A cluster of Drosophila homeobox genes involved in mesoderm differentiation programs

Although genes involved in common developmental programs are usually scattered throughout the metazoan genome, there are some important examples of functionally interconnected regulatory genes that display close physical linkage. In particular the homeotic genes, which determine the identities of body parts, are clustered in the Hox complexes and clustering is thought to be crucial for the proper execution of their developmental programs. Here we describe the organization and functional properties of a more recently identified cluster of six homeobox genes at 93DE on the third chromosome of Drosophila. These genes, which include tinman, bagpipe, ladybird early, ladybird late, C15, and slouch, all participate in mesodermal patterning and differentiation programs and show multiple regulatory interactions among each other. We propose that their clustering, through unknown mechanisms, is functionally significant and discuss the similarities and differences between the 93DE homeobox gene cluster and the Hox complexes.

Evolutionary origins of vertebrate appendicular muscle

The evolution of terrestrial tetrapod species heralded a transition in locomotor strategies. While most fish species use the undulating contractions of the axial musculature to generate propulsive force, tetrapods also rely on the appendicular muscles of the limbs to generate movement. Despite the fossil record generating an understanding of the way in which the appendicular skeleton has evolved to provide the scaffold for tetrapod limb musculature, there is, by contrast, almost no information as to how this musculature arose. Here we examine fin muscle formation within two extant classes of fish. We find that in the teleost, zebrafish, fin muscles arise from migratory mesenchymal precursor cells that possess molecular and morphogenetic identity with the limb muscle precursors of tetrapod species. Chondrichthyan dogfish embryos, however, use the primitive mechanism of direct epithelial somitic extensions to derive the muscles of the fin. We conclude that the genetic mechanism controlling formation of tetrapod limb muscles evolved before the Sarcopterygian radiation.

Two novel Drosophila TAF(II)s have homology with human TAF(II)30 and are differentially regulated during development

TFIID is a multiprotein complex composed of the TATA binding protein (TBP) and TBP-associated factors (TAF(II)s). The binding of TFIID to the promoter is the first step of RNA polymerase II preinitiation complex assembly on protein-coding genes. Yeast (y) and human (h) TFIID complexes contain 10 to 13 TAF(II)s. Biochemical studies suggested that the Drosophila (d) TFIID complexes contain only eight TAF(II)s, leaving a number of yeast and human TAF(II)s (e.g., hTAF(II)55, hTAF(II)30, and hTAF(II)18) without known Drosophila homologues. We demonstrate that Drosophila has not one but two hTAF(II)30 homologues, dTAF(II)16 and dTAF(II)24, which are encoded by two adjacent genes. These two genes are localized in a head-to-head orientation, and their 5' extremities overlap. We show that these novel dTAF(II)s are expressed and that they are both associated with TBP and other bona fide dTAF(II)s in dTFIID complexes. dTAF(II)24, but not dTAF(II)16, was also found to be associated with the histone acetyltransferase (HAT) dGCN5. Thus, dTAF(II)16 and dTAF(II)24 are functional homologues of hTAF(II)30, and this is the first demonstration that a TAF(II)-GCN5-HAT complex exists in Drosophila. The two dTAF(II)s are differentially expressed during embryogenesis and can be detected in both nuclei and cytoplasm of the cells. These results together indicate that dTAF(II)16 and dTAF(II)24 may have similar but not identical functions.

Lbx1 is required for muscle precursor migration along a lateral pathway into the limb

In mammalian embryos, myogenic precursor cells emigrate from the ventral lip of the dermomyotome and colonize the limbs, tongue and diaphragm where they differentiate and form skeletal muscle. Previous studies have shown that Pax3, together with the c-Met receptor tyrosine kinase and its ligand Scatter Factor (SF) are necessary for the migration of hypaxial muscle precursors in mice. Lbx1 and Pax3 are co-expressed in all migrating hypaxial muscle precursors, raising the possibility that Lbx1 regulates their migration. To examine the function of Lbx1 in muscle development, we inactivated the Lbx1 gene by homologous recombination. Mice lacking Lbx1 exhibit an extensive loss of limb muscles, although some forelimb and hindlimb muscles are still present. The pattern of muscle loss suggests that Lbx1 is not required for the specification of particular limb muscles, and the muscle defects that occur in Lbx1(−/−) mice can be solely attributed to changes in muscle precursor migration. c-Met is expressed in Lbx1 mutant mice and limb muscle precursors delaminate from the ventral dermomyotome but fail to migrate laterally into the limb. Muscle precursors still migrate ventrally and give rise to tongue, diaphragm and some limb muscles, demonstrating Lbx1 is necessary for the lateral, but not ventral, migration of hypaxial muscle precursors. These results suggest that Lbx1 regulates responsiveness to a lateral migration signal which emanates from the developing limb.

The role of Lbx1 in migration of muscle precursor cells

The homeobox gene Lbx1 is expressed in migrating hypaxial muscle precursor cells during development. These precursors delaminate from the lateral edge of the dermomyotome and form distinct streams that migrate over large distances, using characteristic paths. The targets of migration are limbs, septum transversum and the floor of the first branchial arch where the cells form skeletal muscle of limbs and shoulders, diaphragm and hypoglossal cord, respectively. We used gene targeting to analyse the function of Lbx1 in the mouse. Myogenic precursor cells delaminate from the dermomyotome in Lbx1 mutants, but migrate in an aberrant manner. Most critically affected are migrating cells that move to the limbs. Precursor cells that reach the dorsal limb field are absent. In the ventral limb, precursors are present but distributed in an abnormal manner. As a consequence, at birth some muscles in the forelimbs are completely lacking (extensor muscles) or reduced in size (flexor muscles). Hindlimb muscles are affected strongly, and distal limb muscles are more affected than proximal ones. Other migrating precursor cells heading towards the floor of the first branchial arch move along the appropriate path in Lbx1 mutants. However, these cells migrate less efficiently and reduced numbers of precursors reach their distal target. At birth, the internal lingual muscle is therefore reduced in size. We suggest that Lbx1 controls the expression of genes that are essential for the recognition or interpretation of cues that guide migrating muscle precursors and maintain their migratory potential.

Plasticity within the lateral somatic mesoderm of Drosophila embryos

Each of 30 Drosophila larval somatic muscles has its individual shape, insertion sites and innervation. From the very beginning, the formation of individual muscles is controlled by a set of muscle identity genes. The four lateral transverse muscles (LT1-LT4) are thought to be specified by the combinatorial activity of Krüppel (Kr), apterous (ap) and muscle specific homeobox (msh) genes whilst the activity of the ladybird (lb) genes is required for proper formation of the neighbouring segmental border muscle (SBM). We have recently shown that ectopic expression of lb changes the identity of Kr-expressing lateral muscle precursors and recruits them to form enlarged or duplicated SBMs. Here we report that loss of msh function leads to a similar transformation resulting in the overproduction of SBMs. Inversely, in msh gain of function embryos, the prospective SBM myoblasts change their identity resulting in the formation of enlarged lateral transverse muscles. These data indicate a key role for the msh and lb genes in the specification and diversification of myoblast lineages from the lateral domain, and reveal a plasticity of cell fate within the somatic mesoderm of Drosophila.

ladybird determines cell fate decisions during diversification of Drosophila somatic muscles

In the mesoderm of Drosophila embryos, a defined number of cells segregate as progenitors of individual body wall muscles. Progenitors and their progeny founder cells display lineage-specific expression of transcription factors but the mechanisms that regulate their unique identities are poorly understood. Here we show that the homeobox genes ladybird early and ladybird late are expressed in only one muscle progenitor and its progeny: the segmental border muscle founder cell and two precursors of adult muscles. The segregation of the ladybird-positive progenitor requires coordinate action of neurogenic genes and an interplay of inductive Hedgehog and Wingless signals from the overlying ectoderm. Unlike so far described progenitors but similar to the neuroblasts, the ladybird-positive progenitor undergoes morphologically asymmetric division. We demonstrate that the ectopic ladybird expression is sufficient to change the identity of a subset of progenitor/founder cells and to generate an altered pattern of muscle precursors. When ectopically expressed, ladybird transforms the identity of neighbouring, Kruppel-positive progenitors leading to the formation of giant segmental border muscles and supernumerary precursors of lateral adult muscles. In embryos lacking ladybird gene function, specification of two ladybird-expressing myoblast lineages is affected. The segmental border muscles do not form or have abnormal shapes and insertion sites while the number of lateral precursors of adult muscles is dramatically reduced. Altogether our results provide new insights into the genetic control of diversification of muscle precursors and indicate a further similarity between the myogenic and neurogenic pathways.

ladybird, a new component of the cardiogenic pathway in Drosophila required for diversification of heart precursors

The embryonic heart precursors of Drosophila are arranged in a repeated pattern of segmental units. There is growing evidence that the development of individual elements of this pattern depends on both mesoderm intrinsic patterning information and inductive signals from the ectoderm. In this study, we demonstrate that two homeobox genes, ladybird early and ladybird late, are involved in the cardiogenic pathway in Drosophila. Their expression is specific to a subset of cardioblast and pericardial cell precursors and is critically dependent on mesodermal tinman function, epidermal Wingless signaling and the coordinate action of neurogenic genes. Negative regulation by hedgehog is required to restrict ladybird expression to two out of six cardioblasts in each hemisegment. Overexpression of ladybird causes a hyperplasia of heart precursors and alters the identity of even-skipped-positive pericardial cells. Loss of ladybird function leads to the opposite transformation, suggesting that ladybird participates in the determination of heart lineages and is required to specify the identities of subpopulations of heart cells. We find that both early Wingless signaling and ladybird-dependent late Wingless signaling are required for proper heart formation. Thus, we propose that ladybird plays a dual role in cardiogenesis: (i) during the early phase, it is involved in specification of a segmental subset of heart precursors as a component of the cardiogenic tinman-cascade and (ii) during the late phase, it is needed for maintaining wingless activity and thereby sustaining the heart pattern process. These events result in a diversification of heart cell identities within each segment.

ladybird, a tandem of homeobox genes that maintain late wingless expression in terminal and dorsal epidermis of the Drosophila embryo

ladybird early and ladybird late genes, tandemly located in the Drosophila 93E homeobox gene cluster, encode highly related homeodomain-containing transcription factors. Here we report the cloning of the complete cDNA sequences of both genes and a study of their expression and regulatory interactions with the segment polarity gene wingless in the epidermis. ladybird genes are co-expressed with wingless in epidermal cells close to the posterior parasegmental boundaries and in terminal regions of the body. In mutant embryos with altered wingless function, transcription of ladybird early and ladybird late is changed; it disappears completely from the epidermis in wingless-embryos, indicating wingless-dependence. After 6 hours of development, wingless expression is maintained by gooseberry in the ventral epidermis. However, in the dorsal epidermis and the terminal regions of the body, expression of wingless is independent of gooseberry but requires a wingless-ladybird regulatory feedback loop. Loss of ladybird function reduces the number of wingless-expressing cells in dorsal epidermis and leads to complete inactivation of wingless in the anal plate. Consequently, mutant ladybird embryos fail to develop anal plates and ubiquitous embryonic expression of either one or both ladybird genes leads to severe defects of the dorsal cuticle. Lack of late wingless expression and anal plate formation can be rescued with the use of a heat-shock-ladybird transgene.

Mouse Lbx1 and human LBX1 define a novel mammalian homeobox gene family related to the Drosophila lady bird genes

We have cloned two novel homeobox genes which are the mouse (Lbx1) and human (LBX1) homologs of the Drosophila lady bird genes. They are highly related not only within the coding region but also in 5' and 3' untranslated regions. Several amino acid residues inside and around the homeodomain, have been conserved between the mammalian Lbx genes and their Drosophila counterparts. The mouse Lbx1 gene is located on chromosome 19 (region D) and the human LBX1 gene maps to the related q24 region of chromosome 10, known as a breakpoint region in translocations t(7;10) and t(10;14) involved in T-cell leukemias. Thus, LBX1 and the protooncogene HOX11 map to a common chromosomal region, as do their Drosophila counterparts, the lady bird and 93Bal genes. The mouse Lbx1 gene is specifically expressed during embryogenesis. From 10.5 days of gestation, Lbx1 expression is detected in the central nervous system and some developing muscles. In the CNS, Lbx1 transcripts are expressed in the dorsal part of the mantle layer of the spinal cord and hindbrain, up to a sharp boundary within the developing metencephalon. Thus, Lbx1 may be inolved in spinal cord and hindbrain differentiation and/or patterning, and its restricted expression pattern could depend upon evolutionarily conserved inductive signals involving some mammalian Wnt and Pax genes, as is the case for Drosophila lady bird genes and wingless or gooseberry.

A distinct class of homeodomain proteins is encoded by two sequentially expressed Drosophila genes from the 93D/E cluster

Homeodomains appear to be one of the most frequently employed DNA-binding domains in a superfamily of transacting factors. It is likely that during evolution several sub-types of homeodomain have evolved from a common ancestral domain, resulting in distinct but closely related DNA-binding preferences. Here we describe the conservation of a distinct type of homeodomain encoded by the Drosophila lady-bird-late (lbl) gene, previously named nkch4 (1). Using degenerate PCR primers corresponding to the most divergent regions of the first and third helix of the Lbl homeodomain we have amplified, from genomic DNA of the fly, a lady-bird-like homeobox fragment. The Drosophila PCR products contained both the lbl (1) and a highly related homeobox sequence, which we named lady-bird-early (lbe). This new Drosophila gene resides directly upstream to lbl and together with tinman/NK4 (2, 3, 4, 5), bagpipe/NK3 (2, 4) S59/NK1 (4, 6) and 93Bal (7) compose the 93D/E homeobox gene cluster. Ibe and lbl are transcribed from the same strand and in a temporal order corresponding to their 5'-3' chromosomal location. Transcripts of both genes are found in the epiderm of Drosophila embryos, in cells known to express a segment polarity gene wingless (8), and their spatial and temporal colinearity of expression strongly suggests that they cooperate during segmentation. The amino-acid composition of both Lady-bird homeodomains differ from that of Antp-type at several positions involved in DNA recognition. These substitutions appear to modify DNA-binding preferences since Lbl homeodomain is unable to recognize the most common homeodomain binding TAAT motif in gel retardation experiments.

[Cavernous hemangioma of the uterine cervix in pregnancy]

Cavernous haemangiomas of the uterine cervix are very rare and usually harmless. Nevertheless, the case reported of a 31-year old multiparous woman in the 34+1 gestational week, who presented herself with a fast growing cervical haemangioma, indicates, that this benign tumour may cause obstetrical complications.

GEBF-I activates the Drosophila Sgs3 gene enhancer by altering a positioned nucleosomal core particle

The enhancer region of the Drosophila melanogaster ecdysone-regulated glue gene, Sgs3, shows dramatic modifications of chromatin structure in strict correlation with changes in gene expression during development. We show that there is a positioned nucleosomal core particle over the enhancer which is displaced or disrupted during gene activation. This transition is prevented in Drosophila larvae mutated in the ecdysone-dependent 2B5 locus, in which Sgs3 is inactive and GEBF-I, a Glue Enhancer Binding Factor, is missing. We have defined the GEBF-I binding sites in vitro and shown that mutation of these sequences abolishes the enhancer activity in vivo. This combined in vitro and in vivo approach reveals new aspects of the dynamic organization of a regulatory element during development and highlights the potential of this model for studies of the relation between chromatin structure and gene activity.

[Vaginal sonography in follow-up of early pregnancies--applications in general practice of established gynecologists]

In 541 early pregnant women transvaginal sonography (TVS) was performed between 5th and 9th week of gestation. The correct gestational age was verified and information on normal development of the embryo was collected with this routine sonographic control. In one-third of 541 patients disturbances of the pregnancy were found directly or a TVS control was recommended. In 116 cases the gestational age, determined by calculating the period since the last menstruation, had to be corrected by sonographic results. In 12 women ectopic pregnancies without any symptoms were found. Only 47 women of 251 evaluated patients had no risk in pregnancy.

A novel homeobox nkch4 gene from the Drosophila 93E region

We have cloned a Drosophilia melanogaster homeobox gene that maps to bands 93D9-E2 on the right arm of the third chromosome, in the proximal region of the NK-homeobox gene cluster. Like NK-1 and nine other known homeobox genes, nkch4 (NK-cluster homeobox 4) contains an intron between the homeodomain codons for Glu44 and Val45. The nkch4 homeodomain sequence is most related to that of the human HOX11 (tcl3) T-cell oncogene (57% homology), but differs from all other homeobox genes at several conserved residues in the third helix of the homeodomain, known to be important for DNA recognition. Low levels of nkch4 transcripts were detected during late stages of embryogenesis as well as in third instar larvae and pupae. In late embryos nkch4 is expressed in the developing CNS.

GEBF-I in Drosophila species and hybrids: the co-evolution of an enhancer and its cognate factor

The activation of the Drosophila melanogaster salivary gland secretion protein gene Sgs-3 is marked by important changes in chromatin structure in the distal regulatory region at -600 bp from the Sgs-3 start site. A stage- and tissue-specific glue enhancer binding factor, GEBF-I, binds in vitro to sequences from this region. Previous studies have revealed considerable variation in the DNA sequences of comparable regions in the related Drosophila species, D. simulans, D. erecta and D. yakuba. We detected GEBF-I-like proteins in these species, which appear to evolve as rapidly as the corresponding DNA sequences, and studied in detail the binding characteristics of the GEBF-I proteins of the two most closely related species, D. melanogaster and D. simulans. In crosses between these species, certain strains produce hybrid larvae which, unexpectedly, synthesised a single intermediate form of the protein. This suggests that the factor is subject to species-specific post-transcriptional modifications. In these hybrid larvae, which carry one D. melanogaster and one D. simulans Sgs-3 gene, the hybrid GEBF-I protein appears equally effective in the induction of both target genes.

[Trial application of transfection tests in feasibility studies for transforming DNA in white blood cells of patients with chronic lymphatic leukemia]

Transfection technique with the use of high molecular DNA was applied for the investigations of peripheral blood white cells DNA transforming properties in patients with chronic lymphatic leukemia B. Using transfection tests in liquid medium (focus assay) and colony forming in soft agar, the differences in L(tk-) cells transformation were noted following an addition of neoplastic DNA. Medium collected over transformants has shown mitogen properties in micro-mitogen tests on cells BALB/c 3T3. No correlation between clinical stage of the disease and the results of tests was observed.

[Control of postoperative vaginal sonographic findings following Shirodkar cerclage]

Up to now postoperative control of the uterine cervix following cerclage was performed by bimanual palpation. Since clinical use of transvaginal sonography it is possible to get objective results about preoperative morphology of the cervix (exact cervical length, dilatation of the cervical canal and opening of internal and external os). Besides postoperative vaginal sonography following cerclage can ascertain lengthening and stabilization of the incompetent cervix and localize the ligature's position. 75 pregnant women between 15th and 30th week of gestation were examined using a 5-MHz vaginal sector scanner probe following Shirodkar cerclage to gain information about the residual cervical length and the distance from the surface of the ectocervix to the ligature's position within the anterior and posterior lip of the cervix. The mean postoperative cervical length was 3.75 cm (1.5 cm-6.5 cm). Compared to the preoperative average length of 3.0 cm (0.5 cm-5.0 cm) the cerclage resulted in an increase of about 25%. The average distance from the surface of the ectocervix to the ligature at anterior lip of the cervix was 1.85 cm, ranging from 0.9 cm to 2.6 cm. The mean value at the posterior lip was 1.56 cm, ranging from 0.8 cm to 2.0 cm. This study showed that the actual positions of ligatures after cerclage operations varied very much. Unsatisfying position can be an explanation why some preterm deliveries can not be prevented. Therefore it is recommended to control the position of the cerclage ligation postoperatively using transvaginal sonography.

[Vaginal sonography versus vaginal palpation: initial experiences in 120 pregnant patients with suspected cervix insufficiency]

In a clinical study a group of pregnant women with suspected cervical incompetence was examined by vaginal sonography. Aim of the investigation was to compare results of performed vaginal palpation with results of sonography. 120 pregnant women with cervical insufficiency between 16th and 33rd week of gestation were examined by a 5-MHz vaginal sectorscanner probe. After focussing sagittal projection of uterine cervix and lower uterine segment the cervical length and opening of the internal os were assessed prior to cerclage. Postoperative vaginal sonography was performed to ascertain lengthening and stabilization of the incompetent cervix. Another group of 50 pregnant women with unsuspicious obstetrical findings were also examined to gain information about normal sonographical morphology and length of the competent uterine cervix. Comparing results of vaginal palpation and vaginal sonography showed, that the cervical length obtained by sonography was constantly higher in all patients than the results obtained by palpation. This difference became more distinct in the group of patients with extreme cervical incompetence. We are of the opinion that vaginal sonography is an objective method revealing the extent of cervical incompetence. Exact measurement of the cervical length and assessment of the internal os are efficient diagnostic criteria. They complete results of cervical palpation and offer precise information concerning an intended cerclage. In case of suspected cervical incompetence continuous sonographical examination can supervise the development of the uterine cervix during pregnancy. In future the number of prophylactic cerclage-operations perhaps decreases by using the technique of transvaginal sonography.

[Effect of therapy on the lymphoid cell distribution in the venous blood of breast cancer patients]

Rosetting properties (E, EAh, EAox, EAC rosettes) and presence of surface immunoglobulins (SIg) were examined on peripheral blood lymphocytes from 30 breast cancer patients immediately prior to therapy and 4 weeks thereafter. Therapy consisted of limited radical surgery followed by combined X-ray and telecobalt radiotherapy. The results were compared to patients who had received the same treatment 1 year ago (n = 13), 2 years ago (n = 13) and 3 to 10 years ago (n = 20). All irradiated patients exhibited a considerable leuko- and lymphopenia with a particular decrease of E and EAh rosettes, and a concommittant relative increase of EAox and EAC rosettes. SIg positive cells showed no significantly different percentages before and after therapy although in absolute counts they were similarly reduced as the other subpopulations after radiotherapy. The possible prognostic influence of radiation induced lymphopenia is discussed without coming to clear conclusions.

Immunological characterization of mononuclear cells and morphological findings in patients with mammary carcinoma

Mononuclear cells from peripheral blood and draining lymph nodes of 40 patients with invasive mammary carcinoma were examined for various immunological cell surface markers including surface membrane immunoglobulins and rosetting properties (E, EA, EAC). No significant relationship could be established to anyone of the following criteria for which the literature reports varying prognostic values: Clinical staging of the disease , histological tumor type, grading, nuclear differentiation, round cell infiltration, perivenous infiltration, sinus histiocytosis, and lymph node reaction patterns (lymphocyte predominance, germinal center predominance, lymphocyte depletion, unstimulated nodes). From the reported results it is concluded that the analysis of lymphocyte cell surface markers in mammary carcinoma is not a suitable parameter for supporting the existence of specific or unspecific anti-tumor immune reactions which may be suspected from certain histological reaction patterns.

Immunological characterization of mononuclear cells in peripheral blood and regional lymph nodes of breast cancer patients

Mononuclear cells from peripheral blood and draining lymph nodes of 40 patients with invasive locoregional breast cancer were examined for immunological cell surface markers (E, EAhuman, EAox, EAC, SIg pos.). Concomitantly, blood lymphocytes from 36 healthy women and axillary and mesenteric lymph-nodes from patients without malignant diseases were tested as controls. In peripheral blood of tumor patients E rosette-forming cells were slightly diminished as compared to the control group, whereas EAox and EAC rosette-forming cells were increased. These differences may be age-dependent rather than tumor-related. In the draining lymph nodes of breast cancer patients as well as in the control lymph nodes, the percentages of EAC rosette-forming cells and SIg positive lymphocytes were significantly increased compared to peripheral blood, whereas E and EAhuman rosette values remained unchanged. Percentages of EAox rosettes on the other hand were strongly diminished in the draining lymph nodes, suggesting that the EAhuman and EAox rosetting techniques detect 2 types of Fc-receptor bearing cells. No significant differences were found between the cell surface marker analysis of tumor-free and metastatic lymph nodes of breast cancer patients and the control lymph nodes.

[Imprint cytology of axillary lymph nodes in breast neoplasms for intraoperative rapid diagnosis]

A total of 385 lymph nodes of patients suffering from breast cancer were examined intraoperatively for the presence of metastases. We applied imprint cytology and stained using the "Diff-Quick" set (3 times 30 seconds). The percentage of correct identifications following instant cytological examination amounted to 94.5 if compared with subsequent paraffin histology. The 21 diagnostic failures were composed of 3 false negative and 18 false positive results. These data make the advantages for routine clinical application quite obvious.