Drosophila protein phosphatase 5 is encoded by a single gene that is most highly expressed during embryonic development

A putative Drosophila melanogaster homologue of mammalian PP5, termed Dm PP5, was identified from cDNA. Dm PP5 comprises a phosphatase catalytic domain preceded by an amino terminal domain containing three tetratricopeptide repeat motifs and shares 60% overall amino acid identity with human PP5. Genomic restriction analysis identified a single Dm PP5 gene that was mapped to the third chromosome at locus 85E10-12 and a strain carrying a deletion that encompasses this gene was identified. Dm PP5 mRNA and protein are more highly expressed in the embryo than at later developmental stages, but their expression levels do not always change synchronously. Dm PP5 protein localises to both the nucleus and the cytoplasm of cells at the periphery of newly cellularized embryos.     

Pax-5 is expressed at the midbrain-hindbrain boundary during mouse development.

The murine paired-box-containing gene 5, Pax-5, is highly homologous to two other Pax genes, Pax-2 and Pax-8. The expression pattern of Pax-5 during mouse embryogenesis was examined by in situ RNA hybridization and compared to those of Pax-2 and Pax-8. Beginning at day 9.5 postcoitum (p.c.), Pax-5 was expressed in the developing brain, predominantly at the midbrain-hindbrain boundary, and in the neural tube. While the neural tube expression pattern overlapped completely with Pax-2 and Pax-8, the expression pattern in the brain was only partially overlapping. Unlike Pax-2 and Pax-8, Pax-5 was not expressed in the developing excretory system, thyroid, eye or ear. Our data suggest that Pax-5 has a role in the development of the central nervous system.     

Hox-3.6: isolation and characterization of a new murine homeobox gene located in the 5' region of the Hox-3 cluster.

Most members of the murine Hox gene system can be grouped into two subclasses based on their structural similarity to either one of the Drosophila homeotic genes Antennapedia (Antp) or Abdominal B (AbdB). All the AbdB-like genes reported thus far are located in the 5' region of their respective cluster. We describe here the isolation, structural characterization and spatio-temporal expression pattern of a new AbdB-like homeobox gene designated Hox-3.6 that is located in the 5' region of the Hox-3 cluster. Hox-3.6 has an extreme posterior expression domain in embryos of 12.5 days of gestation, a feature that has thus far only been observed for the 5' most genes of the Hox-4 cluster. Like the other members of the AbdB subfamily, Hox-3.6 exhibits spatially restricted expression in the hindlimb bud, but the expression domain is antero-proximal in contrast to the postero-distal domain reported for its cognate gene Hox-4.5. Structural analysis of the 5' region revealed the presence of a 35 bp sequence which shares homology and relative 5' position with an upstream sequence present in its two nearest downstream neighbors, Hox-3.2 and -3.1.     

EVX2, a human homeobox gene homologous to the even-skipped segmentation gene, is localized at the 5' end of HOX4 locus on chromosome 2.

We isolated and mapped three new human homeoboxes located on chromosome 2 upstream from the reported seven HOX4 homeobox sequences. Two of them, HOX41 and HOX4H, clearly belong to the HOX gene family, in particular to homology groups 1 and 2, and possibly represent the most 5' HOX4 homeoboxes. A third homeobox 13 kb upstream from HOX41 was identified. Sequencing data show that this is the human homolog of the murine Evx-2 homeobox. Both homeoboxes are closely related to the murine Evx-1 and to the frog Xhox-3 homeoboxes. The four genes represent vertebrate homologs of Drosophila even-skipped (eve), a segmentation gene of the pair-rule class. Human EVX2 sequences belong to an active gene because they are transcribed and properly processed in cells and tissues. We have identified for the first time a homeogene of a different class at a HOX locus. These findings are relevant to the understanding of the evolution of HOX gene clusters and their regulation.     

The keratocan gene is expressed in both ocular and non-ocular tissues during early chick development.

Extracellular matrix (ECM) keratan sulfate proteoglycans (KSPGs) are core proteins with sulfated polylactosamine side chains (KS). The KSPG core protein keratocan gene (Kera) is expressed almost exclusively in adult vertebrate cornea, but its embryonic expression is little known. Embryonic chick in situ hybridization reveals Kera mRNA expression in corneal endothelium from embryonic day (E) 4.5, Hamburger-Hamilton (HH) 25, in stromal keratocytes from E6.5, HH30, and in iris distal surface cells from E8, HH34. As highly sulfated, antibody I22-positive KS increases extracellularly from posterior to anterior across the stroma, nerves enter and populate only anterior stroma and epithelium. RT-PCR and in situ hybridization demonstrate that developmentally regulated Kera mRNA expression initiates in midbrain and dorsolateral mesenchyme at E1, HH7, then spreads caudally in hindbrain and cranial and trunk mesenchyme flanking the neural tube through E2, HH20. Cranial expression extends ventrally through the developing head, and concentrates in mesenchyme surrounding eye anterior regions and cranial ganglia, and in subepidermal pharyngeal arch mesenchyme by E3.5, HH22. Kera expression in the trunk at E3.5, HH22 and E4.5, HH25, is strong in dorsolateral subepidermal, sclerotomal and nephrogenic mesenchymes, but absent in neural tube, dorsal root ganglia, nerve outgrowths, notochord, heart and gut. Early limb buds express Kera mRNA throughout their mesenchyme, then in restricted proximal and distal mesenchymes. I22-positive KS appears only in notochord in E3.5, HH22 and E4.5, HH25, embryos. Results suggest the hypothesis that keratocan, or keratocan with minimally sulfated KS chains, may play a role in structuring ECM for early embryonic cell and neuronal migrations.     

The mouse secreted frizzled-related protein 5 gene is expressed in the anterior visceral endoderm and foregut endoderm during early post-implantation development

The anterior visceral endoderm (AVE) plays an important role in anterior-posterior axis formation in the mouse. The AVE functions in part by expressing secreted factors that antagonize growth factor signaling in the proximal epiblast. Here we report that the Secreted frizzled-related protein 5 (Sfrp5) gene, which encodes a secreted factor that can antagonize Wnt signaling, is expressed in the AVE and foregut endoderm during early mouse development. At embryonic day (E) 5.5, Sfrp5 is expressed in the visceral endoderm at the distal tip region of the embryo and at E6.5 in the AVE opposite the primitive streak. In Lim1 embryos, which lack anterior neural tissue and sometimes form a secondary body axis, Sfrp5-expressing cells fail to move towards the anterior and remain at the distal tip of E6.5 embryos. When compared with Dkk1, which encodes another secreted Wnt antagonist molecule present in the visceral endoderm, Sfrp5 and Dkk1 expression overlap but Sfrp5 is expressed more broadly in the AVE. Between E7.5 and 8, Sfrp5 is expressed in the foregut endoderm underlying the cardiac mesoderm. At E8.5, Sfrp5 is expressed in the ventral foregut endoderm that gives rise to the liver. Additional domains of Sfrp5 expression occur in the dorsal neural tube and in the forebrain anterior to the optic placode. These findings identify a gene encoding a secreted Wnt antagonist that is expressed in the extraembryonic visceral endoderm and anterior definitive endoderm during axis formation and organogenesis in the mouse.     

Caspase-2 is localized at the Golgi complex and cleaves golgin-160 during apoptosis

Caspases are an extended family of cysteine proteases that play critical roles in apoptosis. Animals deficient in caspases-2 or -3, which share very similar tetrapeptide cleavage specificities, exhibit very different phenotypes, suggesting that the unique features of individual caspases may account for distinct regulation and specialized functions. Recent studies demonstrate that unique apoptotic stimuli are transduced by distinct proteolytic pathways, with multiple components of the proteolytic machinery clustering at distinct subcellular sites. We demonstrate here that, in addition to its nuclear distribution, caspase-2 is localized to the Golgi complex, where it cleaves golgin-160 at a unique site not susceptible to cleavage by other caspases with very similar tetrapeptide specificities. Early cleavage at this site precedes cleavage at distal sites by other caspases. Prevention of cleavage at the unique caspase-2 site delays disintegration of the Golgi complex after delivery of a pro-apoptotic signal. We propose that the Golgi complex, like mitochondria, senses and integrates unique local conditions, and transduces pro-apoptotic signals through local caspases, which regulate local effectors.     

Hoxb-5 is expressed in gill arch 5 during pharyngeal arch development of flounder Paralichthys olivaceus embryos.

Hox genes are expressed in domains with clear anterior borders exhibiting 3'-->5' hierarchy in hindbrain and in the pharyngeal area commonly in vertebrate embryos. Teleost embryos form seven pharyngeal arches, the mandibular arch, hyoid arch and the gill arches 1-5. We previously reported that, in Japanese flounder (Paralichthys olivaceus) embryos, Hoxd-4 is expressed from rhombomere 7 to the spinal cord in the central nervous system and at gill arches 2-5. At present, the hierarchy of Hox genes at gill arches 3-5 of teleost fish is unclear. Here, we investigated the expression domains of Hoxb-5 in the flounder embryo by whole-mount in situ hybridization to gain insight into the Hox code at gill arches. The initial signal indicating Hoxb-5 expression was identified in the spinal cord at hatching, corresponding with the prim-5 stage of zebrafish. Then, intense signals were detected from the anterior part of the spinal cord and from the posterior part of the pharyngeal area at 36 h after hatching. By serially sectioning the hybridized embryos, it was found that signal in the pharyngeal area came from the most posterior gill arch 5. Therefore, it is speculated that Hoxb-5 functions in regional identification of gill arch 5 in this teleost.     

The gene encoding tobacco gibberellin 3beta-hydroxylase is expressed at the site of GA action during stem elongation and flower organ development

Gibberellin 3beta-hydroxylase catalyzes the final step in the biosynthetic pathway leading to the plant hormone gibberellin (GA) and, therefore, the in vivo localization of this enzyme should give a direct indication of the site of synthesis of bioactive GAs in plants. We have isolated a cDNA clone, Nty (Nicotiana tabacum GA 3beta-hydroxylase), which encodes a putative GA 3beta-hydroxylase, by RT-PCR using RNA from tobacco shoot apices. Functional analysis, using an NTY protein expressed in Escherichia coli, revealed that Nty encoded an active GA 3beta-hydroxylase. A high expression level of Nty was observed in shoot apices, flowers, roots, young internodes but not in leaves or seeds. We performed more detailed expression analyses using in situ hybridization and histochemical analyses of the GUS activity in transgenic tobacco plants carrying an Nty promoter:GUS fusion gene. These studies revealed that expression of Nty was restricted to specific regions, including actively dividing and elongating cells in the various organs; rib meristem and elongation zones of shoot apices, tapetum and pollen grains in developing anthers and root tips, which are consistent with the sites of GA action. It is proposed that GA actions depend on the modulation of endogenous bioactive GA levels through the regulation of GA 3beta-hydroxylase expression in situ.     

Murine genes related to the Drosophila AbdB homeotic genes are sequentially expressed during development of the posterior part of the body.

The cloning, characterization and developmental expression patterns of two novel murine Hox genes, Hox-4.6 and Hox-4.7, are reported. Structural data allow us to classify the four Hox-4 genes located in the most upstream (5') position in the HOX-4 complex as members of a large family of homeogenes related to the Drosophila homeotic gene Abdominal B (AbdB). It therefore appears that these vertebrate genes are derived from a selective amplification of an ancestral gene which gave rise, during evolution, to the most posterior of the insect homeotic genes so far described. In agreement with the structural colinearity, these genes have very posteriorly restricted expression profiles. In addition, their developmental expression is temporally regulated according to a cranio-caudal sequence which parallels the physical ordering of these genes along the chromosome. We discuss the phylogenetic alternative in the evolution of genetic complexity by amplifying either genes or regulatory sequences, as exemplified by this system in the mouse and Drosophila. Furthermore, the possible role of 'temporal colinearity' in the ontogeny of all coelomic (metamerized) metazoans showing a temporal anteroposterior morphogenetic progression is addressed.