SUMMARYCell-matrix adhesion strongly influences developmental signaling. Resulting impacts on cell migration and tissue morphogenesis are well characterized. However, the in vivo impact of adhesion on fate induction remains ambiguous. Here, we employ the invertebrate chordate Ciona intestinalis to delineate an essential in vivo role for matrix adhesion in heart progenitor induction. In Ciona precardiac founder cells, invasion of the underlying epidermis promotes localized induction of the heart progenitor lineage. We found that these epidermal invasions are associated with matrix adhesion along the pre-cardiac cell/epidermal boundary. Through targeted manipulations of RAP GTPase activity, we were able to manipulate pre-cardiac cell-matrix adhesion. Targeted disruption of precardiac cell-matrix adhesion blocked heart progenitor induction. Conversely, increased matrix adhesion generated expanded induction. We were also able to selectively restore cell-matrix adhesion and heart progenitor induction through targeted expression of CiIntegrin β2. These results indicate that matrix adhesion functions as a necessary and sufficient extrinsic cue for regional heart progenitor induction. Furthermore, time-lapse imaging suggests that cytokinesis acts as an intrinsic temporal regulator of heart progenitor adhesion and induction. Our findings highlight a potentially conserved role for matrix adhesion in early steps of vertebrate heart progenitor specification.
Glycine is a major inhibitory neurotransmitter in the central nervous system of vertebrates. Here, we report the initial development of glycine-immunoreactive (Gly-ir) neurons and fibers in zebrafish. The earliest Gly-ir cells were found in the hindbrain and rostral spinal cord by 20 h post-fertilization (hpf). Gly-ir cells in rhombomeres 5 and 6 that also expressed glycine transporter 2 (glyt2) mRNA were highly stereotyped; they were bilaterally located and their axons ran across the midline and gradually turned caudally, joining the medial longitudinal fascicles in the spinal cord by 24 hpf. Gly-ir neurons in rhombomere 5 were uniquely identified, since there was one per hemisegment, whereas the number of Gly-ir neurons in rhombomere 6 were variable from one to three per hemisegment. Labeling of these neurons by single-cell electroporation and tracing them until the larval stage revealed that they became MiD2cm and MiD3cm, respectively. The retrograde labeling of reticulo-spinal neurons in Tg(glyt2:gfp) larva, which express GFP in Gly-ir cells, and a genetic mosaic analysis with glyt2:gfp DNA construct also supported this notion. Gly-ir cells were also distributed widely in the anterior brain by 27 hpf, whereas glyt2 was hardly expressed. Double staining with anti-glycine and anti-GABA antibodies demonstrated distinct distributions of Gly-ir and GABA-ir cells, as well as the presence of doubly immunoreactive cells in the brain and placodes. These results provide evidence of identifiable glycinergic (Gly-ir/glyt2-positive) neurons in vertebrate embryos, and they can be used in further studies of the neurons' development and function at the single-cell level.
Aim: Since decades, a major part of south-western coastal region of Bangladesh is being affected by water logging – a problem related to climate change along with some manmade activities. Therefore, the study was conducted to assess the causes and consequences of this problem and highlights the responses of affected people to attract policy planners’ intention for taking proper intervention. Place and Duration of Study: The study was conducted in the Laboratory of Plant Ecology, Department of Crop Botany, Bangladesh Agricultural University, Mymensingh, Bangladesh. Methodology: Qualitative and quantitative techniques have been applied to collect and analyze both the primary and secondary sources of data from various waterlogged areas of south west Bangladesh. Results: There is no single or a few factors are responsible for creating water-logging problem rather it is a combination of several factors and their cumulative effects over time. It is revealed from the analysis of primary and secondary sources of information that death of Mathavanga River in the 20th century, execution of Coastal Embankment Project since 1960’s, withdrawing water flow to the Padma River through operating the Farakka barrage after independent of Bangladesh, improper management of rivers, faulty land-use by influential people in the areas, monsoon downpour etc are major causes of the problem. The silted up river systems in area could not drain monsoon rain that occurred even for a couple of days. The consequences brought to inundate hundred thousand hectares of cultivable land unsuitable for crop production. More than one million people are directly affected in the areas and the number is gradually increasing over the years. Water stagnancy around the settlement areas remains 6 to 9 months in a year and many places became permanently waterlogged. The affected people have no other way out but to live with water. The congested water is polluted with salinity, chemical effluents with heavy metals, household debris’s and related other pollutants. Source of safe drinking water is destroyed. Therefore incidences of waterborne and skin diseases are increased. People are living with greatest inhumanity as food, shelter, sanitation, communications, educations and other prime needs are tremendously challenged. Many people lost their occupations and became destitute, some altered their livelihood to much lower grades, and many of them are forced to migrate to city areas. The marooned people demanded to the authority to declare their places as an affected area and sought the government intervention to bring an end to the crisis through operating the Tidal River Management plan and excavating or re-excavating of associated rivers, channels and rivulets. Conclusion: The authority need to pay keen attention to the issue and should take proper initiative to mitigate the water-logging problem permanently to save people living in the south western coastal region of Bangladesh.
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