BRK/Sik expression in the gastrointestinal tract and in colon tumors.

Clones encoding the breast tumor kinase BRK were isolated from a normal human small intestinal cDNA library that was screened with the cDNA encoding the mouse epithelial-specific tyrosine kinase Sik. Although BRK and Sik share only 80% amino acid sequence identity, Southern blot hybridizations confirmed that the two proteins are orthologues. Sik was mapped to mouse distal chromosome 2, which shows conservation of synteny with human chromosome 20q13.3, the location of the BRK gene. BRK expression was examined in the normal gastrointestinal tract, colon tumor cell lines, and primary colon tumor samples. Like Sik, BRK is expressed in normal epithelial cells of the gastrointestinal tract that are undergoing terminal differentiation. BRK expression also increased during differentiation of the Caco-2 colon adenocarcinoma cell line. Modest increases in BRK expression were detected in primary colon tumors by RNase protection, in situ hybridization, and immunohistochemical assays. The BRK tyrosine kinase appears to play a role in signal transduction in the normal gastrointestinal tract, and its overexpression may be linked to the development of a variety of epithelial tumors.

Overexpression of a DEAD box protein (DDX1) in neuroblastoma and retinoblastoma cell lines.

The DEAD box gene, DDX1, is a putative RNA helicase that is co-amplified with MYCN in a subset of retinoblastoma (RB) and neuroblastoma (NB) tumors and cell lines. Although gene amplification usually involves hundreds to thousands of kilobase pairs of DNA, a number of studies suggest that co-amplified genes are only overexpressed if they provide a selective advantage to the cells in which they are amplified. Here, we further characterize DDX1 by identifying its putative transcription and translation initiation sites. We analyze DDX1 protein levels in MYCN/DDX1-amplified NB and RB cell lines using polyclonal antibodies specific to DDX1 and show that there is a good correlation with DDX1 gene copy number, DDX1 transcript levels, and DDX1 protein levels in all cell lines studied. DDX1 protein is found in both the nucleus and cytoplasm of DDX1-amplified lines but is localized primarily to the nucleus of nonamplified cells. Our results indicate that DDX1 may be involved in either the formation or progression of a subset of NB and RB tumors and suggest that DDX1 normally plays a role in the metabolism of RNAs located in the nucleus of the cell.

Comparative genomic hybridization analysis of Y79 and FISH mapping indicate the amplified human mitochondrial ATP synthase alpha-subunit gene (ATP5A) maps to chromosome 18q12-->q21.

The four mitochondrial ATP synthase alpha-subunit (ATP5A) genes map to chromosomes 2, 9, 16, and 18. In this study we have refined the localization of two of these genes by fluorescence in situ hybridization (FISH) to metaphase spreads, and further characterised the involvement of ATP5A in the amplification process in the retinoblastoma cell line Y79. Comparative genomic hybridization (CGH) analysis of Y79 indicated that gene amplification was present on both the short arm of chromosome 2 and the long arm of chromosome 18. FISH indicated that the functional ATP5A gene mapped to 18q12-->q21, the same band location identified by CGH analysis of Y79. An ATP5A pseudogene (ATP5AP1) maps to 9p12. Gains in chromosomal material at 18q12-->q21 likely involve hybridization to amplified copies of the ATP5A gene while gains at 2p24 represent hybridization to the MYCN and DDX1 genes, also amplified in Y79.

Mitochondrial ATP synthase alpha-subunit gene amplified in a retinoblastoma cell line maps to chromosome 18.

The human retinoblastoma cell line Y79 has multiple copies of the MYCN gene and the DEAD box gene DDXI. Both genes have been mapped to chromosome band 2p24. A third gene, encoding the alpha-subunit of mitochondrial ATP synthase (ATPSA), is also amplified in Y79. Here we report that there are at least four human mitochondrial ATPSA-related genes located on four different chromosomes. The ATPSA gene that is amplified in Y79 originates from chromosome 18. In Y79, the amplified copies of both the ATPSA and the MYCN genes are located on a homogeneously staining region (HSR) at chromosome band Ip34.

Hemodynamic parameters of stage 20 to stage 35 chick embryo.

Hemodynamic parameters of the chick embryo from stage 20 (3 d of a 21-d incubation) up to stage 35 (8 d) are described. Normal values of dorsal aortic flow velocity wave forms were measured with a 20-MHz directional-pulsed Doppler velocity meter that was validated to be accurate above 5 mm/s. An analysis of variance was carried out for each of the flow velocity parameters. The correlation coefficient that represents the reproducibility was satisfactory (r > 0.90). There was a 17-fold rise in mean dorsal aortic blood flow (mm3/s). Heart rate doubled from 123 +/- 12 to 239 +/- 8 bpm, and stroke volume increased from 0.14 +/- 0.08 to 1.28 +/- 0.55 mm3. A stage-related rise was seen in peak systolic and mean velocities and peak acceleration. These data may serve as a basis for flow velocity wave form investigation and interpretation in developmental stages of cardiac malformations.