The genetics of teratocarcinoma transplantation: tumor formation in allogeneic hosts by the embryonal carcinoma cell lines F9 and PCC3

Two cultured lines of murine embryonal carcinoma, F9 and PCC3, have been grafted to a variety of allogeneic hosts. The host strains have been classified by their resistance or sensitivity to these carcinomas. Resistance seems to be immunological in nature.Allograft rejection does not correlate withH-2 haplotype, and seems to be controlled by a limited number of recessive factors, presumably histocompatibility genes. We infer that these factors have limited polymorphism in the mouse species. Recombinational analysis of strain A/He has revealed the presence of a recessive factor linked to theH-2 locus. Tumor resistance of strains C57BL/6 and AKR appears to result from the interaction of dominant or semi-dominant factors in theH-2 region with other recessive elements in the genetic background.Though F(1) hybrids between resistant mouse strains and the syngeneic strain 129 are largely tumor-sensitive, a low level of hybrid resistance to F9 has been observed and shown to be eliminated by X-irradiation.

Inducing mutations in the mouse genome with the chemical mutagen ethylnitrosourea

When compared to other model organisms whose genome is sequenced, the number of mutations identified in the mouse appears extremely reduced and this situation seriously hampers our understanding of mammalian gene function(s). Another important consequence of this shortage is that a majority of human genetic diseases still await an animal model. To improve the situation, two strategies are currently used: the first makes use of embryonic stem cells, in which one can induce knockout mutations almost at will; the second consists of a genome-wide random chemical mutagenesis, followed by screening for mutant phenotypes and subsequent identification of the genetic alteration(s). Several projects are now in progress making use of one or the other of these strategies. Here, we report an original effort where we mutagenized BALB/c males, with the mutagen ethylnitrosourea. Offspring of these males were screened for dominant mutations and a three-generation breeding protocol was set to recover recessive mutations. Eleven mutations were identified (one dominant and ten recessives). Three of these mutations are new alleles (Otop1mlh, Foxn1sepe and probably rodador) at loci where mutations have already been reported, while 4 are new and original alleles (carc, eqlb, frqz, and Sacc). This result indicates that the mouse genome, as expected, is far from being saturated with mutations. More mutations would certainly be discovered using more sophisticated phenotyping protocols. Seven of the 11 new mutant alleles induced in our experiment have been localized on the genetic map as a first step towards positional cloning.

Genetic and physical delineation of the region overlapping the progressive motor neuropathy (pmn) locus on mouse chromosome 13

The mouse autosomal recessive mutation progressive motor neuropathy (pmn) results in early onset motor neuron disease with rapidly progressing hindlimb paralysis, severe muscular wasting, and death at 4--6 weeks of age. pmn is thus considered a good animal model for motor neuron diseases and the characterization of the causative gene should help in understanding the biological causes of human spinal muscular atrophies. Here we report the generation of a physical map based on a high-resolution and high-density genetic map encompassing the pmn locus on mouse chromosome 13. We have positioned the pmn locus and a cluster of markers cosegregating with it within a genetic interval of 0.30 cM, delineated by two clusters of markers. We have constructed an approximately 850-kb contig of BACs spanning the pmn critical region. This BAC contig contains the breakpoint of synteny between mouse chromosome 13 and human 1q and 7p regions and lays the foundation for identifying at the molecular level such a breakpoint region. The physical and genetic maps provided a support for the identification of five transcription units positioned in the nonrecombinant interval, and constitute invaluable tools for the identification of other candidate genes for the pmn mutation.

The frissonnant mutant mouse, a model of dopamino-sensitive, inherited motor syndrome

The frissonnant (fri) mutation is an autosomic recessive mutation which spontaneously appeared in the stock of C3H mice. fri mutant mice have locomotor instability and rapid tremor. Since tremor ceases when mutant mice have sleep or are anaesthetized, and because of their obvious stereotyped motor behavior, these mice could represent an inherited Parkinsonian syndrome. We show here that the fri/fri mouse fulfills two out of the three criteria required to validate an experimental model of human disease, that is isomorphism, homology and predictivity. Indeed, fri/fri mice present an important motor deficit accompanying visible tremor and stereotypies. They display some memory deficits as in human Parkinson's desease. l-Dopa and apomorphine (dopaminergic agonists), ropinirole (selective D2 agonist), and selegiline (an monoamino-oxidase B [MAO-B] inhibitor) improve their clinical status. However, neither anatomopathological evidence of nigrostriatal lesion, nor decrease in tyrosine hydroxylase production could be seen.

The CD4 T cell-deficient mouse mutation nackt (nkt) involves a deletion in the cathepsin L (CtsI) gene

We recently reported a novel autosomal recessive mouse mutation designated nackt (nkt). Homozygous mutant mice have diffuse alopecia and a marked reduction in the proportion of CD4+ T cells in the thymus and peripheral lymphoid tissues. Here we show that the CD4 T-cell deficiency is due to a defect in the thymic microenvironment rather than the hematopoietic compartment. Furthermore, we identified the molecular basis of the mutant phenotype by demonstrating that the nkt mutation represents a 118-bp deletion of the cathepsin L (Ctsl) gene which is required for degradation of the invariant chain, a critical chaperone for major histocompatibility complex class II molecules. This finding explains the similarities in skin and immune defects observed in nkt/nkt and Ctsl -/- mice. The data reported here provide further in vivo evidence that the lysosomal cysteine protease cathepsin L plays a critical role in CD4+ T-cell selection in the thymus.

[Murine models for human diseases]

This article is a bibliographic review concerning mouse mutations, spontaneous, induced or genetically engineered, as models of human genetic diseases. Since the beginning of the last century, mouse models have been instrumental in the understanding of the pathogenesis of many diseases and designing of new therapies. A number of recent technological advances in embryo manipulation and many large-scale mutagenesis screens will dramatically increase the availability of new mouse models in the near future. In the "post-genomic" era, mouse mutants will have a significant role as a model system for functional genome analysis of the upcoming whole-genome information of the human and mouse genomes projects.

Genomic organization, chromosomal assignment, and expression analysis of the mouse suppressor of fused gene (Sufu) coding a Gli protein partner

Suppressor of fused (Sufu) is a negative regulator of the Hedgehog pathway both in Drosophila and vertebrates. Here, we report the genomic organization of the mouse Sufu gene (mSufu). This gene comprises 11 exons spanning more than 30 kb and encodes a protein with a putative PEST sequence. DNA-consensus sequences recognized by basic helix-loop-helix (bHLH) proteins, referred to as E-box motifs, are found in the 5' flanking region. Analysis by single-strand conformation polymorphism and radiation hybrid positioned the Sufu locus to the distal end of mouse Chr 19 between D19Mit102 and D19Mit9, near the Fgf8 and dactylin genes. Mouse Sufu is expressed in various tissues, particularly in the nervous system, ectoderm, and limbs, throughout the developing embryo. Sufu binds with all three Gli proteins, with different affinities. This report, in conjunction with recent studies, points out the importance of Sufu in mouse embryonic development.

Three new allelic mouse mutations that cause skeletal overgrowth involve the natriuretic peptide receptor C gene (Npr3)

In 1979, a BALB/cJ mouse was identified with an exceptionally long body. This phenotype was found to be caused by a recessive mutation, designated longjohn (lgj), that mapped to the proximal region of chromosome 15. Several years later, a mouse with a similarly elongated body was identified in an outbred stock after chemical mutagenesis with ethylnitrosourea. This phenotype also was caused by a recessive mutation, designated strigosus (stri). The two mutations were found to be allelic. A third allele was identified in a DBA/2J mouse and was designated longjohn-2J (lgj(2J)). Analysis of skeletal preparations of stri/stri mice indicated that the endochondral ossification process was slightly delayed, resulting in an extended proliferation zone. A recent study reported that mice overexpressing brain natriuretic peptide, one of the members of the natriuretic peptide family, exhibit a skeletal-overgrowth syndrome with endochondral ossification defects. The Npr3 gene coding for type C receptor for natriuretic peptides (NPR-C), which is mainly involved in the clearance of the natriuretic peptides, mapped in the vicinity of our mouse mutations and thus was a candidate gene. The present study reports that all three mutations involve the Npr3 gene and provides evidence in vivo that there is a natriuretic-related bone pathway, underscoring the importance of natriuretic peptide clearance by natriuretic peptide type C receptor.

Mouse Alx3: an aristaless-like homeobox gene expressed during embryogenesis in ectomesenchyme and lateral plate mesoderm

Mouse Alx3 is a homeobox gene that is related to the Drosophila aristaless gene and to a group of vertebrate genes including Prx1, Prx2, Cart1, and Alx4. The protein encoded contains a diverged variant of a conserved peptide sequence present near the carboxyl terminus of at least 15 different paired-class-homeodomain proteins. Alx3 is expressed in mouse embryos from 8 days of gestation onward in a characteristic pattern, predominantly in neural crest-derived mesenchyme and in lateral plate mesoderm. We detected prominent expression in frontonasal head mesenchyme and in the first and second pharyngeal arches and some of their derivatives. High expression was also seen in the tail and in many derivatives of the lateral plate mesoderm including the limbs, the body wall, and the genital tubercle. aristaless-related genes like Alx3, Cart1, and Prx2 are expressed in overlapping proximodistal patterns in the pharyngeal arches. Similar, but more lateral patterns have been described for the Distal-less-related (Dlx) genes. Intriguingly, expression and to some extent function of aristaless and Distal-less in Drosophila also have overlapping as well as complementary aspects. Alx3 was localized to chromosome 3, near the droopy-ear (de) mutation.

The effect of the nonpeptide neurotrophic compound SR 57746A on the progression of the disease state of the pmn mouse

1. The progressive motor neuronopathy (pmn) mouse is an autosomal recessive mutant, in which the homozygotes suffer caudio-cranial degeneration of motor axons and die several weeks after birth. This strain provides the opportunity of testing potential therapeutic strategies for the treatment of motor neurone diseases such as amyotrophic lateral sclerosis. We have performed a study of the effects on the pmn mouse of SR 57746A, an orally-active, non-peptide compound which has been found to exhibit neurotrophic effects in vitro and in vivo. In order to treat the affected mice from birth, the mothers were administered 2.5 mg kg(-1). p.o., SR 57746A every two days until the weaning of the offspring (at day 20); then the offspring were given every two days a dose of 30 microg kg(-1), p.o., until their death. 2. Affected mice treated with SR 57746A had a lifespan 50% longer than that of the vehicle-treated mice (P=0.01). Compared to vehicle-treated pmn mice, SR 57746A improved the performance of the pmn mice in three different behavioural tasks. SR 57746A also maintained the amplitude of the motor evoked response of the gastrocnemius muscle, reduced the distal motor latency, and delayed the occurrence of the spontaneous denervation activity in this muscle. Histological studies indicated that at 20 days of age the mean surface areas of the fibres of the sciatic nerve were higher in SR 57746A-treated than in vehicle-treated mice. 3. At present, SR 57746A is the only orally active, nonpeptide compound known to be capable of delaying the progression of the motor neurone degeneration in pmn mice.

Hotfoot mouse mutations affect the delta 2 glutamate receptor gene and are allelic to lurcher

Hotfoot (ho) is a recessive mouse mutation characterized by cerebellar ataxia associated with relatively mild abnormalities of the cerebellum. It has been previously mapped to Chromosome 6, and at least eight independent alleles have been reported. Here we show that the hotfoot phenotype is associated with mutations in the glutamate receptor ionotropic delta2 gene (Grid2). We have identified a 510-bp deletion in the Grid2 coding sequence in the ho4J allele, resulting in a deletion of 170 amino acids of the extracellular domain of the receptor. Analysis of a second allele, hoTgN37INRA, revealed a 4-kb deletion in the Grid2 transcript. The GRID2 protein in these hotfoot mutants probably has a reduced (or null) activity since the phenotype of hotfoot bears similarities with the previously described phenotype of Grid2 knockout mice. The exceptionally high number of independent alleles at the ho locus is an invaluable tool for investigating the function of the glutamate receptor ionotropic delta2 protein, which so far remains largely unknown.

Structure and expression of Wnt13, a novel mouse Wnt2 related gene

We have identified a novel mouse member of the Wnt family, Wnt13. Among mouse Wnt genes, Wnt13 is most closely related to Wnt2. Sequence comparisons and chromosomal localization strongly suggest that Wnt13, rather than Wnt2, is the mouse orthologue of both the human WNT13 and Xenopus XWnt2 genes. Wnt13 is expressed in the embryonic mesoderm during gastrulation. At later stages, transcripts are detected in the dorsal midline of the diencephalon and mesencephalon, the heart primordia, the periphery of the lung bud and the otic and optic vesicles. These data suggest that Wnt13 function might partially overlap with those of other Wnt genes in the cell signaling mechanisms controlling mesoderm specification during gastrulation and some aspects of brain, heart and lung formation.

A comparative genetic map of rat, mouse and human genomes

The increasing availability of molecular markers and the development of highly efficient gene mapping strategies for the mouse, rat and human genomes have generated vast quantities of information allowing for the progressive refinement of comparative maps. In this publication we report on an updated version of our rat/mouse/human comparative genetic map, based on the mouse map. Databases for mouse, rat and human gene mapping were used for the collection of homologs mapped in the species. The comparative map was constructed with a total of 1,235 mouse loci having known homologs in the rat and/or human: 16 having homologs only in the rat, 884 having only in the human and 335 both in the rat and human. The combined length of the segments conserved between the rat and mouse spans 758 cM on the mouse map. This indicates that about 47% of the mouse genome is now covered by known rat homologous regions. Five novel regions homologous for the rat and mouse were identified. This comparative genetic map should be useful for researchers working on genetic studies in the rat, mouse and human.

Construction of a high-resolution genetic map encompassing the hotfoot locus

Hotfoot (ho) is a mutation affecting posture and movement. We report a new allele associated with the insertion of a transgene and its high-resolution mapping. Analysis of the transgene revealed that two complete and two truncated copies are inserted at the ho locus. The ho locus cosegregated with D6Mit299 in 702 meioses and is confined to a 1.1-cM region between the markers D6Mit122 and D6Mit174. If the order and distances between markers are consistent with previously published mapping data, the position of the ho locus must be revised and placed approximately 30 cM from the centromere. This high-resolution genetic map is the first step towards the positional cloning of the ho mutation.

Vesicle formation and follicular root sheath separation in mice homozygous for deleterious alleles at the balding (bal) locus

The balding (bal) mutation of the mouse is an autosomal recessive mutation that causes alopecia and immunologic anomalies. A new allele was identified by allelism testing after using an interspecific backcross to localize the mutation to the centromeric end of mouse chromosome 18. We investigated the skin and hair histologic lesions of two alleles (bal(J) and bal(Pas)) at this locus and analyzed the expression of several keratinocyte markers and the production of autoantibodies by immunofluorescence on frozen skin sections. The lesions observed included separation of the inner and outer root sheath in anagen follicles resulting in the hair fiber being very easily plucked from the follicle. Vesicles on the ventral tongue, mucocutaneous junction of the eyelid, foot pads, and rarely in skin were also evident. Separation occurred between the basal and suprabasilar cells forming an empty cleft, resembling that observed in human pemphigus vulgaris. Immunofluorescence studies did not reveal the presence of tissue-bound or circulating autoantibodies. Expression of keratinocyte markers in hair follicles was normal. Keratin 6-positive cells were found on either side of the follicular separation suggesting a molecular defect in adhesion molecules between the inner layer of the outer root sheath cells to layers on either sides. This hypothesis has been confirmed by another group who demonstrated that the bal(J) mutation is due to the insertion of a thymidine in the desmoglein 3 gene, resulting in a premature stop codon.

The Sycp1 loci of the mouse genome: successive retropositions of a meiotic gene during the recent evolution of the genus

The murine Sycp1 gene is expressed at the early stages of meiosis. We show that it is composed of a number of small exons and localized on mouse chromosome 3. In the laboratory strains, two retrogenes were also identified. The first one (Sycp1-ps1), on chromosome 7, has accumulated point mutations and deletions and is not transcribed. A second retrogene (Sycp1-ps2), on chromosome 8, is inserted within the continuity of a moderately repeated element, in an intron of another gene (Cad11). The two retroposition events can be dated to distinct periods in the evolution of the Muridae. Sycp1-ps2 has kept features indicative of a relatively recent origin, namely a nearly intact coding region, a poly(A) tail, and 14-bp terminal repeats. Its recent origin was confirmed by the fact that it is found in all the laboratory strains of mice, but neither in a recent isolate from Mus musculus domesticus wild stocks nor in the closely related subspecies M. musculus musculus, M. m. molossinus, M. m. castaneus, and M. m. bactrianus. Appearance of the more ancient Sycp1-ps1 retrogene is concomitant with the radiation of the genus. It is present in various Mus species (M. spretus, M. spicilegus, M. macedonicus, and M. cookii), but neither in the rat nor in the more closely related Pyromis genus. Transposition of retrotranscripts during meiosis and their hereditary establishment thus appear to occur relatively frequently. They may, therefore, play a significant role in the evolutionary process.

The shiverer mutation affects the persistence of Theiler's virus in the central nervous system

Theiler's virus persists in the white matter of the spinal cord of genetically susceptible mice and causes primary demyelination. The virus persists in macrophages/microglial cells, but also in oligodendrocytes, the myelin-forming cells. Susceptibility/resistance to this chronic infection has been mapped to several loci including one tentatively located in the telomeric region of chromosome 18, close to the myelin basic protein locus (Mbp locus). To determine if the MBP gene influences viral persistence, we inoculated C3H mice bearing the shiverer mutation, a 20-kb deletion in the gene. Whereas control C3H mice were of intermediate susceptibility, C3H mice heterozygous for the mutation were very susceptible, and those homozygous for the mutation were completely resistant. This resistance was not immune mediated. Furthermore, C3H/101H mice homozygous for a point mutation in the gene coding for the proteolipid protein of myelin, the rumpshaker mutation, were resistant. These results strongly support the view that oligodendrocytes are a necessary viral target for the establishment of a persistent infection by Theiler's virus.

Regulated expression and RNA processing of transcripts from the Srp20 splicing factor gene during the cell cycle

Eukaryotic splicing factors belonging to the SR family are essential splicing factors consisting of an N-terminal RNA-binding region and a C-terminal RS domain. They are believed to be involved in alternative splicing of numerous transcripts because their expression levels can influence splice site selection. We have characterized the structure and transcriptional regulation of the gene for the smallest member of the SR family, SRp20 (previously called X16). The mouse gene encoding SRp20, termed Srp20, consists of one alternative exon and six constitutive exons and was mapped to a 2-centimorgan interval on chromosome 17. When cells are transfected with SRp20 genomic DNA, both standard and alternatively spliced transcripts and corresponding proteins are produced. Interestingly, in starved (G0) cells, the amount of SRp20 mRNA containing the alternative exon is large, whereas the amount of the standard SRp20 mRNA without the alternative exon is small. When starved cells are stimulated with serum, the alternative form is lost and the standard form is induced. These results suggest that splicing could be regulated during the cell cycle and that this could be, at least in part, due to regulated expression of SR proteins. Consistent with this, experiments with synchronized cells showed an induction of SRp20 transcripts in late G1 or early S. We have also characterized the promoter of SRp20. It lies within a GC-rich CpG island and contains two consensus binding sites for E2F, a transcription factor thought to be involved in regulating the cell cycle. These motifs may be functional since reporter constructs with the SRp20 promoter can be stimulated by cotransfection with E2F expression plasmids.

cDNA isolation, expression, and chromosomal localization of the mouse survival motor neuron gene (Smn)

Spinal muscular atrophy (SMA) is a frequent autosomal recessive disease in human characterized by degeneration of motor neurons of the spinal cord. The genomic region containing the defective gene (5q13) is particularly unstable and prone to large-scale deletions whose characterization led to the identification of the survival motor neuron (SMN) gene, the SMA determining gene encoding a hitherto unknown protein. As an initial step toward the generation of a murine model for SMA, we identified and characterized a full-length murine Smn cDNA. The coding sequence of the mouse Smn gene was found to be 82% identical, at the amino acid level, with the human SMN coding sequence. The Smn locus was mapped to the segment of mouse chromosome 13 exhibiting conservation of synteny with human chromosome 5q11-q23, which contains the SMN gene. However, no evidence for a duplication of the Smn gene was found in the mouse, suggesting that the duplication reported in human is a recent evolutionary event.

[Animal models of hereditary diseases]

A large number of genetic diseases are found both in humans and in one or several animal species. The mouse is a species of choice since, in addition to hundreds of spontaneous mutations which have been described, it is now possible to produce at will a mutation in any gene. This strategy has been used to generate genetically engineered mice which carry genetic defects found in human molecular pathology. Animal models are an invaluable tool to study the pathophysiology of diseases and to test new therapies. However, they are rarely exact replicates of the human disease. Possible origins for these differences are discussed in detail.

Modulation of mRNA levels in the presence of thymocytes and genome mapping for a set of genes expressed in mouse thymic epithelial cells

Modulation of gene expression in mouse thymic epithelium upon culture in the presence of thymocytes (coculture) was studied by comparison of hybridization signatures on a set of nearly 5000 mouse thymus cDNA clones. Forty-nine differentially expressed clones (usually down-regulated in coculture) were characterized by tag sequencing. Many of them corresponded to entities that had not been described previously in the mouse, and were further characterized by genome mapping. This set of genes appears to be involved in growth regulation and differentiation within the thymus.

Rbt (Rabo torcido), a new mouse skeletal mutation involved in anteroposterior patterning of the axial skeleton, maps close to the Ts (tail-short) locus and distal to the Sox9 locus on chromosome 11

Rbt (Rabo torcido) is a new semidominant mouse mutant with a variety of skeletal abnormalities. Heterozygous Rbt mutants display homeotic anteroposterior patterning problems along the axial skeleton that resemble Polycomb group and trithorax gene mutations. In addition, the Rbt mutant displays strong similarities to the phenotype observed in Ts (Tail-short), indicating also a homeotically transformed phenotype in these mice. We have mapped the Rbt locus to an interval of approximately 6 cM on mouse Chromosome (Chr) 11 between microsatellite markers D11Mit128 and D11Mit103. The Ts locus was mapped within a shorter interval of approximately 3 cM between D11Mit128 and D11Mit203. This indicates that Rbt and Ts may be allelic mutations. Sox9, the human homolog of which is responsible for the skeletal malformation syndrome campomelic dysplasia, was mapped proximal to D11Mit128. It is, therefore, unlikely that Ts and Rbt are mouse models for this human skeletal disorder.

A rat mutation producing demyelination (dmy) maps to chromosome 17

A recessive mutation exhibiting severe myelin breakdown, mainly at the level of the lumbar segments of the spinal cord and without any associated inflammation, was discovered in a partially inbred rat colony. Analysis of the segregation patterns of a set of polymorphic microsatellite markers in two inter-strain crosses allowed the mapping of this autosomal recessive mutation to rat Chromosome (Chr) 17, very close to the prolactin (Prl) locus, in a region homologous to human Chr 6p21.2-22.3 and mouse Chr 13. The pathology of the demyelination process and the chromosomal localization indicate that this mutation has no known equivalent in either mouse or human.

The mouse mutation sarcosinemia (sar) maps to chromosome 2 in a region homologous to human 9q33-q34

The autosomal recessive mouse mutation sarcosinemia (sar), which was discovered segregating in the progeny of a male whose premeiotic germ cells had been treated with the mutagen ethylnitrosourea, is characterized by a deficiency in sarcosine dehydrogenase activity. Using an intersubspecific cross, we mapped the sar locus to mouse chromosome 2, approximately 15-18 cM from the centromere. The genetic localization of this locus in the mouse allows the identification of a candidate region in human (9q33-q34) where the homologous disease should map.

Lanceolate hair (lah): a recessive mouse mutation with alopecia and abnormal hair

A new autosomal recessive mutation of the house mouse developed generalized alopecia associated with breakage of abnormal hair shafts. This mutation, named 'lanceolate hair' (symbol: lah), arose in a mutagenesis experiment using ethylnitrosourea. Hair shafts were short with a focal degeneration at the breakpoint characterized by a pronounced enlargement at the apex, resembling a lance head. Plucked hair fibers were 2.0 to 3.5 mm in length with a normal base, suggesting that there was a synchronized developmental defect. Histologic examination of anagen follicles revealed abnormal cornification of the matrix region with degeneration resulting in the focal hair shaft deformity. Catagen follicles showed pronounced follicular dystrophy but telogen follicles were almost normal. There was a marked, persistent thickening of the epidermis associated with a non-scarring, relatively non-inflammatory ichthyosiform dermatitis. These features are found in the Netherton's syndrome of the human, for which this mouse mutation may represent a model. The lah mutation has been localized to the centromeric end of mouse Chromosome 18.

Nucleotide sequence, chromosomal assignment and mRNA expression of mouse hypoxia-inducible factor-1 alpha

The heterodimeric hypoxia-inducible transcription factor HIF-1 is involved in the oxygen-regulated transcription of several genes including erythropoietin. Cloning and sequencing of the alpha-subunit of mouse HIF-1 cDNA revealed a 90% overall homology to human HIF-l alpha but lack of any similarity in the 5' untranslated region and translational start site. Mouse HIF-1 alpha is encoded by an evolutionary conserved single-copy gene located on chromosome 12. We found a widespread constitutive expression of mouse HIf-1 alpha mRNA which was particularly high in lung and kidney. Despite a strong erythropoietin induction, HIF-1 alpha mRNA concentrations were not upregulated in hypoxic mouse tissues.

Murine acariasis: I. Pathological and clinical evidence suggesting cutaneous allergy and wasting syndrome in BALB/c mouse

We describe here a disease related to mite-associated ulcerative dermatitis in BALB/c mice, a strain previously classified as resistant to this condition. The disease was recognized by pruritic cutaneous pathology and wasting. Pathologic studies showed a marked allergic-type inflammation in the skin. The dominant histologic feature was extensive mast cell infiltration in cutaneous lesions and in lymphoid tissues, associated with a greatly elevated serum IgE concentration. The disease was secondary to infestation with an acarian ectoparasite Myocoptes musculinus, and seemed to represent an allergic reaction to the parasite-derived substances, with an associated wasting syndrome. This condition may be a useful experimental model for allergic diseases.

A high-resolution genetic map of mouse chromosome 15 encompassing the Dominant megacolon (Dom) locus

Dominant megacolon (Dom) is one of four mutations in the mouse that can produce a phenotype similar to Hirschsprung disease in human. The Dom gene product is not known, and no candidate region has been defined for a possible human homolog. In this publication we report mapping the Dom locus with high definition, using several intra-and interspecific crosses and a set of 16 Chr 15-specific microsatellites flanking this locus.

The mouse mutation progressive motor neuronopathy (pmn) maps to chromosome 13

Analysis of polymorphic markers segregating in both intra- and interspecific crosses has allowed us to map the autosomal recessive mutation progressive motor neuronopathy (pmn) to mouse Chr 13. Although this mutation, based on its histological description, was reported as a model for infantile spinal muscular atrophy of the Werdnig-Hoffmann type, its localization to a region that is not homologous with human 5q makes it unlikely to be a homologue to SMA. The presence of the Extra-toe (Xt) locus in proximity to pmn will help in the detection of affected progenies before the onset of the degenerative process.

Transient and restricted expression during mouse embryogenesis of Dll1, a murine gene closely related to Drosophila Delta

The Drosophila Delta (Dl) gene is essential for cell-cell communication regulating the determination of various cell fates during development. Dl encodes a transmembrane protein, which contains tandem arrays of epidermal-growth-factor-like repeats in the extracellular domain and directly interacts with Notch, another transmembrane protein with similar structural features, in a ligand-receptor-like manner. Similarly, cell-cell interactions involving Delta-like and Notch-like proteins are required for cell fate determinations in C. elegans. Notch homologues were also isolated from several vertebrate species, suggesting that cell-to-cell signaling mediated by Delta- and Notch-like proteins could also underlie cell fate determination during vertebrate development. However, in vertebrates, no Delta homologues have yet been described. We have isolated a novel mouse gene, Dll1 (delta-like gene 1), which maps to the mouse t-complex and whose deduced amino acid sequence strongly suggests that Dll1 represents a mammalian gene closely related to Drosophila Delta. Dll1 is transiently expressed during gastrulation and early organogenesis, and in a tissue-restricted manner in adult animals. Between day 7 and 12.5 of development, expression was detected in the paraxial mesoderm, closely correlated with somitogenesis, and in subsets of cells in the nervous system. In adult animals, transcripts were detected in lung and heart. Dll1 expression in the paraxial mesoderm and nervous system is strikingly similar to the expression of mouse Notch1 during gastrulation and early organogenesis. The overlapping expression patterns of the Dll1 and Notch1 genes suggest that cells in these tissues can communicate by interaction of the Dll1 and Notch1 proteins. Our results support the idea that Delta- and Notch-like proteins are involved in cell-to-cell communication in mammalian embryos and suggest a role for these proteins in cellular interactions underlying somitogenesis and development of the nervous system.

The mouse Fau gene: genomic structure, chromosomal localization, and characterization of two retropseudogenes

The Fau gene is the cellular homolog of the fox sequence of the Finkel-Biskis-Reilly murine sarcoma virus (FBR-MuSV). FBR-MuSV acquired the Fau gene by transduction in a transcriptional orientation opposite to that of the genomic Fau gene. The genomic structure of the mouse Fau gene (MMFAU) and its upstream elements have been determined and are similar to those of the human FAU gene. The gene consists of five exons and is located on chromosome 19. The first exon is not translated. The promoter region has no well-defined TATA box but contains the polypyrimidine initiator flanked by regions of high GC content (65%) and shows all of the characteristics of a housekeeping gene. The 5' end of the mRNA transcript was determined by 5' RACE analysis and is located, as expected, in the polypyrimidine initiator site. Furthermore, the sequences of two retropseudogenes (Fau-ps1 and Fau-ps2) are reported. Both pseudogenes are approximately 75% identical to the Fau cDNA, but both are shorter due to a deletion at the 5' end and do not encode a functional protein. Fau-prs is interrupted by an AG-rich region of about 350 bp within the S30 region of the Fau cDNA. Fau-ps1 was localized on chromosome 1 and Fau-ps2 on chromosome 7.

Etl2, a novel putative type-I cytokine receptor expressed during mouse embryogenesis at high levels in skin and cells with skeletogenic potential

The regulatory effects of signaling proteins like hormones, growth factors, and cytokines are mediated by specific cell surface receptors which are grouped into distinct families on the basis of structural criteria. Here we report on the isolation and embryonic expression of a novel mouse gene, Etl2 (enhancer trap locus 2) which, based on its deduced amino acid sequence, constitutes a new member of the cytokine type-I receptor family. Among type-I receptors Etl2 is most similar to the alpha subunits of the human ciliary neurotrophic factor (CNTF) receptor and the mouse interleukin-6 (IL6) receptor with 32 and 30% identical amino acids, respectively. From Day 9 p.c. (postcoitum) onward low levels of Etl2 mRNA were detected in mesenchymal cells throughout the embryo and in parts of the nervous system, in particular in the ependymal linings of the spinal cord and the developing brain vesicles and in the neuronal layer of the retina. Highest levels of Etl2 expression were found on Day 12.5 p.c. in the craniofacial mesenchyme and during subsequent development in mesenchymal cells around all developing cartilages. At later stages, Etl2 transcripts were abundant in the dental papilla, the dermis, and hair follicles, as well as in the perichondrium and periost, i.e., in regions containing chondro and osteo progenitor cells. Etl2 mRNA was not detected, however, in mature odontoblasts, chondroblasts, osteoblasts, chondrocytes, and osteocytes. Our results suggest that Etl2 is a new orphan receptor belonging to the type-I cytokine receptor family and that Etl2 might have regulatory functions, particularly in the control of proliferation and/or differentiation of skeletogenic progenitor and other mesenchymal cells.

A high-resolution genetic map of mouse chromosome 5 encompassing the reeler (rl) locus

Using interspecific crosses between BALB/c and Mus spretus (SEG) mice, the murine reeler (rl) gene was mapped to the proximal region of chromosome 5 between the hepatocyte growth factor gene (Hgf) and the D5Mit66 microsatellite. The following order was defined: (centromere)-Cchl2a/Hgf-D5Mit1-D5Nam1/D5-Nam2 -rl/D5Mit61-D5Mit72-Xmv45-Htr5a- Peplb-D5Nam3-D5Mit66. Estimated distances between reeler and the nearest flanking markers D5Nam1 and D5Mit72 are 1.5 and 1.0 cM, respectively (95% confidence level), suggesting that the region could be physically mapped using a manageable number of YAC clones.

The spastic mouse: aberrant splicing of glycine receptor beta subunit mRNA caused by intronic insertion of L1 element

Mice homozygous for the spastic mutation (spa) suffer from a complex motor disorder resulting from reduced CNS levels of the adult glycine receptor isoform GlyRA, which is composed of ligand-binding alpha 1 and structural beta polypeptides. The beta subunit-encoding gene (Glyrb) was mapped near the spa locus on mouse chromosome 3. In spa/spa mice, aberrant splicing of the beta subunit pre-mRNA strikingly diminishes the CNS contents of full-length transcripts, whereas truncated beta subunit mRNAs accumulate. This is a result of exon skipping, which causes translational frameshifts and premature stop codons. Intron 5 of the spa Glyrb gene contains an L1 transposable element that apparently is causal for the aberrant splicing of beta subunit transcripts.

Human inositol 1,4,5-trisphosphate type-1 receptor, InsP3R1: structure, function, regulation of expression and chromosomal localization

We have isolated cDNA clones encoding an inositol 1,4,5-trisphosphate receptor type 1 (InsP3R1) from human uteri and a leukaemic cell line, HL-60. Northern-blot analysis showed that approx. 10 kb of InsP3R1 mRNA is expressed in human uteri, oviducts and HL-60 cells. The predicted amino acid sequence of human InsP3R1 (2695 amino acids) has 99% identity with that of the mouse SI-/SII- splicing counterpart. Western-blot analysis with anti-(mouse InsP3R1) antibodies showed that InsP3R1 protein of human uteri and oviducts of approx 220 kDa is immunostained. Northern-blot analysis of HL-60 cell differentiation along the neutrophilic lineage induced by retinoic acid or dimethylsulphoxide showed an accompanying enhanced expression of InsP3R1 mRNA. Immunohistochemical analysis of the cerebella of spinocerebellar degeneration patients showed a variable loss of Purkinje cells with an altered pattern of immunostaining. The InsP3R1 gene (Insp3r1) was localized to the 3P25-26 region of human chromosome 3. The data presented here clearly show that InsP3R1 exists widely in human tissues and may play critical roles in various kinds of cellular functions.

Msx1 is close but not allelic to either Hm or Hx on mouse chromosome 5

The Msx1 homeobox locus has been mapped in relation to the mutations hammer-toe (Hm) and hemimelic extra toes (Hx). Msx1 is expressed in the developing limb, while limb development is affected by the Hm and Hx mutations. Hm and Hx are very tightly linked loci. In interspecific crosses, the segregation of either mutation was followed in relation to polymorphic alleles of Msx1, Il6, and En2, to give a fine map around the mutant loci. Our results show that Msx1 is not allelic to either of the mutations, but is located about 3 cM from them. Il6 did not recombine with either Hm or Hx and, therefore, provides a point of access for the analysis of these mutations at the molecular level.