The murine Hox-2 cluster of homeo box containing genes maps distal on chromosome 11 near the tail-short (Ts) locus

Two probes derived from a mouse recombinant lambda-clone (H24.1), that contains a sequence closely homologous to the Drosophila antennapedia homeo box, were mapped to mouse chromosome (MMU) 11 by filter hybridization of somatic cell hybrid DNA. This sequence is highly homologous to a human homeo box gene (HOX2) and appears to represent one of the two genes in the Hox-2 cluster previously assigned to MMU 11. To regionally map the Hox-2 cluster, we have carried out in situ hybridization of the two H24.1 probes and of an independently isolated Hox-2 probe. The autoradiographic silver grain distributions were similar in all three experiments with a peak over band 11D. This region contains the locus for the tail-short (Ts) mutation which causes skeletal abnormalities in heterozygotes and early embryonic death in homozygotes.     

Sequence analysis of the murine Hox-2.2, -2.3, and -2.4 homeo boxes: evolutionary and structural comparisons

We have determined the nucleotide sequences and deduced the amino acid sequences of three tandemly arranged murine boxes of the Hox-2 homeo box gene complex on mouse chromosome 11 (Hox-2.2, -2.3, and -2.4). The type and position of differences with other sequenced homeo boxes were analyzed. Hox-2.2 is nearly identical with its cognate human homeo box Hu-2. Hox-2.3 shares 59 of 61 amino acids with the Antennapedia homeo domain of Drosophila and the MM-3 homeo domain of Xenopus and shows 60 of 61 amino acid identity with human HuC1. Hox-2.3, MM-3, and HuC1 also share a stretch of six glutamic acid residues followed by a stop codon 15-20 amino acids 3' of the homeo domain. Hox-2.4 is relatively divergent from most of the other homeo boxes sequenced to date; however, it matches the Hox-3.1 murine homeo domain at 60 of 61 positions. Sequence comparisons with other murine homeo domains, together with previous studies of their genomic organization and chromosomal location, provide support for the hypothesis of a large-scale duplication resulting in the two major murine homeo box gene complexes Hox-1 and Hox-2.     

Genetic and cytogenetic localisation of the homeo box containing genes on mouse chromosome 6 and human chromosome 7.

Probes from the m6 homeo box cluster were mapped to mouse chromosome 6 by somatic cell genetics, in situ hybridisation, and by a Mus spretus--Mus musculus backcross mapping system. In addition, the testis-specific homeo box containing cDNA, clone, HBT-1, has been mapped using the same back-cross system and the B X D recombinant inbred strain set. Close genetic and physical linkage between the m6 cluster and HBT-1 was demonstrated, positioning these sequences to the same local cluster of homeo box containing genes. The map location of this cluster between IgK and Tcrb coincides with the morphological mutation hypodactyly (Hd). Synteny has been observed between a region of mouse chromosome 6 and the long arm of human chromosome 7 encompassing the markers Cpa, Tcrb and Try-1. Here we localise human sequences hybridising to the mouse m6 probes to the short arm of chromosome 7, breaking the region of synteny.     

A Mouse Homeo Box Gene, Hox-1.5, and the Morphological Locus, Hd, Map to within 1 Cm on Chromosome 6

Mo-10, a homeo box-containing sequence in the Hox-1 complex of genes referred to as Hox-1.5, was found to be polymorphic in inbred and wild mice, and a strain distribution of three allelic forms of Hox-1.5 are reported. The position of Hox-1.5 was mapped in backcross experiments to within 1 cM of the hypodactyly locus on chromosome 6. This identifies the Hd mutation as a useful model for the examination of homeo box expression during mammalian development.     

Isolation and regional localization of the murine homeobox-containing gene Hox-3.3 to mouse chromosome region 15E

A murine homeobox-containing cDNA clone has been isolated from an adult spinal cord library. Using in situ hybridization and somatic cell genetics techniques, the newly isolated homeobox gene has been mapped to mouse chromosome region 15E. Because of its chromosomal location, we called this gene locus Hox-3.3. Nucleotide sequence analysis revealed that the Hox-3.3 gene represents the murine cognate of the human homeobox gene c8. The presumptive organization of the murine Hox-3 homeobox gene cluster is discussed.     

Chromosomal localization of the human homeo box-containing genes, EN1 and EN2

The human homologs of the mouse homeo box-containing genes, En-1 and En-2, which show homology to the Drosophila engrailed gene, have been isolated. The human EN1 gene was mapped to chromosome 2 by analysis of mouse-human somatic cell hybrids. The human EN2 gene was localized to chromosome 7, 7q32-7qter, by analysis of rodent-human somatic cell hybrids and cell lines carrying portions of chromosome 7.     

Identification of a putative gamma-aminobutyric acid (GABA) receptor subunit rho2 cDNA and colocalization of the genes encoding rho2 (GABRR2) and rho1 (GABRR1) to human chromosome 6q14-q21 and mouse chromosome 4.

Screening of a genomic DNA library with a portion of the cDNA encoding the gamma-aminobutyric acid (GABA) receptor subunit rho1 identified two distinct clones. DNA sequencing revealed that one clone contained a single exon from the rho1 gene (GABBR1) while the second clone encompassed an exon with 96% identity to the rho1 gene. Screening of a human retina cDNA library with oligonucleotides specific for the exon in the second clone identified a 3-kb cDNA with an open reading frame of 1395 bp. The predicted amino acid sequence of this cDNA demonstrates 30 to 38% similarity to alpha, beta, gamma, and delta GABA receptor subunits and 74% similarity to the GABA rho1 subunit suggesting that the newly isolated cDNA encodes a new member of the rho subunit family, tentatively named GABA rho2. Polymerase chain reaction (PCR) amplification of rho1 and rho2 gene sequences from DNA of three somatic cell hybrid panels maps both genes to human chromosome 6, bands q14 to q21. Tight linkage was also demonstrated between restriction fragment length variants (RFLVs) from each rho gene and the Tsha locus on mouse chromosome 4, which is homologous to the CGA locus on human chromosome 6q12-q21. These two lines of evidence confirm that GABRR1 and newly identified GABRR2 map to the same region on human chromosome 6. This close physical association and high degree of sequence similarity raises the possibility that one rho gene arose from the other by duplication.     

Assignment of the Human Homologue of the mTRiC-P5 Gene (TRICS) to Band 1q23 by Fluorescence in Situ Hybridization

The TCP1 ring complex (TRiC) is a molecular chaperone involved in actin and tubulin folding. Little is known about the components of this complex. The first component identified was TCP1, a protein coded by a gene in the t -complex locus on mouse chromosome 17. This locus is involved in several embryonic defects, male sterility, and the transmission ratio distortion. In humans, the t-complex genes map to chromosome 6. Other components of TRiC are thought to be TCP1-related proteins. Recently, a mouse cDNA coding for one of these proteins has been cloned and named mTRiC-P5. Here we report the cloning of a partial human cDNA clone, homologous to mTRiC-P5, and its chromosome localization by fluorescence in situ hybridization. The human TRiC-P5 gene (TRIC5) maps to human chromosome 1q23, a region known to be a preferential chromosomal breakpoint involved in leukemia. Therefore, even if TCP1 and TRiC-P5 are related proteins and are found in the same protein complex, they are not coded by syntenic genes in humans.     

Localization of histidase to human chromosome region 12q22----q24.1 and mouse chromosome region 10C2----D1

The human gene for histidase (histidine ammonia-lyase; HAL), the enzyme deficient in histidinemia, was assigned to human chromosome 12 by Southern blot analysis of human X mouse somatic cell hybrid DNA. The gene was sublocalized to region 12q22----q24.1 by in situ hybridization, using a human histidase cDNA. The homologous locus in the mouse (Hal) was mapped to region 10C2----D1 by in situ hybridization, using a cell line from a mouse homozygous for a 1.10 Robertsonian translocation. These assignments extend the conserved syntenic region between human chromosome 12 and mouse chromosome 10 that includes the genes for phenylalanine hydroxylase, gamma interferon, peptidase, and citrate synthase. The localization of histidase to mouse chromosome 10 suggests that the histidase regulatory locus (Hsd) and the histidinemia mutation (his), which are both known to be on chromosome 10, may be alleles of the histidase structural gene locus.     

Isolation and chromosomal localization of the human En-2 gene

By low stringency hybridization we have isolated from a human cosmid genomic library sequences homologous with a probe from the Drosophila engrailed gene. Partial nucleotide sequence analysis shows a consensus splice acceptor site followed by an open reading frame (ORF) that can encode 104 amino acids; the first 94 amino acids have 71% identity with the Drosophila engrailed protein. The shared region contains a homeo domain and is within the region of engrailed shared with the Drosophila invected gene and the mouse En-1 and En-2 genes. At the amino acid level, the human sequence is 85% identical with the mouse En-1 gene and 100% identical with the mouse En-2 gene. Hybridization against a panel of human-hamster somatic cell hybrids maps this human En-2 gene to chromosome 7, and regional mapping by in situ hybridization to human chromosomes localizes it to region 7q36 at the end of the long arm.     

Characterization of a cluster of human high/ultrahigh sulfur keratin-associated protein genes embedded in the type I keratin gene domain on chromosome 17q12-21

Low stringency screening of a human P1 artificial chromosome library using a human hair keratin-associated protein (hKAP1.1A) gene probe resulted in the isolation of six P1 artificial chromosome clones. End sequencing and EMBO/GenBank(TM) data base analysis showed these clones to be contained in four previously sequenced human bacterial artificial chromosome clones present on chromosome 17q12-21 and arrayed into two large contigs of 290 and 225 kilobase pairs (kb) in size. A fifth, partially sequenced human bacterial artificial chromosome clone data base sequence overlapped and closed both of these contigs. One end of this 600-kb cluster harbored six gene loci for previously described human type I hair keratin genes. The other end of this cluster contained the human type I cytokeratin K20 and K12 gene loci. The center of the cluster, starting 35 kb downstream of the hHa3-I hair keratin gene, contained 37 genes for high/ultrahigh sulfur hair keratin-associated proteins (KAPs), which could be divided into a total of 7 KAP multigene families based on amino acid homology comparisons with previously identified sheep, mouse, and rabbit KAPs. To date, 26 human KAP cDNA clones have been isolated through screening of an arrayed human scalp cDNA library by means of specific 3'-noncoding region polymerase chain reaction probes derived from the identified KAP gene sequences. This screening also yielded four additional cDNA sequences whose genes were not present on this gene cluster but belonged to specific KAP gene families present on this contig. Hair follicle in situ hybridization data for single members of five different KAP multigene families all showed localization of the respective mRNAs to the upper cortex of the hair shaft.     

Establishment of the mouse chromosome 7 region with homology to the myotonic dystrophy region of human chromosome 19q

A number of genetic markers, including ATP1A3, TGFB, CKMM, and PRKCG, define the genetic region on human chromosome 19 containing the myotonic dystrophy locus. These and a number of other DNA probes have been mapped to mouse chromosome 7 utilizing a mouse Mus domesticus/Mus spretus interspecific backcross segregating for the genetic markers pink-eye dilution (p) and chinchilla (cch). The establishment of a highly syntenic group conserved between mouse chromosome 7 and human chromosome 19q indicates the likely position of the homologous gene locus to the human myotonic dystrophy gene on proximal mouse chromosome 7. In addition, we have mapped the muscle ryanodine receptor gene (Ryr) to mouse chromosome 7 and demonstrated its close linkage to the Atpa-2, Tgfb-1, and Ckmm cluster of genes. In humans, the malignant hyperthermia susceptibility locus (MHS) also maps close to this gene cluster. The comparative mapping data support Ryr as a candidate gene for MHS.     

The structural gene for transferrin (TF) maps to 3q21----3qter

A cloned human cDNA for transferrin (TF) was used as hybridization probe in analysing a series of rodent x human somatic cell hybrids for the presence of human TF sequences. The assignment to chromosome 3 was further refined to region 3q21----3qter using hybrids that carried a translocated chromosome 3 and fibroblasts from a patient trisomic for this region. The gene for TF therefore maps to the same region as the gene for transferrin receptor (TFR) thereby defining an iron transport region on 3q2 to which the transferrin-related tumor associated antigen p97 may also belong. It follows that the genes for pseudocholinesterase (CHE1), ceruleoplasmin (CP) and alpha-2HS-glycoprotein (A2HS) which belong to the, as yet unassigned, linkage group of TF, now also map to chromosome 3 in man.     

The L-isoaspartyl/D-aspartyl protein methyltransferase gene (PCMT1) maps to human chromosome 6q22.3-6q24 and the syntenic region of mouse chromosome 10.

We have mapped the genes for the human and mouse L-isoaspartyl/D-aspartyl protein carboxyl methyltransferase (EC 2.1.1.77) using cDNA probes. We determined that the human gene is present in chromosome 6 by Southern blot analysis of DNA from a panel of mouse-human somatic cell hybrids. In situ hybridization studies allowed us to confirm this identification and further localize the human gene (PCMT1) to the 6q22.3-6q24 region. By analyzing the presence of an EcoRI polymorphism in DNA from backcrosses of C57BL/6J and Mus spretus strains of mice, we localized the mouse gene (Pcmt-1) to chromosome 10, at a position 8.2 +/- 3.5 cM proximal to the Myb locus. This region of the mouse chromosome is homologous to the human 6q24 region.