Cognate homeo-box loci mapped on homologous human and mouse chromosomes

Assignment of the HOX2 and HOX3 gene clusters to the bovine chromosome regions 19q17-qter and 5q14-23

The homeobox 2 (HOX2) and homeobox 3 (HOX3) clusters have been chromosomally assigned in cattle by in situ hybridization. The probes employed were a murine probe for the mapping of HOX2 to 19q17-qter and human probes for the mapping of HOX3 to 5q14-q23. These assignments confirm the chromosomal assignment of two syntenic groups, consisting of loci located on human chromosome 12 (bovine chromosome 5) and the long arm of human chromosome 17 (bovine chromosome 19).

Molecular etiology of gut malformations and diseases

This review describes recent advances using animal models in the analysis of the molecular controls of gastrointestinal development, with specific attention to mutations causing maldevelopment similar to those seen in human gut malformations. By focusing on specific human gut pathologic conditions and maldevelopment, we describe the probable roles of signaling pathways, including the hedgehog pathway, the bone morphogenic protein pathway, and the role of the homeotic genes.

Theoretical approaches to the analysis of homeobox gene evolution

The homeobox gene system presents a unique model for experimental and theoretical analyses of gene evolution. Homeobox genes play a role in patterning the embryonic development of diverse organisms and as such are likely to have been fundamental to the evolution of the specialized body plans of many animal species. The organization of Hox-genes in chromosomal, clusters in many species implicates gene duplication as a prominent mechanism in the evolution of this multigene family. I review here various theoretical analyses that have contributed to our understanding of the molecular evolution of this class of developmental control genes. This article also illustrates relationships between theoretical predictions and experimental studies and outlines future avenues for the evolutionary analysis of developmental systems.

Genetic linkage analysis of the murine developmental mutant velvet coat (Ve) and the distal chromosome 15 developmental genes Hox-3.1, Rar-g, Wnt-1, and Krt-2

We have identified restriction fragment length polymorphisms between Mus musculus and Mus spretus for the Chromosome 15 loci Hox-3, Wnt-1, Krt-2, Rar-g, and Ly-6. We followed the inheritance of these alleles in interspecific genetic test crosses between velvet coat (Ve) heterozygotes and M. spretus. The results suggest a gene order and recombination distances (in cM) of Ly-6-22-Wnt-1-2-Ve/Krt-2/Rar-g-3-Hox-3. No recombination was found between Ve, Krt-2, and Rar-g. The data also provide evidence for the hypothesis of a large-scale genomic duplication involving homologous gene pairs on mouse Chromosomes 15 and 11.

Chromosome assignments of the human TNF p55 and p75 receptor genes

At least two different receptor molecules have been described that are capable of binding tumor necrosis factor alpha, a cytokine that plays an important role in inflammation and antitumor activity. Comparative analyses at the nucleotide sequence level suggest that these receptors are members of a newly defined protein family that also includes human and rat nerve growth factor receptors. In this study, we determine the chromosome assignments of the human TNF alpha receptor genes, one of which may have evolved as part of a conserved Hox locus-containing chromosome segment.

Greig syndrome associated with an interstitial deletion of 7p: confirmation of the localization of Greig syndrome to 7p13

An 11-month-old infant with Greig cephalopolysyndactyly syndrome and mild developmental delay is described. High-resolution chromosomal analysis showed a de novo interstitial deletion of chromosome 7p with breakpoints located at p13 and p14. Cytogenetic analysis of polymorphisms of the heterochromatin in the pericentromeric region suggested the deleted chromosome was of paternal origin. This case confirms the localization of Greig syndrome to 7p13 and emphasizes the importance of performing cytogenetic studies on patients with Mendelian disorders who have unusual findings or cognitive abnormalities in a disorder usually associated with normal intellect. Review of clinical features in published reports of patients with a deletion involving 7p13 showed a number to have features overlapping with Greig syndrome. Because of this, we suggest that cytogenetic aberrations, particularly chromosomal microdeletions, may represent a significant etiology for Greig syndrome.

Mapping of the Hox-3.1 and Myc-1.2 genes on chromosome 15 of the mouse by restriction fragment length variations

Restriction endonuclease fragment length variations (RFLV) were detected by use of the cDNA probe Hox-3.1 for the homeo box-3.1 gene and also the c-myc oncogene probe for exon 2. RFLV of Hox-3.1 were found in HindIII restriction patterns, and RFLV of the Myc-1.2 gene in EcoRV patterns. From the RFLV, the Hox-3.1 and Myc-1.2 genes were mapped on chromosome 15. Three-point cross test data showed that the frequency of recombination is 26.4% between Myc-1.2 and Gpt-1, 30.2% between Gpt-1 and Gdc-1, and 9.4% between Gdc-1 and Hox-3.1. The following order of these genes is proposed, Myc-1.2--Gpt-1--Gdc-1--Hox-3.1. All laboratory strains carry the Hox-3.1a and Myc-1.2a alleles. Among strains of wild origin, domesticus strains carry only the Hox-3.1a and Myc-1.2a alleles, as do the laboratory strains. One strain of brevirostris carries the Hox-3.1a and Myc-1.2b alleles. Other wild subspecies from Europe and Asia, M. m. musculus, M. m. castaneus, M. m. molossinus, Chinese mice of wild origin, and M. m. yamashinai carry the Hox-3.1b and Myc-1.2b alleles.

Isolation and characterization of ERBB3, a third member of the ERBB/epidermal growth factor receptor family: evidence for overexpression in a subset of human mammary tumors

A related DNA fragment distinct from the epidermal growth factor receptor and ERBB2 genes was detected by reduced stringency hybridization of v-erbB to normal genomic human DNA. Characterization of the cloned DNA fragment mapped the region of v-erbB homology to three exons with closest identity of 64% and 67% to a contiguous region within the tyrosine kinase domains of the epidermal growth factor receptor and ERBB2 proteins, respectively. cDNA cloning revealed a predicted 148-kDa transmembrane polypeptide with structural features identifying it as a member of the ERBB gene family, prompting us to designate the gene as ERBB3. It was mapped to human chromosome 12q13 and was shown to be expressed as a 6.2-kilobase transcript in a variety of normal tissues of epithelial origin. Markedly elevated ERBB3 mRNA levels were demonstrated in certain human mammary tumor cell lines. These findings suggest that increased ERBB3 expression, as in the case of epidermal growth factor receptor and ERBB2, may play a role in some human malignancies.

Lineage-restricted expression of homeobox-containing genes in human hematopoietic cell lines

We investigated the role of homeobox-containing genes in human hematopoiesis because homeobox genes (i) control cell fate in the Drosophila embryo, (ii) are expressed in specific patterns in human embryos, and (iii) appear to function as transcription factors that control cell phenotype in other mammalian organs. Using four homeobox probes from the HOX2 locus and a previously undescribed homeobox cDNA (PL1), we screened mRNAs from 18 human leukemic cell lines representing erythroid, myeloid, and T- and B-cell lineages. Complex patterns of lineage-restricted expression are observed: some are restricted to a single lineage, while others are expressed in multiple lineages. No single homeobox gene is expressed in all types of hematopoietic cells, but each cell type exhibits homeobox gene expression. HOX2.2 and -2.3 homeobox-containing cDNAs were cloned from an erythroleukemia cell (HEL) cDNA library, while the homeobox cDNA PL1 was isolated from a monocytic cell (U-937) library. Differentiation of HEL and K-562 cells with various inducers results in modulation of specific homeobox transcripts. In addition, HOX2.2 is expressed in normal bone marrow cells. We have demonstrated (i) lineage-restricted expression of five homeobox genes in erythroid and monocytic cell lines; (ii) expression of additional homeobox genes in other cell lineages (HL-60 and lymphoid cells); (iii) expression of one homeobox gene in normal marrow cells; and (iv) modulation of expression during differentiation. These data suggest that these genes play a role in human hematopoietic development and lineage commitment.

Duplication of large genomic regions during the evolution of vertebrate homeobox genes

The phylogenetic relationships of 21 murine Antp-class (Drosophila mutation Antennapedia-type class) homeobox genes have been analyzed, and several groups of related genes have been identified. The murine Antp-class homeobox genes are localized within four gene clusters. The similar structural organization of the four gene clusters strongly suggests that genes within a group of related Antp-class homeobox genes are derived from duplications of large genomic regions. After the duplication, the gross structures of the homeobox gene clusters have been maintained over a long period of evolutionary time, indicating that the specific organization of genes within a cluster may be of functional importance.

Remarkable intron and exon sequence conservation in human and mouse homeobox Hox 1.3 genes

A high degree of conservation exists between the Hox 1.3 homeobox genes of mice and humans. The two genes occupy the same relative positions in their respective Hox 1 gene clusters, they show extensive sequence similarities in their coding and noncoding portions, and both are transcribed into multiple transcripts of similar sizes. The predicted human Hox 1.3 protein differs from its murine counterpart in only 7 of 270 amino acids. The sequence similarity in the 250 base pairs upstream of the initiation codon is 98%, the similarity between the two introns, both 960 base pairs long, is 72%, and the similarity in the 3' noncoding region from termination codon to polyadenylation signal is 90%. Both mouse and human Hox 1.3 introns contain a sequence with homology to a mating-type-controlled cis element of the yeast Ty1 transposon. DNA-binding studies with a recombinant mouse Hox 1.3 protein identified two binding sites in the intron, both of which were within the region of shared homology with this Ty1 cis element.

Remarkable intron and exon sequence conservation in human and mouse homeobox Hox 1.3 genes

A high degree of conservation exists between the Hox 1.3 homeobox genes of mice and humans. The two genes occupy the same relative positions in their respective Hox 1 gene clusters, they show extensive sequence similarities in their coding and noncoding portions, and both are transcribed into multiple transcripts of similar sizes. The predicted human Hox 1.3 protein differs from its murine counterpart in only 7 of 270 amino acids. The sequence similarity in the 250 base pairs upstream of the initiation codon is 98%, the similarity between the two introns, both 960 base pairs long, is 72%, and the similarity in the 3' noncoding region from termination codon to polyadenylation signal is 90%. Both mouse and human Hox 1.3 introns contain a sequence with homology to a mating-type-controlled cis element of the yeast Ty1 transposon. DNA-binding studies with a recombinant mouse Hox 1.3 protein identified two binding sites in the intron, both of which were within the region of shared homology with this Ty1 cis element.

A new family of mouse homeo box-containing genes: molecular structure, chromosomal location, and developmental expression of Hox-7.1

Two families of homeo box-containing genes have been identified in mammals to date, the Antennapedia- and engrailed-like homeo boxes, based on the sequence similarity to those from Drosophila. Here, we report the isolation of a homeo box-containing gene that belongs to a new family of which there are at least three related genes in the mouse genome. The homeo box of this new gene shows remarkable similarity to the Drosophila Msh homeo box that we designate as the prototype for this family. The gene maps to the proximal end of mouse chromosome 5 and does not cosegregate with any known homeo box-containing gene. We designate this locus Hox-7.1. In situ hybridizations to mouse embryos at different stages show a unique pattern of expression, as compared to other homeo box-containing genes described thus far. Hox-7.1 transcripts are detected in 9.5-day-old embryos in the neural crest, developing limb bud, and visceral arches. Later, this gene is expressed in regions of the face that are derived from neural crest and in the interdigital mesenchymal tissues in both the fore- and hindlimbs.

Characterization of deletions of chromosome 7 short arm occurring as primary karyotypic anomaly in acute myeloid leukaemia

Three patients with an acute myeloid leukaemia (AML) showed a deletion of the short arm of chromosome 7 with loss of the deleted material. The 7p- anomaly originated from either a terminal or an interstitial deletion and it represented the only karyotypic aberration in all the three cases. According to the clinical, morphological and immunological features of this series of patients, a 7p- chromosome appears to be associated with a group of AML with myelodysplastic features in the bone marrow, including secondary disorders in patients treated for a previous malignancy.

Hox-5.1 defines a homeobox-containing gene locus on mouse chromosome 2

We have isolated a murine homeobox-containing gene, Hox-5.1, by virtue of its relatedness to the Hox-1.4 gene. In situ hybridization to metaphase spreads mapped Hox-5.1 to band D of mouse chromosome 2. Sequence comparisons indicate that Hox-5.1 is the murine homolog of the human C13 homeobox-containing gene. Hox-5.1 also bears significant similarity to the Xenopus Xhox-1A homeobox-containing gene and the Drosophila deformed homeotic gene at N-terminal and homeobox regions. Hox-5.1 transcripts were detected in mouse embryos, in adult mouse testis, kidney, heart, and intestine, and in mouse embryonal carcinoma cells treated with retinoic acid. In situ hybridization to sections from whole mouse embryos revealed Hox-5.1 expression in spinal cord and prevertebrae.

The ras-related ral gene maps to chromosome 7p15-22

Human cDNAs coding for the new protein ral that shares 50% homology with the ras proteins have been recently isolated. A 600-bp fragment carrying mainly the coding region was used to localize the ral gene by hybridization with sorted chromosomes and in situ hybridization. Direct molecular hybridization on sorted chromosomes using a single laser illumination allowed the assignment of the ral gene to a region of the flow karyotype containing chromosomes 7, 8 and X. With dual laser analysis ral was assigned to the fraction containing chromosome 7. In the 331 human metaphases hybridized with the 3H-labelled insert, the silver grain distribution showed a unique major signal on chromosome 7p15-22.

Genetic markers on chromosome 7

Chromosome 7 is frequently associated with chromosome aberrations, rearrangements, and deletions. It also contains many important genes, gene families, and disease loci. This brief review attempts to summarise these and other interesting aspects of chromosome 7. With the rapid accumulation of cloned genes and polymorphic DNA fragments, this chromosome has become an excellent substrate for molecular genetic studies.

The Hox-2 homeo box gene complex on mouse chromosome 11 is closely linked to Re

Restriction fragment length polymorphisms have been identified between inbred strains of mice for the homeo box gene complex Hox-2. These genetic markers were used to follow the segregation of different Hox-2 alleles among recombinant inbred strains of mice and among the progeny of a three point genetic cross. The results place the Hoax-2 locus approximately 1 cM from the rex (Re) locus on mouse chromosome 11.

A mouse homeobox containing gene on chromosome 11: sequence and tissue-specific expression

We have molecularly cloned a mouse homeobox containing gene by isolating cDNA and genomic clones. The gene is located in a previously described cluster on chromosome 11 (Hart et al. (1985) Cell 43, 9-18) and was identified as the Hox2.3 gene. We present the complete mRNA sequence of this gene and describe similarities to other homeobox containing genes, among which its human homologue, the cl gene. High expression of the Hox2.3 gene was found in kidney, testis, and spinal cord of adult mice, in the spinal cord of 12.5-17.5 day embryos and in differentiating EC cells depending on their treatment. Three different treatments of the pluripotent EC cell line P19, each leading to the induction of a specific differentiation pathway, resulted in all cases in induction of Hox2.3; however, major quantitative differences in this response were observed.

AvaII RFLP at the human apolipoprotein CII (APO CII) gene locus

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Human homeo box-containing genes located at chromosome regions 2q31----2q37 and 12q12----12q13

Four human homeo box-containing cDNAs isolated from mRNA of an SV40-transformed human fibroblast cell line have been regionally localized on the human gene map. One cDNA clone, c10, was found to be nearly identical to the previously mapped Hox-2.1 gene at 17q21. A second cDNA clone, c1, which is 87% homologous to Hox-2.2 at the nucleotide level but is distinct from Hox-2.1 and Hox-2.2, also maps to this region of human chromosome 17 and is probably another member of the Hox-2 cluster of homeo box-containing genes. The third cDNA clone, c8, in which the homeo box is approximately 84% homologous to the mouse Hox-1.1 homeo box region on mouse chromosome 6, maps to chromosome region 12q12----12q13, a region that is involved in chromosome abnormalities in human seminomas and teratomas. The fourth cDNA clone, c13, whose homeo box is approximately 73% homologous to the Hox-2.2 homeo box sequence, is located at chromosome region 2q31----q37. The human homeo box-containing cluster of genes at chromosome region 17q21 is the human cognate of the mouse homeo box-containing gene cluster on mouse chromosome 11. Other mouse homeo box-containing genes of the Antennapedia class (class I) map to mouse chromosomes 6 (Hox-1, proximal to the IgK locus) and 15 (Hox-3). A mouse gene, En-1, with an engrailed-like homeo box (class II) and flanking region maps to mouse chromosome 1 (near the dominant hemimelia gene). Neither of the class I homeo box-containing genes--c8 and c13--maps to a region of obvious homology to chromosomal positions of the presently known mouse homeo box-containing genes.

Molecular approaches to developmental genetics and pathology

New insights into gene structure and expression and the observation that homeobox-containing genes, the t-complex, and oncogenes are expressed also in humans contribute to the understanding of normal and pathobiological mechanisms of embryonal and fetal development.

Homeo box genes in murine development

Considerable information has accumulated on mouse homeo box gene organization and expression. Homeo box genes are expressed in a wide variety of tissues, developmental stages, and cell lines. How can this be interpreted in view of the relationship of these genes to Drosophila morphogenetic loci? One view is that homeo box genes control determinative decisions by modulating transcription of as yet unidentified target genes. Proponents of this view are faced with two tasks: to identify developmental processes that are controlled by homeo box genes, and to identify the target genes that mediate this control. Such target genes might be identified on the basis of in vitro homeo domain-DNA interactions. Candidate morphogenetic processes might be identified on the basis of the observed patterns of homeo box gene expression. It must be stressed that finding expression in a given tissue in no way demonstrates that the expression is necessary for the determination of that tissue. The role of Drosophila homeo box genes in determinative decisions is based upon analysis of mutants to demonstrate that the pattern of homeo box gene expression determines the morphogenetic outcome. To test whether the expression of a mouse homeo box gene is involved in a determinative decision, one must disrupt the normal pattern of expression of that gene and observe the resulting morphogenetic effect. In mouse this can be approached by looking for allelism with known morphogenetic loci, by isolating mutants in homeo box genes through large-scale mutagenesis screens, or by introducing altered homeo box genes into transgenic mice. One of the most intriguing possibilities is that homeo box genes are involved in regional specification along the anteroposterior axis. In situ hybridization and Northern blot analysis have demonstrated that at least four different homeo box genes display distinct regional patterns of expression along the anteroposterior axis of the developing CNS. The expression of each of these genes has a unique anterior boundary from which expression extends posteriorly within the CNS. Hox 1.5 expression has an anterior boundary within the hindbrain just posterior to the pontine flexure. The anterior boundary of Hox 2.1 expression lies more posteriorly within the medulla of the hindbrain. Weak expression of Hox 2.5 is detected in the spinal cord just posterior to the first cervical vertebra, and maximal expression is found posterior to the second cervical vertebra.(ABSTRACT TRUNCATED AT 400 WORDS)