 kilobases. Thus, we achieved 99.7% coverage of 21q. We also sequenced 281,116 bp from the short arm. The structural features identified include duplications that are probably involved in chromosomal abnormalities and repeat structures in the telomeric and pericentromeric regions. Analysis of the chromosome revealed 127 known genes, 98 predicted genes and 59 pseudogenes.

Maturation of epidermal Langerhans cells in vitro is accompanied by downregulation of 4F2 (CD98) as determined by differential display.

Following short-term culture, Langerhans cells mature morphologically and functionally into potent immunostimulatory cells. As regulation of gene expression accompanies this maturation process, it is likely that differentially expressed genes are involved in the maturation events. Using the recently described method of differential display, we generated cDNA expression patterns starting with mRNA of murine epidermal Langerhans cells isolated either directly (fLC) or following 3 d cultivation (cLC). Five hundred putative differentially expressed cDNA fragments were recovered from the gel. For a part of the fragments differential expression was confirmed by dot blot and Southern hybridization procedures. These cDNA fragments were subcloned and sequenced following the verification step. Database searches revealed that unknown genes as well as already characterized genes were identified. A cDNA fragment preferentially hybridizing with fLC was identified as the murine surface marker 4F2 (CD98). Downregulation of the activation marker 4F2/CD98 was confirmed by additional analysis at the mRNA and protein level. The downregulation of 4F2 surface expression on cLC is compatible with the notion that the committed, terminally differentiated cLC downregulate proteins involved in proliferation and cell survival.

A bioadaptive approach for experimental pain research in humans using laser-evoked brain potentials.

In order to find an experimental approach counteracting habituation in experimental pain research using short infrared laser stimulation in humans we developed a bioadaptive method based on subject's report on painfulness of stimulation (pain report; PR). After determination of the initial relationship between the energy of the laser stimulus and the corresponding PRs, the approach continuously adjusts the intensity of noxious stimuli so that PR is kept constant across time. Each difference between the PR evoked by the actual laser stimulus and the desired PR leads to an increase or decrease of the laser output energy value for the next stimulation with the desired PR proportional to the PR difference as well as to the slope of the initial correlation function between laser energy and corresponding PRs. This method has been applied in a study with nine volunteers. Results show that the approach leads to a constant PR by increasing the laser output energy by 0.01 mJ/s per mm2 on the average. Furthermore, an analysis of the laser-evoked brain potentials (LEPs) recorded from Cz was performed for the first and second half of stimuli. However, no significant changes in latencies or amplitudes of the main LEP components recorded at 210 ms (N210) and 350 ms (P350) were found. The method seems to be useful for different approaches in experimental and clinical pain research.

PCR-amplified cDNA probes for verification of differentially expressed genes.

Differential display has proven to be a powerful technique for the detection and isolation of differentially expressed genes. By generating reproducible cDNA expression patterns, it is possible to compare gene expression by two or more cell types, developmental stages or tissues and to isolate as yet unknown differentially expressed genes. A sensitive method is necessary to verify the differential expression of the isolated cDNAs. Here we describe the use of adaptor-ligated. PCR-amplified total cDNA of the two cell types compared as a probe for Southern hybridizations with the isolated cDNAs.