A 2-Mb YAC Contig and Physical Map Covering the Chromosome 8q12 Breakpoint Cluster Region in Pleomorphic Adenomas of the Salivary Glands

Pleomorphic adenomas are benign epithelial tumors originating from the major and minor salivary glands. Extensive cytogenetic studies have demonstrated that they frequently show chromosome abnormalities involving chromosome 8, with consistent breakpoints at 8q12. In previous studies, we have shown that these breakpoints are located in a 9-cM interval betweenMOS/D8S285 and D8S260. Here, we describe directional chromosome walking studies starting from D8S260 as well as D8S285. Using the CEPH and ICRF YAC libraries, these studies resulted in the construction of two nonoverlapping YAC contigs of about 2 and 5 Mb, respectively. Initial fluorescencein situhybridization (FISH) analysis suggested that the majority of 8q12 breakpoints clustered within the 2-Mb contig, which was mapped to the centromeric part of chromosome band 8q12. This contig has at least double coverage and consists of 34 overlapping YAC clones. The localization of the YACs was confirmed by FISH analysis. On the basis of mapping data of landmarks with an average spacing of 65 kb as well as restriction enzyme analysis, a long-range physical map was established for the chromosome region spanned by the 2-Mb contig. The relative positions of various known genes and expressed sequence tags within this contig were also determined. Subsequent FISH analyses of pleomorphic adenomas using YACs as well as cosmids revealed that all but two of the 8q12 breakpoints in the primary tumors tested mapped within a 300-kb interval between theMOSproto-oncogene and STS EM156. The target gene affected by the chromosome aberrations mapping within this interval was recently shown to be thePLAG1gene, which encodes a novel zinc finger protein.     

Distribution of extracellular matrix proteins in odontogenic tumours and developing teeth.

The distribution of two cellular fibronectins (cFn), tenascin, laminin, as well as type VII collagen was studied in 14 benign odontogenic tumours of epithelial (ameloblastoma) and epithelial-ectomesenchymal (ameloblastic fibroma) origins, as well as in developing human teeth by immunocytochemical means using monoclonal antibodies (Mabs). An extradomain sequence-A-containing form of cFn (EDA-cFn) was seen in the extracellular matrix (ECM) of all tumours studied and in the mesenchyme of the developing tooth germs, indicating that cFn in these tissues are predominantly produced locally. A form of cFn containing an oncofetal domain (Onc-cFn), hitherto found only in carcinomas, was detected focally in the stroma of most ameloblastomas but was absent from ameloblastic fibromas and tooth germs. Tenascin was strongly expressed in the basement membrane (BM) zone of all odontogenic tumours and in that of the early tooth germs. Focal absence of laminin and type VII collagen from the BM of some ameloblastomas and the presence of Onc-cFn in the ECM of most ameloblastomas may correlate with their aggressive behaviour. The results also suggest that EDA-cFn and tenascin are involved in epithelial-mesenchymal interactions during tooth development and in odontogenic tumours.     

L’electromyographie du penis: Une nouvelle exploration du muscle lisse caverneux et de son controle neurologique?

The authors have investigated the electrical activity of corpus cavernous, first according to Wagner and Gerstenberg’ method, then, since one year, according to Stief method, in the basal state and following intracavernosal injection of vasoactive agents, or following various stimulation tests. They have found again the electrical activity described by these authors, but have been confronted with the difficulty in quantifying the data. Specially single potential analysis seems to them little reliable and reproducible for an objective interpretation. At this stage of their experience, they test two simpler criteria interpretation: the richness of the electrical activity, and the reactivity of the recording to various stimulations. Their preminary results suggest a correlation between those criteria and the state of the autonomic nervous system of the penis.     

Complete sequences of the rRNA genes of Drosophila melanogaster

In this, the first of three papers, we present the sequence of the ribosomal RNA (rRNA) genes of Drosophila melanogaster. The gene regions of D. melanogaster rDNA encode four individual rRNAs: 18S (1,995 nt), 5.8S (123 nt), 2S (30 nt), and 28S (3,945 nt). The ribosomal DNA (rDNA) repeat of D. melanogaster is AT rich (65.9% overall), with the spacers being particularly AT rich. Analysis of DNA simplicity reveals that, in contrast to the intergenic spacer (IGS) and the external transcribed spacer (ETS), most of the rRNA gene regions have been refractory to the action of slippage-like events, with the exception of the 28S rRNA gene expansion segments. It would seem that the 28S rRNA can accommodate the products of slippage-like events without loss of activity. In the following two papers we analyze the effects of sequence divergence on the evolution of (1) the 28S gene "expansion segments" and (2) the 28S and 18S rRNA secondary structures among eukaryotic species, respectively. Our detailed analyses reveal, in addition to unequal crossing-over, (1) the involvement of slippage and biased mutation in the evolution of the rDNA multigene family and (2) the molecular coevolution of both expansion segments and the nucleotides involved with compensatory changes required to maintain secondary structures of RNA.