Disease relevance of lab

• During embryogenesis, Scr accumulation is observed in a discrete spatiotemporal pattern that includes the labial and prothoracic ectoderm, the subesophageal ganglion of the ventral nerve cord and the visceral mesoderm of the anterior and posterior midgut [1].

High impact information on lab

• The activity of both target genes is required for normal expression of another homeotic gene, labial, in cells of the adhering midgut epithelium [2].
• Midway through embryogenesis, dpp is expressed in the visceral mesoderm, and enhances the expression of the homeotic gene labial in the underlying midgut endoderm [3].
• This reporter expression in Drosophila embryos is dependent upon endogenous labial and exd, suggesting that the ability of this Hox/Pbx site to interact with labial-related proteins has been evolutionarily conserved [4].
• A bipartite Hox/Pbx binding motif is located within this enhancer, and in vitro DNA binding experiments showed that the vertebrate labial-related protein Hoxb1 will cooperatively bind to this site in a Pbx/Exd-dependent manner [4].
• Isolation, structure, and expression of labial, a homeotic gene of the Antennapedia Complex involved in Drosophila head development [5].

Biological context of lab

• Thus Lab, and most probably other Hox proteins, selects different DNA sequences in regulating downstream target genes [6].
• During embryonic development of the Drosophila brain, the Hox gene labial is required for the regionalized specification of the tritocerebral neuromere [7].
• Misexpression of posterior Hox genes in the embryonic neuroectoderm results in a labial loss-of function phenotype and a corresponding lack of Labial protein expression in the tritocerebrum [7].
• A functional analysis of Antennapedia and Ultrabithorax protein domains shows that the transcriptional repression of labial requires homeodomain-DNA interactions but is not dependent on a functional hexapeptide [7].
• A 32 bp element contained within the 0.5 kb region functions as a labial disc enhancers for pb [8].

Anatomical context of lab

• One consequence of dpp expression is the induction of labial (lab) in the underlying endoderm cells [9].
• We provide evidence for tissue specific interactions between various Hox genes and demonstrate the induction of endodermal labial (lab) by ectopically expressed Ultrabithorax outside the visceral mesoderm (VMS) [10].
• An induction process occurring between the mesodermal and the endodermal germ layers has recently been described in the regulation of the Drosophila homeotic gene labial (lab) [11].
• The spatial restriction within the CNS is correlated with and may be due to a differential timing of expression in the labial and first thoracic ectoderm [12].
• The protein is also observed in the subesophageal ganglia of both larvae and adults, as well as in the labial and first thoracic imaginal discs [12].

Associations of lab with chemical compounds

• These studies have uncovered a set of labial olfactory responses to a small spectrum of human-related odorants, such as isovaleric acid, butylamine, and several ketones and oxocarboxylic acids [13].
• Expression of the labial group Hox gene HrHox-1 and its alteration induced by retinoic acid in development of the ascidian Halocynthia roretzi [14].
• We have used the CapFinder technology, without the library construction step, to amplify and clone full-length cDNAs expressed in the labial palps (CO2-sensing organs) of the moth Cactoblastis cactorum [15].

Physical interactions of lab

• We have identified a single essential Labial (LAB)/EXD-binding site in a Decapentaplegic (DPP)-responsive enhancer of the homeotic gene lab which drives expression in the developing midgut [16].

Regulatory relationships of lab

• We conclude that the Hox genes Sex combs reduced and proboscipedia control an appendage organizer and cell autonomous fate determination during embryonic labial palp development in Tribolium [17].
• The extracellular dpp protein migrates from the visceral mesoderm across the apposing endodermal cell layer in a region of the endoderm that expresses the homeotic gene labial (lab) [18].
• Although Scr is expressed commonly in the presumptive posterior maxillary and labial segment in all three insects, the thoracic expression domains vary [19].
• Under mild heat-shock conditions, the Teashirt protein induces an almost complete transformation of the labial to prothoracic segmental identity, when expressed before 8 hours of development [20].
• Consistent with its role in development, during embryogenesis Arrowhead is expressed in each abdominal segment and in the labial segment [21].

Other interactions of lab

• Drosophila proboscipedia (pb; HoxA2/B2 homolog) mutants develop distal legs in place of their adult labial mouthparts [22].
• Prior developmental genetic analyses have shown that labial (lab) and Deformed (Dfd) are homeotic genes that function in the development of the embryonic (larval) and adult head [23].
• We also describe the phenotypic consequences of HTH antimorph activity in derivatives of the wing, labial and genital discs [24].
• Developmental and evolutionary implications of labial, Deformed and engrailed expression in the Drosophila head [23].
• Examination of the terminal phenotype of null and hypomorphic alleles of Rg-pbx has shown that inactivation of the Rg-pbx gene leads to loss of the thoracic segments and the adjacent labial segment of the Drosophila embryo [25].

Analytical, diagnostic and therapeutic context of lab

• Scanning electron microscopy at the time of segment formation reveals two regions of defects in the segmentation pattern: anteriorly the labial lobe and thoracic segments T1 and T2 are fused; posteriorly, abdominal segments A5-7 are disrupted [26].
• Molecular cloning, by a novel approach, of a cDNA encoding a putative olfactory protein in the labial palps of the moth Cactoblastis cactorum [15].
• The programmed death of the labial gland was examined by electron microscopy and measurement of protein synthesis as well as measurement of DNA synthesis, end-labeling of single strand breaks, and pulsed-field gel electrophoresis [27].
• Identification of candidate downstream genes for the homeodomain transcription factor Labial in Drosophila through oligonucleotide-array transcript imaging [28].

References