bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular definition of the morphogenetic and regulatory functions and the cis-regulatory elements of the Drosophila Abd-B homeotic gene
Authors: Boulet Anne M. , Lloyd Alan , Sakonju Shigeru 
Published: April 2021

Abstract
The Abdominal-B (Abd-B) gene, a member of the Drosophila bithorax complex, is required during development to specify the identity of parasegments 10– 14. Based on genetic studies, Casanova, J., Sánchez-Herrero, E. and Morata, G. (1986) Cell 47, 627-636, proposed that the Abd-B gene consists of two distinct elements that provide a morphogenetic (m) function in PS 10-13 and a regulatory (r) function in PS 14, where it represses m function. Here we present molecular confirmation of this genetic model. . Using specific antibodies, we show that the 55x103Mr and 30x103MrAbd-B proteins, predicted by cDNA analysis, are indeed present in PS 10-13 and PS 14, respectively. We also examine Abd-B mRNA and protein expression patterns in embryos mutant for either the m or r function. These data allow us to unambiguously assign m function to the 55x103Mr protein and r function to the 30x103Mr protein. Furthermore, as postulated by the model, transcription of the mRNA encoding the m protein is derepressed in PS 14 in the absence of r function. We have also studied the effect of mutations mapping in the infra-abdominal (iab) region located downstream of the Abd-B gene. Genetic studies suggest that the iab region contains crv-acting regulatory elements controlling Abd-B expression in PS 10-12. We present molecular evidence for the presence of downstream crs-regulatory elements by analyzing Abd-B mRNA and protein patterns in iab-6 and iab-7 embryos. Our analysis reveals the presence of parasegment and cell-specific regulatory elements of the Abd-B gene within each iab region. The Abd-B gene may provide a model for the understanding of similarly complex homeotic genes in higher organisms.
The large upstream control region of the Drosophila homeotic gene Ultrabithorax
Authors: Irvine Kenneth D. , Helfand Stephen L. , Hogness David S. 
Published: April 2021

Abstract
Ultrabithorax (Ubx) is a Drosophila homeotic gene that determines the segmental identities of parts of the thorax and abdomen. Appropriate Ubx transcription requires a long upstream control region (UCR) that is defined genetically by the bithoraxoid (bxd) and postbithorax (pbx) subfunction mutations. We have directly analyzed UCR functions by the examination of β-galactosidase expression in flies containing Ubx-lacZ fusion genes. 35 kb of UCR DNA confers upon β-galactosidase an expression pattern that closely parallels normal Ubx expression throughout development. In contrast, 22 kb of UCR DNA confers fewer features of normal Ubx expression, and with 5 kb of UCR DNA the expression pattern has no resemblance to Ubx expression except in the visceral mesoderm. We have also shown that bxd chromosome breakpoint mutants form a comparable 5’ deletion series in which the severity of the effect on Ubx expression correlates with the amount of upstream DNA remaining in the mutant. In Ubx-lacZ fusions containing 22 kb of UCR DNA, and in comparable bxd mutants, there is a persistent pair-rule pattern of metameric expression in early development, demonstrating that there are distinct mechanisms with different sequence requirements for the initial activation of Ubx in different metameres. The correction of this pair-rule pattern later in embryogenesis shows that there are also distinct mechanisms for the activation of Ubx at different times during development.
Expression of FGF receptor gene in rat development
Authors: Wanaka Akio , Milbrandt Jeffrey , Johnson Eugene M. 
Published: April 2021

Abstract
We examined the expression of FGF-receptor (FGF-R) mRNA during rat development with in situ hybridization histochemistry. Embryonic tissues (E9, E12, E14, E17) and postnatal neural tissues (Pl, P7, P14, adult) were examined. We detected significant levels of FGF-R mRNA in various tissues at different developmental stages. As postulated by previous studies using other methods, FGF-R gene expression was observed primarily in mesoderm- and neuroectodenn-derived tissues. In the nervous system, the pattern of gene expression was developmentally regulated; in embryos, FGF-R mRNA was mainly detected in the ependymal layer of the central nervous system (CNS). Postnatally, FGF-R transcripts were observed in specific neuronal populations, such as hippocampal neurons. FGF-R mRNA was also found in sensory systems such as trigeminal and dorsal root ganglia in late stage embryos; however, FGF-R mRNA decreased in the postnatal period. FGF-R mRNA expression was modulated in the developing retina: FGF-R messages were observed in the pigment epithelium and neuroblast layer at embryonic stages; in the postnatal period, they were found in the ganglion cell and inner granular layer. In non-neuronal embryonic tissues, a wide variety of organs expressed FGF-R message. Particularly, the prevertebral column, bone, kidney and skin showed high levels of expression. These observations reinforce the idea that FGF exerts effects on the development of various tissues.
Mutually repressive interactions between the gap genes giant and Krüppel define middle body regions of the Drosophila embryo
Authors: Kraut Rachel , Levine Michael 
Published: April 2021

Abstract
The gap genes play a key role in establishing pair-rule and homeotic stripes of gene expression in the Dros-ophila embryo. There is mounting evidence that overlapping gradients of gap gene expression are crucial for this process. Here we present evidence that the segmentation gene giant is a bona fide gap gene that is likely to act in concert with hunchback, Krüppel and knirps to initiate stripes of gene expression. We show that Krüppel and giant are expressed in complementary, non-overlapping sets of cells in the early embryo. These complementary patterns depend on mutually repressive interactions between the two genes. Ectopic expression of giant in early embryos results in the selective repression of Krüppel, and advanced-stage embryos show cuticular defects similar to those observed in Krüppel− mutants. This result and others suggest that the strongest regulatory interactions occur among those gap genes expressed in nonadjacent domains. We propose that the precisely balanced overlapping gradi-ents of gap gene expression depend on these strong regulatory interactions, coupled with weak interactions between neighboring genes.
‘Unmasking’ of stored maternal mRNAs and the activation of protein synthesis at fertilization in sea urchins
Authors: Kelso-Winemiller Leslie C. , Winkler Matthew M. 
Published: April 2021

Abstract
The isolation and in vitro assay of maternal mRNPs has led to differing conclusions as to whether maternal mRNAs in sea urchin eggs are in a repressed or ‘masked’ form. To circumvent the problems involved with in vitro approaches, we have used an in vivo assay to determine if the availability of mRNA and/or components of the translational machinery are limiting protein synthesis in the unfertilized egg. This assay involves the use of a protein synthesis elongation inhibitor to create a situation in the egg in which there is excess translational machinery available to bind mRNA. Eggs were fertilized and the rate of entry into polysomes of individual mRNAs was measured in inhibitor-treated and control embryos using 32P-labeled cDNA probes. The fraction of ribosomes in polysomes and the polysome size were also determined. The results from this in vivo approach provide strong evidence for the coactivation of both mRNAs and components of the translational machinery following fertilization. The average polysome size increases from 7.5 ribosomes per message in 15 min embryos to approximately 10.8 ribosomes in 2h embryos. This result gives additional support to the idea that translational machinery, as well as mRNA, is activated following fertilization. We also found that individual mRNAs are recruited into polysomes with different kinetics, and that the fraction of an mRNA in polysomes in the unfertilized egg correlates with the rate at which that mRNA is recruited into polysomes following fertilization.
Hβ58, an insertional mutation affecting early postimplantation development of the mouse embryo
Authors: Radice Glenn , Lee James J. , Costantini Frank 
Published: April 2021

ABSTRACT
The generation and analysis of insertional mutations affecting mouse embryogenesis provides a powerful method to identify new genes that function in early development. In this paper, we describe an insertional mutation that inteferes with postimplantation mouse development beginning at the time of gastrulation. Embryos homozygous for the Hβ58 transgenic insertion developed normally through the early postimplantation, egg cylinder stage (day 6.5 of development). At the primitive streak stage (day 7.5), however, they began to display characteristic abnormalities, including a retardation in the growth of the embryonic ectoderm (the earliest identifiable defect), and in some cases abnormalities of the amnion and chorion. Homozygotes continued to develop for 2–3 more days, reaching the size of a normal 8.5 day embryo, and formed tissues representative of all three germ layers, including several differentiated cell types. The site of insertion was mapped, by a combination of cytogenetic and genetic methods, to chromosome 10, and it appeared to define a new genetic locus. The inserted transgene provided a probe to clone and characterize the mutant locus, as well as the corresponding wild-type locus. In addition to an insertion of 10–20 copies of the transgene, the mutant locus contained a deletion of 2–3 kb of DNA found at the wild-type locus, and possibly an insertion of mouse repetitive DNA. However, genomic sequences on both sides of the insertion site remained co-linear in the wildtype and mutant genomes, and no chromosomal abnormalities could be detected. Five single copy DNA probes spanning the insertion site were tested for their ability to hybridize to RNA from 8.5 day embryos; one of the probes (located within the region deleted from the mutant chromosome) hybridized to a 2.7 kb mRNA encoded at the H/158 locus, thus identifying a gene whose disruption appears to be responsible for the mutant phenotype.
Differential expression of two cadherins in Xenopus laevis
Authors: Angres B. , Müller A. H. J. , Kellermann J. , Hausen P. 
Published: April 2021

ABSTRACT
Using a cadherin fraction from Xenopus tissue culture cells as an immunogen, two monoclonal antibodies were obtained that allowed the characterization of two distinct cadherins in the Xenopus embryo.
The two cadherins differ in molecular weight, in thentime of appearance during development and in their spatial pattern of expression.
One of the antigens was identified as E-cadherin. It appears in the embryonic ectoderm during gastrulation when epidermal differentiation commences and it disappears from the neural plate area upon neural induction.
The second antigen could not be allocated to any of the known cadherin subtypes and was termed U-cadherin. It is present in the egg and becomes deposited in newly formed inner cell membranes during cleavage, the outer apical membranes of the embryo remaining devoid of the cadherin throughout development. U-cadherin is found on membranes of all cells up to the late neurula stages. A conspicuous polarized expression of the antigen on the membranes of individual inner cells suggests its participation in the segregation of cell layers and organ anlagen.
These findings are discussed in the context of current hypotheses on the role of cadherins in establishing the spatial structure of the embryo.
Two homologous regulatory genes, lin-12 and glp-1, have overlapping functions
Authors: Lambie Eric J. , Kimble Judith 
Published: April 2021

ABSTRACT
Two homologous genes, lin-12 and glp-1, encode transmembrane proteins required for regulatory cell interactions during C. elegans development. Based on their single mutant phenotypes, each gene has been thought to govern a distinct set of cell fates. We show here that lin-12 and glp-1 are functionally redundant during embryogenesis: Unlike either single mutant, the lin-12 glp-1 double mutant dies soon after hatching. Numerous cellular defects can be observed in these Lag (for lin-12 and glp-1) double mutants. Furthermore, we have identified two genes, lag-1 and lag-2, that appear to be required for both lin-12 and glp-1 -mediated cell interactions. Strong loss-of-function lag. mutants are phenotypically indistinguishable from the lin-12 glp-1 double; weak lag mutants have phenotypes typical of lin-12 and glp-1 single mutants. We speculate that the lin-12 and glp-1 proteins are biochemically interchangeable and that their divergent roles in development may rely largely on differences in gene expression.
The murine Hox-2 genes display dynamic dorsoventral patterns of expression during central nervous system development
Authors: Graham Anthony , Maden Malcolm , Krumlauf Robb 
Published: April 2021

ABSTRACT
This report demonstrates that the genes in the murine Hox-2 cluster display spatially and temporally dynamic patterns of expression in the transverse plane of the developing CNS. All of the Hox-2 genes exhibit changing patterns of expression that reflect events during the ontogeny of the CNS. The observed expression correlates with the timing and location of the birth of major classes of neurons in the spinal cord. Therefore, it is suggested that the Hox-2 genes act to confer rostrocaudal positional information on each successive class of newly born neurons. This analysis has also revealed a striking dorsal restriction in the patterns of Hox-2 expression in the spinal cord between 12.5 and 14.5 days of gestation, which does not appear to correlate with any morphological structure. The cellular retinol binding protein (CRBP) shows a complementary ventral staining pattern, suggesting that a number of genes are dorsoventrally restricted during the development of the CNS. The expression of Hox-2 genes has also been compared with the Hox-3.1 gene, which exhibits a markedly different dorsoventral pattern of expression. This suggests that, while genes in the different murine Hox clusters may have similar A-P domains of expression, they are responding to different dorsoventral patterning signals in the developing spinal cord.
Pathfinding in the central nervous system and periphery by identified embryonic Drosophila motor axons
Authors: Sink Helen , Whitington Paul M. 
Published: April 2021

ABSTRACT
We have studied the pattern of axon outgrowth from the identified embryonic Drosophila motorneurons, RP1, RP3, RP4 and RP5, from the onset of axonogenesis to the time of arborization over target muscles. Lucifer Yellow was intracellularly injected into each of these neurons to obtain a detailed description of the morphology of their growth cones and of the pathways that they follow. We have divided the sequence of axon growth from these neurons into five major phases. In the first phase, the growth cone of each RP axon grows medially along its contralateral homologue along the anterior commissure. Each RP axon follows a separate path across the midline in the anterior commissure. After crossing the ventral midline, the axons wrap around specific contralateral RP somata. In the second phase, each axon grows posteriorly and dorsally down the contralateral longitudinal connective, fasciculating with the other RP axons. In the third phase, the axons turn into the intersegmental nerve via the anterior nerve root, then cross over to the segmental nerve, before contacting the external surfaces of intermediate muscles 15/16. They do not fasciculate with the pioneering aCC and RP2 axons at this time. In the fourth phase, the axons advance laterally across the ventral muscle group. During this phase, each axon extends processes over a number of inappropriate muscles as well as contacting its correct, target muscle. In the final phase, the processes to inappropriate muscles are withdrawn, generating the mature pattern of motor axon projections. There is no consistent, clear difference between the RP motorneurons in the relative timing of axon outgrowth.
Normal segmentation and size of the primary sympathetic ganglia depend upon the alternation of rostrocaudal properties of the somites
Authors: Goldstein Ronald S. , Kalcheim Chaya 
Published: April 2021

ABSTRACT
Metameric organization of the dorsal root ganglia (DRG) and ventral roots depends on the alternation of rostrocaudal properties within the somites. In addition, the size of DRG is likely to be regulated by the adjacent mesoderm, because unilateral creation of a paraxial mesoderm with only rostral somitic (RS) halves, leads to the development of non-segmented DRG that are larger and contain more cells than the sum of the contralateral, control DRG. We have now extended our studies of the role of the paraxial mesoderm in the morphogenesis of the peripheral nervous system (PNS) to another metameric PNS component, the sympathetic ganglia (SG). The development of the primary sympathetic chain was studied in chick-quail chimeras with multiple half-somite grafts using quantitative morphometric analysis. In the presence of an exclusively rostral or caudal somitic mesoderm, segmentation of the initially homogeneous primary sympathetic chain into ganglia is prevented. Therefore, the SG, like the DRG and ventral roots, require the normal rostrocaudal alternation of the somitic mesoderm for segmental morphogenesis.
On embryonic day 4 (E4), there is a 38% average decrease in the volume of the primary sympathetic chain opposite a RS mesoderm, compared with the primary chain on the unoperated side. This is in contrast to the average increase of 27% in the volume of the DRG opposite the grafted mesoderm in the same embryos. Our results, and classical observations, have led us to propose a model in which the mesoderm controls DRG and SG size by modulating the partition of migrating NC precursors between the anlage of these two ganglion types. According to this model, the reduction in SG volume and concomitant increase in DRG volume observed opposite RS grafts, results from the arrest in the DRG anlage of neural crest cells that normally migrate to the SG.
Analysis of high PSA N-CAM expression during mammalian spinal cord and peripheral nervous system development
Authors: Boisseau Sylvie , Nedelec Joël , Poirier Véronique , Rougon Geneviève , Simonneau Michel 
Published: April 2021

ABSTRACT
Using a monoclonal antibody that recognizes specifically a high polysialylated form of N-CAM (high PSA N-CAM), the temporal and spatial expression of this molecule was studied in developing spinal cord and neural crest derivatives of mouse truncal region. Temporal expression was analyzed on immunoblots of spinal cord and dorsal root ganglia (DRGs) extracts microdissected at different developmental stages. Analysis of the ratio of high PSA N-CAM to total N-CAM indicated that sialylation and desialylation are independently regulated from the expression of polypeptide chains of N-CAM. Motoneurons, dorsal root ganglia cells and commissural neurons present a homogeneous distribution of high PSA N-CAMs on both their cell bodies and their neurites. Sialylation of N-CAM can occur in neurons after their aggregation in peripheral ganglia as demonstrated for dorsal root ganglia at E12. Furthermore, peripheral ganglia express different levels of high PSA N-CAM. With in vitro models using mouse neural crest cells, we found that expression of high PSA N-CAM was restricted to cells presenting an early neuronal phenotype, suggesting a common regulation for the expression of high PSA N-CAM molecules, neurofilament proteins and sodium channels. Using perturbation experiments with endoneuraminidase, we confirmed that high PSA N-CAM molecules are involved in fasciculation and neuritic growth when neurons derived from neural crest grow on collagen substrata. However, we demonstrated that these two parameters do not appear to depend on high PSA N-CAM molecules when cells were grown on a fibronectin substratum, indicating the existence of a hierarchy among adhesion molecules.
cactus, a maternal gene required for proper formation of the dorsoventral morphogen gradient in Drosophila embryos
Authors: Roth Siegfried , Hiromi Yasushi , Godt Dorothea , Nüsslein-Volhard Christiane 
Published: April 2021

Abstract
The dorsoventral pattern of the Drosophila embryo is mediated by a gradient of nuclear localization of the dorsal protein which acts as a morphogen. Establishment of the nuclear concentration gradient of dorsal protein requires the activities of the 10 maternal ‘dorsal group’ genes whose function results in the positive regulation of the nuclear uptake of the dorsal protein. Here we show that in contrast to the dorsal group genes, the maternal gene cactus acts as a negative regulator of the nuclear localization of the dorsal protein.
While loss of function mutations of any of the dorsal group genes lead to dorsalized embryos, loss of cactus function results in a ventralization of the body pattern. Progressive loss of maternal cactus activity causes progressive loss of dorsal pattern elements accompanied by the expansion of ventrolateral and ventral anlagen. However, embryos still retain dorsoventral polarity, even if derived from germline clones using the strongest available, zygotic lethal cactus alleles. In contrast to the loss-of-function alleles, gain-of-function alleles of cactus cause a dorsalization of the embryonic pattern. Genetic studies indicate that they are not overproducers of normal activity, but rather synthesize products with altered function. Epistatic relationships of cactus with dorsal group genes were investigated by double mutant analysis. The dorsalized phenotype of the dorsal mutation is unchanged upon loss of cactus activity. This result implies that cactus acts via dorsal and has no independent morphogen function. In all other dorsal group mutant backgrounds, reduction of cactus function leads to embryos that express ventrolateral pattern elements and have increased nuclear uptake of the dorsal protein at all positions along the dorsoventral axis. Thus, the cactus gene product can prevent nuclear transport of dorsal protein in the absence of function of the dorsal group genes. Genetic and cytoplasmic transplantation studies suggest that the cactus product is evenly distributed along the dorsoventral axis. Thus the inhibitory function that cactus product exerts on the nuclear transport of the dorsal protein appears to be antagonized on the ventral side. We discuss models of how the action of the dorsal group genes might counteract the cactus function ventrally.