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PubMed1983

Inhibition of rat embryonic development by the intrauterine administration of alpha-difluoromethylornithine.

Decarboxylation of L-ornithine by L-ornithine decarboxylase (ODC; E.C.4.1.1.17.) is the initial step in the biosynthesis of putrescine, ODC activity is generally low in most tissues, marked increases are associated with rapid tissue growth and particularly with mammalian embryogenesis. 0.5 mg/kg of DL-alpha-difluoromethylornithine (DFMO) (irreversible inhibitor of ODC) was administered to uterine horns of Long-Evans adult rats during the 4th day of pregnancy. As control material, saline (0.15 M) was administered to contralateral uterine horn. The animals were sacrificed on different days, the uterine horns were removed and the number of implant of implanted embryos were counted. DNA, RNA, protein and dry weight content in implantation sites (5th day of pregnancy) indicated that decidualization following DFMO took place normally but that embryonic growth was arrested in the treated horn. When 100 micrograms of putrescine were added together with DFMO, the embryotoxic effect was absent.

Animals↗

PubMed1980

Inhibition of murine embryonic development by alpha-difluoromethylornithine, an irreversible inhibitor of ornithine decarboxylase.

The activities of ornithine decarboxylase (ODC) and S-adenosyl-L-methionine decarboxylase (SAMDC) and the concentrations of putrescine, spermidine and spermine were measured in mouse uterus placenta and foetus during gestation. The prominent post-implantation biochemical changes in the intact uterus were associated mainly with the deciduomata and significant ODC activity was located in the embryo. Administration of the irreversible inhibitor of ODC, alpha-difluoromethylornithine, DFMO, 2% inthe drinking water during days 5-8 of gestation, abolished the inareases in uterine ODC activity, putrescine and spermidine concentrations and enhanced the activity of SAMDC. Treated animals showed no signs of pregnancy when autopsied on day 18. The alterations in deciduomal weight and the changes in uterine DNA, RNA and protein content indicated that decidualization following DFMO took place normaly but that embryonic growth was arrested. Treatment on single days with DFMO, 200 mg/kg every six h, revealed optimal contragestational effects on day 8 which corresponded exactly to the time of the peak in deciduomal ODC activity. Treatment with DFMO at times other than during the vulnerable period of days 5-8 has less prominent effects on gestation. An increase in ODC activity appears to be an essential factor during a short, but critical, period after implantation for continued murine embryonal growth.

Adenosylmethionine Decarboxylase↗

PubMed1982

Ionic behaviors and nerve growth factor dependence in developing embryonic chick ganglia. I. Studies with intact dorsal root ganglia.

We have recently shown that intact and dissociated 8-day embryonic (E8) chick dorsal root ganglia (DRG) lose the ability to regulate their intracellular Na+, K+ levels when deprived of nerve growth factor (NGF) for 6 h; recovery occurs within minutes of NGF presentation. These ganglionic neurons are believed to depend on NGF for survival and neurite production over a defined period of embryonic life--between about E6 and E15 in the chick. Using intact DRG from E6-E16 chick embryos we determined developmental changes in: (i) 22Na+ accumulation in the presence and absence of NGF, or in the presence of ouabain; and (ii) intra- and extracellular fluid spaces. Sodium accumulation, in the presence of NGF, increases from E6 to E10. It parallels the total fluid space under ouabain but then decreases conspicuously between E10 and E16, despite little change in the latter. NGF thus prevents Na+ accumulation during the early period, and becomes increasingly irrelevant for this behavior in later (after E10) development. These data are interpreted as indicating that: (i) NGF is required for ionic control by DRG neurons up to E10; and (ii) indigenous behaviors for the control of ion pump mechanism(s) are progressively acquired by these cells from E10 to E16, in parallel with the decreasing ionic relevance of NGF. These findings are consistent with the view that the ionic responses to NGF correlate closely with the survival and neurite-promoting effects of this factor.

Age Factors↗

PubMed1999

Sperm integrity is critical for normal mitotic division and early embryonic development.

The human zygote relies on the paternal gamete to provide the centrosome component essential for the first mitotic division. It is not known whether normal centrosome function requires an intact spermatozoon, or whether donation of an isolated paternal centrosome component can result in normal zygotes and embryos. To explore this possibility, mature human oocytes were microinjected with either intact or dissected spermatozoa. Fertilization and cleavage rates were documented; nuclear and cytoskeletal changes were observed with fluorescent immunocytochemistry; and chromosomal normality was assessed with fluorescent in-situ hybridization. A pilot study was performed to identify cytoskeletal features suggestive of centrosome function. Unfertilized oocytes and tripronucleate (3PN) zygotes from in-vitro fertilization or intracytoplasmic sperm injection were assessed to confirm the sequence of the landmarks of human fertilization. Oocytes injected with mechanically-dissected spermatozoa appear to be capable of normal pronuclear formation and embryonic cleavage, but do not undergo normal mitotic division. Although decondensed, apposed nuclei are noted in combination with diffuse cytoskeleton assembly, no spindle was detected in any zygote resulting from the injection of a dissected spermatozoon. Analysis of selected embryos resulting from dissected sperm injection revealed chromosomal mosaicism in the majority of specimens. The lack of a bipolar spindle, in combination with chromosomal mosaicism, suggests abnormalities of the mitotic apparatus when sperm integrity is impaired following dissection.

Cell Nucleus↗

PubMed2004

Induction and improved embryonic development by the nucleus of Pander in associated avian blastoderm parts: influence of delta or gamma ooplasm.

After placing in vitro, central subgerminal ooplasm (containing a central nucleus of Pander) from a quail germ disc of a prelaid egg (before symmetrization) on the upper layer of an isolated chicken antisickle, we observed the induction of a radially oriented preneural plate (without interference of chordamesoblast). This observation suggests the primary existence during the period of symmetrization in utero of an until now unknown temporospatially linked "vertical" effect, emanating from the nucleus of Pander, on the parallel (pre)neural plate anlage forming part of the area centralis in the overlying blastoderm. For comparison, we "sandwiched" in vitro a quail sickle endoblast fragment between the deep side of the upper layer of an isolated chicken antisickle region and a central subgerminal ooplasmic mass. This resulted in a colonization of the subgerminal ooplasmic mass by quail sickle endoblast cells followed by improved neurulation and/or gastrulation phenomena. The latter never occurs in the absence of central subgerminal ooplasm. In both types of experiments there seems to exist a common link between the observed induction phenomena: the presence of delta ooplasm in the involved deep structures. Indeed, the nucleus of Pander contains delta ooplasm as well as the structures derived from it, i.e., endophyll with primordial germ cells and sickle endoblast-derived cells after colonization of the neighboring central ooplasm (present study). Therefore, we think that the preneural plate-inducing effect observed after placing a nucleus of Pander on the antisickle region is due to the presence of a factor in the delta ooplasm that diffuses in the neighborhood. The appearance of gastrulation phenomena in the second type of experiment seems to be due to colonization of the more peripheral part of the central subgerminal ooplasm containing the more superficial and peripheral gamma ooplasm in which Rauber's sickle material can develop. This suggests that the kind of involved ooplasm (delta or gamma) can predetermine the inductive activity of the deep structures that contain it: the central part of the nucleus of Pander and/or endophyll for preneurulation phenomena and sickle endoblast (in the presence of central subgerminal ooplasm) for gastrulation and/or neurulation phenomena.

Animals↗

PubMed2001

Semiquantitative analysis of the expression of GABA-A receptor subunits in the developing embryonic chick brain stem.

The expression levels of seven types of gamma-aminobutyric acid-A (GABA-A) receptor subunits (alpha1, beta2, beta3, beta4, gamma1, gamma2, and gamma4) were quantified in the embryonic chick brain stem at 2 to 20 d of incubation (E2 to E20) and just after hatching. The expression level of mRNA was measured by using semiquantitative reverse transcription-polymerase chain reaction (RT-PCR). When property regions were amplified, two products were observed for each of the beta2, beta4, and gamma2 subunits because of alternative splicing. These were named beta2S and beta2L, beta4S and beta4L, and gamma2S and gamma2L for shorter and longer fragments, respectively. Transcripts of alpha1, beta2L, beta2S, beta3, beta4L, beta4S, gamma1, and gamma2S subunits were first detected from E2 to E5 brain stems. The expression level of each subunit increased gradually with development and reached a plateau at E9 to E12. In contrast, a delay occurred in the appearance of both the gamma4 and gamma2L subunits, which were not detected until E8 to E10. The absence of gamma4 and/or gamma2L subunits may explain differences in the pharmacological characteristics of GABA-A receptors at the early stages of development.

Alternative Splicing↗

PubMed1989

Bimodal and graded expression of the Xenopus homeobox gene Xhox3 during embryonic development.

A Xenopus laevis homeobox gene, Xhox3, has been isolated using the homeobox of the Drosophila pair-rule gene even skipped as a hybridization probe. Xhox3 is first transcribed at the midblastula transition; RNA levels peak at the early neurula stage and decrease thereafter. During the early period of Xhox3 expression, the gastrula and neurula stages, transcripts are found in a graded fashion along the anteroposterior (A-P) axis in the mesoderm and are most concentrated at the posterior pole. In the late period of expression, the tailbud and tadpole stage, transcripts are concentrated at the two ends of the embryo: in the anterior nervous system and posterior tail bud. Analysis of Xhox3 expression in experimentally perturbed embryos shows that different A-P fates in the mesoderm are correlated with different levels of Xhox3 expression. Based on these results and those with other frog homeobox genes, we propose a role for homeobox genes in the patterning of the A-P embryonic axis.

Amino Acid Sequence↗

PubMed1984

Motoneuron death and motor unit size during embryonic development of the rat.

Chronic paralysis of rat embryos during the last 4 to 6 prenatal days causes a diminution in skeletal muscle fiber numbers but inhibits motoneuron death. Consequently, as paralyzed muscles develop, an increased number of motoneurons attempts to form synapses at a reduced number of synaptic sites. Paralyzed muscle fibers receive their synapses at a single endplate, as in control muscles, but these endplates are hyperinnervated, with about twice the normal number of inputs. Counts of axons, synaptic inputs, and muscle units showed that motoneurons normally contact a maximum number of muscle fibers shortly before birth, and this number remains stable for several days postnatal until it finally is reduced to the adult number. The average motor unit size in paralyzed embryos at the time of birth was the same as in controls. We suggest that it is not necessary to postulate the existence of competition between embryonic nerve terminals in order to explain regulation of the number of muscle fibers initially contacted by a motoneuron. Motoneuron death was not immediately affected by paralysis, but paralysis "rescued" all motoneurons whose death normally would have occurred 24 hr or more after the time when paralysis was initiated, regardless of when this was. This implies that the peak period for determination to die is during embryonic day 14, when myotube formation is just beginning and no recognizable endplate structures are present in muscles. When paralyzed, motoneurons normally destined to die are capable of forming a normal number of functional nerve-muscle contacts.

Animals↗

PubMed1994

Calpain localization changes in coordination with actin-related cytoskeletal changes during early embryonic development of Drosophila.

Calpain, a calcium-dependent intracellular protease, was identified in Drosophila melanogaster. Drosophila calpain has an amino acid sequence highly homologous to those of mammalian calpains and exhibits a distinct domain structure consisting of cysteine protease and calcium-binding domains. Specific antibodies raised against a recombinant calpain fragment were used to identify the localization of calpain in developing Drosophila embryos. Calpain was first detected near the anterior pole and in posterior region of the embryo just after fertilization. The anterior calpain disappeared during the cleavage cycles. On the other hand, the posterior calpain moved to the posterior pole when polar buds were formed, and condensed just below the pole cells. At cleavage cycles 8 and 9, when nuclei reached the egg surface, calpain was localized between the nuclei at the surface beneath the precleavage furrows. Co-staining experiments with anti-actin antibody revealed that calpain condenses specifically at the edge of and between actin caps that underlie the plasma membrane immediately above each nucleus. These results indicate that calpain is involved in the dynamic changes in the embryonic cytoskeleton, especially actin-related structures, during early embryogenesis prior to cellularization.

Actins↗

PubMed2001

Evolutionarily conserved nuclear migration genes required for early embryonic development in Caenorhabditis elegans.

The nudF and nudC genes of the fungus Aspergillus nidulans encode proteins that are members of two evolutionarily conserved families. In A. nidulans these proteins mediate nuclear migration along the hyphae. The human ortholog of nudF is Lis1, a gene essential for neuronal migration in the developing cerebral cortex. The mammalian ortholog of nudC encodes a protein that interacts with Lis1. We have identified orthologs of nudC and Lis1 from the nematode Caenorhabditis elegans. Heterologous expression of the C. elegans nudC ortholog, nud-1, complements the A. nidulans nudC3 mutant, demonstrating evolutionary conservation of function. A C. elegans nud-1::GFP fusion produces sustained fluorescence in sensory neurons and embryos, and transient fluorescence in the gonad, gut, vulva, ventral cord, and hypodermal seam cells. Fusion of GFP to C. elegans lis-1 revealed expression in all major neuronal processes of the animal as well as the multinucleate spermathecal valves and adult seam cells. Phenotypic analysis of either nud-1 and lis-1 by RNA interference yielded similar phenotypes, including embryonic lethality, sterility, altered vulval morphology, and uncoordinated movement. Digital time-lapse video microscopy was used to determine that RNAi-treated embryos exhibited nuclear positioning defects in early embryonic cell division similar to those reported for dynein/dynactin depletion. These results demonstrate that the LIS-1/NUDC-like proteins of C. elegans represent a link between nuclear positioning, cell division, and neuronal function.

Animals↗

PubMed2005

Transcriptional control of Shh/Ptc1 signaling in embryonic development.

In vivo profiling of signal-directed gene expression patterns is a major bottleneck in studying developmental biology. A signal molecule initiates its specific gene expression pattern through the activation of certain transcription factor (TF); however, tissue heterogeneity often masks this pattern due to intercellular complexity of other signal transduction pathways. To decipher the synergistic regulation of signal-directed gene expression in the tissue level, we report here a unique transcriptional responsive element (TRE) existing in the 5'-upstream promoter regions (5'-UPR) of the genes responding to the Shh/Ptc1 signal transduction pathway during feather placode development in chicken embryos. By locating the TRE homologue and its interactive TF, we were able to reveal the gene expression pattern of the Shh/Ptc1 signaling. We firstly demonstrated that homology profiling of the 5'-UPR of the genes, Gli1, TGF-beta2 and Msx2, responding to the Shh/Ptc1 signaling showed a more than 70% conserved region. Computer alignment of the consensus sequences in the conserved region revealed a 37-nucleotide TRE sequence, containing two regulatory elements homologous to human and mouse Gli-binding sites. Activation of this newly identified Shh/Ptc1-responsive TRE by active Smo signaling in chicken hepatoepithelial carcinoma cells elicited a strong synergistic expression of the Shh/Ptc1-downstream genes. Based on previous bioinformatics and the present experimental findings, we successfully established an in vivo signaling model for the Shh/Ptc1-directed embryonic feather morphogenesis.

Amino Acid Sequence↗

PubMed2005

Embryonic development of Galloisiana yuasai Asahina, with special reference to external morphology (insecta: Grylloblattodea).

The embryogenesis of Grylloblattodea, one of the most primitive of the polyneopteran orders, is described using Galloisiana yuasai with special reference to external morphology. The egg membranes are characterized by an endochorion crossed by numerous vertical aeropyles and a fairly thin vitelline membrane, features shared by Mantophasmatodea. The inner layer formation is of the fault type. Serosal elements in the amnioserosal fold differentiate into hydropylar cells, to function in water absorption together with specialized amniotic structures, i.e., an amniotic strand and a thickened amnion. The germ band is of the short germ type. The germ band immerses deep into the yolk after its full elongation along the egg surface, and in this respect blastokinesis closely resembles that of Mantophasmatodea. The embryological features, i.e., those on egg membranes and blastokinesis, may suggest a closer affinity of Grylloblattodea and Mantophasmatodea. Appendages, ectodermal invaginations, and sternal and pleural sclerites are discussed in the light of serial homology, to provide a new basis for elucidating the insect body plan. Appendages are divided into the proximal coxopodite and distal telopodite, the former being divided further into the subcoxa and coxa. Subcoxal and coxal elements are identified in the mandible as well as in the abdominal appendages. The subcoxa is divided into the epimeron and episternum by the pleural suture in thoracic segments. Likewise, in the abdominal segments the subcoxa is divided into two, although the homologs of the epimeron and episternum are not sclerotized, and in the labial segment the subcoxal derivative or the postmentum is divided into the submentum and mentum. Two coxal endites bulge out from the medial side of the gnathal appendages. The mandibular molar and incisor, maxillary lacinia and galea, and labial glossa and paraglossa are serially homologous with each other. In the thoracic segments the original embryonic sternum or "protosternum" is largely replaced by subcoxal elements, and merely remains as a small anterior presternum and a posterior spinasternum. A major part of the venter is represented by the derivatives of the episternum such as an extensive basisternum, katepisternum, and trochantin and the medial element of the epimeron. The pleuron is derived from the episternal elements or the anepisternum and preepisternum, which bears a spiracle in the mesothorax and metathorax, and the lateral element of the epimeron. The homolog of the preepisternum in the prothorax is the cervical sclerite, but with no spiracle developed. A median ventral invagination arises in the thoracic segments as a spina, and the homolog of the spina develops into the eversible sac in the first abdominal segment.

Animals↗

PubMed2006

Structural and ultrastructural analysis of embryonic development of Prochilodus lineatus (Valenciennes, 1836) (Characiforme; Prochilodontidae).

This survey was performed to characterize the embryogenesis of Prochilodus lineatus. Seven stages of embryo development were identified--zygote, cleavage, blastula, gastrula, segmentation, larval and hatching--after a period of incubation of 22 h (24 degrees C) or 14 h (28 degrees C). The following cleavage pattern was identified: the first plane was vertical (2 blastomeres); the second was vertical and perpendicular to the first (4 blastomeres); the third was vertical and parallel to the first (4 x 2); the fourth cleavage was vertical and parallel to the second (4 x 4); the fifth was vertical and parallel to the first (4 x 8); and the sixth cleavage was horizontal (64 blastomeres). At the blastula stage (3.0-4.0 h (24 degrees C); 1.66-2.0 h (28 degrees C)) irregular spaces were detected and periblast structuring was initiated. At the gastrula stage (4.0-8.0 h (24 degrees C); 3.0-6.0 h (28 degrees C)) the epiboly, convergence and cell movements, as well as the formation of embryonic layers, had begun. The segmentation stage (10.0-15.0 h (24 degrees C); 7.0-10.0 h (28 degrees C)) was characterized by a rudimentary formation of organs and systems (somites, optic vesicle and intestinal delimitation). The embryo at the larval stage (16.0-21.0 h (24 degrees C); 11.0-13.0 h (28 degrees C)) showed a free tail, more than 25 somites, an optic vesicle and a ready-to-hatch larval shape. The blastomeres at cleavage stage had disorganized nuclei indicating high mitotic activity. At gastrula, the blastomeres and the periblast had euchromatic nuclei and a large number of mitochondria and vesicles. The yolk was organized into globose sacs, which were dispersed into small pieces prior to absorption.

Animals↗

PubMed2004

Molecular cloning and developmental expression patterns of thyroid hormone receptors and T3 target genes in the turbot (Scophtalmus maximus) during post-embryonic development.

Thyroid hormones (TH) are pleiotropic factors important for many developmental and physiological functions in vertebrates and particularly in amphibian metamorphosis. Their effects are mediated by two specific receptors (TRalpha and TRbeta), which are ligand-dependent transcription factors, members of the nuclear hormone receptor superfamily. Besides their pivotal role in amphibian metamorphosis, TH are also critical for fish metamorphosis. As this later role of TH is less studied, we analyzed their action in the turbot (Scophtalmus maximus), a metamorphosing flat fish. We describe the isolation of sequences for the turbot orthologs of a number of Xenopus genes, which are induced during amphibian metamorphosis. Developmental expression of these genes during turbot metamorphosis was studied by several methods and the expression patterns of these genes compared with those in Xenopus and flounder. We find that the period between the onset and the end of eye migration (day 22 to day 30 post-hatching) most likely corresponds to the metamorphic climax with either high TRalpha or high TH levels. Our results show that in contrast to amphibians, it is TRalpha and not TRbeta mRNA that is up-regulated during metamorphosis. Our results highlight the notion that TH regulates, through a rise of TR expression, a genetic cascade during turbot metamorphosis. The fact that TH regulates metamorphosis in amphibian and teleost fishes suggests that TH-regulated metamorphosis is a post-embryonic process conserved in most vertebrates.

Animals↗

PubMed1992

c-ros: the vertebrate homolog of the sevenless tyrosine kinase receptor is tightly regulated during organogenesis in mouse embryonic development.

The c-ros proto-oncogene is the vertebrate homologue of the Drosophila sevenless tyrosine kinase receptor. Examination of c-ros mRNA transcripts in the mouse embryo reveals a stringent pattern of expression. Only kidney, intestine and lung exhibit ros-specific RNA using sensitive techniques such as RNAase protection and in situ hybridization. The temporal and spatial arrangement of c-ros transcripts is coincident with the phenotypic induction and proliferation of epithelium during organogenesis of the kidney and intestine. The data provide evidence for a role of c-ros in the obligate cell-cell interactions that characterize the morphogenic induction and proliferation of epithelial cells in the kidney, intestine and lung. The c-ros tyrosine kinase receptor may provide a signal transduction pathway for epithelial-mesenchymal interactions.

Animals↗

PubMed1996

Expression of the beta 4 integrin subunit in the mouse heart during embryonic development: retinoic acid advances beta 4 expression.

Using immunohistochemical techniques as well as in situ hybridization we were able to elicit the expression pattern of the beta 4 integrin subunit in the murine heart during development. We show that beta 4 is not expressed in the heart before E13 and is afterwards restricted to the endocardium of the atrioventricular canal, the outflow tract, and the venous valves in the right atrium. As these are all sites of high shear stress in the heart, we propose a role for alpha 6 beta 4 in the tight adhesion of the endocardial cells to their basement membranes in these segments. Moreover, mouse embryos were treated with all-trans retinoic acid, which was previously shown to induce congenital malformations, among which malformations of the heart. We show an advanced expression without ectopic localization of cardiac beta 4 after the administration of retinoic acid. This advanced appearance of beta 4 was also shown in extracardiac tissue like migrating neural crest cells. Several hypotheses on the mechanism of beta 4 up-regulation and a possible role for alpha 6 beta 4 in the development of heart malformations after the administration of retinoic acid are discussed.

Animals↗

PubMedDate not supplied

Supernumerary lumbar rib: manifestation of basic alteration in embryonic development of ribs.

Supernumerary ribs (SNR) are a common variant in some strains of mice used in standard teratology bioassays. We have previously demonstrated that increased incidence of SNR may be induced by a wide variety of xenobiotics and/or general maternal stress. The significance of this defect in cross-species extrapolations has been problematic and recent studies, including this one, have shown that this anomaly is more complex than previously thought. The SNR in mice have a bimodal distribution composed of 'rudimentary ribs' (RR) with a mode of 0.3-0.4 mm and 'extra ribs' (ER) with a mode of 0.9-1.1 mm. The studies reported here examine the relationship between the presence of SNR and the 13th rib length and the gross morphological development of the anomaly. Supernumerary ribs were induced in CD-1 mice by surgical stress (subcutaneous micropump implanted on gestational day (GD), restraint stress (GD8), food and water deprivation (GD8) or maternal administration of the pesticide dinoseb (50 mg kg-1 on GD7 and GD8). Fetuses from untreated litters were also examined. Dinoseb-treated mice were killed on GD14, 15, 16 or 17. All other groups were killed on GD17. The lengths of the 13th and 14th ribs were measured and other anomalies were recorded. Femur length was used as an indicator of fetal size. The SNR frequency was higher in all treatment groups compared to controls. We found that ER and RR were morphologically distinct. The ER were flat ended and distally joined by a cartilaginous portion, while RR were usually rounded distally and were without cartilaginous extensions. The 13th ribs were significantly longer in fetuses having SNR than in those not having SNR, whether treated or untreated. This relationship was present in all fetal ages examined and with both ER and RR groups. These results suggest that SNR are indicative of basic alterations in the development of the axial skeleton.

2,4-Dinitrophenol↗

PubMed1998

Genomic organization of DHR38 gene in Drosophila: presence of Alu-like repeat in a translated exon and expression during embryonic development.

The recombinant lambda clone 4-2 containing the genomic region of the Drosophila hormone receptor 38 (DHR 38) gene, homologous to mammalian neuronal growth factor I-B (NGFI-B), was isolated by radioactive labelled oligonucleotide hybridization. The nucleotide sequence of the genomic clone revealed three exons that encode the functional domains of the protein. The N-terminal exon1 had no homology at the amino acid level with NGFI-B, the mammalian homologue. A glutamine-rich region, probably involved in transcriptional activation, was observed at the C-terminal part of this exon. A similar motif is also present upstream in another reading frame of the same strand. Both motifs are preceded by a repetitive non-anucleotide sequence containing an AluI site, resembling a duplicated human Alu-sequence. A monomeric version of this sequence, coding similarly for an oligoglutamine peptide, occurs at a surprisingly high frequency in other regulatory genes in Drosophila. In contrast to mammalian Alu sequences, this sequence is found almost exclusively in the coding regions of Drosophila genes, but not in the non-coding parts of the genes. The DNA-binding domain with two zinc-fingers, and at least part of the ligand-binding peptide, is coded by the largest middle exon2 in DHR38 and exhibits up to 100% homology in short peptide motifs to its mammalian counterpart, where these domains are split into exons 3, 4, 5, and 6. However, the length, information content, stop codon, and splice site are conserved in the last exons in both fly and rat. In situ hybridization to 0-24 h wholemount embryos showed strong expression of DHR38 in neurogenic regions and in the intestinal tract during embryogenesis, suggesting a spatial and temporal control of transcription, partially analogous to the central nervous system-specific expression of NGFI-B in mammals.

Amino Acid Sequence↗