IL9 maps to mouse chromosome 13 and human chromosome 5

Mouse and human cDNA clones encoding the T-cell and mast cell growth factor P40, now designated IL-9, were used to identify DNA restriction fragment length polymorphisms (RFLPs) in sets of somatic cell hybrids and between inbred strains of mice and interspecific backcross progeny. Segregation of mouse and human chromosomes among somatic cell hybrids indicated a location on mouse chromosome 13 and human chromosome 5. RFLPs were identified among inbred strains of mice. Analysis of chromosome 13 alleles for Tcrg, Dhfr, and Il-9 in an interspecific cross between Mus musculus and NFS/N or C58/J mice indicates that IL-9 is distal to Tcrg and Proximal to Dhfr.     

A human SHC-related sequence maps to chromosome 17, the SHC gene maps to chromosome 1

The SHC gene encodes a protein that is thought to act as an adapter in many signal transduction pathways; the SHC protein probably facilitates the activation of RAS proteins in response to a variety of factors. We have mapped the human SHC gene and have identified a new SHC-related sequence. We have sequenced the region corresponding to the SHC 3 UTR from both loci and have mapped cosmids by fluorescence in situ hybridization. The human SHC gene maps to the proximal long arm of chromosome 1 and the SHC-related sequence maps to the proximal long arm of chromosome 17. A number of cancers have been positioned in the proximal long arm of chromosome 1; this is of interest given the oncogenic potential of the SHC protein.     

Six loci mapped on to human chromosome 2p are assigned to sheep chromosome 3p

Six loci, apoliproprotein B (including Ag(x) antigen), immunoglobulin kappa constant region (IGKC), luteinizing hormone/choriogonadotrophin receptor, avian myelocytomatosis viral related oncogene, neuroblastoma derived, ornithine decarboxylase, and proopiomelanocortin (adrenocorticotropin/beta-lipotropin) (POMC), were newly assigned to sheep chromosome 3p using a chromosomally characterized minipanel of sheep-hamster cell hybrids. Isotopic in situ hybridization of IGKC to sheep chromosome 3p22–p17 is reported, confirming the cell hybrid assignment. As these loci are all known to map to human chromosome 2p, this study demonstrates that this chromosomal segment is extensively conserved in sheep. Only POMC has been previously assigned to cattle chromosome 11, which is the equivalent of sheep chromosome 3p. Therefore, we predict that the other loci assigned in this study to sheep 3p are likely to be located on cattle 11. The provisional assignment of an additional locus, annexin-like to sheep chromosome 3p is also reported.     

The cellular response to chromosome breakage

DNA double-strand breaks (DSBs) are among the most deleterious types of damage that can occur in the genome of eukaryotic cells because failure to repair them can lead to loss of genetic information and chromosome rearrangements. DSBs can arise by failures in DNA replication and by exposure to environmental factors, such as ionizing radiations and radiomimetic chemicals. Moreover, they might arise when telomeres undergo extensive erosion, leading to the activation of the DNA damage response pathways and the onset of apoptosis and/or senescence. Importantly, DSBs can also form in a programmed manner during development. For example, meiotic recombination and rearrangement of the immunoglobulin genes in lymphocytes require the generation of site- or region-specific DSBs through the action of specific endonucleases. Efficient DSB repair is crucial in safeguarding genome integrity, whose maintenance in the face of DSBs involves branched signalling networks that switch on DNA damage checkpoints, activate DNA repair, induce chromatin reorganization and modulate numerous cellular processes. Not surprisingly, defects in these networks result in a variety of diseases ranging from severe genetic disorders to cancer predisposition and accelerated ageing.     

Introduction to chromosome dynamics in mitosis

To ensure that the genetic information, replicated in the S-phase of the cell cycle, is correctly distributed between daughter cells at mitosis, chromatin duplication and chromosome segregation are highly regulated events. Since the early 1980's, our knowledge of the mechanisms governing these two events has greatly increased due to the use of genetic and biochemical approaches. We present here, first, an overview of the replication process, highlighting molecular aspects involved in coupling replication with chromatin dynamics in mitosis. The second part will present the current understanding of chromosome condensation and segregation during mitosis in higher eukaryotes. Finally, we will underline the links that exist between replication and mitosis.     

A Molecular approach to chromosome organization

A 315 kb walk in the genetically well characterized rosy region of the Drosophila chromosomes permits a molecular analysis of chromosome organization. Polytene chromosome bands in this region range from less than 7 kb to about 160 kb and the level of DNA replication is constant within bands and among bands and interbands. A good numerical and topographical correspondence is found between chromomeric units and genetic units.     

Resistance to xenobiotic-induced autoimmunity maps to chromosome 1

Although evidence indicates that environmental factors play a major role in precipitating systemic autoimmunity in genetically susceptible individuals, little is known about the mechanisms involved. Certain heavy metals, such as mercury, are potent environmental immunostimulants that produce a number of immunopathologic sequelae, including lymphoproliferation, hypergammaglobulinemia, and overt systemic autoimmunity. Predisposition to such metal-induced immunopathology has been shown to be influenced by both MHC and non-MHC genes, as well as susceptibility to spontaneous lupus, in mice and other experimental animals. Among the various mouse strains examined to date, the DBA/2 appears to uniquely lack susceptibility to mercury-induced autoimmunity (HgIA), despite expressing a susceptible H-2 haplotype (H-2d). To define the genetic basis for this trait, two genome-wide scans were conducted using F2 intercrosses of the DBA/2 strain with either the SJL or NZB strains, both of which are highly susceptible to HgIA. A single major quantitative trait locus on chromosome 1, designated Hmr1, was shown to be common to both crosses and encompassed a region containing several lupus susceptibility loci. Hmr1 was linked to glomerular immune complex deposits and not autoantibody production, suggesting that DBA/2 resistance to HgIA may primarily involve the later stages of disease pathogenesis. Identification and characterization of susceptibility/resistance genes and mechanisms relevant to the immunopathogenesis of mercury-induced autoimmunity should provide important insights into the pathogenesis of autoimmunity and may reveal novel targets for intervention.     

Assignment of the porcine loci for MYOD1 to chromosome 2 and MYF5 to chromosome 5

Porcine-specific polymerase chain reaction (PCR) and a pig–rodent somatic cell hybrid panel were used to map two members of the MyoD gene family. MYOD1 was assigned to pig chromosome 2 and MYF5 to chromosome 5.     

End-to-end chromosome attachments in mitotic interphase and their possible significance to meiotic chromosome pairing

Cytological studies on telophase and early prophase in roottip cells of several plant species (Allium cepa, 2n=16; four Crepis species, including Crepis capillaris, 2n=6; Callitriche hermaphroditica, 2n=6; Nigella arvensis, 2n=12; Secale cereale, 2n=14) revealed that chromosome ends are attached two by two forming chains of chromosomes (interphase associations). In these chains homologous chromosomes are presumably located adjacent to each other. In Crepis capillaris it was observed that the two nucleolar chromosomes form a separate ring one end attached to the ring of the four remaining chromosomes and the other end attached to the nucleolus. It is proposed that these end-to-end attachments have significance for chromosome pairing in meiosis. The adjacent location of homologous chromosomes in the interphase associations would facilitate rapid and regular synapsis.     

A glutaminase (gis) gene maps to mouse chromosome 1, rat chromosome 9, and human chromosome 2

A rat cDNA clone encoding a portion of phosphate-activated glutaminase was used to identify DNA restriction fragment length polymorphisms (RFLPs) in sets of somatic cell hybrids and between wild-derived and inbred strains of mice. Segregation of rat and mouse chromosomes among somatic cell hybrids indicated assignment to rat chromosome 9 and mouse chromosome 1. Analysis of chromosome 1 alleles for several genes in an interspecific cross between Mus spretus and C3H/HeJ-gld/gld mice indicates that glutaminase can be positioned within 5.5 +/- 2.0 cM proximal to Ctla-4. Similarly, human-hamster somatic cell hybrids were examined for RFLPs, and four human EcoRI restriction fragments were found to hybridize with the rat glutaminase probe. Two of these restriction fragments cosegregated and mapped to human chromosome 2 in a region that is syntenic with mouse chromosome 1 and rat chromosome 9.     

Group 3 chromosome bin maps of wheat and their relationship to rice chromosome 1

The focus of this study was to analyze the content, distribution, and comparative genome relationships of 996 chromosome bin-mapped expressed sequence tags (ESTs) accounting for 2266 restriction fragments (loci) on the homoeologous group 3 chromosomes of hexaploid wheat (Triticum aestivum L.). Of these loci, 634, 884, and 748 were mapped on chromosomes 3A, 3B, and 3D, respectively. The individual chromosome bin maps revealed bins with a high density of mapped ESTs in the distal region and bins of low density in the proximal region of the chromosome arms, with the exception of 3DS and 3DL. These distributions were more localized on the higher-resolution group 3 consensus map with intermediate regions of high-mapped-EST density on both chromosome arms. Gene ontology (GO) classification of mapped ESTs was not significantly different for homoeologous group 3 chromosomes compared to the other groups. A combined analysis of the individual bin maps using 537 of the mapped ESTs revealed rearrangements between the group 3 chromosomes. Approximately 232 (44%) of the consensus mapped ESTs matched sequences on rice chromosome 1 and revealed large- and small-scale differences in gene order. Of the group 3 mapped EST unigenes approximately 21 and 32% matched the Arabidopsis coding regions and proteins, respectively, but no chromosome-level gene order conservation was detected.     

Homoeology of rye chromosome arms to wheat

Summary Cytological markers such as diagnostic C-bands, telocentrics, and translocations were used to identify the arms of rye chromosomes associated with wheat chromosomes at metaphase I in ph1b mutant wheat × rye hybrids. Arm homoeologies of rye chromosomes to wheat were established from the results of metaphase I pairing combined with available data on the chromosomal location of homoeoloci series in wheat and rye. Only arms 1RS, 1RL, 2RL, 3RS, and 5RS showed normal homoeologous relationships to wheat. The remaining arms of rye appeared to be involved in chromosome rearrangements that occurred during the evolution of the genus Secale. We conclude that a pericentric inversion in chromosome 4R, a reciprocal translocation between 3RL and 6RL, and a multiple translocation involving 4RL, 5RL, 6RS, and 7RS are present in rye relative to wheat.     

Linkage of typical pseudoachondroplasia to chromosome 19

Pseudoachondroplasia (PSACH) is an autosomal dominant dwarfing condition associated with disproportionate short stature, marked joint deformities, and early onset osteoarthritis. Previous linkage studies have excluded linkage to cartilage and noncartilagenous extracellular matrix candidate genes. Here, we report mapping the pseudoachondroplasia gene to chromosome 19. Maximum lod scores of 4.70, 4.15, and 4.86 at θ - 0.00 were found for D19S212, D19S215, and D19S49, respectively. Multipoint analysis suggests the following order: D19S253-D19S199-(D19S212/PSACH/Dl9S215)-D19S222-D19S49.     

Recessive microencephaly linked to the X chromosome

A family with X-linked recessive microcephaly is reported. As patients there were found 8 men or boys respectively out of 3 generations, all of them being related by their mentally healthy mothers. Besides microcephaly the patients showed growth retardation and obesity. Some of them, in addition, had various anomalies as inguinal or umbilical hernias, cryptorchism, tapering fingers, contractures, deeply rooted thumbs and club-feet. There were no hints for a metabolic defect or a chromosomal aberration. The dermatoglyphics could be investigated in 5 patients and showed in all of them a shifting of the axial triradius into the distal position t'. Comparing the own findings with case reports on X-linked microcephalies, the above mentioned family was found not to correspond to any of these observations. It is assumed that in this family, a new disease has occurred which until now has not yet been described, so that the X-linked microcephalies seem to be a heterogenous group of disease from the genetic point of view.     

Dicentric chromosome due to an unusual fusion

Summary The case of a very mild 18p—syndrome is reported. In a mentaly retarded girl was recovered karyotype with 45 chromosomes. The absent chromosomes G and E (18) were replaced by a submetacentric, dicentric chromosome, originated from an unusual fusion. The examination of serum immunoglobulins revealed the deficiency of IgA.

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Zusammenfassung Es wird über einen Fall von mäßigem 18p—Syndrom berichtet. Bei einem mentalretardierten Mädchen wurde ein Karyotyp mit 45 Chromosomen festgestellt. Das fällende Chromosom war mit einem submetazentrischen und gleichzeitig dizentrischen Chromosom ersetzt, das durch eine sehr ungewöhnliche Fusion entstand. Die Untersuchung der Immunglobuline hat einen deutlichen -A-Globulin-Mangel gezeigt.