The dynamics of secretion during sea urchin embryonic skeleton formation

Wilt, Fred H.; Killian, Christopher E.; Hamilton, Patricia; Croker, Lindsay

doi:10.1016/j.yexcr.2008.01.036

Cited by 58 publications

(61 citation statements)

References 33 publications

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“…Calcein is a fluorescent calcium-binding dye that does not permeate through membranes, channels, or pumps. Calcein was shown to enter the PMCs and label intracellular calcium and the spicules (22,24,25,28,29). In a correlative study, it was shown that calcein labeling does faithfully track calcium distributions (24), and this is assumed to be the case in the study presented here.…”

supporting

confidence: 50%

Calcium transport into the cells of the sea urchin larva in relation to spicule formation

Vidavsky

Addadi

Schertel

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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We investigated the manner in which the sea urchin larva takes up calcium from its body cavity into the primary mesenchymal cells (PMCs) that are responsible for spicule formation. We used the membrane-impermeable fluorescent dye calcein and alexa-dextran, with or without a calcium channel inhibitor, and imaged the larvae in vivo with selective-plane illumination microscopy. Both fluorescent molecules are taken up from the body cavity into the PMCs and ectoderm cells, where the two labels are predominantly colocalized in particles, whereas the calcium-binding calcein label is mainly excluded from the endoderm and is concentrated in the spicules. The presence of vesicles and vacuoles inside the PMCs that have openings through the plasma membrane directly to the body cavity was documented using high-resolution cryo-focused ion beam-SEM serial imaging. Some of the vesicles and vacuoles are interconnected to form large networks. We suggest that these vacuolar networks are involved in direct sea water uptake. We conclude that the calcium pathway from the body cavity into cells involves nonspecific endocytosis of sea water with its calcium.

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supporting

confidence: 50%

Calcium transport into the cells of the sea urchin larva in relation to spicule formation

Vidavsky

Addadi

Schertel

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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“…The rays elongate rapidly for Ϸ3 days, while the existing rays thicken. ACC is most probably introduced into the mineralization site by the cells in vesicles that fuse with the syncytial membrane (15). The spicule is tightly surrounded by this membrane, with no interstitial water solution detectable at any stage (16).…”

mentioning

confidence: 99%

Transformation mechanism of amorphous calcium carbonate into calcite in the sea urchin larval spicule

Politi

Metzler²,

Abrecht³

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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385

423

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Sea urchin larval spicules transform amorphous calcium carbonate (ACC) into calcite single crystals. The mechanism of transformation is enigmatic: the transforming spicule displays both amorphous and crystalline properties, with no defined crystallization front. Here, we use X-ray photoelectron emission spectromicroscopy with probing size of 40–200 nm. We resolve 3 distinct mineral phases: An initial short-lived, presumably hydrated ACC phase, followed by an intermediate transient form of ACC, and finally the biogenic crystalline calcite phase. The amorphous and crystalline phases are juxtaposed, often appearing in adjacent sites at a scale of tens of nanometers. We propose that the amorphous-crystal transformation propagates in a tortuous path through preexisting 40- to 100-nm amorphous units, via a secondary nucleation mechanism.

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“…Many genes, including many of the downstream effector genes that were identified in the present study, show non-uniform patterns of expression within the PMC syncytium, with high levels of transcripts accumulating at sites of skeletal rod growth (Harkey et al, 1992; Guss et al, 1997). There is evidence from the expression of transgenes within the PMC syncytium that mRNAs remain localized predominantly in the PMC cell body in which they were synthesized (Harkey et al, 1995;Makabe et al, 1995;Wilt et al, 2008), a finding which suggests that local variations in mRNA abundance within the syncytium arise through the local regulation of gene transcription, rather than by an indirect mechanism (e.g. the diffusion and selective trapping of mRNAs).…”

Section: Regulation Of the Pmc Grn By Extrinsic Signalsmentioning

confidence: 99%

The genomic regulatory control of skeletal morphogenesis in the sea urchin

2012

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SUMMARYA central challenge of developmental and evolutionary biology is to understand how anatomy is encoded in the genome. Elucidating the genetic mechanisms that control the development of specific anatomical features will require the analysis of model morphogenetic processes and an integration of biological information at genomic, cellular and tissue levels. The formation of the endoskeleton of the sea urchin embryo is a powerful experimental system for developing such an integrated view of the genomic regulatory control of morphogenesis. The dynamic cellular behaviors that underlie skeletogenesis are well understood and a complex transcriptional gene regulatory network (GRN) that underlies the specification of embryonic skeletogenic cells (primary mesenchyme cells, PMCs) has recently been elucidated. Here, we link the PMC specification GRN to genes that directly control skeletal morphogenesis. We identify new gene products that play a proximate role in skeletal morphogenesis and uncover transcriptional regulatory inputs into many of these genes. Our work extends the importance of the PMC GRN as a model developmental GRN and establishes a unique picture of the genomic regulatory control of a major morphogenetic process. Furthermore, because echinoderms exhibit diverse programs of skeletal development, the newly expanded sea urchin skeletogenic GRN will provide a foundation for comparative studies that explore the relationship between GRN evolution and morphological evolution. KEY WORDS: Gene regulatory network, Primary mesenchyme, Sea urchin, Skeletal morphogenesis, SkeletonThe genomic regulatory control of skeletal morphogenesis in the sea urchin Kiran Rafiq, Melani S. Cheers and Charles A. Ettensohn* DEVELOPMENT 580 this library allowed us to identify several components of the PMC GRN, including delta (Sweet et al., 2002), the transcription factors alx1 and erg (Zhu et al., 2001; Ettensohn et al., 2003), and several biomineralization-related genes (Illies et al., 2002; Cheers and Ettensohn, 2005;Livingston et al., 2006). In the present study, we greatly expand the current PMC GRN model by identifying many additional morphoregulatory genes and by uncovering regulatory inputs into these genes. Our work extends the value of the PMC GRN as a model developmental GRN and establishes a framework for understanding the genomic circuitry that encodes a major anatomical feature. MATERIALS AND METHODS Embryo cultureStrongylocentrotus purpuratus embryos were obtained and cultured at 15°C as described previously (Zhu et al., 2001). The PMC cDNA library and expressed sequence tag (EST) collectionThe construction and arraying of the PMC cDNA library has been described (Zhu et al., 2001;Livingston et al., 2006). Briefly, the library was generated from polyA(+) RNA that was isolated from micromeres (presumptive PMCs) that were cultured until sibling control embryos reached the mid-gastrula stage, ~36 hours post-fertilization. The cDNA library was not normalized or subtracted in any way. Reverse transcription was primed usin...

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The dynamics of secretion during sea urchin embryonic skeleton formation

Cited by 58 publications

References 33 publications

Calcium transport into the cells of the sea urchin larva in relation to spicule formation

Calcium transport into the cells of the sea urchin larva in relation to spicule formation

Transformation mechanism of amorphous calcium carbonate into calcite in the sea urchin larval spicule

The genomic regulatory control of skeletal morphogenesis in the sea urchin

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