Biomedical subjects

M L Steen

Publications and source records attributed to M L Steen.

6 recordsLinked to original sources

PubMed1989

Primary structure of a mouse mastocytoma proteoglycan core protein.

The complete nucleotide sequence of a mouse mastocytoma proteoglycan core protein mRNA was determined. The mRNA, estimated to contain 1.1 kb, encodes a protein with an Mr of 16715. A 21-amino acid-residue region of the protein is composed of alternating serine and glycine residues. Southern-blot analysis of mouse genomic DNA with cDNA containing sequences corresponding to the Ser-Gly repeat region revealed more than 15 gene fragments. Hybridization with a probe corresponding to the N-terminal portion of the core protein identified two fragments, and cDNA covering the C-terminal part of the core protein and the 3' untranslated part of the mRNA hybridized to a single fragment. Antibodies against the core protein, obtained after immunization of rabbits with a fusion protein, reacted with both chondroitin sulphate proteoglycans and heparin proteoglycans produced by the tumour. In immunoblotting of a microsomal fraction from the mastocytoma, the antiserum recognized a single protein (Mr 17,000), which probably represents the core protein before glycosylation.

Aggrecans↗

PubMed1988

A rapidly evolving region in the immunoglobulin heavy chain loci of rat and mouse: postulated role of (dC-dA)n.(dG-dT)n sequences.

The nucleotide sequences of the introns that are located between the C4 exon and the first membrane exon of mouse and rat immunoglobulin epsilon-chain genes have been determined. The rat intron sequence was found to contain four separate clusters of repetitive sequences all of which consisted of (dC-dA)n.(dG-dT)n dinucleotide repeats. A comparison between this chromosomal region in mouse and rat revealed four deletions or duplications, three of which have occurred inside or at the borders of the CA clusters. Rearrangements have occurred inside or at the borders of all four repeats after the evolutionary separation of mouse and rat. The sequence comparison reveals in addition a duplication, connected to the CA repeats, which has occurred early in evolution, before the evolutionary divergence of mouse and rat. These findings suggest that (dC-dA)n.(dG-dT)n sequences are potential targets for recombination events.

Animals↗

PubMed1988

Localization of the rat immunoglobulin lambda light chain locus to chromosome 11.

Previous experiments using rat/mouse somatic cell hybrids have localized the rat c-myc gene to chromosome 7 (Sümegi et al. 1983), the rat immunoglobulin kappa locus to chromosome 4 (Perlmann et al. 1985), and the rat immunoglobulin heavy chain locus to chromosome 6 (Pear et al. 1986). Using a similar approach, we now report the localization of the rat immunoglobulin lambda light chain locus to chromosome 11.

Animals↗

PubMed1987

The immunoglobulin lambda locus in rat consists of two C lambda genes and a single V lambda gene.

The immunoglobin lambda locus of the rat has been studied. Germ-line V lambda and C lambda genes were isolated from recombinant-phage libraries and characterized by nucleotide sequencing. The results showed that the lambda locus of the rat contains one single V lambda gene and two C lambda genes, thus representing one of the least complex lambda loci so far characterized. The two C lambda genes are separated by a spacer approx. 3 kb long. Two J segments are located at the 5' side of each C lambda gene. One of the C lambda genes (C lambda 1) probably represents a pseudogene, as the J lambda 1 segments have non-functional recombination and splice signals. The organization of the rat lambda locus resembles that of mouse, except that only one cluster is present in the rat. Thus since the evolutionary separation of the rat and mouse species ten MYR ( = 10(6) years) ago, either one cluster has been lost from the rat, or duplicated in the mouse.

Animals↗

PubMed1985

Nonfunctional immunoglobulin light chain transcripts in two IgE-producing rat immunocytomas; implications for the allelic exclusion and transcription activation processes.

The rearrangement and expression of immunoglobulin light-chain genes have been studied in two IgE-producing immunocytomas, IR2 and IR162. In the IR2 tumor only one of the kappa-chain alleles is rearranged, expressing a full-length kappa-chain polypeptide. In IR162 one of the kappa-chain alleles is functionally rearranged, expressing a 1200-nucleotide (nt) long mRNA, which encodes a functional 23-kDal kappa-chain polypeptide. The second kappa-chain allele is aberrantly rearranged; i.e., a different V region is connected to a position that is located between the J cluster and the C kappa exon. Two mRNAs which are 750 and 850 nt are transcribed from the aberrantly rearranged allele, both of which appear to encode a 12-kDal polypeptide consisting of a signal sequence that is connected directly to the C region. The levels of expression from the two kappa-chain alleles are approximately the same, suggesting that no specific mechanism exists to suppress expression of a nonfunctional allele. The rat genome contains a single lambda-chain locus which includes two C-region exons. Although this locus remains in the germ-line configuration in the IR2 and the IR162 tumors, transcripts from the C lambda I and C lambda II regions were detected at a low level in both tumors. These transcripts were detected in RNA from the immunocytomas but not in rat liver RNA indicating that expression is tissue-specific. They lacked V-region sequences and resemble so-called sterile transcripts which are expressed at a low level from unrearranged mu- and kappa-chain genes.

Alleles↗

PubMed1984

Rat immunoglobulin E heavy chain locus.

A 2100 base-pair long sequence has been established which covers all four constant domains of the rat epsilon-chain. An analysis of messenger RNA from an immunoglobulin E producing rat immunocytoma revealed two separate epsilon-chain mRNA species, 2.3 X 10(3) and 2.8 X 10(3) base-pairs long. The latter mRNA encodes the membrane binding form of the epsilon-chain. The membrane exons which are located approximately 2 X 10(3) base-pairs away from the 3'-side of the CH4 exon were also sequenced. A comparison between the rat and mouse epsilon-chains at the protein sequence level revealed an overall homology of 80% which, as expected, is considerably higher than the homology found between rat and human epsilon-chains. The fourth constant domain together with the two membrane exons exhibited the highest degree of homology, 81 to 89%. Only two differences were found when the epsilon-chains from LOU and Sprague Dawley rats were compared. The most striking difference at the nucleotide sequence level between the rat, mouse, and human epsilon genes was found within the first intron. The mouse genome contains a unique 366 base-pair long sequence in this region. The inserted sequence is repetitive and present in approximately 100 copies in the mouse genome. It is flanked by 22 base-pair long direct repeats and contains also 14 base-pair long inverted repeats, thus having properties in common with transposable elements.

Animals↗