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Biomedical subjects

E E Max

Publications and source records attributed to E E Max.

At least 73 records · Page 4Linked to original sources
PubMed1983

Rabbit immunoglobulin kappa genes: structure of a germline b4 allotype J-C locus and evidence for several b4-related sequences in the rabbit genome.

To investigate the genetic mechanism by which certain rabbits can express immunoglobulins unexpected on the basis of their pedigree (i.e., "latent" allotypes), we have begun a study of the rabbit immunoglobulin kappa gene locus. Here we report the structure of a germline genomic clone that encodes the b4 allotype of rabbit kappa immunoglobulin and corresponds to the kappa gene expressed by the rabbit-mouse hybridoma 12F2. The nucleotide sequences of the joining (J) and constant (C) regions reveal structures generally similar to the homologous mouse and human loci, although only one of the five J-like sequences of this rabbit gene is apparently expressed. Southern blotting analysis of DNA from several rabbit allotypic strains by using probes derived from the cloned b4 gene demonstrates that, in contrast to mouse and human, rabbits possess multiple kappa-related sequences. Rabbits of the nominal b4, b5, b6, and b9 allotypes each contain at least two b4-related sequences that are associated with their own J regions and that are highly homologous to the cloned b4 gene in both coding and flanking regions.

Animals↗
PubMed1983

The role of rabbit immunoglobulin allotypes in an immune network.

The expression of latent allotypes is a well documented phenomenon in rabbits. Speculation about their molecular genetic basis and the mechanisms that control expression of these unexpected markers lead inevitably to questions about the Ig gene complement of the rabbit. This central question is under current study using probes derived originally from the mRNA of rabbit-mouse hybridomas secreting rabbit Ig chains. Some of the basic features of rabbit Ig genes are already clear from these studies, and DNA fragments that might encode latent allotypes have been identified with the first set of probes. Further gene closing sequencing should shortly provide a definitive answer to the question of latent allotypy and will also provide a detailed understanding of nominal Ig expression in rabbits.

Amino Acid Sequence↗
PubMed1982

Duplication and deletion in the human immunoglobulin epsilon genes.

The human IgE gene encodes a polypeptide chain that is involved in allergic reactions and in the immune response to parasitic disease in man. We have cloned three chromosomal regions corresponding to this sequence and find that two of them derive from curiously duplicated gene segments that also encode IgA constant-region genes. One of the IgE sequences corresponds to the active gene, and its structure defines a complete amino acid sequence of the human IgE constant region. The other cloned segment is a pseudogene from which the first two IgE coding domains have been deleted and replaced by a switch-like sequence that also occurs close to the normal IgE gene. The third IgE segment remains unlinked to the other heavy-chain genes. Evidently, the epsilon-alpha locus has been the site of several complicated genetic rearrangements during recent evolutionary time.

Amino Acid Sequence↗
PubMed1982

A processed human immunoglobulin epsilon gene has moved to chromosome 9.

Processed genes--genes that resemble processed RNA transcripts rather than interrupted genomic sequences--have been identified as dispersed members of several gene families. Here we describe a processed gene that is one of the three human IgE-like sequences present in the human genome. The processed IgE gene has precisely lost its three intervening sequences, thereby fusing its four coding domains. The homology of the gene to its functional counterpart ends in an adenine-rich tail followed by an 11-base-pair sequence that is directly repeated 150 base pairs 5' to its first coding domain. In addition, the processed gene is located on human chromosome 9 rather than on chromosome 14, the site of the active immunoglobulin locus. The structure and evident mobility of this sequence support the concept that sequences can move about in the genome via RNA intermediates and that processed genes are a prominent feature of genomic structure.

Animals↗
PubMed1981

The nucleotide sequence of a 5.5-kilobase DNA segment containing the mouse kappa immunoglobulin J and C region genes.

We have determined the nucleotide sequence of a 5.5-kilobase segment of cloned mouse DNA which includes regions encoding two parts of the mouse kappa immunoglobulin gene: the J regions (amino acids 96-108 of the kappa chain) and the C region (residues 109-214). This sequence allows us to rule out interruptions in the germline constant region coding segment as well as the presence of additional functional J genes in the sequenced DNA segment, although two weak homologies to J regions have been found. The complete sequence also allows us to identify a single occurrence of the heptanucleotide palindrome thought to play a role in V/J joining. This palindrome, midway between J and C regions, is the site of aberrant joining in the plasmacytoma MPC11 and may be a target for such aberrant recombination of other kappa genes. In addition, computer analysis of the J sequences suggests that those closest to the C region arose by the most recent duplication event.

Animals↗
PubMed1981

Two kappa immunoglobulin genes are expressed in the myeloma S107.

We have cloned two rearranged kappa immunoglobulin genes from the mouse myeloma cell line S107, and find that both are expressed. One gene, designated S107A, encodes the secreted kappa chain that participates in phosphocholine binding and expression of the T-15 idiotype. The other gene, designated S107B, as described here, contains an unusual junction between a V region unrelated to that of S107A and a different J region. The V-J junction preserves the triplet reading frame, but 6 nucleotides have been deleted at the recombination site. Nucleotide sequence analysis of the germline V-region precursor of S107B in comparison with other germline kappa-variable sequences reveals an "extra" 2 nucleotides in S107B between codon 95 and the palindromic heptanucleotide CACAGTG previously implicated in V-J recombination; this difference may be relevant to the 6 nucleotide deletion. Both S107A and S107B genes are expressed in the S107 cell as protein products, but unlike the S107A kappa chain, the S107B protein product is not secreted into the medium. The expression of these two kappa genes in the S107 cell has implications for theories of allelic exclusion.

Alleles↗
PubMed1981

Recombination events that activate, diversify, and delete immunoglobulin genes.

Immunoglobulin kappa light-chain diversity arises, in large part, from an array of germ-line V-region genes that undergo somatic recombination with one of four active J-region segments. The diversity provided by this combinational system is increased by a recombination mechanism that allows variation of crossover points so as to generate additional diversity at a critical region of the light chain. The elaborate mechanism for generating diversity is accompanied not only by considerable waste, in terms of unused V and J regions in a given cell, but also by a range of aberrant recombinants that fail to produce active immunoglobulin genes.

Animals↗
PubMed1980

Cloned human and mouse kappa immunoglobulin constant and J region genes conserve homology in functional segments.

The human immune system offers special advantages for study of the development and evolution of the immune response. A variety of human cell lines are available that are arrested at various stages of development, and human genes provide a convenient evolutionary point of comparison with the already well characterized genes of the mouse. In this paper, we describe the procedure we have used to clone the human kappa chain genes in both germline and rearranged configurations. We have taken advantage of distantly related probes derived from the mouse and nonstringent conditions of hybridization to find the human genes among phage lambda recombinants formed with partially purified genomic restriction fragments of human DNA. In addition to establishing a physical map of the human kappa C and J regions, we have determined the entire sequence of a germline human constant region gene (the Inv3 allele) and two of its J segments, as well as the V/J recombination site of an active human kappa chain gene. For purposes of comparison, we also determined the sequence of the chromosomal mouse constant region gene and its flanking sequences. Although mouse and human sequences have changed extensively during the 70 million years since the two species diverged. significant blocks of homology have been conserved selectively. Some of these have obvious significance in terms of DNA and RNA splicing reactions. By forming heteroduplex structures between mouse and human genes we were able to identify four human J regions that are much more stringently conserved throughout their coding sequences than are the C region genes. In addition, the middle j structure (J3) of the mouse (which is thought to be inactive) appears to be missing from the human genome.

Animals↗
PubMed1980

Variation in the crossover point of kappa immunoglobulin gene V-J recombination: evidence from a cryptic gene.

Analysis of amino acid and nucleotide sequences of kappa immunoglobulin chains and their genes has led to the hypothesis that the exact site of V-J joining in these genes varies and that this variation is partially responsible for generating amino acid diversity at the recombination site. To assess this hypothesis we have cloned and determined the sequence of one of the two V-J recombinant genes carried by the plasmacytoma MOPC173 and the V region germline precursor of this gene. We find that this V region has been joined to a J segment at a crossover point that indeed differs from the one previously described. This recombination has occurred in such a way as to produce an out of phase, missense reading frame and, hence, a cryptic light chain gene. This result directly supports the cross-over-point variation hypothesis but also indicates that the flexibility of this reaction is accompanied by a cost to the organism in terms of the generation of missense genes.

Amino Acid Sequence↗
PubMed1979

A kappa-immunoglobulin gene is formed by site-specific recombination without further somatic mutation.

The active gene for a kappa light chain is formed by a somatic recombination event that joins one of several hundred variable region genes to one of a series of recombination sites (J-segments) encoded close to the kappa constant region gene. The nucleotide sequences of cloned germ line and somatically recombined genes define the precise organisation of these genetic segments and the site and nature of the recombination event that joined them. Apart from somatic recombination, no further alteration of ther germ line sequence has occurred. The J-segment is of special interest as it encodes signals for both DNA and RNA splicing and provides a means of generating further immunoglobulin gene diversity.

Animals↗
PubMed1979

Sequences of five potential recombination sites encoded close to an immunoglobulin kappa constant region gene.

Immunoglobulin kappa chain gene formation involves site-specific somatic recombination between one of several hundred germ-line variable region genes and a joining site (or "J segment") encoded close to the constant region gene. We have cloned and determined the nucleotide sequence of major portions of the recombination region of the mouse kappa gene and discovered a series of five such J segments spread out along a segment of DNA 2.4 kilobases from the kappa constant region gene. These J segments encode the 13 COOH-terminal amino acids of the variable region, probably including amino acids involved in the antigen combining site and in heavy/light chain contacts. The J segments also display striking sequence homology to one another in both their coding and immediately flanking sequences. Major elements of a short palindrome--CAC(TA)GTG--are preserved adjacent to the recombination sites of both variable and J region genes and constitute inverted repeats at both ends of the sequences to be joined. These palindromes can be written as a hypothetical stem structure that draws variable and J regions together, providing a possible molecular basis for the DNA joining event. Four of the J segments that we have discovered encode amino acid sequences already found in myeloma proteins. By altering the frame of recombination, we can account for additional light chain amino acid sequences, suggesting that the V/J joining event might generate antibody diversity somatically both by using different combinations of variable and J region genes and by using alternative joining frames.

Animals↗
PubMed1978

Purification and characterization of chick intestine brush border membrane. Effects of 1alpha(OH) vitamin D3 treatment.

A new technique has been developed for the isolation of membrane vesicles from the vitamin D-deficient and vitamin D-treated chick intestinal brush border membrane. The technique involves removal of nuclei from a low speed pellet by discontinuous sucrose gradient centrifugation. The resulting intact brush borders are then homogenized in 0.5 M Tris and the membrane fragments purified on a glycerol gradient. This preparation represents a 20-fold purification of the brush border marker sucrase. After 1alpha-hydroxyvitamin D3 treatment there is a significant increase in membrane phospholipid phosphorous, an alteration in the fatty acid composition of the phosphatidylcholine fraction of membrane phospholipid, and a decrease in sucrase specific activity.

Animals↗
PubMed1975

Phenylalanine hydroxylase activity in liver biopsies from hyperphenylalaninemia heterozygotes: deviation from proportionality with gene dosage.

Liver biopsy samples from the patients with hyperphenylalaninemia have an average of 5 percent of the normal hydroxylase activity. The parents of the patients have between 7.3 percent (excluding the value for one parent) and 10 percent of the normal hepatic hydroxylase activity. An explanation for these findings involves negative interallelic complementation, which involves protein-protein interaction between subunits in a multimeric enzyme. In support of this model is the evidence that rat liver phenylalanine hydroxylase is a multimeric protein composed of two electrophoretically distinguishable subunits.

Alleles↗
PubMedDate not supplied

A conserved sequence in the immunoglobulin J kappa-C kappa intron: possible enhancer element.

Several functionally important genetic elements (such as the TATA box, mRNA splice sequences, poly(A) addition signal) were first detected as short segments of unexplained sequence homology within non-coding regions of different genes. A short region of unknown sequence in the intron between the human J kappa and C kappa immunoglobulin coding regions was found to be sufficiently homologous to the corresponding segment of the mouse gene to form stable heteroduplexes. Although no specific function has yet been definitely ascribed to this region (which we call the kappa intron conserved region, or KICR), some functional significance has been inferred from the findings that (1) activation of B lymphocytes induces a DNase hypersensitivity site in this region and (2) deletions including this region reduce expression of kappa genes introduced into lymphoid cells. To delineate the KICR more precisely and to test the generality of the sequence conservation in a third species, we have sequenced this region of the human and mouse genes and have examined the corresponding region of a recently cloned rabbit kappa gene. We find a segment of about 130 base pairs (bp) that shows striking conservation in all three species, demonstrating homology significantly higher than within the C kappa coding region itself. Two short sequences from the J kappa-C kappa intron that were noted by other investigators to be homologous to proposed 'enhancer' sequences both lie within the conserved region.

Animals↗