Structure of two genes at the gooseberry locus related to the paired gene and their spatial expression during Drosophila embryogenesis

Requirements for hedgehog, a segmental polarity gene, in patterning larval and adult cuticle of Drosophila

Mutations of the hedgehog gene are generally embryonic lethal, resulting in a lawn of denticles on the ventral surface. In strong alleles, no segmentation is obvious and the anteroposterior polarity of ventral denticles is lost. Temperature shift analysis of a temperature-sensitive allele indicates an embryonic activity period for hedgehog between 2.5 and 6 hr of embryonic development (at 25 degrees) and a larval/pupal period from 4 to 7 days of development (at 25 degrees). Mosaic analysis of hedgehog mutations in the adult cuticle indicates a series of defined defects associated with the failure of appropriate hedgehog expression. In particular, defects in the distal portions of the legs and antenna occur in association with homozygous hedgehog clones in the posterior compartment of those structures. Because the defects are associated with homozygous clones, but are not co-extensive, a type of "domineering" nonautonomy is proposed for the activity of the hedgehog gene.

A human protein specific for the immunoglobulin octamer DNA motif contains a functional homeobox domain

The homeobox domain is shared by Drosophila homeotic proteins, yeast mating type proteins, and some functionally uncharacterized mammalian proteins. A lymphoid-restricted human protein that binds to the immunoglobulin octamer regulatory motif was shown to contain an amino acid sequence that has 33% amino acid identity with the consensus sequence of the previously cloned homebox domains. This homeobox gene was localized to chromosome 19, thus mapping separately from other human homebox genes. A mutant protein containing amino acid substitutions within a putative helix-turn-helix motif in the homeobox domain did not bind DNA detectably. This human homeobox protein was shown to bind the same DNA sequence as the homeobox domains of the yeast mating type proteins and Drosophila homeotic protein, suggesting that homeobox proteins may have closely related DNA binding characteristics.

The molecular genetics of embryonic pattern formation in Drosophila

Analysis of the genes that control the early events of Drosophila embryogenesis is providing details of the molecular processes underlying the positional specification of cells. There are two distinct phases: the first precedes the cellularization of the blastoderm embryo and is associated with a cascade of interactions between transcriptional regulators; the second occurs after cellularization and depends on communication between cells. These processes may be conserved in a wide range of invertebrates and vertebrates.

Spatial regulation of engrailed expression in the Drosophila embryo

Novel patterns of engrailed RNA were observed in early Drosophila embryos injected with cycloheximide, an inhibitor of protein synthesis. From these patterns, we infer that there are several superimposed systems of spatial regulation which in combination localize engrailed expression in the embryo. Activation of engrailed transcription progresses with an anterior-to-posterior polarity. Superimposed are systems of negative regulation that repress expression in the anterior 30% of the embryo and in the interbands between stripes. We suggest that products of known segmentation genes are the repressors that suppress engrailed expression in interbands.

Isolation of the Drosophila segmentation gene runt and analysis of its expression during embryogenesis

runt is one of the genes required for establishment of the segmented body pattern of the Drosophila embryo. We have isolated DNA sequences containing this gene using P-element transposon tagging. Southern blot analyses of six different DNA rearrangements that are associated with runt mutations revealed a minimal region of 8.5-kb of DNA that was important for function. In germ line transformation experiments, a 14.5-kb segment of DNA that spanned this minimal region provided significant, although not full, levels of runt activity. The runt gene encoded a 2.6-kb poly(A)+ RNA that underwent a series of dynamic changes in its spatial and temporal patterns of accumulation during embryogenesis. The runt RNA was most abundant at the blastoderm stage when it showed the seven stripes of expression characteristic of other Drosophila pair-rule genes.

polyhomeotic: a gene required for the embryonic development of axon pathways in the central nervous system of Drosophila

Hypomorphic alleles of the locus polyhomeotic (ph) produce multiple, homeotic-like transformations in adult flies that mimic dominant mutations in the Antennapedia and Bithorax complexes. Analysis of null alleles of ph has revealed a complex, embryonically lethal phenotype that includes cell death of the ventral epidermis and abnormalities in the patterns of expression of homeotic and segmentation genes. There is also a dramatic alteration in the pattern of axon pathways in the central nervous system, such that the wild-type array of segmentally repeated commissures and connectives is replaced by bundles of axons confined to the hemiganglia of origin. It is possible that this axonal phenotype is the result of loss of neuronal identity caused by abnormal homeotic and segmentation gene expression.

Pax 1, a member of a paired box homologous murine gene family, is expressed in segmented structures during development

The mouse genome contains at least three copies of sequences homologous to the "paired box", a conserved domain in several Drosophila segmentation genes of the pair-rule and segment polarity classes. Overlapping phages were isolated from two different genomic libraries using the Drosophila gooseberry distal paired box as a probe. The hybridizing sequences are highly homologous to the conserved Drosophila paired box sequences. A single 3.1 kb Pax 1 (paired box gene) transcript was detected during embryonic development, whereas no transcripts were detected in adult tissues. Detailed in situ hybridization analyses with frozen embryonic sections demonstrated Pax 1 transcripts in the perichordal zone of the developing vertebral column. The expression pattern suggests a role for this gene in the formation of segmented structures of the mouse embryo.