Distinct Developmental Pathways Research Articles

Developmental changes in the manifestation of a phonological deficit in dyslexic children learning to read a regular orthography.

In a longitudinal study, the development of phonological processing abilities was studied in 19 dyslexic, 17 weak, and 19 normal readers learning to read in Dutch. Among other abilities, phonological awareness and rapid automatized naming were assessed in kindergarten, in 1st grade, and in 6th grade. Dyslexic and weak readers had impairments in rapid naming from kindergarten through 6th grade. Their impairments in phonological awareness at the level of phonemes became manifest in 1st grade and tended to disappear at the end of primary school. However, in a second cross-sectional study, including 13 dyslexic and 25 normal readers, dyslexic children's awareness of phonemes was hampered when task demands increased. The various manifestations of a phonological deficit follow distinct developmental pathways. (PsycINFO Database Record (c) 2016 APA, all rights reserved)

Reproductive allocation by the blow fly Lucilia sericata in response to protein limitation

Abstract.Adult females of the anautogenous blow fly Lucilia sericata (Meigen) (Diptera: Calliphoridae) were fed standardized meals of liquidized liver, in quantities shown to range around the minimum required to initiate yolk deposition. Females from each feeding regime were dissected at daily intervals between 4 and 11 days of age; the number and stage of development of all oöcytes were recorded. Once an initial threshold quantity of protein was ingested, yolk deposition was initiated in all available oöcytes. Subsequently, one of two distinct developmental pathways was followed: arrested development in all oöcytes at an early stage of yolk deposition, or more extensive yolk deposition followed by progressive oösorbtion and the maturation of small batches of eggs. The proportion of females showing oösorbtion relative to arrested follicular development increased with increasing protein meal size, suggesting that the difference in response may be triggered by a second protein threshold, either side of which the arrested development or oösorbtion pathways are followed. The behaviour observed may reflect strategies to maximize reproductive output in this short‐lived, resource‐limited insect species. Flies that display arrested development may have sufficient protein to mature few if any complete eggs, but may subsequently be able to mature a full egg‐batch if they obtain further protein meals; this possibility is offset by the risk of death before finding such a meal. Flies that show oöcyte development and oösorbtion produce smaller egg batches more quickly and hence have a higher probability of achieving at least some reproductive output. By initiating yolk deposition in all oöcytes, female L. sericata retain the potential to adopt either developmental pathway, depending on subsequent protein intake.

An expanded domain of fgf3 expression in the hindbrain of zebrafish valentino mutants results in mis-patterning of the otic vesicle.

The valentino (val) mutation in zebrafish perturbs hindbrain patterning and, as a secondary consequence, also alters development of the inner ear. We have examined the relationship between these defects and expression of fgf3 and fgf8 in the hindbrain. The otic vesicle in val/val mutants is smaller than normal, yet produces nearly twice the normal number of hair cells, and some hair cells are produced ectopically between the anterior and posterior maculae. Anterior markers pax5 and nkx5.1 are expressed in expanded domains that include the entire otic epithelium juxtaposed to the hindbrain, and the posterior marker zp23 is not expressed. In the mutant hindbrain, expression of fgf8 is normal, whereas the domain of fgf3 expression expands to include rhombomere 4 through rhombomere X (an aberrant segment that forms in lieu of rhombomeres 5 and 6). Depletion of fgf3 by injection of antisense morpholino (fgf3-MO) suppresses the ear patterning defects in val/val embryos: Excess and ectopic hair cells are eliminated, expression of anterior otic markers is reduced or ablated, and zp23 is expressed throughout the medial wall of the otic vesicle. By contrast, disruption of fgf8 does not suppress the val/val phenotype but instead interacts additively, indicating that these genes affect distinct developmental pathways. Thus, the inner ear defects observed in val/val mutants appear to result from ectopic expression of fgf3 in the hindbrain. These data also indicate that val normally represses fgf3 expression in r5 and r6, an interpretation further supported by the effects of misexpressing val in wild-type embryos. This is in sharp contrast to the mouse, in which fgf3 is normally expressed in r5 and r6 because of positive regulation by kreisler, the mouse ortholog of val. Implications for co-evolution of the hindbrain and inner ear are discussed.

Light regulated modulation of Z-box containing promoters by photoreceptors and downstream regulatory components, COP1 and HY5, in Arabidopsis.

The Z-box is one of the light-responsive elements (LREs) found in the promoters of light inducible genes. We have studied the light responsive characteristics of Z-box containing synthetic as well as native promoters. We show that promoters with Z-box as a single LRE or paired with another LRE can respond to a broad spectrum of light. The response is primarily mediated by phyA, phyB and CRY1 photoreceptors at their respective wavelengths of light. We have demonstrated that CAB1 and Z-GATA containing promoters are down-regulated in hy5 mutants in the light. On the other hand, a promoter with Z-box alone is down-regulated in hy5 mutants both in dark and in light conditions, suggesting involvement of a similar regulatory system in the regulation of the promoter in two distinct developmental pathways: skotomorphogenesis and photomorphogenesis. Furthermore, similar to the CAB1 promoter, a Z-GATA containing promoter is derepressed in cop1 mutants in the dark. DNA-protein interaction studies reveal the presence of a DNA-binding activity that is specific to Z-box. These results provide insights into the regulation of the Z-box LRE mediated by various light signaling components.

Analysis of the TGF beta functional pathway in epithelial ovarian carcinoma.

Epithelial ovarian carcinoma is often diagnosed at an advanced stage of disease and is the leading cause of death from gynaecological neoplasia. The genetic changes that occur during the development of this carcinoma are poorly understood. It has been proposed that IGFIIR, TGFβ1 and TGFβRII act as a functional unit in the TGFβ growth inhibitory pathway, and that somatic loss-of-function mutations in any one of these genes could lead to disruption of the pathway and subsequent loss of cell cycle control. We have examined these 3 genes in 25 epithelial ovarian carcinomas using single-stranded conformational polymorphism analysis and DNA sequence analysis. A total of 3 somatic missense mutations were found in the TGFβRII gene, but none in IGFRII or TGFβ1. An association was found between TGFβRII mutations and histology, with 2 out of 3 clear cell carcinomas having TGFβRII mutations. This data supports other evidence from mutational analysis of the PTEN and β-catenin genes that there are distinct developmental pathways responsible for the progression of different epithelial ovarian cancer histologic subtypes. © 2001 Cancer Research Campaign http://www.bjcancer.com

Boys with Reading Disabilities and/or ADHD

We examined distinctions in the early childhood characteristics of boys with reading disabilities (RD) and/or attention-deficit/ hyperactivity disorder (ADHD). A four-group mixed design consisting of boys identified at age 11 with reading disabilities only (RD only; n = 46), reading disabilities and ADHD (RD/ADHD; n = 16), ADHD only (n = 20), and a comparison group (n = 281) was utilized. Differences on receptive and expressive language and temperament for ages 3 and 5 were investigated. Analyses indicated that the boys from the RD-only group performed worse on measures of receptive and expressive language. The results also indicated that boys from the RD/ADHD groups consistently performed worse on measures of receptive language and exhibited more behaviors indicative of an undercontrolled temperament. In summary, we suggest that reading disabilities and ADHD represent moderately unique disorders that frequently co-occur and are characterized by distinct developmental pathways.

Regulation of T Cell Cytokine Production by Dendritic Cells Generated in Vitro from Hematopoietic Progenitor Cells

When dendritic cells (DC) present antigens to T cells, reciprocal cellular interactions occur that lead to cytokine production. This cytokine response is regulated by specific properties of DC, notably their maturation/activation status and perhaps their origin. The latter possibility prompted us to determine if DC produced along distinct developmental pathways induced distinct T cell responses. Hematopoietic progenitor cells with the potential to differentiate into multiple lineages of cells were induced to differentiate into DC along two pathways. One leads to the formation of lymphoid-related DC but not of monocyte-derived DC and is induced by culture of CD34+ cells with flt-3 ligand (F), c-kit ligand (K), GM-CSF (Gm), IL-1β (“1”), and IL-7 (“7”) (FKGm17). Another pathway with distinct molecular requirements supports in part monocyte-derived DC and is induced by the cytokines F, K, Gm, TNF-α (T), and IL-4 (“4”) (FKGmT4). DC produced along these two pathways were isolated by flow cytometry and compared. They differed only slightly in phenotype and morphology and both induced Th1-type cytokine production in MLR (mixed lymphocyte reactions). However, on a cell-per-cell basis, FKGm17-DC produced more IL-18 or IL-12 and induced more IFN-γ by T cells in MLR. Such superior properties were not intrinsically determined by the origin of the DC but were induced by FKGm17 cytokines. We conclude that lymphoid-related DC have the potential to induce Th1 T cell responses but that environmental signals strongly influence T-cell-stimulating properties of DC.

Type IIA procollagen in development of the human intervertebral disc: regulated expression of the NH(2)-propeptide by enzymic processing reveals a unique developmental pathway.

Type II collagen can be synthesized in two forms generated by alternative splicing of the precursor mRNA. Type IIA procollagen, which contains a cysteine-rich domain in the NH(2)-propeptide (exon 2), is produced by precartilage and noncartilage epithelial and mesenchymal cells, and type IIB procollagen, without the cysteine-rich domain, is characteristic of chondrocytes. Mice lacking type II collagen fail to develop intervertebral discs. We have previously shown that the human intervertebral disc and notochord synthesize primarily the type IIA form of procollagen. Therefore, we investigated the distribution of type IIA procollagen during early disc development in humans. By processes of radioactive in situ hybridization and fluorescence immunohistochemistry, we localized mRNA and protein of type IIA procollagen, type I collagen, and type III collagen in fetal intervertebral disc specimens ranging from day 42 (embryonic stage 17) to day 101 (week 14.5) of gestation. Antibodies to the three distinct domains of type IIA procollagen: the NH(2)-propeptide, the fibrillar domain, and the COOH-propeptide were used. The earliest stage of developing intervertebral disc (42 days, stage 17) was characterized by diffuse synthesis of types I and III collagens in the dense zone (intervertebral area) and synthesis of type IIA procollagen by the chondrocyte progenitor cells surrounding the disc. The notochord cells synthesized and deposited into the notochordal sheath all three fibrillar collagens. By 54 days (stage 22), the developing disc was clearly divided into three regions: 1.) the outer annulus, characterized by synthesis and deposition of types I and III collagens; 2.) the inner annulus, characterized by synthesis and deposition of type IIA collagen containing the NH(2)-propeptide but devoid of the COOH-propeptide (pN-procollagen); and 3.) the notochord, the cells of which synthesized and deposited of all three fibrillar collagens. In later stages of fetal development (72-101 days), a change in type IIA procollagen processing was observed in the cells of the inner annulus: even though these cells continued to synthesize type IIA procollagen, they deposited into the extracellular matrix (ECM) only the processed fibrillar domain, with the NH(2)-propeptide removed. This finding indicates that there is a developmentally regulated change in the processing of type IIA procollagen NH(2)-propeptide in the cells of the inner annulus. This mechanism is in contrast to previously shown developmental regulation of the cysteine-rich domain of the NH(2)-propeptide by alternative splicing of the precursor mRNA. Although the cells of the inner annulus have been identified as chondrocytes, based on their shape and synthesis of characteristic ECM components, they appear to represent a distinct developmental pathway characterized by their synthesis and differential processing of type IIA procollagen. This developmental pattern may prove important for disc regeneration.

CTL priming by CD8+ and CD8 dendritic cells in vivo

Two distinct developmental pathways are driving the formation of myeloid- and lymphoid-related dendritic cells (DC) which differ in anatomical localization and phenotype. In terms of function, it has been hypothesized that only the myeloid-related CD8– DC are able to initiate immune responses, whereas the lymphoid-related CD8+ DC have been suggested to induce tolerance. Here we show that both subsets activate CD8+ T cells in vitro and induce protective anti-viral CTL responses in vivo. Thus, vaccine strategies using peptide-pulsed DC do not have to take into account DC subsets for priming.

CTL priming by CD8(+) and CD8(-) dendritic cells in vivo.

Two distinct developmental pathways are driving the formation of myeloid- and lymphoid-related dendritic cells (DC) which differ in anatomical localization and phenotype. In terms of function, it has been hypothesized that only the myeloid-related CD8(-) DC are able to initiate immune responses, whereas the lymphoid-related CD8(+) DC have been suggested to induce tolerance. Here we show that both subsets activate CD8(+) T cells in vitro and induce protective anti-viral CTL responses in vivo. Thus, vaccine strategies using peptide-pulsed DC do not have to take into account DC subsets for priming.

Differential Biological Activities of Mammalian Id Proteins in Muscle Cells

Id proteins are helix-loop-helix (HLH) transcription factors that lack DNA-binding domains. These proteins form inactive heterodimers with basic HLH (bHLH) factors, inhibiting their DNA-binding and transcriptional activities. Consistent with a proposed role for Id proteins as inhibitors of terminal differentiation, Id1 and Id3 have been shown to negatively regulate myogenesis in cultured muscle cells. Here we have investigated the possibility that Id2 and/or Id4 can act in a similar manner. Surprisingly, while overexpression of Id2 resulted in inhibition of differentiation of Sol 8 myoblast cells, overexpression of Id4 did not. Sol 8 cells stably transfected with Id4 showed no apparent changes in expression of muscle-specific genes upon differentiation. DNA-binding activities present at the muscle creatine kinase (MCK) enhancer E-box and transcription of the MCK enhancer were not altered in Id4-overexpressing cells, compared with vector-transfected cells. Id2 is also a more potent inhibitor of protein/DNA complex formation at the MCK-R enhancer E-box than Identifiedin vitro.Therefore, our data support the notion that members of the Id family might be involved in the regulation of distinct developmental pathways.

Rescue of the embryonic lethal hematopoietic defect reveals a critical role for GATA-2 in urogenital development.

Mutations resulting in embryonic or early postnatal lethality could mask the activities of any gene in unrelated and temporally distinct developmental pathways. Targeted inactivation of the transcription factor GATA-2 gene leads to mid-gestational death as a consequence of hematopoietic failure. We show here that a 250 kbp GATA-2 yeast artificial chromosome (YAC) is expressed strongly in both the primitive and definitive hematopoietic compartments, while two smaller YACs are not. This largest YAC also rescues hematopoiesis in vitro and in vivo, thereby localizing the hematopoietic regulatory cis element(s) to between 100 and 150 kbp 5' to the GATA-2 structural gene. Introducing the YAC transgene into the GATA-2(-/-) genetic background allows the embryos to complete gestation; however, newborn rescued pups quickly succumb to lethal hydroureternephrosis, and display a complex array of genitourinary abnormalities. These findings reveal that GATA-2 plays equally vital roles in urogenital and hematopoietic development.

A juvenile hormone agonist reveals distinct developmental pathways mediated by ecdysone-inducible broad complex transcription factors.

Juvenile hormone (JH) is an important regulator of insect development that, by unknown mechanisms, modifies molecular, cellular, and organismal responses to the molting hormone, 20-hydroxyecdysone (20E). In dipteran insects such as Drosophila, JH or JH agonists, administered at times near the onset of metamorphosis, cause lethality. We tested the hypothesis that the JH agonist methoprene acts by interfering with function of the Broad Complex (BRC), a 20E-regulated locus encoding BTB/POZ-zinc finger transcription factors essential for metamorphosis of many tissues. We found that methoprene, administered by feeding or by topical application, disrupts the metamorphic reorganization of the central nervous system, salivary glands, and musculature in a dose-dependent manner. As we predicted, methoprene phenocopies a subset of previously described BRC defects; it also phenocopies Deformed and produces abnormalities not associated with known mutations. Interestingly, methoprene specifically disrupts those metamorphic events dependent on the combined action of all BRC isoforms, while sparing those that require specific isoform subsets. Thus, our data provide independent pharmacological evidence for the model, originally based on genetic studies, that BRC proteins function in two developmental pathways. Mutations of Methoprene-tolerant (Met), a gene involved in the action of JH, protect against all features of the "methoprene syndrome." These findings have allowed us to propose novel alternative models linking BRC, juvenile hormone, and MET.

Suppression of distinct ovo phenotypes in the Drosophila female germline by maleless- and Sex-lethal.

Mutations in ovo result in several different phenotypes, which we show are due to the regulation of distinct developmental pathways. Two X (female) germ cells require ovo+ activity for viability, but 1X (male) germ cells do not. In our study, we observed suppression of the ovo germline-lethality phenotype in loss-of-function maleless (mle) females indicating that ovo+ and mle+ have opposing effects in female germ cells; or that they are hierarchically related. Gain-of-function Sex-lethal (Sxl) alleles and male specific lethal-2 alleles did not suppress the ovo germline death phenotype. Many of the surviving germ cells in females mutant for both ovo and mle showed ovarian tumors. In contrast to the germline viability phenotype, we did observe suppression of the tumor phenotype in females heterozygous for gain-of-function alleles of Sxl. Further, females mutant for some hypomorphic ovo alleles were rendered fertile by Sxl gain-of-function alleles. Thus, ovo+ is required for at least two distinct functions, one involving mle+, and one mediated by Sxl+ gene products. The existence of ovo+ functions independent of mle+ and Sxl+ is likely.

Dendritic cells.

Dendritic cells are potent stimulators of immune responses against foreign antigens. Recent advances in this area include the delineation of distinct developmental pathways for different dendritic cell subsets; the emerging concept that one dendritic cell subset has regulatory functions that may contribute to induction of tolerance to self antigens; increased understanding of the interaction of dendritic cells with microbial products and viruses, such as HIV; and the application of dendritic cells for immunotherapy in certain cancers and possibly for the induction of transplantation tolerance.

Developmental and Morphogenetic Gene Regulation inHaliotis rufescensLarvae at Metamorphosis

The planktonic larva of the red abalone, Haliotis rufescens, must develop competence and recognize an appropriate exogenous morphogenetic cue before it can settle and metamorphose. The molecular mechanisms underlying the development of larval competence and the induction of metamorphosis in this and other marine invertebrates are only now starting to be understood. In Haliotis, some of the morphogenetic cues, chemosensory receptors, and receptor-mediated signal transduction pathways controlling the induction of metamorphosis from the planktonic larva to the benthic post-larva have been identified. To ascertain how these initial signaling pathways regulate the global changes that occur at metamorphosis, we have investigated the expression of two classes of genes: (i) those that are expressed but not thought to be functionally required in the veliger larva, and (ii) those that exhibit marked changes in tissue-specific expression induced at metamorphosis. Expression of the genes encoding a larval chymotrypsin and a muscle-specific tropomyosin reveal two distinct developmental pathways governing gene expression and metamorphosis in Haliotis; changes in the synthesis of other proteins and in morphology support this conclusion. One of these pathways, termed the morphogenetic pathway, is linked directly to the processes of settlement and metamorphosis; the induction of tropomyosin in the adult columellar muscle progenitors 48 hr after induction of metamorphosis provides the best and most direct evidence at the molecular level for the existence of this pathway in Haliotis. The other pathway, which we have termed the anticipatory (or preparatory) pathway, is first activated prior to or at the attainment of larval competence, and is induced again at metamorphosis. The induction of expression of a chymotrypsin gene in migrating digestive amoebocytes in the larva, and the depletion of tropomyosin mRNA from cells of the larval retractor muscle, provide molecular evidence for this program. We review here the patterns of expression of these genes, and suggest that the uncoupling of these pathways reflects an adaptation of Haliotis larval development to meet the future demands of benthic life.

Zebrafishwnt8andwnt8bshare a common activity but are involved in distinct developmental pathways

The specification of the vertebrate body plan is dependent on numerous signaling molecules, including members of the Wnt family. We have identified two zebrafish wnt8 paralogs related to Xwnt-8B and Xwnt-8, respectively. A RT-PCR assay demonstrated that wnt8 is expressed maternally, with transcripts detected throughout embryogenesis, whereas wnt8b transcripts were first detected during late gastrulation. The wnt8 transcripts at 50% epiboly are spatially restricted to those cells at the blastoderm margin, overlying gsc-expressing cells in the axial hypoblast. During late gastrulation, wnt8 was no longer detected in the marginal cells at the dorsal midline and by mid-segmentation, transcripts were found in the presumptive tail bud. In contrast, wnt8b expression is spatially restricted to prospective neuroepithelium, and later to neural-specific structures. Overexpression of both wnts results in two major phenotypes: radialized embryos and embryos with anterior defects. These phenotypes were preceded by significant changes in the spatial expression patterns of gsc and ntl transcripts, reminiscent of activities of Xwnt-8 in Xenopus, and consistent with a role for wnt8 in the specification or patterning of mesoderm.

Embryo Sac Morpho-structural Analysis of Developmental Pathways of Fertilization Failure, Seed Abortion and Poor Germination in Cassava (Manihot esculenta Crantz).

Embryo sac developmental examination in four cultivated Asian cassava clones: ‘Rayong 3’ (MMex 57×Mven 307), ‘Rayong 60’ (MCol 1684×Rayong 1), ‘Rayong 90’ (CMC 76×V 43, Sarakarn 1993), and ‘CMR 25-105-112’ (27-77-10×Rayong 3, Kawano et al. 1990) was conducted to elucidate the reproductive and conventional breeding barriers (fertilization failure, seed abortion and poor germination) in the genus Manihot. Late pre- and post-pollination embryology revealed absence of functional megaspore mother cell and megagametophytes respectively. Malformed megagametophytes were characterized with reduction in embryo sac volume (8-12.5% of normal), devoid of nucleate cells especially, polar and the antipodal cells, massively vacuolated with no recognizable zygotes or embryos. Regular embryo sacs commenced degeneration 8 days after anthesis in unfertilized ovules of all zero pollinated pistils. Degeneration signal initiated from its thin cell wall and transducted radially inwards and outwards to the central cell and the surrounding nucellus respectively. Both integuments (inner and outer) as well as the nucellus of functional (possessing nucleate cells) and non-functional (deprived of nucleate cells) megagametophytes appeared healthy and developed normally. Physical seed analysis showed that phenotypically normal but functionally deprived ‘pseudo-seed’ (without endosperm and embryo) and ‘true seed’ are produced at a ratio of approximately 1:2. Two distinct but complementary developmental pathways of fertilization failure, seed abortion as well as poor germination in cassava have been identified. They are: 1. Ovules devoid of functional megaspore due to lack of megasporocyte during megasporogenesis and 2. Embryo sacs devoid of nucleate cells due to mitotic inactivity at megagametogenesis resulting in structurally and functionally deprived megagametophyte but morphologically normal ovules. These pathways, either separately or collectively are implicated as largely responsible for the reproductive and conventional breeding barriers in the genus Manihot.

Chromophore-assisted laser inactivation of patched protein switches cell fate in the larval visual system of Drosophila.

The Drosophila segment-polarity gene patched (ptc) is an integral component of the segmentation gene cascade acting in the early embryo. At later stages of embryogenesis, ptc is expressed in the primordia of epithelial placodes of a specific portion of the brain, the optic lobes. Mutant analysis shows that the lack of ptc activity alters the fate of optic-lobe primordia precursors. In ptc mutants they give rise to supernumerary neurons in the larval light-sensory system, termed Bolwig organ, which is derived from precursor cells next to the optic-lobe anlagen. We specifically eliminated ptc protein by chromophore-assisted laser inactivation (CALI) in late wild-type embryos. Such embryos show a normal segment pattern, but they develop phenocopies equivalent to the phenotype of ptc mutant Bolwig organs. Our results demonstrate that the CALI technique can be applied to separate genetic functions at different developmental stages of a living organism and that the segment-polarity gene ptc is redeployed to functionally discriminate between distinct developmental pathways in adjacent pools of precursor cells.

An investigation of the specification of unequal cleavages in leech embryos

Leech embryos develop via stereotyped cell divisions, many of which are unequal. The first division generates identifiable cells, blastomeres AB and CD, which normally follow distinct developmental pathways. When these two cells are dissociated and cultured in isolation, their fates remain distinct and are reminiscent of normal development, but their typical cleavage patterns are disrupted; cell AB undergoes relatively few cell divisions, giving rise to a variable number of macromeres and micromeres, while cell CD cleaves many times, usually forming a poorly organized set of macromeres, embryonic stem cells (teloblasts), and micromeres. We have investigated the hypothesis that the abnormal cleavage pattern of isolated CD blastomeres is due to removal of mechanical constraints normally imposed by cell AB. We find that when cell CD is constrained in vitro to mimic its in vivo shape, it cleaves more normally.