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Genomic structure and chromosomal mapping of the human CD22 gene.

The human CD22 gene is expressed specifically in B lymphocytes and likely has an important function in cell-cell interactions. A nearly full length human CD22 cDNA clone was used to isolate genomic clones that span the CD22 gene. The CD22 gene is spread over 22 kb of DNA and is composed of 15 exons. The first exon contains the major transcriptional start sites. The translation initiation codon is located in exon 3, which also encodes a portion of the signal peptide. Exons 4 to 10 encode the seven Ig domains of CD22, exon 11 encodes the transmembrane domain, exons 12 to 15 encode the intracytoplasmic domain of CD22, and exon 15 also contains the 3' untranslated region. A minor form of CD22 mRNA likely results from splicing of exon 5 to exon 8, skipping exons 6 and 7. A 4.6-kb XbaI fragment of the CD22 gene was used to map the chromosomal location of CD22 by fluorescence in situ hybridization. The hybridization locus was identified by combining fluorescent images of the probe with the chromosomal banding pattern generated by an Alu probe. The results demonstrate that CD22 is located within the band region q13.1 of chromosome 19. Two closely clustered major transcription start sites and several minor start sites were mapped by primer extension. Similarly to many other lymphoid-specific genes, the CD22 promoter lacks an obvious TATA box. Approximately 4 kb of DNA 5' of the transcription start sites were sequenced and found to contain multiple Alu elements. Potential binding sites for the transcriptional factors NF-kappa B, AP-1, and Oct-2 are located within 300 bp 5' of the major transcription start sites. A 400-bp fragment (bp -339 through +71) of the CD22 promoter region was subcloned into a pGEM-chloramphenicol acetyltransferase vector and after transfection into B and T cells was found to be active in both B and T cells. Further studies of the CD22 gene should lead to a greater understanding of the expression of CD22 during B cell development and differentiation.

Antigens, CD↗

Chromosome mapping in Alcaligenes eutrophus CH34.

Mutants and mobilizing plasmids were developed as genetic tools in Alcaligenes eutrophus CH34. In order to map the chromosome, spontaneous and ethyl methane sulphonate (EMS)-induced mutants (mostly auxotrophs) were isolated. Another source of mutants was provided by the phenomenon of temperature-induced mortality and mutagenesis that is observed at 37 degrees C and is characteristic of many metallotolerant strains of A. eutrophus. Plasmid pULB113 (RP4::miniMu) was used to map the available mutations. Twenty-five loci were ordered in a circular map. pMOL50, a rearranged derivative of plasmid pMOL28, which was obtained in a survivor at 37 degrees C and displayed chromosome mobilizing activity (Cma+), was also used to mobilize chromosomal markers: resulting linkages were stronger than with pULB113, allowing confirmation of the circularity of the A. eutrophus CH34 chromosome with a small number of crosses.

Alcaligenes↗

Developmental characterization and chromosomal mapping of a LacZ transgene expressed in the mouse apical ectodermal ridge.

The apical ectodermal ridge (AER) has an essential role in limb morphogenesis involving the specification of the proximal-distal axis of the limb. During the analysis of transgenic mice that harbor a LacZ transgene, we detected strong expression of beta-galactosidase within the AER of developing embryos. In this mouse line, called Z16, the bacterial LacZ gene is linked to a Herpes simplex virus immediate early promoter that is normally silent in mice. Embryos from other independent mouse lines harboring the same DNA construct exhibited no AER specific staining. Thus, it appears that the LacZ transgene in the Z16 line is expressed in the AER in response to regulatory influences from genomic DNA flanking the integration site. By fluorescent in situ hybridization, the transgene insertion site was mapped to chromosome 12. Hemizygous and homozygous transgenic mice appear normal and are fertile. AER specific beta-galactosidase staining was detected by 9.5 days post coitum in the forelimb and hindlimb bud. beta-galactosidase staining could be seen throughout the development of the limbs up to 14.5 days post coitum when expression was restricted to the distal-most regions of the digits of the hindlimbs. The loss of beta-galactosidase staining between digits correlated with the onset of programmed cell death, or apoptosis, in the digit interzones. LacZ expression in this transgenic line represents a useful marker for studying AER function in limb specification during mouse embryogenesis.

Animals↗

Mapping chromosome landmarks in the centromere I region of Neurospora crassa.

Chromosome translocation breakpoints, RFLP heterozygosity in partial chromosome duplications, and RFLP-marked crossover events have been used as chromosomal landmarks to find the position and orientation of cloned regions flanking centromere I of Neurospora crassa. Determination of physical:genetic ratios in genomic regions flanking the loci mei-3, un-2, and his-2 supports previous evidence indicating that recombinational activity is lower in regions flanking centromere I than in the general N. crassa genome. The homogeneous distribution of crossover events found in these regions suggests that there is not a gradient of crossover inhibition in the vicinity of centromere I. Thus, a largely extended centromeric effect and/or a general crossover inhibitory effect operating on linkage group I (LGI) could constitute the basis of these abnormal physical:genetic ratios. A DNA element containing about 76% A+T was isolated from the centromeric end of a cloned region on LGIR. The fragment includes a previously undescribed DNA sequence, highly repeated in the Neurospora genome, which may correspond to centromeric DNA.

Base Composition↗

Genomic structure and chromosomal mapping of the mouse nov gene.

The nov gene encodes a cysteine-rich protein that is overexpressed in avian nephroblastomas. It is a member of the CCN family of proteins, all of which are involved in cell growth. Genomic and cDNA clones encompassing the mouse nov gene have been isolated and characterized. The mouse nov gene is highly conserved with the human and chick nov genes at the level of nucleotide sequence and genomic organization. The exon structure reflects the modular organization of the NOV protein in a number of structural domains. These are highly conserved with other members of the CCN family, as is the distribution of 38 of its 40 cysteine residues. The nov gene maps to chromosome 15, between D15 Mit 153 and D15 Mit 183, in a region of conserved synteny with human chromosome 8.

Amino Acid Sequence↗

Chromosomal mapping of five highly conserved murine homologues of the Drosophila RING finger gene seven-in-absentia.

Seven-in-absentia (sina) is epistatic to all other known genes in the sevenless-ras signaling pathway, which mediates R7 photoreceptor formation in the Drosophila eye. The murine genome contains several closely related sina homologues (Siah1A-D, Siah2) that are also likely to participate in ras signaling. As part of a genetic and biochemical analysis of the mammalian Siah genes, we have used gene-specific probes to map the chromosomal positions of each family member. Here we report their chromosomal positions in relation to a number of known mouse mutations and also describe an analysis of the human Siah genes. By comparing the complexity of the Siah genes in these two mammalian species we have gained further insight into which members of this murine multigene family are likely to be functional.

Amino Acid Sequence↗

Molecular cloning, tissue distribution, and chromosomal mapping of the human epithelial Ca2+ channel (ECAC1).

Functional and morphological analyses indicated that the epithelial Ca2+ channel (ECaC), which was recently cloned from rabbit kidney, exhibits the defining properties for being the gatekeeper in transcellular Ca2+ (re)absorption. Its human homologue provides, therefore, a molecular basis for achieving a better understanding of Ca2+ mal(re)absorption. By applying the RACE technique, the full-length cDNA of human ECaC (HGMW-approved symbol ECAC1) was obtained. It consisted of 2,772 bp with an open reading frame of 2,187 bp encoding a protein of 729 amino acids with a predicted molecular mass of 83 kDa. Phylogenetic analysis indicated that this highly selective Ca2+ channel exhibits a low level of homology (<30%) to other Ca2+ channels, suggesting that it belongs to a new family. hECaC was highly expressed in kidney, small intestine, and pancreas, and less intense expression was detected in testis, prostate, placenta, brain, colon, and rectum. These ECaC-positive tissues also expressed the 1,25-dihydroxyvitamin D3-sensitive calcium-binding proteins, calbindin-D9K and/or calbindin-D28K. The human ECaC gene mapped to chromosome 7q31.1-q31.2. Taken together, the conspicuous colocalization of hECaC and calbindins in organs that are not prime regulators of plasma Ca2+ levels could illustrate new pathways in cellular Ca2+ homeostasis.

Amino Acid Sequence↗

Ovol2, a mammalian homolog of Drosophila ovo: gene structure, chromosomal mapping, and aberrant expression in blind-sterile mice.

The ovo gene family consists of evolutionarily conserved genes including those cloned from Caenorhabditis elegans, Drosophila melanogaster, mouse, and human. Here we report the isolation and characterization of mouse Ovol2 (also known as movol2 or movo2) and provide evidence supporting the existence of multiple Ovol2 transcripts. These transcripts are produced by alternative promoter usage and alternative splicing and encode long and short OVOL2 protein isoforms, whose sequences differ from those previously reported. Mouse and human OVOL2 genes are expressed in overlapping tissues including testis, where Ovol2 expression is developmentally regulated and correlates with the meiotic/postmeiotic stages of spermatogenesis. Mouse Ovol2 maps to chromosome 2 in a region containing blind-sterile (bs), a spontaneous mutation that causes spermatogenic defects and germ cell loss. No mutation has been detected in the coding region of Ovol2 from bs mice, but Ovol2 transcription was dramatically reduced in testes from these mice, suggesting that Ovol2 is expressed in male germ cells.

Amino Acid Sequence↗

Molecular genetics of phosphorylase kinase: cDNA cloning, chromosomal mapping and isoform structure.

A deficiency in phosphorylase kinase is responsible for several forms of glycogen storage disease which differ in heredity and affected tissues. This is so because phosphorylase kinase consists of four different subunits and has multiple tissue-specific isoforms. To elucidate the molecular basis of phosphorylase kinase deficiencies, the cDNAs encoding the subunits alpha and beta were cloned and sequenced. Each subunit was shown to be encoded by a single gene. The alpha subunit gene was mapped to chromosome Xq12-q13 and the beta subunit gene to chromosome 16q12-q13. Isoform cDNAs reveal differential mRNA splicing. Thus, the stage is set for the molecular characterization of the genes and their deficiency mutations.

Amino Acid Sequence↗

Restriction fragment length polymorphism and chromosome mapping of a mouse homeo box gene, Hox-2.1.

Restriction endonuclease fragment length polymorphisms (RFLPs) were found using the cDNA probe Hox-2.1 for the homeo box-2.1 gene in the mouse. Polymorphism was detected in restriction patterns generated by fragments from HindIII digestion. The great majority of laboratory strains of mice carries the Hox-2.1a allele. Only two laboratory strains carry the Hox-2.1b allele. Among strains of wild origin, the European subspecies (Mus m. domesticus, M. m. brevirostris, and M. m. musculus) and some Asian subspecies (M. m. castaneus) carry the Hox-2.1a allele. The subspecies from Far Eastern countries (M. m. molossinus, Chinese mice of wild origin, and M. m. yamashinai) carry the Hox-2.1b allele. Using the RFLP, the Hox-2.1 gene was mapped on chromosome 11. Three-point cross test data showed that the recombination frequency is 29.6% between the Hba and the Hox-2.1 genes and 23.5% between the Hox-2.1 and the Es-3 genes. The gene order of Hba-Hox-2.1-Es-3 has been confirmed.

Animals↗

Chromosomal mapping of mouse myelin basic protein gene and structure and transcription of the partially deleted gene in shiverer mutant mice.

The gene for mouse myelin basic protein (MBP) was mapped to chromosome 18 by hybridization of cloned MBP probes to DNA from hamster-mouse hybrid cell lines, showing it to be linked to the shiverer mutation which causes abnormal CNS myelination. Genomic blotting experiments show that in the mutants five of six exons which constitute the wild-type gene have been deleted. In shiverer brains the steady state level of transcripts that initiate correctly at the 5' end of the remaining exon 1 is reduced 16-fold. These RNAs are not spliced correctly and are not efficiently polyadenylated. It is proposed that the partial deletion of the MBP gene is an important part of the shiverer lesion.

Animals↗

The human peroxisomal multifunctional protein involved in bile acid synthesis: activity measurement, deficiency in Zellweger syndrome and chromosome mapping.

The dehydrogenation of 24R,25R-varanoyl-CoA, the physiological intermediate formed during the peroxisomal breakdown of the bile acid intermediate trihydroxycoprostanic acid, was studied in human liver. The reaction appeared to be catalyzed by two different enzymes. A first one, present in the cytosol, did not discriminate between the four possible varanoyl-CoA isomers and did not require the CoA moiety. The second enzymic activity was associated with peroxisomes and acted only on the 24R,25R-isomer, in which the 24-hydroxy group possesses the D-configuration. The D-specific dehydrogenase is part of a 79 kDa protein which represents the human counterpart of a recently discovered second multifunctional protein in rat liver peroxisomes, named multifunctional protein 2 (MFP-2). Human MFP-2, like its rat counterpart, is also responsible for the formation (by hydratation) of 24R,25R-varanoyl-CoA. A deficiency of MFP-2 in Zellweger liver could be demonstrated immunologically by using antibodies against the rat enzyme and enzymically -- after removal of the cytosol -- by using 24R,25R-varanoyl-CoA. The gene coding for MFP-2 was mapped to chromosome 5q2.3.

3-Hydroxyacyl CoA Dehydrogenases↗

Human ethanol-inducible P450IIE1: complete gene sequence, promoter characterization, chromosome mapping, and cDNA-directed expression.

The human P450IIE1 gene, coding for an ethanol-inducible nitrosamine-metabolizing P-450, was isolated from a lambda EMBL3 genomic library and completely sequenced. The human gene spanned 11,413 base pairs and contained nine exons and a typical TATA box. Upstream and downstream DNAs of 2788 and 559 base pairs were also sequenced and compared to the rat gene. Significant areas of sequence similarity were observed within 140 base pairs upstream of the transcription start site in the rat and human genes. Human DNA 539 base pairs upstream of the transcription start site was inserted into the expression vector pSVOAL delta 5', and luciferase activity was detected when the constructs were introduced into a rat hepatoma cell line. The activity was over 100-fold lower than that of pRSVL, a Rous sarcoma virus LTR-driven luciferase gene. By use of panels of rodent-human cell hybrids, the gene was mapped to chromosome 10 (CYP2E locus). A full-length cDNA, constructed with the first exon of the genomic clone and a partial cDNA clone, was expressed in COS cells and found to code for N-nitrosodimethylamine demethylase activity.

Animals↗

Mapping chromosomal homologies between humans and two langurs (Semnopithecus francoisi and S. phayrei) by chromosome painting.

Chromosomal homologies were established between human and two Chinese langurs (Semnopithecus francoisi, 2n = 44, and S. phayrei, 2n = 44) by chromosome painting with chromosome-specific DNA probes of all human chromosomes except the Y. Both langur species showed identical hybridization patterns in addition to similar G-banding patterns. In total, 23 human chromosome-specific probes detected 30 homologous chromosome segments in a haploid langur genome. Except for human chromosomes 1, 2, 6, 16 and 19 probes, which each gave signals on two non-homologous langur chromosomes respectively, all other probes each hybridized to a single chromosome. The results indicate a high degree of conservation of chromosomal synteny between human and these two Chinese langurs. The human chromosome 2 probe painted the entire euchromatic regions of langur chromosomes 14 and 19. Human chromosome 1 probe hybridized to three regions on langur autosomes, one region on langur chromosome 4 and two regions on langur chromosome 5. Human 19 probe hybridized on the same pattern to one region on chromosome 4 and to two regions on langur chromosome 5, where it alternated with the human chromosome 1 probe. Human 6 and 16 probes both hybridized to one region on each of the two langur autosomes 15 and 18. Only two langur chromosomes (12 and 21) were each labelled by probes specific for two whole human chromosomes (14 and 15 and 21 and 22 respectively). Comparison of the hybridization patterns of human painting probes on these two langurs with the data on other Old World primates suggests that reciprocal and Robertsonian translocations as will as inversions could have occurred since the divergence of human and the langurs from a common ancestor. This comparison also indicates that Asian colobines are karyotypically more closely related to each other that to African colobines.

Animals↗

Mapping chromosome band 11q23 in human acute leukemia with biotinylated probes: identification of 11q23 translocation breakpoints with a yeast artificial chromosome.

Translocations involving chromosome 11, band q23, are frequent recurring abnormalities in human acute lymphoblastic and acute myeloid leukemia. We used 19 biotin-labeled probes derived from genes and anonymous cosmids for hybridization to metaphase chromosomes from leukemia cells that contained four translocations involving band 11q23: t(4;11)(q21;q23), t(6;11)(q27;q23), t(9;11)(p22;q23), and t(11;19)(q23;p13). The location of the cosmid probes relative to the breakpoint in 11q23 was the same in all translocations. Of the cosmid clones containing known genes, CD3D was proximal and PBGD, THY1, SRPR, and ETS1 were distal to the breakpoint on 11q23. Hybridization of genomic DNA from a yeast clone containing yeast artificial chromosomes (YACs), that carry 320 kilobases (kb) of human DNA including CD3D and CD3G genes, showed that the YACs were split in all four translocations. These results indicate that the breakpoint at 11q23 in each of these translocations occurs within the 320 kb encompassed by these YACs; whether the breakpoint within the YACs is precisely the same in the different translocations is presently unknown.

Adult↗

Cloning, disruption and chromosomal mapping of yeast LEU3, a putative regulatory gene.

The LEU3 gene of the yeast Saccharomyces cerevisiae, which is involved in the regulation of at least two LEU structural genes (LEU1 and LEU2), has been cloned by complementation of leu3 mutations and shown to reside within a 5.6-kb fragment. Transformation of leu3 mutants with LEU3-carrying multicopy plasmids restored normal, leucine-independent growth behavior in the recipients. It also restored approximately wild-type levels of isopropylmalate isomerase (LEU1) and beta-isopropylmalate dehydrogenase (LEU2), which were strongly reduced when exogenous leucine was supplied. Strains containing a disrupted leu3 allele were constructed by deleting 0.7-kb of LEU3 DNA and inserting the yeast HIS3 gene in its place. Like other leu3 mutants, these strains were leaky leucine auxotrophs, owing to a basal level of expression of LEU1 and LEU2. Southern transfer and genetic analyses of strains carrying a disrupted leu3 allele demonstrated that the cloned gene was LEU3, as opposed to a suppressor. Disruption of LEU3 was performed also with a diploid and shown to be nonlethal by tetrad analysis. Northern transfer experiments showed that the LEU3 gene produces mRNA approximately 2.9 kilonucleotides in length. The leu3 marker was mapped to chromosome XII by the spo11 method. Linkage to ura4 by about 44 centiMorgans places leu3 on the right arm of this chromosome.

Chromosome Mapping↗

Structure and chromosome mapping of the human SIX4 and murine Six4 genes.

Six4, a member of the homeobox gene subfamily (Six), is expressed in a developmentally regulated fashion, and supposed to be involved in embryogenesis. We cloned the human SIX4 and murine Six4 genomic DNAs and determined their structures. The structure, including the 5' upstream region of both genes, was well conserved suggesting the conserved function and regulation of these genes. Human SIX4 was mapped to chromosome 14q23.

Amino Acid Sequence↗

Gene structure and chromosome mapping of the human small-conductance calcium-activated potassium channel SK1 gene (KCNN1).

Small-conductance, calcium-activated potassium channels contribute to the afterhyperpolarization in central neurons and other cell types. Because these channels regulate neuronal excitability, defects in their genes could cause excitability disorders. The human cDNA encoding one such channel, SK1 (KCNN1), was recently cloned. Here we describe the gene structure of KCNN1 and its localization by radiation hybrid mapping to chromosome 19p13.1.

Animals↗