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PubMed1997

Control of cell fates and segmentation in the Drosophila mesoderm.

The primordia for heart, fat body, and visceral and somatic muscles arise in specific areas of each segment in the Drosophila mesoderm. We show that the primordium of the somatic muscles, which expresses high levels of twist, a crucial factor of somatic muscle determination, is lost in sloppy-paired mutants. Simultaneously, the primordium of the visceral muscles is expanded. The visceral muscle and fat body primordia require even-skipped for their development and the mesoderm is thought to be unsegmented in even-skipped mutants. However, we find that even-skipped mutants retain the segmental modulation of the expression of twist. Both the domain of even-skipped function and the level of twist expression are regulated by sloppy-paired. sloppy-paired thus controls segmental allocation of mesodermal cells to different fates.

Animals↗
PubMed2005

Non-uniformity in the regional pattern of Lewy pathology in brains of dementia with Lewy bodies.

We examined the regional pattern of Lewy pathology in brains of dementia with Lewy bodies (DLB) to clarify whether Lewy pathology uniformly progresses or not. Thirty-five autopsied DLB cases were examined using alpha-synuclein-immunohistochemistry, and the regional degree of Lewy pathology in the brainstem, diencephalon and cerebral cortex was quantitatively evaluated. Consequently, we found that the regional pattern of Lewy pathology differed according to the pathological subtype, and was divided into three types: type 1 showed a brainstem-predominant pattern, type 2 was almost equal for the brainstem and cerebral cortex, and type 3 showed a cerebral cortex-predominant pattern. The limbic type/pure and common forms were mainly composed of type 1, whereas the neocortical type/common and Alzheimer's disease (AD) forms were mainly composed of type 3. These findings suggest the possibility that Lewy pathology of the limbic type/pure and common forms mainly progresses from the brainstem to the cerebrum, whereas that of the neocortical type/common and AD forms mainly progresses from the cerebrum to the brainstem. Cases with type 1 Lewy pathology mainly developed parkinsonism, whereas those with type 3 Lewy pathology mainly developed dementia. This corresponded to most of the limbic type/ pure and common forms which developed parkinsonism, whereas most of the neocortical type/common and AD forms developed dementia. Type 1 cases may thus be clinically diagnosed as having Parkinson's disease (PD) with dementia. These findings suggest that PD has clinico-pathological continuity with DLB, and that the regional pattern of Lewy pathology is not uniform.

Aged↗
PubMed1998

Curve walking in freely moving crayfish (Procambarus clarkii)

The curve walking of freely moving crayfish trained to walk along a curved path during homing behaviour was investigated using a video-analysis system. The leg kinematics and leg phase relationships, as well as the relationship between stepping patterns and body axis rotation measured relative to external references, were studied. The anterior and posterior extreme positions of the power stroke (AEP and PEP, respectively) and step amplitudes were analysed. As in a previous study on crayfish curve walking on a treadmill, PEPs were more posterior in outer legs (the legs on the outside of the turn) than in the inner legs. As a result, outer legs showed larger step amplitudes than inner legs. Leg kinematics varied within each walking sequence. AEP leg angles (the angles between the body and leg axes at the AEP) tended to decrease over time for inner legs and increase for outer legs. This leg angle drift was present mainly in the anterior legs and it suggests that these legs did not completely compensate for the body rotation after each step. In addition, leg angle asymmetries in a direction opposite to that of leg angle drift were observed at the start of each curve-walking sequence, suggesting that the extensive training (3 weeks) may have allowed crayfish to anticipate the leg angle drift. The rotational component of curve walking showed a discontinuous pattern, with the animal's body axis turning towards the inside of the curve only periodically. Analysis of cross-correlation functions showed that the angular acceleration of the body axis in the direction of the turn occurred during the power strokes of inner legs 2 and 5 and outer leg 4. While the tripod formed by these three legs showed in-phase relationships, the legs of the corresponding contralateral tripod (outer legs 2 and 5 and inner leg 4) were not in phase. We hypothesize that inner legs 2 and 5 and outer leg 4 act synergically causing the inward body rotation observed in curve-walking crayfish and that some of the asymmetries found in step geometry may be a passive phenomenon due to the body rotation.

Journal Article↗
PubMed2004

Opposing FGF and retinoid pathways: a signalling switch that controls differentiation and patterning onset in the extending vertebrate body axis.

Construction of the trunk/caudal region of the vertebrate embryo involves a set of distinct molecules and processes whose relationships are just coming into focus. In addition to the subdivision of the embryo into head and trunk domains, this "caudalisation" process requires the establishment and maintenance of a stem zone. This sequentially generates caudal tissues over a long period which then undergo differentiation and patterning in the extending body axis. Here we review recent studies that show that changes in the signalling properties of the paraxial mesoderm act as a switch that controls onset of differentiation and pattern in the spinal cord. These findings identify distinct roles for different caudalising factors; in particular, Fibroblast Growth Factor (FGF) inhibits differentiation in the caudal stem zone, while Retinoic acid (RA) provided rostrally by somitic mesoderm is required for neuronal differentiation and establishment of ventral neural pattern. Furthermore, the mutual opposition of FGF and RA pathways controls not only neural differentiation but also mesoderm segmentation and might also underlie the progressive assignment of rostrocaudal identity by regulating Hox gene availability and activation.

Animals↗
PubMed2000

Extracellular matrix environment influences chondrogenic pattern formation in limb bud micromass culture: experimental verification of theoretical models.

Various theoretical models have been proposed to explain the periodicity in the pattern of limb chondrogenesis, but experimental comparison of these models have seldom been performed properly. In the present study, micromass culture of limb bud mesenchyme cells was undertaken to test the validity of three theoretical models: the reaction-diffusion model, the cell sorting model, and the mechanochemical model. Computer simulations were undertaken to predict the factors that can affect the coarseness of the chondrogenic pattern. According to the predictions, we performed micromass culture of limb mesenchyme in collagen and agarose gel. Then we carried out time-lapse observation to analyze the cell movement during pattern formation. From computer simulations it was theoretically predicted that changes in the surrounding extracellular matrix should alter the periodicity of the chondrogenic pattern in vitro, and we found that pattern changes actually occurred under different culture conditions. When compared with the culture in a liquid medium, the chondrogenic pattern became less coarse when the cells were cultured in collagen or agarose gel, and the pattern change appeared to be independent of the cell differentiation. Time-lapse observation revealed a decrease in cell motility when the cells were cultured in gel. It was found that both the reaction-diffusion and cell sorting models fit the pattern change produced and that the mechanochemical model is not primarily important in the chondrogenic pattern formation in vitro.

Agar↗
PubMed1996

Germ cell-specific DNA and RNA binding proteins p48/52 are expressed at specific stages of male germ cell development and are present in the chromatoid body.

Proteins homologous to the Xenopus oocyte mRNA binding proteins mRNP3+4 and designated p48/52 have been identified in male mouse germ cells (1993: Dev Biol 158:90-100). Western and North-western blots of extracts from testes and isolated germ cells indicate that p48/52 are present during meiosis but reach their highest levels postmeiotically at a time when many mRNAs are stored. Here we analyze the cellular and subcellular distribution of p48/52 in rat and mouse testes by LM and EM immunocytochemistry using an anti-mRNP3+4 antibody. Immunolabeling was found to be predominantly cytoplasmic and specific to germ cells at certain periods during their development. p48/52 were first detected in early pachytene spermatocytes at stage V of the seminiferous cycle and progressively increased during the remainder of meiotic prophase to a post-meiotic peak in steps 1-8 round spermatids; thereafter, labeling gradually declined as elongated spermatids underwent nuclear condensation and elongation. A proportionally higher concentration of cytoplasmic immunolabeling was found within the lacunae of the anastomotic granulofilamentous network of the chromatoid body. The pattern of synthesis of these mRNA binding proteins together with their association with the chromatoid body suggests a role as germ cell-specific mRNA stabilizing and/or storage proteins.

Animals↗
PubMed2000

Molecular mechanisms of development of the gastrointestinal tract.

The gut offers a complex but rich organ system to study visceral pattern formation. The gut is an early evolutionary advance. Data supports that the molecular controls of gut pattern formation are be conserved across species. The gut develops in a stereotyped manner in many different species, by using a basic mechanism of development, the epithelial-mesenchymal interaction. Signaling between the endoderm and mesoderm is essential for normal gut development. The signaling molecules involved are just being described and include factors known to be critical in embryonic development of other systems. The gut has four major patterned axes: anterior-posterior (AP), dorsal-ventral (DV), left-right (LR), and radial (RAD). The molecular pathways used to control pattern in each of these axes are the subject of this review. Major advances in the understanding of AP and LR axis formation in the gut have been described within the past few years. RAD and DV axes are now hot topics for investigation. Despite advances in these areas of gut development, basic events remain poorly understood. Discovery of specific factors that control gut pattern formation may provide a template for the study of pattern formation in other visceral/organ systems.

Animals↗
PubMed2003

Neurocan in the embryonic avian heart and vasculature.

The chondroitin sulfate proteoglycan (CSPG) neurocan was previously considered to be nervous-system specific. However, we have found neurocan in the embryonic heart and vasculature. In stage 11 quail embryos, neurocan was prominently expressed in the myocardium, dorsal mesocardium, heart-forming fields, splanchnic mesoderm, and vicinity of the extraembryonic vaculature, and at lower levels in the endocardium. A comparison of neurocan staining with QH1 staining of vascular endothelial cells demonstrates that neurocan is frequently expressed by cells adjacent to endothelial cells, rather than by endothelial cells themselves. In some cases, a dispersed subset of cells are neurocan-positive in a field of cells that otherwise appear uniform in morphology. Later in development, neurocan expression becomes relatively limited to the nervous system. However, even in 10-day embryos, neurocan is expressed in the chorio-allantoic membrane in the tissue that separates closely packed, small-diameter blood vessels. In summary, our results suggest that neurocan may function as a barrier that regulates vascular patterning during development.

Animals↗
PubMed2005

Vertebrate myotome development.

The embryonic myotome generates both the axial musculature and the appendicular muscle of the fins and limbs. Early in embryo development the mesoderm is segmented into somites, and within these the primary myotome forms by a complex series of cellular movements and migrations. A new model of primary myotome formation in amniotes has emerged recently. The myotome also includes the muscle progenitor cells that are known to contribute to the secondary formation of the myotome. The adult myotome contains satellite cells that play an important role in adult muscle regeneration. Recent studies have shed light on how the growth and patterning of the myotome occurs.

Animals↗
PubMed2005

Pigment cell distributions in different tissues of the zebrafish, with special reference to the striped pigment pattern.

The orderly pigment pattern of zebrafish (Danio rerio) is a good model system for studying how spatial patterns form in animals. Recent molecular genetic studies have shown that interactions between the pigment cells play major roles in pattern formation. In the present study, we performed comparative transmission electron microscopy of pigment cells, in order to clarify the structural interactions of pigment cells in tissues with and without a striped pattern. In patterned tissues, pigment cells were distributed as a one-cell-thick sheet. The layer order of the sheets is always kept strictly. In tissues without a striped pattern, the layer order was often disturbed or the cells were distributed in a scattered, double-sheeted, or an accumulated pile. Our observations suggest that the underlying mechanism that controls the vertical order of the pigment cells is related to that controlling the stripe pattern.

Animals↗
PubMed2006

Tracheid analysis and modeling of the minor veins of the coleus and smilax leaves.

Tracheid analysis was carried out on the veinlets and minor veins of the coleus (Solenostemon scutellarioides [L.] Codd) leaf. Third- to fifth-order, or minor, veins average 3.4 tracheids in tandem and they bipartition islets when these enclosed islets reach a critical size; both these features of vein length and islet size contribute to a self-similar process of vein pattern generation. An areole was calculated to be initially comprised of about ten cells making the patterning event for vein formation requiring only a few cells. An algorithmic model developed here for minor vein formation includes five production rules, and this computer model explains the 3-4 tracheids per minor vein, presence of isolated tracheids, the structure of veinlets, and the elaborate branching patterns of veinlets in coleus and other plants.

Body Patterning↗
PubMed1998

Distalless expression in crustaceans and the patterning of branched limbs.

In Drosophila, Distalless (Dll) is critical in establishing the proximal/distal axis of the leg. Lack of proper Dll expression causes distal limb structures to be truncated or lost. Dll expression was examined through the course of development in the limbs of two crustaceans, Triops and Nebalia. Because the limbs of these two species are branched, they provide a comparison to the uniramous (unbranched) leg of Drosophila. In Triops and Nebalia, development of limb branches is not tightly coupled with Dll expression: in some cases, branches can arise prior to Dll expression and in others, certain branches never express Dll. These data suggest that, while Dll may indeed initiate overall limb outgrowth, limb branches are unlikely to be patterned by a simple iteration of the mechanism patterning the unbranched leg of Drosophila.

Animals↗