Differential expression of the GTL2 gene within the callipyge region of ovine chromosome 18

The inheritance pattern of the skeletal muscle hypertrophy phenotype caused by the callipyge gene has been characterized as polar overdominance. We hypothesized that this trait may be caused by a gain or loss of gene expression because of the reversible nature of the phenotype in paternal vs. maternal inheritance. Suppression subtraction cDNA probes were made from skeletal muscle mRNA of normal (NN) and callipyge (C(Pat)N(Mat)) animals and hybridized to Southern blots containing bacterial artificial chromosomes (BACs) that comprise a physical contig of the callipyge region. The CN-NN probes hybridized to two ovine and seven bovine BACs. Sequence analysis of fragments within those BACs indicated short regions of similarity to mouse gene trap locus (gtl2). Northern blots analysis of RNA from hypertrophy-responsive muscles show a population of GTL2 mRNA centred around 2.4 kb that were abundantly expressed in 14-day prenatal NN and C(Pat)N(Mat) lambs but were down-regulated in day 14 and day 56 postnatal NN lambs. The expression of GTL2 remained elevated in 14- and 56-day-old C(Pat)N(Mat) lambs as well as in 56-day-old N(Pat)C(Mat) and CC lambs. Expression of GTL2 in the supraspinatus, which does not undergo hypertrophy, was very low for all genotypes and ages. Isolation of cDNA sequences show extensive alternative splicing and a lack of codon bias suggesting that GTL2 does not encode a protein. The mutation of the callipyge allele has altered postnatal expression of GTL2 in muscles that undergo hypertrophy and will help identify mechanisms involved in growth, genomic imprinting and polar overdominance.     

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.     

Long-range restriction site mapping of a syntenic segment conserved between human chromosome 1 and mouse chromosome 3

A linkage map determined from segregation analysis of 338 meiotic events in an interspecific mouse cross was utilized to help investigate genomic organization of a linkage group conserved between human chromosome 1p and mouse chromosome 3. Using pulsed-field gel electrophoresis, the genes encoding the lymphocyte adhesion molecule human CD2/murine Ly-37, the alpha 1-subunit of Na, K-ATPase, the beta-subunit of thyrotropin, the beta-subunit of nerve growth factor, and muscle adenylate deaminase were similarly positioned on long-range restriction maps in both species. These studies indicate that the development of detailed genetic maps using interspecific Mus crosses facilitates rapid analysis of murine genomic organization and may enable physical mapping of syntenic regions within the human genome. Moreover, the data suggest profound conservation of genomic organization during mammalian evolution.     

Structural organization of a segment of chromosome, containing the vir gene of Bordetella pertussis

To study the structural arrangement of the chromosomal region containing vir genes of Bordetella pertussis the corresponding 15 kb fragment of Bordetella pertussis chromosomal DNA has been cloned. The sequence homology to an earlier characterized Bordetella pertussis genetical element RSBP1 and flanked by two 400 bp inverted repeats has been shown to be located at an end of a BamHI fragment. The restriction map of Bordetella pertussis 475 coincides with the previously published maps of Bordetella pertussis Tohama and 18323 permitting one to conclude the definite conservatism of the cloned sequence. The preliminary data obtained make possible mapping of the RSBP1 homologous sequence adjacent to adenylate cyclase, agglutinin 2 and pertussis toxin genes. The possible role of RSBP1 elements in the regulation of Bordetella virulence is suggested.     

Molecular characteristics of the porcine DLK1 and MEG3 genes

Imprinted genes play important roles in embryo survival and postnatal growth regulation. The DLK1 and MEG3 (previously GTL2) genes are linked and reciprocally imprinted in several mammals, but their imprinting status is still unknown in pigs. In this study, we report polymorphisms, imprinting status and QTL analyses of the porcine DLK1 and MEG3 genes. Muscle and adipose DNA and RNA samples from 30-day-old animals generated with reciprocal crosses between the Korean native pig (KNP) and Yorkshire breeds were used to analyse DLK1 and MEG3 variation and expression. The samples exhibited paternal expression of DLK1 and maternal expression of MEG3 in pigs. These results indicated that the imprinting status of the DLK1 and MEG3 genes is conserved across mammalian species. By linkage analyses, we assigned the DLK1 and MEG3 genes to the telomeric region of SSC7. By QTL analyses, we confirmed a significant polar overdominance (POD) effect in DLK1 , which was previously detected for several growth traits in pigs. However, no significant POD effect was found with the MEG3 locus.     

Potential symbiosis-specific genes uncovered by sequencing a 410-kilobase DNA region of the Bradyrhizobium japonicum chromosome

The physical and genetic map of the Bradyrhizobium japonicum chromosome revealed that nitrogen fixation and nodulation genes are clustered. Because of the complex interactions between the bacterium and the plant, we expected this chromosomal sector to contain additional genes that are involved in the maintenance of an efficient symbiosis. Therefore, we determined the nucleotide sequence of a 410-kb region. The overall G+C nucleotide content was 59.1%. Using a minimum gene length of 150 nucleotides, 388 open reading frames (ORFs) were selected as coding regions. Thirty-five percent of the predicted proteins showed similarity to proteins of rhizobia. Sixteen percent were similar only to proteins of other bacteria. No database match was found for 29%. Repetitive DNA sequence-derived ORFs accounted for the rest. The sequenced region contained all nitrogen fixation genes and, apart from nodM, all nodulation genes that were known to exist in B. japonicum. We found several genes that seem to encode transport systems for ferric citrate, molybdate, or carbon sources. Some of them are preceded by -24/-12 promoter elements. A number of putative outer membrane proteins and cell wall-modifying enzymes as well as a type III secretion system might be involved in the interaction with the host.     

Cloning,characterization and chromosome mapping of the human SMAP1 gene

Stromal membrane associated protein (smap-1) is a new murine cell surface molecule on the stromal cells. The murine smap-1 protein is induced in stromal cells by the contact with erythroid cells, which suggests that this protein may be involved in the haematopoietic progenitor cells to stromal cells interactions.Here we report the structure, map location and expression analysis of the human SMAP1 gene, which cover approximately 100 kb on chromosome 6 between D6S455 and D6S1673 markers. This gene is composed of 11 exons and encodes a 468-amino-acid protein, which shows an 86% of homology with the murine smap-1 protein. The expression of smap-1 in erythropoietic organs as well as the correlation with the erythropoietic activity of the haematopoietic organs suggest that smap-1 is induced in stromal cells by the contact with erythroid cells, defining smap-1 as a key molecule that induced an erythropoietic microenvironment in haematopoietic organs. The high sequence conservation between murine and human SMAP1, as well as its expression in bone marrow, strongly suggest conserved functions of this protein in both organisms. Recently, a constitutional translocation t(6;10)(q13;q22) has been described in a patient with severe aplastic anaemia. SMAP1 gene localizes to 6q13 and is probably implicated in erythropoiesis, therefore it remains as an interesting candidate gene.     

High-resolution mapping of a minor histocompatibility antigen gene on mouse chromosome 2

Minor histocompatibility (H) loci are significant tissue transplantation barriers but are poorly understood at the genetic and molecular level. We describe the construction of a high-resolution genetic map that positions a class II MHC-restricted minor H antigen locus and orders 12 other genes and genetic markers within the we-un interval of mouse Chromosome (Chr) 2. An intersubspecific backcross between 10.UW/Sn-H-3 ^b and CAST/Ei, an inbred stock of Mus musculus castaneus, was used for this purpose. A total of 1168 backcross mice were generated, and 71 we-un recombinants were identified. Significant compression of the genetic map in males versus females and transmission distortion of CAST-derived we, un, and A ^w genes were observed. Monoclonal T cell lines specific for two minor H alloantigens, Hd-1^a and Hd2^a, encoded by gene(s) that map to the we-un interval were used to antigen type the backcross mice. The results suggest the Hd-1^a and Hd-2^a antigens are most likely encoded by a single gene, now referred to as H-3b. The determined gene order is we-0.09±0.09-Itp-0.62±0.23-D2Mit77-0.26±0.15[Evi-4, Pcna, Prn-p]-0.26±0.15-Scg-1-0.44±0.19-[Bmp2a, D2Mit70]-0.09±0.09-[D2Mit19, D2Mit46]-1.59±0.36-D2Mit28-0.97±0.28-D2Lerl-1.50±0.35-H-3b-0.26±0.15-un (% recombination±1 SE). Because the average resolution of the backcross is 0.09 cM, the backcross panel should facilitate the physical mapping and molecular identification of a number of genes in this chromosome region.     

Physical mapping of the HOXA1 gene and the hnRPA2B1 gene in a YAC contig from human chromosome 7p14-p15

A cluster of homeobox-containing genes (HOXA) and a heterogeneous nuclear ribonucleoprotein (hnRPA2B1) have both previously been assigned to chromosome 7p15 by in situ hybridization. In this report, we constructed a YAC contig from chromosome 7p14-p15, between markers D7S2496 and D7S1838, and determined the position of the HOXA1 gene and the hnRPA2B1 gene in this YAC contig. Received: 19 November 1996 / Revised: 2 January 1997     

Genetic mapping of the rat Lcn2 gene to chromosome 3

The expression of rat 24p3, encoded by the Lcn2 gene, has been associated with rat mammary carcinomas initiated by the neu oncogene (Stoesz and Gould, 1995). In this study, we assign the Lcn2 gene to rat chromosome band 3q12 by genetic linkage analysis.