Region Of Chr Research Articles

Genetic Mapping of 21 Genes on Mouse Chromosome 11 Reveals Disruptions in Linkage Conservation with Human Chromosome 5

We report a high-resolution genetic map of 21 genes on the central region of mouse Chr 11. These genes were mapped by segregation analysis of more than 1650 meioses from three interspecific backcrosses. The order of these genes in mouse was compared to the previously established gene order in human. Eighteen of the 21 genes map to human Chr 5, and 2 of the genes define a proximal border for the region of homology between mouse Chr 11 and human Chr 17. Our results indicate a minimum of four rearrangements within the 10-cM region of synteny homology between mouse Chr 11 and human Chr 5. In addition, the linkage conservation is disrupted by groups of genes that map to mouse Chrs 13 and 18. These data demonstrate that large regions of conserved linkage can contain numerous chromosomal microrearrangements that have occurred since the divergence of mouse and human ancestors. Comparison of the mouse and human maps with data for other species provides an emerging picture of mammalian chromosome evolution.

Sequence variation and chromosomal mapping of the murine Cdkn2a tumor suppressor gene.

Twenty-nine mouse strains were examined for sequence variation of the Cdkn2a (p16 xNK4~) tumor suppressor gene by single-strand conformation polymorphism (SSCP) and direct sequence analyses. Polymorphisms were observed at nucleotides 53 and 61 of exon lot and at nucleotide 33 of exon 113; the polymorphism of nucleotide 53 of exon let resulted in an amino acid substitution. The mouse strains were distributed into three groups of variants. The polymorphisms in Elet segregated into two groups which cosegregated with those of El13 for all but one strain, the latter of which comprised the third group. With recombinant inbred strains derived from intervariant crosses, the Cdkn2a gene was mapped to the same approximate location as microsatellite markers D4MIT77 and D4MIT245 on Chromosome (Chr) 4. The Cdkn2a gene encodes a tumor suppressor that functions as an inhibitor of the cyclin D-dependent kinases, CDK4 and CDK6 (Kamb et al. 1994; Nobori et al. 1994; Quelle et al. 1995a; Serrano et al. 1993). These kinases regulate the transition of cells through the G1 phase of the cell cycle by controlling the functional status of the retinoblastoma protein (pRB), also a tumor suppressor (Serrano et al. 1993). As components of a common pathway for regulation of G1 passage, the inactivation of either pRb or Cdkn2a appears to be selected in various cancers (Otterson et al. 1994). The Cdkn2a gene was identified at the site of common deletion in several types of cancer on human Chr 9p21 and the syntenic region of mouse Chr 4 (Kamb et al. 1994; Nobori et al. 1994, Quelle et al. 1995a). Both the human and mouse homologs of the Cdkn2a yield two unique transcripts that utilize alternative exons 1 (Elet and El13) and incorporate exon 2 in alternative reading frames via the same splice acceptor site (Mao et al. 1995; Quelle et al. 1995b; Stone et al. 1995). The et form encodes the tumor suppressor Cdkn2a, while the 13-form encodes a 19-kDa protein (p19ARF), which is a suspected tumor suppressor (Quelle et al. 1995b). Each of the three exons of the Cdkn2a gene were polymerase chain reaction (PCR)-amplified from normal lung DNA of 29 mouse strains (27 inbred, 1 congenic, and 1 wild). When examined by SSCP and direct sequence analyses, sequence polymorphisms within Elet and El13 were revealed (Fig. 1). The polymorphisms of Elet and El13 cosegregated as three allelic forms. One form consisted of an adenine and a cytodine at nucleotides 53 (codon 18) and 61 (codon 21) of Elet, respectively, and a thymidine at nucleotide 33 (codon 11) of El13 and was present in 20 inbred strains, the congenic strain B10.D2(58N)Sn and the wild strain Mus spretus. The second form was observed in one strain (MA/M4J) and possessed the same El13 sequence as form 1, but possessed a cytidine and adenine at nucleotides 53 and 61 of Elet, respectively. Six inbred strains possessed form 3, which also had a cytidine and an adenine at nucleotides 53 and 61 of Elet, respectively, and a cyElct 10 60 allele 1 ' OCTGCAOACAGACTCKT~CAGCrC~GCrCCOCCCA~CGTGTGCATGACGTGCGG allele 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C . . . . . . . A . . allele 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C . . . . . . . C . .

Paternal transmission of the mouse Thp mutation is lethal in some genetic backgrounds

Thp is a large deletion on chromosome 17 which includes the maternal lethal gene Tme. Documentation of inheritance patterns suggests that Tme is an imprinted gene which is required for viability; maternal deletion is lethal while paternal deletion is viable. However, paternal transmission of Thp is rarely the expected 50%. We show here that paternally inherited Thp is lethal in some strains, providing evidence of an incompletely penetrant, dosage sensitive lethal allele of a locus that probably maps to the hairpin tail region of chr. 17. Interpretation of the various phenotypes associated with loss of the putative Tme gene, lgf2r, may need to be revised in view of these observations. Dev Genet 20:23–28, 1997. © 1997 Wiley-Liss, Inc.

Paternal transmission of the mouse Thp mutation is lethal in some genetic backgrounds.

Thp is a large deletion on chromosome 17 which includes the maternal lethal gene Tme. Documentation of inheritance patterns suggests that Tme is an imprinted gene which is required for viability; maternal deletion is lethal while paternal deletion is viable. However, paternal transmission of Thp is rarely the expected 50%. We show here that paternally inherited Thp is lethal in some strains, providing evidence of an incompletely penetrant, dosage sensitive lethal allele of a locus that probably maps to the hairpin tail region of chr. 17. Interpretation of the various phenotypes associated with loss of the putative Tme gene, Igf2r, may need to be revised in view of these observations.

Assignment of the CD45-AP Gene to the Centromeric End of Mouse Chromosome 19 and Human Chromosome 11q13.1–q13.3

CD45-AP is a recently identified phosphorylated protein that specifically associates with the leukocyte-specific transmembrane glycoprotein CD45. The gene for CD45-AP,Ptprcap(protein tyrosine phosphatase, receptor type c polypeptide associated protein), was mapped in mouse by typing the progeny of two multilocus crosses using the mouse CD45-AP cDNA as a Southern hybridization probe. The CD45-AP gene mapped to the centromeric region of Chr 19 proximal to the genesFth, Cd5,andPcna-rs.The gene for the human CD45-AP homologue,PTPRCAP,was localized to chromosome band 11q13.1–q13.3 by fluorescencein situhybridization using human genomic CD45-AP DNA as a hybridization probe. The genetic mapping of thePtprcap/PTPRCAPgenes extends the previously defined synteny conservation of various genes that have been assigned to these regions of the mouse and the human chromosomes.

The methylenetetrahydrofolate reductase (Mthfr) gene maps to distal mouse chromosome 4.

Species: Mouse Locus name: 5,10-Methylenetetrahydrofolate reductase Locus symbol: Mthfr Map position: Distal Chromosome (Chr) 4, Cen t romere D4Mit13-1.06 cM _+ 0.75-Mthfr-l.06 +_ 1.06-D4Mit42 Method of mapping: Mthfr was localized by RFLP analysis of 94 animals from an interspecific backcross panel ((C57BL/6JEi x SPRET/Ei)F 1 x SPRET/Ei) provided by The Jackson Laboratory, Bar Harbor, Me. (BSS panel) [1]. To verify the localization, RFLP analysis was performed on 94 animals from the reciprocal cross ((C57BL/6J x Mus spretus)F 1 x C57BL/6J) (BSB panel) (Fig. 1) [1]. Database deposit information: The data are available from the Mouse Genome Database, accession number MGD-CREX-672. Molecular reagents: A 727-bp mouse cDNA was obtained by reverse transcription/PCR of mouse brain RNA, with primer sequences based on sequence data of a mouse genomic clone (Pai et al. unpublished). The 5' primer (5 ' -ATGGTGAACGAGGCCAGAGGAA-3' ) began at the ATG translation initiation start site, and the 3' primer (5 ' -GCAGGCCTTCACAAAGCTGAAGA-3' ) ended at bp 727 of the mouse cDNA. Sequence analysis verified the identity of the PCR product (Frosst, results not shown). The mouse cDNA was labeled by random priming and hybridized to Southern blots of TaqI-digested mouse genomic DNA. Allele detection: Allele detection was performed by RFLP analysis of a TaqI polymorphism. The C57BL/6J strain has an allele of approximately 6.5 kb, while the Mus spretus strain has an allele of approximately 4.2 kb. A constant band of approximately 3.3 kb was seen in both strains. Previously identified homologs: Human MTHFR has been mapped to the p36.3-p36.2 region of Chr 1 by in situ hybridization [2]. Discussion: M T H F R cata lyzes the conve r s ion of 5,10methylenetetrahydrofolate to 5-methyltetrahydrofolate, the primary circulatory form of folate. 5-Methyltetrahydrofolate serves as the carbon donor for homocysteine remethylation to methionine. Recently, a common mutation in MTHFR (a C ~ T substitution at bp 677 resulting in an alanine to valine missense mutation) was proposed as a genetic risk factor for neural tube defects in man [3,4,5]. This mutation requires low folate status in plasma for the development of mild hyperhomocysteinemia [6]. This genetic-nutrient interactive effect is consistent with the multifactorial model for neural tube defects and with the established role of folic acid in reducing the recurrence and occurrence of this developmental anomaly. The curly-tail (cO mouse is a mouse model for neural tube defects; it is thought to closely mimic the human disorder with

Sex-determining genes on mouse autosomes identified by linkage analysis of C57BL/6J-YPOS sex reversal.

A powerful approach for identifying mammalian primary (gonadal) sex determination genes is the molecular genetic analyses of sex reversal conditions (that is, XX individuals with testicular tissue and XY individuals with ovarian tissue). Here we determined the number and chromosomal location of autosomal and X-linked genes that cause sex reversal in C57BL/6J (B6) mice carrying a Y chromosome of Mus domesticus poschiavinus origin (YPOS). B6 XYPOS mice develop either as females with exclusively ovarian tissue or as true hermaphrodites with ovarian and testicular tissue. In contrast, the YPOS chromosome is fully masculinizing on most other inbred strain backgrounds. B6-YPOS sex reversal appears to result from the incompatibility of the Sry (sex determining region, Y chromosome) allele carried on the YPOS chromosome with B6-derived autosomal or X-linked loci. We found strong evidence for the location of one gene, designated tda1 (testis-determining, autosomal 1), at the distal end of Chromosome (Chr) 4 and a second gene, tda2, in the central region of Chr 2. A third gene, tda3, on Chr 5 is implicated, but the evidence here is not as strong. We suggest that B6 alleles at these loci predispose XYPOS fetuses to ovarian tissue development, but no single locus or combination of loci is necessary and sufficient to cause sex reversal. The TDA proteins may regulate Sry expression or form complexes with the SRY protein to regulate other genes, or the tda genes may be activated or repressed by the SRY protein.

Localization of bovine lymphocyte antigen (BoLA) DYA and class I loci to different regions of Chromosome 23

The class II loci of the major histocompatibility complex (MHC)of humans (HLA) and mice (H-2) are embedded among other lociof the MHC, which spans approximately 4 mb of DNA and has arecombination length of about 2 cM (Campbell and Trowsdale1993; Himmelbauer et al. 1993).In contrast, recombination analysis of class II genes in thebovine lymphocyte antigen complex (BoLA) revealed two distinctclusters of class II loci about 17 cM apart (Anderson et al. 1988).One cluster designated IIa contains the bovine homologs of thehuman DQ and DR gene families and is tightly linked to otherBoLA genes, including HSP70, CYP21, and several class I loci(Bishop et al. 1994). The second cluster, IIb, contains the DYA,DYB, DOB loci and a novel class II gene designated DIB (Stoneand Muggli-Cockett 1990). The disruption of the BoLA class IIloci into two clusters suggests that the BoLA complex has under-gone significant rearrangements not yet observed in the MHCs ofhumans or mice, but that apparently have occurred in the MHCs ofchickens (Miller et al. 1994) and swine (Smith et al. 1995). Alter-natively, the bovine class IIa and IIb gene clusters could be inphysical proximity but undergo frequent recombinant owing to oneor more recombination hotspots. Recombination hotspots havebeen reported in the HLA and H-2 regions (Shiroishi et al. 1990;Steinmetz et al. 1986; Yoshino et al. 1994), and anomalous re-combination frequencies in this region among individual bullshave been reported (Park et al. 1995).To test whether the BoLA IIb cluster mapped to a differentchromosomal location than the other BoLA loci, we performedfluorescence in situ hybridization (FISH) analysis of bovine Chro-mosome (Chr) 23, using large insert clones containing DYA orclass I sequences as fluorescent probes. In this report, we demon-strate that DNA probes containing bovine DYA sequences map toa different region of Chr 23 than does DNA containing class Isequences, consistent with the reported recombination distance of17 cM between these genes.Recombinant clones of bacterial artificial chromosomes(BACs) containing DYA or class I sequences were isolated byPCR screening of a bovine BAC library (Cai et al. 1995) withprimer pairs that have been previously described (Van Eijk et al.1992; Garber et al. 1994). Authenticity of each clone was con-firmed by sequencing of the respective PCR products and com-paring with published sequences.BAC clones 6 and 76 were identified by PCR as containingDYA and class I sequences, respectively, and DNAs from theseclones were prepared for FISH. The sequence of the PCR productfrom BAC 6 differed at only a single position,

Chromosomal mapping of human angiotensinogen gene and human renin gene by fluorescence in situ hybridization (FISH) in transgenic mice.

We attempted to apply FISH to chromosomal mapping of the human angiotensinogen (hAG) and human renin (hRN) transgenes which are carried by the parental strains of the Tsukuba hypertensive mouse. We report here that the hAG gene is mapped in the C2 region of Chr 19 and the hRN gene in the A1 region of Chr 6.

444 A molecular genetic view of cancer progression

Cancer development is thought to be caused by a sequence of genetic changes, but the details of these genetic progression events are only partially understood and many important cancer genes still remain to be cloned. This presentation will highlight new strategies for dissecting the multi-step progression of breast and prostate cancer. Comparative genomic hybridization (CGH) has enabled the identification of chromosomal regions likely to harbor important genes for tumorigenesis, metastasis and drug resistance as illustrated here by three examples of breast and prostate cancer research: 1) Amplification of the 20q13 chr region was found in breast cancer suggesting the location of a new important oncogene. 2) Distant metastases of breast cancer were often found to be remotely, if at all, clonally related with the primary tumors. Measurements of e. g. prognostic factors from the primary tumors may therefore not reflect the biological properties of metastatic tumor cells. 3) In prostate cancer, amplification of the Xq12 region, the site of the human androgen receptor (AR) gene, emerged in conjunction with the development of resistance to androgen deprivation. A Ramplification was found in ≈ 25% of recurrent prostate tumors and apparently facilitated tumor cell growth in low androgen concentrations. These clinical implications of CGH illustrate the power of new genetic screening tools in dissecting the genetic basis of cancer progression.

Mapping of theSca1andpcdGenes on Mouse Chromosome 13 Provides Evidence That They Are Different Genes

It is well established that large chromosomal segments have remained intact during the evolution of different mammalian species. Thus, mapping information for a gene in mammalian species facilitates mapping the same gene in another mammalian species. In addition, phenotypically similar diseases that map to linkage conserved regions in two species may be caused by mutations in the same gene. Spinocerebellar ataxia type 1 (SCA1) is a dominantly inherited human disorder characterized by progressive ataxia, dysarthria, and dysmetria. SCA1 maps to the short arm of human chromosome (Chr) 6 in the 6p23-p22 region. SCA1 is caused by the expansion of an unstable CAG repeat located within the coding region of a novel protein, ataxin-1, Purkinje cell degeneration (pcd) is a recessively inherited mouse disorder characterized by a moderate ataxia, usually noted by 3-4 weeks of age. Progressive degeneration of Purkinje cells is the underlying pathogenesis in this disorder. The pcd gene was assigned to mouse Chr 13 because it showed linkage to extra toes (Xt) and pearl (pe). Some doubt about this assignment existed, however, because the calculated genetic distance between pcd and Xt was 32 cM and that between pcd and pe was 18 cM. If pcd is located inmore » Chr 13, its placement relative to Xt and pe suggests that it would be located in the region that shares linkage homology with the region that shares linkage homology with the region of human Chr 6 that contains SCA1. Here, we present data that confirm the assignment of pcd to Chr 13, map the mouse Sca1 gene to Chr 13, and eliminate Sca1 as a candidate gene for pcd. 11 refs., 1 tab.« less

A behavioral assessment of Ts65Dn mice: a putative Down syndrome model

Mice which are trisomic for only the human chromosome (Chr) 21-homologous segment of mouse Chr 16 (segmental trisomy), including a portion of the Down syndrome region of human Chr 21, have recently been developed. Since these segmentally trisomic mice, designated Ts(17 16)65Dn, survive to adulthood, they may represent a mouse model for the study of Down syndrome. A partial characterization of their behavioral phenotype was undertaken by evaluating the sensorimotor reflexes, exploration, locomotor activity, emotionally and spatial learning in 16 male Ts65Dn mice (TS) and 16 control (CO) littermates. No sensorimotor deficits appeared in TS compared to CO mice. By contrast, head-dipping behaviour in the hole board was increased in TS mice with respect to the CO group, showing a higher repetition rate of previously explored holes. Crossings in the open field and total arm entries in the plus maze were higher in TS than in the CO group during the dark phase of the light-dark (LD) cycle under red light, but not during the light phase of the LD cycle under white light. Entries into the open arms of the plus maze were increased overall in TS mice when compared to CO mice, but no differences were found in time spent in the open arms. TS mice showed impaired place learning in the Morris water maze, whereas they were able to reach the same performance as CO animals incued learning. Thus, absence of sensorimotor deficits, increased exploration, hyperactivity under certain experimental conditions and a moderate impairment of spatial learning were the principal characteristics observed in TS mice compared to their CO littermates.

Cloning of the murine homolog of the leukemia-associated PML gene

PML, a Ring-finger protein, participates in the disruption of normal myeloid differentiation when fused to the retinoic acid receptor alpha (RAR alpha) by the translocation between chromosomes (Chrs) 15 and 17 in acute promyelocytic leukemia (APL). As an initial step in the characterization of PML in species other than human, a murine cDNA clone of the PML gene was isolated and sequenced, and the intron/exon organization of the murine locus determined. The predicted amino acid sequence of the mouse PML protein shows 80% similarity to that of its human homolog. However, the mouse and human proteins show greater than 90% similarity in the proposed functional domains of the proteins. Despite its role in the etiology of APL, PML expression is not detectably altered during granulocytic differentiation in a murine in vitro system. Chromosomal localization of the Pml locus by somatic cell hybrids and by linkage analysis indicates that the gene maps to a region of mouse Chr 9 with known linkage homology to the region on human Chr 15q to which PML has been localized.

Cell cycle regulation of the cyclin A, cdc25C and cdc2 genes is based on a common mechanism of transcriptional repression.

The S/G2-specific transcription of the human cdc25C gene is due to the periodic occupation of a repressor element ('cell cycle-dependent element'; CDE) located in the region of the basal promoter. Protein binding to the major groove of the CDE in G0 and G1 results in a phase-specific repression of activated transcription. We now show that CDE-mediated repression is also the major principle underlying the periodic transcription of the human cyclin A and cdc2 genes. A single point mutation within the CDE results in a 10- to 20-fold deregulation in G0 and an almost complete loss of cell cycle regulation of all three genes. In addition, the cdc25C, cyclin A and cdc2 genes share an identical 5 bp region ('cell cycle genes homology region'; CHR) starting at an identical position, six nucleotides 3' to the CDE. Strikingly, mutation of the CHR region in each of the three promoters produces the same phenotype as the mutation of the CDE, i.e. a dramatic deregulation in G0. In agreement with these results, in vivo DMS footprinting showed the periodic occupation of the cyclin A CDE in the major groove, and of the CHR in the minor groove. Finally, all three genes bear conspicuous similarities in their upstream activating sequences (UAS). This applies in particular to the presence of NF-Y and Sp1 binding sites which, in the cdc25C gene, have been shown to be the targets of repression through the CDE.(ABSTRACT TRUNCATED AT 250 WORDS)

Cloning, structural analysis and mapping of the mouse selenocysteine tRNA([Ser]Sec) gene (Trsp).

The tRNA([Ser]Sec) molecule mediates the synthesis of selenoproteins by incorporating selenocysteine into specific UGA codons upon translation of mRNAs that encode selenocysteine-containing proteins. The mouse gene encoding tRNA([Ser]Sec) (Trsp) was isolated from a genomic library and sequenced. The mouse sequence is colinear with its tRNA product, and contains a C to T transition relative to the homologous genes in other vertebrates except rat. Transcriptional control motifs found 5' to the tRNA coding region included a TATA element, a PSE element and an SPH motif which is associated with an octamer motif. A Northern hybridization analysis showed highest expression in the testis, followed by thymus, spleen, kidney, ovary, brain, liver, heart and skeletal muscle. Surprisingly, the expression level was lowest in embryonic stem cells. These results suggest a tissue-specific transcriptional control. Using restriction fragment length variants (RFLVs) in interspecific backcross mice between Mus musculus (C3H strain) and Mus spretus, the Trsp gene was mapped to the proximal region of mouse Chr 7, cosegregating with octamer-binding transcription factor-2 (Otf2).

Mapping of the Insulin Promoter Factor I Gene ( Ipf1) to Distal Mouse Chromosome 5

We have identified sequence variants in the 3′ untranslated region of the insulin promoter factor 1 ( Ipf1) cDNA sequence in mice and used a PCR-based oligonucleotide hybridization assay to map the Ipf1 gene to distal mouse chromosome (Chr) 5. An identical 12-bp insertion in the 3′ untranslated region of the mouse Ipf1 gene sequence is present in Mus spretus and Mus m. musculus Czech II mice, two feral strains used for meiotic mapping by backcross analysis. The human IPF1 gene homolog would be expected to map to either chromosome 13q12-q14 or 7pter-q21 based on homology of synteny of other loci in this region of mouse Chr 5. Given its genetic map position, the Ipf1 gene may be part of a cassette of homeodomain-containing transcription factors involved in the development of the pancreas and other foregut-derived organs.

Thirteen genes (Cebpb, E2f1, Tcf4, Cyp24, Pck1, Acra4, Edn3, Kcnb1, Mc3r, Ntsr, Cd40, Plcg1andRcad) that probably lie in the distal imprinting region of mouse Chromosome 2 are not monoallelically expressed

Seven imprinted genes are currently known in the mouse but none have been identified yet in the distal imprinting region of mouse Chromosome (Chr) 2, a region which shows striking linkage conservation with human chromosome 20q13. Both maternal duplication/paternal deficiency and its reciprocal for distal Chr 2 lead to mice with abnormal body shapes and behavioural abnormalities. We have tested a number of candidate genes, that are either likely or known to lie within the distal imprinting region, for monoallelic expression. These included 3 genes (Cebpb, E2f1 and Tcf4) that express transcription factors, 2 genes (Cyp24 and Pck1) that are involved in growth, 5 genes (Acra4, Edn3, Kcnb1, Mc3r and Ntsr) where a defect could lead to neurological and probably behavioural problems, and 3 genes (Cd40, Plcg1 and Rcad) that are less obvious candidates but sequence information was available for designing primers to test their expression. On/off expression of each gene was tested by reverse transcription-polymerase chain reaction (RT-PCR) analysis of RNA extracted from tissues of mice with maternal duplication/paternal deficiency and its reciprocal for the distal region of Chr 2. None of the 13 genes is monoallelically expressed in the appropriate tissues before and shortly after birth which suggests that these genes are not imprinted later in development. This study has narrowed down the search for imprinted genes, and valuable information on which genes have been tested for on/off expression is provided. Since there is considerable evidence of conservation of imprinting between mouse and human, we would predict that the 13 genes are not imprinted in human. Five of the genes: E2f1, Tcf4, Kcnb1, Cd40 and Rcad, have not yet been mapped in human. However, because of the striking linkage conservation observed between mouse Chr 2 and human chromosome 20, we would expect these genes to map on human chromosome 20q13.

Synaptotagmin genes on mouse chromosomes 1, 7, and 10 and human chromosome 19.

The synaptotagmins (p65s) are abundant secretory vesicle membrane proteins with calcium and phospholipid binding domains that may function in calcium-dependent exocytosis in neurons and some endocrine cells. Mutations of synaptotagmin in C. elegans and Drosophila result in weakness and uncoordinated movement and are lethal (Nonet et al. 1993; Di Antonio et al. 1993). cDNAs encoding three isoforms of rat synaptotagmin have been cloned (Perin et al. 1990, 1991; Geppert et al. 1991; Mizuta et al. 1994). There is 40% overall amino acid sequence identity among the three proteins, concentrated in a region that is highly homologous to the C 2 regulatory domain of protein kinase C. The synaptotagmin genes are differentially expressed in various brain regions, Syt3 is also expressed in pituitary, thyroid, pancreatic islets, and several hormone-secreting cell lines (Mizuta et al. 1994). To evaluate the synaptotagmins as candidate genes for mouse neurological mutants, we mapped the three mouse synaptotagmin genes, using the rat cDNAs and two interspecific backcrosses. Restriction fragment length polymorphisms for Sytl, Syt2, and Syt3 were identified by digestion of genomic DNA from strains CAST/El, SPRET/Ei, and C57BL/6J (The Jackson Laboratory, Bar Harbor, Me.) and hybridization with cDNA probes (Table 1). The rat cDNA probes for Sytl (Perin et al. 1990), Syt2 (Geppert et ai. 1991; Perin et al. 1990), and Syt3 (Mizuta et al. 1994) were previously described. Primers for the Mit microsatellite markers (Dietrich et al. 1992) were obtained from Research Genetics (Birmingham, Ala.). Synaptotagmin 1 was previously localized to human Chromosome (Chr) 12 cen-q21 (Perin et ai. 1991), a region that includes two conserved groups on mouse Chrs 10 and 15. No linkage was observed between Sytl and markers for mouse Chr 15. However, analysis of markers from Chr 10 demonstrated linkage (Fig. 1A). The observed gene order and distances on distal region of mouse Chr 10 were: centromere-DlOMitlO-lO.7 +_ 5.8-Syti-10.7 + 5.8DlOMit136-7.1 +_ 4.9-DlOMitl4. Sytl is thus located within the large conserved linkage group on human Chr 12 and mouse Chr 10 that includes the region between phenylalanine hydroxylase and Erbb3 (Taylor et al. 1993). Recent mapping of two neurological mutants in this region, grizzled and jittery, relative to molecular markers (Kapfhamer and Burmeister, 1994) indicates that Sytl is located distal to both. On the basis of the reported linkage of Syt2 to the renin gene in the rat, we tested linkage between Syt2 and markers near Renl on mouse Chr 1 (Fig. 1B). The following gene order and distances were observed: centromere-D1Mit5-19.2 +_ 7.7-D1Mit140-11.5 +_ 6.3-Syt2-15.4 + 5.0-D1Mit37. Syt2 thus maps to a conserved linkage group on mouse Chr 1 and human Chr lq that includes 39 mapped genes (Seldin et al. 1993). Since no mapping data were available for Syt3, we probed The

Mouse Elk oncogene maps to chromosome X and a novel Elk oncogene ( Elk3) maps to chromosome 10

The Elk protein is a member of the Ets family found in both vertebrates and invertebrates. Human ELK1 encoded by ELK1 binds alone or together with serum response factor to DNA and regulates gene expression in a variety of biological processes. Using a panel of interspecific backcross mice, we have mapped the Elk oncogene ( Elk) and a novel type Elk oncogene ( Elk3), closely related to ELK1. Elk maps to Chr X, and Elk3 maps to the proximal region of Chr 10.

Characterization and mapping of three new mammalian ATP-binding transporter genes from an EST database

Analysis of the human expressed sequence tag (EST) database identified four clones that contain sequences of previously uncharacterized genes, members of the ATP-binding cassette (ABC) superfamily. Two new ABC genes (EST20237, 31252) are located at Chromosome (Chr) 1q42 and 1q25 respectively in humans, as determined by FISH; at locations distinct from previously mapped genes of this superfamily. Two additional clones, EST 600 and EST 1596, were found to represent different ATP-binding domains of the same gene, ABC2. This gene was localized to 9q34 in humans by FISH and to the proximal region of Chr 2 in mice by linkage analysis. All genes display extensive diversity in sequence and expression pattern. We present several approaches to characterizing EST clones and demonstrate that the analysis of EST clones from different tissues is a powerful approach to identify new members of important gene families. Some drawbacks of using EST databases, including chimerism of cDNA clones, are discussed.