bluuebunny/crossref_metadata_2025_split huggingface dataset:
Developmental expression of rat cardiac troponin I mRNA
Authors: Ausoni Simonetta , Nardi Costanza De , Moretti Paolo , Gorza Luisa , Schiaffino Stefano 
Published: April 2021

ABSTRACT
We have isolated and sequenced a full-length cDNA clone of rat cardiac troponin I (Tnl). The amino acid sequence of rat cardiac Tnl is highly similar to that of other mammalian species in the portion of the molecule (residues 33–210) that is also homologous to skeletal muscle Tnl isoforms. In contrast, a lower degree of similarity is present in the cardiac Tnl-specific amino terminal extension (residues 1–32). This region contains a conserved serine residue that has been shown to be selectively phosphorylated by cAMP-dependent protein kinase. Cardiac Tnl mRNA is weakly expressed in the 18-day fetal heart and accumulates in neonatal and postnatal stages. No difference can be demonstrated between Tnl mRNAs present in fetal and postnatal heart by RNAase protection assays. The fetal and neonatal, but not the adult heart, contain significant amounts of slow skeletal Tnl transcripts, detected by oligonucleotide probes specific for the 5′- and 3′-untranslated regions of slow skeletal Tnl mRNA. In situ hybridization studies show that cardiac and slow skeletal Tnl mRNAs are coexpressed in the rat heart from embryonic day 11 throughout fetal and perinatal stages. Changes in troponin isoform expression during development may be responsible for the difference in calcium sensitivity and in the response to β-adrenergic stimulation between fetal and adult heart.
The Msh-like homeobox genes define domains in the developing vertebrate eye
Authors: Monaghan A. Paula , Davidson Duncan R. , Sime Christina , Graham Elizabeth , Baldock Richard , Bhattacharya Shomi S. , Hill Robert E. 
Published: April 2021

ABSTRACT
The mouse Hox-7.1 gene has previously been shown to be related to the Drosophila Msh homeobox-containing gene. Here we report the isolation of a new member of this family which resides at an unlinked chromosomal location and has been designated Hox-8.1. Both Hox-7.1 and Hox-8.1 are expressed in the mouse embryo during the early stages of eye development in a distinct spatial and temporal relationship. Hox-8.1 is expressed in the surface ectoderm and in the optic vesicle before invagination occurs in regions corresponding to the prospective corneal epithelium and neural retina, respectively. Hox-7.1 is expressed after formation of the optic cup, marking the domain that will give rise to the ciliary body. The activity of these genes indicates that the inner layer of the optic cup is differentiated into three distinct compartments before overt cellular differentiation occurs. Our results suggest that these genes are involved in defining the region that gives rise to the inner layer of the optic cup and in patterning this tissue to define the iris, ciliary body and retina.
Expression of nerve growth factor (NGF) receptors in the developing inner ear of chick and rat
Authors: Bartheld Christopher S. Von , Patterson Susan L. , Heuer Josef G. , Wheeler Esther F. , Bothwell Mark , Rubel Edwin W. 
Published: April 2021

ABSTRACT
The expression of nerve growth factor receptors (NGFRs) was studied in the developing inner ear with in situ hybridization in chick embryos and with immunocytochemistry in rat embryos to determine sites of possible functions of NGF or NGF-like molecules in inner ear development. NGFR expression in the chick otocyst and acoustic ganglion is compared with epithelial differentiation and the onset of afferent innervation as determined with fluorescent carbocyanine tracers.
In the inner ear of the chick embryo, NGFR mRNA expression shows an alternating pattern in mesenchymal and epithelial tissues. NGFR mRNA is heavily expressed in the mesenchyme surrounding the otocyst (E2 –3), ceases at E3 –5, and reappears in a thin layer of mesenchymal cells surrounding the membraneous epithelia (E5 –13). In the otocyst epithelium, NGFR mRNA expression develops in one anterior and one posterior focus at E3 –4.5. NGFR mRNA is expressed in the primordia of the ampullary cristae (E5 –7) and possibly the anlage of the utricle; label transiently concentrates in the planum semilunatum of the cristae ampullares and in superior portions of the semicircular canals at E9, but is not seen in differentiating hair cells. In the acoustic ganglion, NGFR mRNA expression begins at E4; at the same time, the first peripheral acoustic nerve processes penetrate the otic epithelium (E4 –4.5). The acoustic ganglia remain weakly NGFR mRNA-labeled in the posthatch animal.
In the rat embryo, NGFR immunoreactivity is present in the auditory placode at E9, in the periotic mesenchyme at E9 –10, and in the medial half of the otocyst at E10 –11. At E12, epithelial NGFR expression becomes restricted anteriorly and posteriorly in a pattern similar to that of the chick otocyst and ceases at E13. NGFR immunoreactivity appears transiently in pillar cells of the cochlea in the third week of gestation. NGFR and NGFR mRNA is expressed after Ell in the acoustic ganglia. While NGFR transcripts are expressed in the cochlear ganglion cell bodies, NGFR protein becomes restricted to neuronal processes by the third week of gestation. The vestibular, but not the cochlear (spiral) ganglia remain NGFR-labeled in the adult rat.
Onset of NGFR mRNA expression in the acoustic ganglion during the period of afferent fiber ingrowth into the otocyst epithelium is consistent with the hypothesis that NGF-like molecules may have a neurotrophic function for acoustic ganglion cells. Transient expression of NGFRs in secretory cells of the vestibular endorgan and pillar cells in the organ of Corti implicate a role for neurotrophins in the differentiation of these epithelial cell types.
Nuclear translocation of fibroblast growth factor during Xenopus mesoderm induction
Authors: Shiurba Robert A. , Jing Naihe , Sakakura Teruyo , Godsave Susan F. 
Published: April 2021

ABSTRACT
Mesoderm induction, the earliest inductive cell–cell interaction in vertebrate embryogenesis, is thought to be mediated by polypeptide growth factors including fibroblast growth factor (FGF). Here we present an immunocytochemical analysis of FGF during mesoderm induction in Xenopus laevis. Antibodies to both basic and acidic FGF were immunoreactive with oocytes and early embryos. Immunostaining was predominantly intracellular and was concentrated in the marginal zone and vegetal pole throughout cleavage and blastula stages. In addition, basic FGF (bFGF) antibodies showed intense nuclear staining in these regions, at and following the mid-blastula transition, when embryonic transcription begins. Acidic FGF (aFGF) also appeared in some nuclei at these stages. Taken together the evidence suggests that FGF is prepositioned in mesoderm-forming regions and is actively involved in mesoderm induction in vivo.
The cellular environment controls the expression of engrailed-like protein in the cranial neuroepithelium of quail-chick chimeric embryos
Authors: Gardner Charles A. , Barald Kate F. 
Published: April 2021

ABSTRACT
We have previously shown that one of two chicken engrailed-like genes, chick En-2, is expressed in a restricted region of the early chick embryo brain: the mes/metencephalon (Gardner et al. 1988). In this study, we examine the role of the cellular environment in regulation of engrailed-like (En) protein expression in quail-chick chimeric embryos. Two types of transplant surgery were performed at the 9-15 somite stage to produce chimeric embryos. In the first, the mid-mesencephalic vesicle or caudal mesencephalic vesicle alar plate (which is En protein-positive) was transplanted from a quail embryo into an En protein-negative region of chick neuroepithelium, the prosencephalon (mMP and cMP grafts, respectively). In the second reciprocal surgery, prosencephalic alar plate which is En protein-negative, was transplanted into the En protein-positive mesencephalic vesicle (PM grafts). A polyclonal antiserum, aEnhb-1, which recognizes chick
En proteins (Davis et al. 1991) was used to identify En-positive cells 48 h after surgery. In mMP embryos, 71 % of integrated grafts had lost En expression (n=17). In contrast, in cMP grafts, 93% of integrated grafts continued to stain with the antiserum (n=14). In addition, in 86 % of these embryos, the graft induced adjacent chick host diencephalic cells to become En protein-positive as well. All PM grafts contained aEnhb-1 -positive cells; such cells never expressed this protein in their normal environment. These early changes in En protein expression correlate well with the morphological changes observed in similar graft surgeries assayed later in development. Thus, our results are consistent with the hypothesis that En genes play a role in the regionalization of the early cranial neuroepithelium.
Segmental expression of an engrailed-class gene during early development and neurogenesis in an annelid
Authors: Wedeen Cathy J. , Weisblat David A. 
Published: April 2021

ABSTRACT
ht-en protein, an annelid homolog of the Drosophila engrailed protein, is expressed during both early development and neurogenesis in embryos of the leech, Helobdella triserialis. In Helobdella as in Drosophila, early expression is in segmentally iterated stripes of cells within the posterior portion of the segment and later expression is in cells of the segmental ganglia. These findings suggest that dual expression of an en-class gene was present in a common ancestor of annelids and arthropods.
Development to term of mouse androgenetic aggregation chimeras
Authors: Mann Jeff R. , Stewart Colin L. 
Published: April 2021

ABSTRACT
Diploid androgenetic eggs contain two sperm-derived genomes, and only rarely develop to the early somite stage. Also, previous studies have indicated that androgenetic eggs cannot be rescued in aggregation chimeras beyond embryonic stages. Paradoxically, in blastocyst injection chimeras made with androgenetic embryonic stem (ES) cells of the 129/Sv strain, we previously obtained considerable improvement in developmental potential. Although considerable death occurred in utero, overtly normal chimeric fetuses and occasional postnatal chimeras that developed skeletal abnormalities were observed.
Consequently, we have re-evaluated the developmental potential of androgenetic aggregation chimeras utilizing androgenetic eggs of the 129/Sv strain, and of the BALB/c and CD-I strains for comparison. Regardless of strain, androgenetic aggregation chimeras were generally more inviable than previously observed with androgenetic ES cell chimeras, and often the embryoproper was abnormal even when an androgenetic contribution was detected only in the extra-embryonic membranes. This is at least a partial explanation of the greater viability of androgenetic ES cell chimeras, as ES cells do not colonize significantly certain extra-embryonic tissues. Nevertheless, in the 129/Sv strain, occasional development of chimeras to term was obtained, and one chimera that survived postnatally developed identical skeletal abnormalities to those observed previously in androgenetic ES cell chimeras. This result demonstrates that at least one example of paternal imprinting is faithfully conserved in androgenetic ES cells. Also, the postnatal chimerism shows that androgenetic eggs can give rise to terminally differentiated cell types, and are therefore pluripotent. In contrast, only possibly one BALB/c and no CD-I androgenetic aggregation chimeras developed to term. Therefore, the developmental potential of androgenetic aggregation chimeras is to some extent dependent on mouse strain.
EP-cadherin in muscles and epithelia of Xenopus laevis embryos
Authors: Levi Giovanni , Ginsberg Dorit , Girault Jeanne-Marie , Sabanay Ilana , Thiery Jean Paul , Geiger Benjamin 
Published: April 2021

ABSTRACT
EP-cadherin is a novel Xenopus Ca+2-dependent adhesion molecule, which shares comparable homology with mouse E- and P-cadherins (Ginsberg, De Simone and Geiger; 1991, Development 111, 315–325). We report here the patterns of expression of this molecule in Xenopus laevis embryos at different developmental stages ranging from cleavage to postmetamorphic. EP-cadherin is already expressed in the oocyte and egg and can then be detected in close association with the membrane of all blastomeres up to late blastula stages. Starting at late gastrula stages, the level of EP-cadherin expression increases sharply in non-neural ectodermal cells, in the somites and in the notochord; it persists in endodermal cells and decreases rapidly in all migratory cells. During neurulation the level of EP-cadherin expression declines gradually in the nervous system and is undetectable here throughout later development except in the optic nerve and in the neural part of the olfactory organ. This pattern continues during later development so that in the tailbud stage and up to metamorphosis the most prominent staining is detected in the epidermis and skeletal muscle. After metamorphosis, the molecule gradually disappears from the muscle tissue and the major site of expression remains the skin.
EP-cadherin is invariably present in close association with the cell membrane. In the muscle it is associated with the sarcolemma at regions of myoblast-myoblast or myotube-myotube contact. In epidermal cells, EP-cadherin is usually coexpressed with E-cadherin. Yet, while E-cadherin staining is always restricted to the basolateral aspects of the cells, EP-cadherin is often distributed throughout the plasmalemma including the apical surface.
Organization of the Drosophila head as revealed by the ectopic expression of the Ultrabithorax product
Authors: González-Reyes Acaimo , Morata Ginés 
Published: April 2021

ABSTRACT
By using a hsp70–Ubx fusion gene, we have ectopically expressed a Ubx product in the embryonic head primordia and studied the developmental effects on the larval head. We find that after high and persistent levels of Ubx product, the head is replaced by three (Cl, C2 and C3) abdominal-like denticle belts. The C2 and C3 belts are the homeotic transformations of parasegments 1 and 2, respectively, while the Cl belt probably derives from the transformation and subsequent fusion of the most anterior procephalic primordia. On the basis of their response to the Ubx product and other arguments, we propose that the larval head is made of two genetically distinct components; one is the procephalon and the anterior region of the mandibular lobe, and the other is part of the parasegmental trunk and includes parasegments 1 and 2. Our results also indicate that most or all the larval head structures derive from precursor cells of ventral origin.
Polar axis fixation in Fucus zygotes: components of the cytoskeleton and extracellular matrix
Authors: Quatrano Ralph S. , Brian Leigh , Aldridge Joyce , Schultz Thomas 
Published: April 2021

Abstract
Polar axis formation and polar axis stabilization (or fixation) can be separated and analyzed in synchronously developing zygotes of the brown alga Fucus. Extensive experimental evidence points to a role for both the cytoskeleton and the extracellular matrix (ECM) in the process of axis fixation in Fucus. A structural complex composed of the cytoskeleton and the ECM has been postulated to stabilize membrane asymmetries generated as a result of axis-forming vectors. This axis stabilizing complex (ASC) may take the form of transmembrane connections between the cytoskeleton on the cytoplasmic face and the ECM on the external side of the plasma membrane, similar to focal contacts in animal cells. At present we know of two components in the proposed ASC of Fucus: an adhesive sulfated glycoprotein which is localized in the ECM, and an actin network which is localized on the adjoining cytoplasmic face. This preliminary report describes evidence for the presence of molecules in two-celled Fucus embryos that are similar to those found in focal contacts in animal cells, i.e. vinculin, integrin and vitronectin. However, their localization and interaction with each other relative to the polar axis has yet to be determined. These initial observations will provide the basis to pursue further an analysis of these components in the process of polar axis fixation.
Retinoic acid and chick limb bud development
Authors: Tickle C. 
Published: April 2021

Abstract
The chick limb bud is a powerful experimental system in which to study pattern formation in vertebrate embryos. Exogenously applied retinoic acid, a vitamin A derivative, can bring about changes in pattern and, on several grounds, is a good candidate for an endogenous morphogen. As such, the local concentration of retinoic acid might provide cells with information about their position in relation to one axis of the limb. Alternatively, retinoic acid may be part of a more complex signalling system.
Homeobox genes are possible target genes for regulation by retinoic acid in the limb. In particular, one homeobox gene, XlHbox 1 is expressed locally in the mesenchyme of vertebrate forelimbs and might code for an anterior position. When the pattern of the chick wing is changed by retinoic acid or by grafts of signalling tissue such that anterior cells now form posterior structures, the domain of XlHbox 1 expression expands rather than contracts. The expansion of XlHbox 1 expression correlates with shoulder girdle abnormalities.
Retinoic acid application leads to visible changes in bud shape and this allows dissection of the way in which patterning is co-ordinated with morphogenesis. Results of recombination experiments and studies of changes in the apical ridge and proliferation in the mesenchyme suggest the following scheme: retinoic acid is involved in specification of position of mesenchyme cells; this specification determines their local interaction with the ridge that controls ridge morphology; the thickened apical ridge permits local proliferation in the underlying mesenchyme.
The recent advances in molecular biology that permit analysis of the expression of various interesting genes in developing limbs hold out the promise that further investigation may soon allow a complete account of the patterning process in one part of the vertebrate embryo.
Dominant gain-of-function mutations that lead to misregulation of the C. elegans heterochronic gene lin-14, and the evolutionary implications of dominant mutations in pattern-formation genes
Authors: Ruvkun Gary , Wightman Bruce , Bürglin Thomas , Arasu Prema 
Published: April 2021

Abstract
The heterochronic gene lin-14 controls the temporal sequence of developmental events in the C. elegans postembryonic cell lineage. It encodes a nuclear protein that is normally present in most somatic cells of late embryos and LI larvae but not in later larval stages or adults. Two lin-14 gain-of-function mutations cause an inappropriately high level of the lin-14 nuclear protein late in development. These mutations delete 3′ untranslated sequences from the lin-14 mRNAs and identify a negative regulatory element that controls the formation of the lin-14 protein temporal gradient. The 21 kb lin-14 gene contains 13 exons that are differentially spliced to generate two lin-14 protein products with variable N-terminal regions and a constant C-terminal region. No protein sequence similarity to any proteins in various databases was found.
The temporal and cellular expression patterns of lin-14 protein accumulation is altered by mutations in the heterochronic genes lin-4 and lin-28. The lin-4 gene is required to down-regulate lin-14 protein levels during the mid-Ll stage. The lin-4 gene product could be the trans-acting factor that binds to the negative regulatory element in the lin-14 3′ untranslated region. In contrast, the lin-28 gene activity positively regulates lin-14 protein levels during early LI. Thus, these genes act antagonistically to regulate the lin-14 temporal switch.
The normal down-regulation of lin-14 within 10 h of hatching is not determined by the passage of time per se, but rather is triggered when feeding induces post-embryonic development. Loss of lin-28 gene activity causes precocious down-regulation of lin-14 protein levels before feeding, whereas loss of lin-4 gene activity does not affect the level of lin-14 protein before feeding. These data suggest that to trigger the lin-14 temporal switch, the lin-4 gene is up-regulated after feeding which in turn down-regulates lin-14 via its 3’ untranslated region.
We speculate on the evolutionary implications of dominant mutations in pattern-formation genes.
Cytoplasmic and cortical determinants interact to specify ectoderm and mesoderm in the leech embryo
Authors: Nelson Brad H. , Weisblat David A. 
Published: April 2021

Abstract
In leech embryos, segmental ectoderm and mesoderm are produced by a pair of sister cells located near the animal and vegetal poles, respectively. We have investigated the mechanism that localizes ectodermal and mesodermal fates along the animal-vegetal axis. The results of cleavage arrest and cell ablation experiments suggest that the full range of normal cell interactions are not required for this process. However, when the animal and vegetal hemispheres are separated by re-orientation of the first cleavage plane from meridional to equatorial, the ectodermal fate co-segregates with the animal hemisphere and the mesodermal fate with the vegetal hemisphere. Two pools of yolk-deficient cytoplasm, called teloplasm, are located at the animal and vegetal poles of the zygote, but separation of the animal and vegetal teloplasms is not sufficient for the segregation of ectodermal and mesodermal fates. Rather, complete segregation of fates requires an equatorial cleavage orientation that separates not only the two teloplasms, but also the animal and vegetal cortical regions. This, in conjunction with previous findings, indicates that ectodermal determinants are localized to the cell cortex in the animal hemisphere of the zygote. We propose that these determinants segregate to the ectodermal precursor and interact with factors in teloplasm to transform the fate of this cell from a mesodermal ground state to ectoderm.
Polarity of the ascidian egg cortex before fertilization
Authors: Sardet Christian , Speksnijder Johanna , Terasaki Mark , Chang Patrick 
Published: April 2021

Abstract
The unfertilized ascidian egg displays a visible polar organization along its animal-vegetal axis. In particular, the myoplasm, a mitochondria-rich subcortical domain inherited by the blastomeres that differentiate into muscle cells, is mainly situated in the vegetal hemisphere. We show that, in the unfertilized egg, this vegetal domain is enriched in actin and microfilaments and excludes microtubules. This polar distribution of microfilaments and microtubules persists in isolated cortices prepared by shearing eggs attached to a polylysine-coated surface. The isolated cortex is further characterized by an elaborate network of tubules and sheets of endoplasmic reticulum (ER). This cortical ER network is tethered to the plasma membrane at discrete sites, is covered with ribosomes and contains a calse-questrin-like protein. Interestingly, this ER network is distributed in a polar fashion along the animal-vegetal axis of the egg: regions with a dense network consisting mainly of sheets or tightly knit tubes are present in the vegetal hemisphere only, whereas areas characterized by a sparse tubular ER network are uniquely found in the animal hemisphere region. The stability of the polar organization of the cortex was studied by perturbing the distribution of organelles in the egg and depolymerizing microfilaments and microtubules. The polar organization of the cortical ER network persists after treatment of eggs with nocodazole, but is disrupted by treatment with cytochalasin B. In addition, we show that centrifugal forces that displace the cytoplasmic organelles do not alter the appearance and polar organization of the isolated egg cortex.
These findings taken together with our previous work suggest that the intrinsic polar distribution of cortical membranous and cytoskeletal components along the animal-vegetal axis of the egg are important for the spatial organization of calcium-dependent events and their developmental consequences.