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The diversity in the skeletal features of coral species is an outcome of their evolution, distribution and habitat. Here, we explored, from macro- to nano-scale, the skeletal structural and compositional characteristics of three coral species belonging to the genus Balanophyllia having different trophic strategies. The goal is to address whether the onset of mixotrophy influenced the skeletal features of B. elegans, B. regia, and B. europaea. The macroscale data suggest that the presence of symbiotic algae in B. europaea can lead to a surplus of energy input that increases its growth rate and skeletal bulk density, leading to larger and denser corals compared to the azooxanthellate ones, B. regia and B. elegans. The symbiosis would also explain the higher intra-skeletal organic matrix (OM) content, which is constituted by macromolecules promoting the calcification, in B. europaea compared to the azooxanthellate species. The characterization of the soluble OM also revealed differences between B. europaea and the azooxanthellate species, which may be linked to diverse macromolecular machineries responsible for skeletal biosynthesis and final morphology. Differently, the crystallographic features were homogenous among species, suggesting that the basic building blocks of skeletons remained a conserved trait in these related species, regardless of the trophic strategy. These results show changes in skeletal phenotype that could be triggered by the onset of mixotrophy, as a consequence of the symbiotic association, displaying remarkable plasticity of coral skeletons which repeatedly allowed this coral group to adapt to a range of changing environments throughout its geological history.

The diversity in the skeletal features of coral species is an outcome of their evolution, distribution and habitat. Here, we explored, from macro- to nano-scale, the skeletal structural and compositional characteristics of three coral species belonging to the genus Balanophyllia having different trophic strategies. The goal is to address whether the onset of mixotrophy influenced the skeletal features of B. elegans, B. regia, and B. europaea. The macroscale data suggest that the presence of symbiotic algae in B. europaea can lead to a surplus of energy input that increases its growth rate and skeletal bulk density, leading to larger and denser corals compared to the azooxanthellate ones, B. regia and B. elegans. The symbiosis would also explain the higher intra-skeletal organic matrix (OM) content, which is constituted by macromolecules promoting the calcification, in B. europaea compared to the azooxanthellate species. The characterization of the soluble OM also revealed differences between B. europaea and the azooxanthellate species, which may be linked to diverse macromolecular machineries responsible for skeletal biosynthesis and final morphology. Differently, the crystallographic features were homogenous among species, suggesting that the basic building blocks of skeletons remained a conserved trait in these related species, regardless of the trophic strategy. These results show changes in skeletal phenotype that could be triggered by the onset of mixotrophy, as a consequence of the symbiotic association, displaying remarkable plasticity of coral skeletons which repeatedly allowed this coral group to adapt to a range of changing environments throughout its geological history.

Spherulites are radial distributions of acicular crystals, common in biogenic, geologic, and synthetic systems, yet exactly how spherulitic crystals nucleate and grow is still poorly understood. To investigate these processes in more detail, we chose scleractinian corals as a model system, because they are well known to form their skeletons from aragonite (CaCO3) spherulites, and because a comparative study of crystal structures across coral species has not been performed previously. We observed that all 12 diverse coral species analyzed here exhibit plumose spherulites in their skeletons, with well-defined centers of calcification (CoCs), and crystalline fibers radiating from them. In 7 of the 12 species, we observed a skeletal structural motif not observed previously: randomly oriented, equant crystals, which we termed "sprinkles". In Acropora pharaonis, these sprinkles are localized at the CoCs, while in 6 other species, sprinkles are either layered at the growth front (GF) of the spherulites, or randomly distributed. At the nano- and micro-scale, coral skeletons fill space as much as single crystals of aragonite. Based on these observations, we tentatively propose a spherulite formation mechanism in which growth front nucleation (GFN) of randomly oriented sprinkles, competition for space, and coarsening produce spherulites, rather than the previously assumed slightly misoriented nucleations termed "non-crystallographic branching". Phase-field simulations support this mechanism, and, using a minimal set of thermodynamic parameters, are able to reproduce all of the microstructural variation observed experimentally in all of the investigated coral skeletons. Beyond coral skeletons, other spherulitic systems, from aspirin to semicrystalline polymers and chocolate, may also form according to the mechanism for spherulite formation proposed here. STATEMENT OF SIGNIFICANCE: Understanding the fundamental mechanisms of spherulite nucleation and growth has broad ranging applications in the fields of metallurgy, polymers, food science, and pharmaceutical production. Using the skeletons of reef-building corals as a model system for investigating these processes, we propose a new spherulite growth mechanism that can not only explain the micro-structural diversity observed in distantly related coral species, but may point to a universal growth mechanism in a wide range of biologically and technologically relevant spherulitic materials systems.

Spherulites are radial distributions of acicular crystals, common in biogenic, geologic, and synthetic systems, yet exactly how spherulitic crystals nucleate and grow is still poorly understood. To investigate these processes in more detail, we chose scleractinian corals as a model system, because they are well known to form their skeletons from aragonite (CaCO3) spherulites, and because a comparative study of crystal structures across coral species has not been performed previously. We observed that all 12 diverse coral species analyzed here exhibit plumose spherulites in their skeletons, with well-defined centers of calcification (CoCs), and crystalline fibers radiating from them. In 7 of the 12 species, we observed a skeletal structural motif not observed previously: randomly oriented, equant crystals, which we termed "sprinkles". In Acropora pharaonis, these sprinkles are localized at the CoCs, while in 6 other species, sprinkles are either layered at the growth front (GF) of the spherulites, or randomly distributed. At the nano- and micro-scale, coral skeletons fill space as much as single crystals of aragonite. Based on these observations, we tentatively propose a spherulite formation mechanism in which growth front nucleation (GFN) of randomly oriented sprinkles, competition for space, and coarsening produce spherulites, rather than the previously assumed slightly misoriented nucleations termed "non-crystallographic branching". Phase-field simulations support this mechanism, and, using a minimal set of thermodynamic parameters, are able to reproduce all of the microstructural variation observed experimentally in all of the investigated coral skeletons. Beyond coral skeletons, other spherulitic systems, from aspirin to semicrystalline polymers and chocolate, may also form according to the mechanism for spherulite formation proposed here. STATEMENT OF SIGNIFICANCE: Understanding the fundamental mechanisms of spherulite nucleation and growth has broad ranging applications in the fields of metallurgy, polymers, food science, and pharmaceutical production. Using the skeletons of reef-building corals as a model system for investigating these processes, we propose a new spherulite growth mechanism that can not only explain the micro-structural diversity observed in distantly related coral species, but may point to a universal growth mechanism in a wide range of biologically and technologically relevant spherulitic materials systems.

UnlabelledWe assessed the association between the single-nucleotide polymorphism (SNP) rs58542926 in the transmembrane 6 superfamily member 2 (TM6SF2) gene and fatty liver disease in obese youth. We genotyped the TM6SF2 rs58542926 SNP in a multiethnic cohort of 957 obese children and adolescents (42% Caucasians, 28% African Americans, 30% Hispanics). All underwent an oral glucose tolerance test, a liver panel, and a lipid profile. Of them, 454 children underwent a magnetic resonance imaging study to assess hepatic fat content and 11 underwent liver biopsy to assess the degree of disease severity. The minor allele of the rs58542926 SNP was associated with high hepatic fat content in Caucasians and African Americans (all P < 0.05), with high alanine aminotransferase levels in Hispanics (P < 0.05) and a more favorable lipoprotein profile (lower low-density lipoprotein, small dense low-density lipoprotein, and very small low-density lipoprotein) in Caucasians and Hispanics (all P < 0.05). The liver biopsy showed a higher prevalence of fibrosis (P = 0.04) and a higher nonalcoholic fatty liver disease activity score (P = 0.05) in subjects carrying the minor allele than in those homozygous for the common allele. Moreover, we observed a joint effect among the TM6SF2 rs58542926, the PNPLA3 rs738409, and the GCKR rs1260326 SNPs in determining intrahepatic fat accumulation (P < 0.05).ConclusionThe rs58542926 SNP in the TM6SF2 gene is associated with pediatric nonalcoholic fatty liver disease but may confer protection against cardiovascular risk.

BackgroundTall cell variant (TCV) and diffuse sclerosing variant (DSV) of papillary thyroid cancer are aggressive subtypes, for which tumors ≤1 cm have not been exclusively studied.MethodsThe SEER database (1988-2009) was used to compare characteristics of TCV ≤1 cm (mTCV) and DSV ≤1 cm (mDSV) with classic papillary thyroid microcarcinoma (mPTC). Survival was analyzed with the Kaplan-Meier method and log-rank test, and risk factors for nodal metastases with chi-square analysis and binary logistic regression.ResultsThere were 97 mTCV, 90 mDSV, and 18,260 mPTC patients. mTCV incidence increased by 79.9% (p=0.153) over the study period, while mDSV incidence decreased by 10.3% (p=0.315). Compared to classic mPTC, mTCV tended to be larger on average (7.1 mm vs. 5.3 mm, p7 mm (odds ratio (OR) 4.4 [CI 1.5-13.6]) and nodal metastasis with multifocality (OR 5.4 [CI 1.3-23.4]) and extrathyroidal extension (OR 5.8 [CI 1.3-25.4]). No statistically significant predictors of extrathyroidal extension or nodal metastasis in mDSV were observed.ConclusionsAggressive variants of mPTC tend to exhibit more aggressive pathologic characteristics than classic mPTC, but survival appears to be similar. Treatment with total thyroidectomy and central lymphadenectomy may be warranted if the diagnosis can be made pre- or intraoperatively.