A linkage map of mouse chromosome 19: definition of comparative mapping relationships with human chromosomes 10 and 11 including the MEN1 locus.

A linkage map of mouse Chromosome (Chr) 19 was constructed using an interspecific cross and markers defined by restriction fragment length variants. The map includes 20 markers, 9 of which had not been mapped previously in the mouse. The data further defined the relationship between genes on mouse Chr 19 and those on the long arm of human Chr 10 and the pericentric region of the long arm of human Chr 11. The comparative mapping analysis suggests that the proximal segment of mouse Chr 19 may contain the MEN1 locus and that the current study has identified additional genes that may be useful for positional cloning of this putative tumor suppressor gene.     

A new mouse insertional mutation that causes sensorineural deafness and vestibular defects.

This article describes a new recessive insertional mutation in the transgenic line TgN2742Rpw that causes deafness and circling behavior in mice. Histologic analysis revealed virtually complete loss of the cochlear neuroepithelium (the organ of Corti) in adult mutant mice. In association with the neuroepithelial changes, there is a dramatic reduction of the cochlear nerve supply. Adult mutants also show morphological defects of the vestibular apparatus, including degeneration of the saccular neuroepithelium and occasional malformation of utricular otoconia. Audiometric evaluations demonstrated that the mice displaying the circling phenotype are completely deaf. Molecular analysis of this mutant line revealed that the transgenic insertion occurred without creating a large deletion of the host DNA sequences. The mutant locus was mapped to a region on mouse chromosome 10, where other spontaneous, recessive mutations causing deafness in mice have been mapped.     

Fine mapping of the circling (cir) gene on the distal portion of mouse chromosome 9

Circling mice manifest profound deafness, head-tossing, and bi-directional circling behavior, which they inherit in autosomal recessive manner. Histologic examination of the inner ear reveals abnormalities of the region around the organ of Corti, spiral ganglion neurons, and outer hair cells. A genetic linkage map was constructed for an intraspecific backcross between cir and C57BL/6J mice. The cir gene was mapped to a region between D9Mit116/D9Mit15 and D9Mit38 on mouse chromosome (Chr) 9. Estimated distances between cir and D9Mit116, and between cir and D9Mit38 were 0.70 +/- 0.40 and 0.23 +/- 0.23 cM, respectively. Order of the markers was defined as follows: centromere - D9Mit182 - D9Mit51/D9Mit79/D9Mit310 - D9Mit212/D184 - D9Mit116/D9Mit15 - cir - D9Mit38 - D9Mit20 - D9Mit243 - D9Mit16 - D9Mit55/D9Mit125 - D9Mit281. On the basis of genetic mapping, we constructed a yeast artificial chromosome (YAC) contig across the cir region. The cir gene is located between the lactotransferrin (ltf) and microtubule-associated protein (map4) genes. The distal portion of mouse Chr 9 encompassing the cir region is homologous with human chromosome 3p21, which contains the Deafness, form B: Autosomal Recessive Deafness (DFNB6) locus. Therefore, the circling mouse is a potential animal model for DFNB6 deafness in humans.     

A linkage map of mouse Chromosome 1 using an interspecific cross segregating for the gld autoimmunity mutation

An interspecific backross was used to define a high resolution linkage map of mouse Chromosome (Chr) 1 and to analyze the segregation of the generalized lymphoproliferative disease (gld) mutation. Mice homozygous for gld have multiple features of autoimmune disease. Analysis of up to 428 progeny from the backcross [(C3H/HeJ-gld x Mus spretus)F₁ x C3H/HeJ-gld] established a map that spans 77.6 cM and includes 56 markers distributed over 34 ordered genetic loci. The gld mutation was mapped to a less than 1 cM segment on distal mouse Chr 1 using 357 gld phenotype-positive backcross mice. A second backcross, between the laboratory strains C57BL/6J and SWR/J, was examined to compare recombination frequency between selected markers on mouse Chr 1. Significant differences in crossover frequency were demonstrated between the interspecific backcross and the inbred laboratory cross for the entire interval studied. Sex difference in meiotic crossover frequency was also significant in the laboratory mouse cross. Two linkage groups known to be conserved between segments of mouse Chr 1 and the long arm of human Chrs 1 and 2 where further defined and a new conserved linkage group was identified that includes markers of distal mouse Chr 1 and human Chr 1, bands q32 to q42.     

Targeted point mutagenesis of mouse Kcnq1: phenotypic analysis of mice with point mutations that cause Romano-Ward syndrome in humans

Inherited long QT syndrome is most frequently associated with mutations in KCNQ1, which encodes the primary subunit of a potassium channel. Patients with mutations in KCNQ1 may show only the cardiac defect (Romano-Ward syndrome or RWS) or may also have severe deafness (Jervell and Lange-Nielsen syndrome or JLNS). Targeted disruption of mouse Kcnq1 models JLNS in that mice are deaf and show abnormal ECGs. However, the phenotype is broader than that seen in patients. Most dramatically, the inner ear defects result in a severe hyperactivity/circling behavior, which may influence cardiac function. To understand the etiology of the cardiac phenotype in these mice and to generate a potentially more useful model system, we generated new mouse lines by introducing point mutations associated with RWS. The A340E line phenocopies RWS: the repolarization phenotype is inherited in a dominant manner and is observed independent of any inner ear defect. The T311I line phenocopies JLNS, with deafness associated with inner hair cell malfunction.     

Curly bare (cub), a new mouse mutation on chromosome 11 causing skin and hair abnormalities,and a modifier gene (mcub) on chromosome 5

In the outcrossing of a new recessive mouse mutation causing hair loss, a new wavy-coated phenotype appeared. The two distinct phenotypes were shown to be alternative manifestations of the same gene mutation and attributable to a single modifier locus. The new mutation, curly bare (cub), was mapped to distal Chr 11 and the modifier (mcub) was mapped to Chr 5. When homozygous for the recessive mcub allele, cub/cub mice appear hairless. A single copy of the dominant Mcub allele confers a full, curly coat in cub/cub mice. Reciprocal transfer of full-thickness skin grafts between mutant and control animals showed that the skin phenotype was tissue autonomous. The hairless cub/cub mcub/mcub mice show normal contact sensitivity responses to oxazolone. The similarity of the wavy coat phenotype to those of Tgfa and Egfr mutations and the map positions of cub and mcub suggest candidate genes that interact in the EGF receptor signal transduction pathway.     

Effects of congenital deafness in the cochlear nuclei of Shaker-2 mice: An ultrastructural analysis of synapse morphology in the endbulbs of Held

It is well established that manipulation of the sensory environment can significantly alter central auditory system development. For example, congenitally deaf white cats exhibit synaptic alterations in the cochlear nucleus distinct from age-matched, normal hearing controls. The large, axosomatic endings of auditory nerve fibers, called endbulbs of Held, display reduced size and branching, loss of synaptic vesicles, and a hypertrophy of the associated postsynaptic densities on the target spherical bushy cells. Such alterations, however, could arise from the cat's genetic syndrome rather than from deafness. In order to examine further the role of hearing on synapse development, we have studied endbulbs of Held in the shaker-2 (sh2) mouse. These mice carry a point mutation on chromosome 11, affecting myosin 15 and producing abnormally short stereocilia in hair cells of the inner ear. The homozygous mutant mice are born deaf and develop perpetual circling behavior, although receptor cells and primary neurons remain intact at least for the initial 100 days of postnatal life. Endbulbs of Held in 7-month old, deaf sh2 mice exhibited fewer synaptic vesicles in the presynaptic ending, the loss of intercellular cisternae, and a hypertrophy of associated postsynaptic densities. On average, postsynaptic density area for sh2 endbulbs was 0.23 ± 0.19 μm² compared to 0.07 ± 0.04 μm² (p < 0.001) for age-matched, hearing littermates. These changes at the endbulb synapse in sh2 mice resemble those of the congenitally deaf white cat and are consistent with the idea that they represent a generalized response to deafness.     

Mapping of the calcium-sensing receptor gene (CASR) to human Chromosome 3q13.3-21 by fluorescence in situ hybridization,and localization to rat Chromosome 11 and mouse Chromosome 16

The calcium-sensing receptor (CASR), a member of the G-protein coupled receptor family, is expressed in both parathyroid and kidney, and aids these organs in sensing extracellular calcium levels. Inactivating mutations in the CASR gene have been described in familial hypocalciuric hypercalcemia (FHH) and neonatal severe hyperparathyroidism (NSHPT). Activating mutations in the CASR gene have been described in autosomal dominant hypoparathyroidism and familial hypocalcemia. The human CASR gene was mapped to Chromosome (Chr) 3q13.3-21 by fluorescence in situ hybridization (FISH). By somatic cell hybrid analysis, the gene was localized to human Chr 3 (hybridization to other chromosomes was not observed) and rat Chr 11. By interspecific backcross analysis, the Casr gene segregated with D16Mit4 on mouse Chr 16. These findings extend our knowledge of the synteny conservation of human Chr 3, rat Chr 11, and mouse Chr 16.     

Identification of a novel point mutation of mouse proto-oncogene c-kit through N-ethyl-N-nitrosourea mutagenesis

Manipulation of the mouse genome has emerged as an important approach for studying gene function and establishing human disease models. In this study, the mouse mutants were generated through N-ethyl-N-nitrosourea (ENU)-induced mutagenesis in C57BL/6J mice. The screening for dominant mutations yielded several mice with fur color abnormalities. One of them causes a phenotype similar to that shown by dominant-white spotting (W) allele mutants. This strain was named Wads because the homozygous mutant mice are white color, anemic, deaf, and sterile. The new mutation was mapped to 42 cM on chromosome five, where proto-oncogene c-kit resides. Sequence analysis of c-kit cDNA from Wads(m/m) revealed a unique T-to-C transition mutation that resulted in Phe-to-Ser substitution at amino acid 856 within a highly conserved tyrosine kinase domain. Compared with other c-kit mutants, Wads may present a novel loss-of-function or hypomorphic mutation. In addition to the examination of adult phenotypes in hearing loss, anemia, and mast cell deficiency, we also detected some early developmental defects during germ cell differentiation in the testis and ovary of neonatal Wads(m/m) mice. Therefore, the Wads mutant may serve as a new disease model of human piebaldism, anemia, deafness, sterility, and mast cell diseases.     

Susceptibility to streptozotocin-induced diabetes is mapped to mouse chromosome 11

To study the contribution of beta-cell vulnerability to susceptibility to diabetes, we studied beta-cell vulnerability to a single high dose of streptozotocin (STZ) in an animal model of type 2 diabetes, the NSY mouse, a sister strain of the STZ-sensitive NOD mouse, in comparison with the STZ-resistant C3H mouse. NSY mice were found to be extremely sensitive to STZ. Introgression of a single Chr 11, where STZ-sensitivity was mapped in the NOD mouse, from NSY mice converted STZ-resistant C3H mice to STZ-sensitive. Two nucleotide substitutions were identified in the nucleoredoxin gene, a positional and functional candidate gene for STZ-induced diabetes on Chr 11. These data, together with the co-localization of type 1 (Idd4) and type 2 (Nidd1n) susceptibility genes on Chr 11, suggest that the intrinsic vulnerability of pancreatic beta cells is determined by a gene or genes on Chr 11, which may also contribute to susceptibility to spontaneous diabetes.     

A rat homolog of the mouse deafness mutant jerker (je)

An autosomal recessive deafness mutant was discovered in our colony of Zucker (ZUC) rats. These mutants behave like shaker-waltzer deafness mutants, and their inner ear pathology classifies them among neuroepithelial degeneration type of deafness mutants. To determine whether this rat deafness mutation (−) defines a unique locus or one that has been previously described, we mapped its chromosomal location. F₂ progeny of (Pbrc:ZUC × BN/Crl) A/a B/b H/h+/− F₁ rats were scored for coat color and behavioral phenotypes. Segregation analysis indicated that the deafness locus might be loosely linked with B on rat Chromosome (Chr) 5 (RNO5). Therefore, 40 −/− rats were scored for BN and ZUC alleles at four additional loci, D5Mit11, D5Mit13, Oprd1, and Gnb1, known to map to RNO5 or its homolog, mouse Chr 4 (MMU4). Linkage analysis established the gene order (cM distance) as D5Mit11–(19.3)–B–(17.9)–D5Mit13–(19.2)–Oprd1–(21.5) − (1.2) Gnb1, placing the deafness locus on distal RNO5. The position of the deafness locus on RNO5 is similar to that ofjerker (je) on MMU4; the phenotypes and patterns of inheritance of the deafness mutation and je are also similar. It seems likely that the mutation affects the rat homolog of je. The rat deafness locus should, therefore, be named jerker and assigned the gene symbol Je. Received: 13 June 1995 / Accepted: 4 January 1996     

The genes encoding E-selectin (SELE) and lymphotactin (SCYC1) lie on separate chicken chromosomes although they are closely linked in human and mouse

Three differentially expressed selectin genes (SELE, SELP, and SELL), important in the initial stages of leukocyte extravasation, have been reported in mammals. All three genes map close to the chemokine SCYC1 (small inducible cytokine subfamily C, member 1) in a large conserved chromosomal segment that extends from RXRG (retinoic acid receptor, gamma) to TNNT2 (troponin T2) on Chromosome (Chr) 1 in both human and mouse. In the mouse, we demonstrate that Sele is flanked by Prrx1 (paired-related homeobox gene 1) and Scyc1 and define the order of, and distances between, loci as centromere-Prrx1-(0.7+/-0.7 cM)-Sele-(1.2+/-0.9 cM)-Scyc1-telomere. In the chicken, we isolated BAC clones containing PRRX1, SELE, and SCYC1 and positioned them by fluorescent in situ hybridization. SELE and PRRX1 mapped to the short arm of chicken Chr 8 and SCYC1 mapped to the region equivalent to 1q11-1q13 on the long arm of chicken Chr 1. The location of SELE on chicken Chr 8 was independently established by linkage analysis of COM0185, an (AT)16 microsatellite locus identified in a BAC clone that contained SELE. COM0185 was linked to several loci that mapped to one end of chicken Chr 8, with the order of loci, and genetic distances (in cM) between them defined as MSU0435, MSU0325-(7.8+/-3.7)-COM0185-(5.8+/-3.2)-ROS0338-(9.6+/-4.0)-ABR0322-(3.8+/-2.6)-GLUL. We have therefore positioned an evolutionary breakpoint in mammals and chickens between SELE and SCYC1. Furthermore, comparative mapping analysis of the RXRG-TNNT2 chromosomal segment that is conserved on human and mouse Chr 1 indicates that it is divided into four segments in the chicken, each of which maps to a different chromosome.     

Linkage mapping of fifty-eight new rat microsatellite markers

Fifty-eight new anonymous simple sequence repeats (SSR) were generated and mapped to various rat chromosomes. Among them two genes (rat homologs for human cadherin-14 and mouse fibroblast growth factor-related protein) were mapped on Chromosomes (Chrs) 2 and 11 respectively. The majority of markers were generated from a small insert genomic library specific to Chr 11, 13, 14, and 15. Twenty new markers were mapped to Chr 13, which is known to contain a blood pressure quantitative trait locus (QTL). Several approaches to obtain microsatellite markers are described. The protocols and newly generated markers should be useful for ongoing rat genome project. Received: 24 April 1998 / Accepted: 23 June 1998     

Genetic mapping of the human and mouse phospholipase C genes

To determine chromosome positions for 10 mouse phospholipase C (PLC) genes, we typed the progeny of two sets of genetic crosses for inheritance of restriction enzyme polymorphisms of each PLC. Four mouse chromosomes, Chr 1, 11, 12, and 19, contained single PLC genes. Four PLC loci, Plcb1, Plcb2, Plcb4, and Plcg1, mapped to three sites on distal mouse Chr 2. Two PLC genes, Plcd1 and Plcg2, mapped to distinct sites on Chr 8. We mapped the human homologs of eight of these genes to six chromosomes by analysis of human × rodent somatic cell hybrids. The map locations of seven of these genes were consistent with previously defined regions of conserved synteny; Plcd1 defines a new region of homology between human Chr 3 and mouse Chr 8. Received: 24 January 1996 / Accepted: 2 April 1996     

A multipoint genetic linkage map of mouse chromosome 18

We have mapped 13 loci on mouse Chromosome 18 by Southern blot analysis of restriction fragment length polymorphisms among progeny from an interspecific backcross: (C57BL/6J X Mus spretus) X M. spretus. Complete haplotype analysis of 136 of these progeny was used to establish gene order and estimate genetic distances between loci. The gene order (from centromere to telomere) and recombination distances (in centimorgans) were as follows: PGK-1rs5-4.3-Tpi-10-11.8-(Egr-1, Hmg17-rs9)-2.1-Fgfa-2.2-Grl-1-10.1-(Cdx-1, Csfmr, Pdgfrb, Pdea, Rps14)-2.1-Adrb-2-22.9-Mbp. Pgk-1rs5, Tpi-10, Hmg17-rs9, and Rps14 had not been previously mapped in the mouse; Egr-1 had only been syntenically assigned to mouse Chr 18. Nine of the loci, spanning 18 cM, have homologs on the distal long arm of human Chr5--a region rich in genes encoding growth factors and receptors. An additional previously unmapped gene, Drd-1, predicted to be on mouse Chr 18 based on its human chromosomal location, was mapped to the middle region of mouse Chr 13.     

Chromosomal Mapping of Two Members of the Human Dynein Gene Family to Chromosome Regions 7p15 and 11q13 near the Deafness Loci DFNA 5 and DFNA 11

We mapped expressed tagged sequences (ESTs) corresponding to two human dynein heavy chain genes: β heavy chain of the outer dynein arm and heavy chain isotype 1B (DYH1B), by using somatic cell hybrids and radiation hybrid panels. The EST for the β heavy chain of the outer dynein arm mapped to chromosome region 7p15, and the EST for DYH1B mapped to 11q13.5. Two loci for nonsyndromic forms of deafness, DFNA5 and DFNA11, have previously been mapped to these two chromosomal regions. Including the gene for the axonemal light chain, hp28, we have mapped three different dynein genes near loci for different forms of nonsyndromic deafness. The hypothesis that mutations in some dynein genes are associated with nonsyndromic deafness should now be tested.     

The α-subunit of the skeletal muscle sodium channel is encoded proximal to Tk-1 on mouse Chromosome 11

Recent evidence suggests that the human neuromuscular disorders, hyperkalemic periodic paralysis and paramyotonia congenita, are both caused by genetic defects in the -subunit of the adult skeletal muscle sodium channel, which maps near the growth hormone cluster (GH) on Chromosome (Chr) 17q. In view of the extensive homology between this human chromosome and mouse Chr 11, we typed an interspecies backcross to determine whether the murine homolog (Scn4a) of this sodium channel gene mapped within the conserved chromosomal segment. The cytosolic thymidine kinase gene, Tk-1, was also positioned on the genetic map of Chr 11. Both Scn4a and Tk-1 showed clear linkage to mouse Chr 11 loci previously typed in this backcross, yielding the map order: Tr ^J-(Re, Hox-2, Krt-1)-Scn4a-Tk-1. No mouse mutant that could be considered a model of either hyperkalemic periodic paralysis or paramyotonia congenita has been mapped to the appropriate region of mouse Chr 11. These data incorporate an additional locus into the already considerable degree of homology observed for these human and mouse chromosomes. These data are also consistent with the view that the conserved segment region may extend to the telomere on mouse Chr 11 and on human 17q.     

Chromosome mapping of the growth hormone receptor gene in man and mouse

Pituitary growth hormone (GH) is essential for normal growth and development in animals and GH deficiency leads to dwarfism. This hormone acts via specific high-affinity cell surface receptors found in liver and other tissues. The recent cloning and sequencing of cDNAs encoding human and rabbit GH receptors (GHR) has demonstrated that this receptor is unrelated to any previously described cell membrane receptor or growth factor receptor. We have used the cloned human GHR cDNA to map the GHR locus to the proximal short arm of human chromosome 5, region p13.1----p12, and to mouse chromosome 15 by Southern blot analysis and in situ hybridization. While human chromosome 5 carries several genes for hormone and growth factor receptors, GHR is the only growth-related gene so far mapped to the short arm. Inasmuch as GHR is the first gene with apparently homologous loci on human chromosome 5 and mouse chromosome 15, it identifies a new homologous conserved region. In humans, deficiency of GH receptor activity probably causes Laron-type dwarfism, an autosomal recessive disorder prevalent in Oriental Jews. In mice, the autosomal recessive mutation miniature (mn) is characterized by severe growth failure and early death and has been mapped to chromosome 15. Our assignment of Ghr to mouse chromosome 15 suggests this as a candidate gene for the mn mutation.