RNA-Seq identifies SPGs as a ventral skeletal patterning cue in sea urchins

Abstract

The sea urchin larval skeleton offers a simple model for formation of developmental patterns. The calcium carbonate skeleton is secreted by primary mesenchyme cells (PMCs) in response to largely unknown patterning cues expressed by the ectoderm. To discover novel ectodermal cues, we performed an unbiased RNA-Seq-based screen and functionally tested candidates; we thereby identified several novel skeletal patterning cues. Among these, we show that SLC26a2/7 is a ventrally expressed sulfate transporter that promotes a ventral accumulation of sulfated proteoglycans, which is required for ventral PMC positioning and skeletal patterning. We show that the effects of SLC perturbation are mimicked by manipulation of either external sulfate levels or proteoglycan sulfation. These results identify novel skeletal patterning genes and demonstrate that ventral proteoglycan sulfation serves as a positional cue for sea urchin skeletal patterning.

The small GTPase Arf6 regulates sea urchin morphogenesis

“…This may be due to defects in the ability of PMCs to receive chemotactic cues, to form a syncytium, or to migrate in general. To address these questions, we first assayed for the transcript level changes of VegfR10 , Vegf3 and Prestin that had previously been shown to be important for directed migration of PMCs (Adomako-Ankomah and Ettensohn, 2013; Duloquin et al, 2007; Lapraz et al, 2006; Piacentino et al, 2016; Sodergren et al, 2006), as well as genes Kirrell and Hypp1164 that may regulate PMC fusion (Rafiq et al, 2014) (Fig. S6A).…”

Function and regulation of microRNA‐31 in development and disease

“…For proper skeletogenesis, the PMCs need to differentiate, undergo an epithelial‐to‐mesenchymal transition, fuse with each other, and localize into the correct pattern (Sharma and Ettensohn, ; Rafiq et al, ; Lyons et al, ; Saunders and McClay, ; McClay, ). The complexity of the signals received by the PMCs is not known, but the process of PMC positioning or patterning is, in part, dependent on VEGF (Vascular Endothelial Growth Factor) signaling, ALK4/5/7 (Transforming Growth Factor Beta receptors), SLC26A2/7 (Solute Carriers 26a2 and 7), LOX (Lipoxygenase), and BMP5/8 (Bone Morphogenetic Proteins 5 and 8) (Duloquin et al, ; Adomako‐Ankomah and Ettensohn, , ; Piacentino et al, , ,). Knockdown of miR‐31 resulted in a significant decrease in the length of dorsoventral connecting rods, formation of extra tri‐radiates, as well as PMC patterning defects in the sea urchin gastrulae (Stepicheva and Song, ).…”

A Conserved Role for VEGF Signaling in Specification of Homologous Mesenchymal Cell Types Positioned at Spatially Distinct Developmental Addresses in Early Development of Sea Urchins

“…Thus, if SM requires stimulation of VEGF receptor to alter gene expression, and thereby their future migratory behavior, it stands to reason that at the time of their ingression little to no VEGF ligand is in the blastocoel to induce the behavioral change. Thus, the random, directionless movement initially seen in E. tribuloides SM may be explained by the duration of ligand production and secretion, as well as its subsequent diffusion into a blastocoel filled with sulfated macromolecules that may play a role in SM migration (Katow and Solursh, ; Solursh and Katow, ; Fujita et al., ; Piacentino et al., ). An experimental hypothesis motivated by these observations is that overexpression of vegf RNA in this echinoid should diminish the observed random movement.…”

“…In euechinoids, proper positioning of SM into their ring‐like alignment after their ingression into the blastocoel, as well as their specification, requires cues from VEGF and FGF signaling in the nearby ectoderm (Duloquin et al., ; Röttinger et al., ; Adomako‐Ankomah and Ettensohn, ; McIntyre et al., ; Piacentino et al., ). In the euechinoid echinoids Paracentrotus lividus, Hemicentrotus pulcherrimus, Strongylocentrotus purpuratus , and Lytechinus variegatus , mRNA of vegf (also called vegf3 ) is spatially restricted proximal to the sites of spiculogenesis at two ventrolateral positions near the endodermal‐ectodermal boundary, and mRNA of its receptor vegfr is expressed specifically in the SM lineage (Duloquin et al., ; Fujita et al., ; Li et al., ; Adomako‐Ankomah and Ettensohn, ).…”