Plate-like Guanine Biocrystals Form via Templated Nucleation of Crystal Leaflets on Preassembled Scaffolds

Controlling the morphology of crystalline materials is challenging, as crystals have a strong tendency toward thermodynamically stable structures. Yet, organisms form crystals with distinct morphologies, such as the plate-like guanine crystals produced by many terrestrial and aquatic species for light manipulation. Regulation of crystal morphogenesis was hypothesized to entail physical growth restriction by the surrounding membrane, combined with fine-tuned interactions between organic molecules and the growing crystal. Using cryo-electron tomography of developing zebrafish larvae, we found that guanine crystals form via templated nucleation of thin leaflets on preassembled scaffolds made of 20-nm-thick amyloid fibers. These leaflets then merge and coalesce into a single plate-like crystal. Our findings shed light on the biological regulation of crystal morphogenesis, which determines their optical properties

Plate-like Guanine Biocrystals Form via Templated Nucleation of Crystal Leaflets on Preassembled Scaffolds

Controlling the morphology of crystalline materials is challenging, as crystals have a strong tendency toward thermodynamically stable structures. Yet, organisms form crystals with distinct morphologies, such as the plate-like guanine crystals produced by many terrestrial and aquatic species for light manipulation. Regulation of crystal morphogenesis was hypothesized to entail physical growth restriction by the surrounding membrane, combined with fine-tuned interactions between organic molecules and the growing crystal. Using cryo-electron tomography of developing zebrafish larvae, we found that guanine crystals form via templated nucleation of thin leaflets on preassembled scaffolds made of 20-nm-thick amyloid fibers. These leaflets then merge and coalesce into a single plate-like crystal. Our findings shed light on the biological regulation of crystal morphogenesis, which determines their optical properties

Plate-like Guanine Biocrystals Form via Templated Nucleation of Crystal Leaflets on Preassembled Scaffolds

Controlling the morphology of crystalline materials is challenging, as crystals have a strong tendency toward thermodynamically stable structures. Yet, organisms form crystals with distinct morphologies, such as the plate-like guanine crystals produced by many terrestrial and aquatic species for light manipulation. Regulation of crystal morphogenesis was hypothesized to entail physical growth restriction by the surrounding membrane, combined with fine-tuned interactions between organic molecules and the growing crystal. Using cryo-electron tomography of developing zebrafish larvae, we found that guanine crystals form via templated nucleation of thin leaflets on preassembled scaffolds made of 20-nm-thick amyloid fibers. These leaflets then merge and coalesce into a single plate-like crystal. Our findings shed light on the biological regulation of crystal morphogenesis, which determines their optical properties

Plate-like Guanine Biocrystals Form via Templated Nucleation of Crystal Leaflets on Preassembled Scaffolds

Controlling the morphology of crystalline materials is challenging, as crystals have a strong tendency toward thermodynamically stable structures. Yet, organisms form crystals with distinct morphologies, such as the plate-like guanine crystals produced by many terrestrial and aquatic species for light manipulation. Regulation of crystal morphogenesis was hypothesized to entail physical growth restriction by the surrounding membrane, combined with fine-tuned interactions between organic molecules and the growing crystal. Using cryo-electron tomography of developing zebrafish larvae, we found that guanine crystals form via templated nucleation of thin leaflets on preassembled scaffolds made of 20-nm-thick amyloid fibers. These leaflets then merge and coalesce into a single plate-like crystal. Our findings shed light on the biological regulation of crystal morphogenesis, which determines their optical properties

Cellular and metabolic characteristics of pre-leukemic hematopoietic progenitors with GATA2 haploinsuficiency

Mono-Allelic germline disruptions of the transcription factor GATA2 result in a propensity for developing myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML) affecting more than 85% of carriers. How a partial loss of GATA2 functionality enables leukemic transformation occurring years later in life, is unclear. This question is unsolved mainly due to lack of informative models, as Gata2 heterozygote mice do not develop hematologic malignancies. Here we show that two different germline Gata2 mutations (tgERG/GATA2het and tgERG/Gata2L359V) accelerate AML in mice expressing the human hematopoietic stem cell regulator ERG. Analysis of ERG/Gata2het fetal liver and bone marrow derived hematopoietic cells revealed a distinct pre-leukemic phenotype. This was characterized by enhanced transition from stem to progenitor state, increased proliferation, and a striking mitochondrial phenotype, consisting of highly expressed Oxidative- Phosphorylation related gene-sets, elevated oxygen consumption rates, and notably, markedly distorted mitochondrial morphology. Importantly, the same mitochondrial gene-expression signature was observed in human AMLs harboring GATA2 aberrations. Similar to the observations in mice, non-leukemic bone marrows from children with germline GATA2 mutation demonstrated marked mitochondrial abnormalities. Thus, we observed the tumor suppressive effects of GATA2 in two germline Gata2 genetic mouse models. As oncogenic mutations often accumulate with age, Gata2 deficiency mediated priming of hematopoietic cells for oncogenic transformation may explain the earlier occurrence of MDS/AML in patients with GATA2 germline mutation. The mitochondrial phenotype is a potential therapeutic opportunity for prevention of leukemic transformation in these patients

Cellular and metabolic characteristics of pre-leukemic hematopoietic progenitors with GATA2 haploinsuficiency.

Mono-Allelic germline disruptions of the transcription factor GATA2 result in a propensity for developing myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML) affecting more than 85% of carriers. How a partial loss of GATA2 functionality enables leukemic transformation occurring years later in life, is unclear. This question is unsolved mainly due to lack of informative models, as Gata2 heterozygote mice do not develop hematologic malignancies. Here we show that two different germline Gata2 mutations (tgERG/GATA2het and tgERG/Gata2L359V) accelerate AML in mice expressing the human hematopoietic stem cell regulator ERG. Analysis of ERG/Gata2het fetal liver and bone marrow derived hematopoietic cells revealed a distinct pre-leukemic phenotype. This was characterized by enhanced transition from stem to progenitor state, increased proliferation, and a striking mitochondrial phenotype, consisting of highly expressed Oxidative- Phosphorylation related gene-sets, elevated oxygen consumption rates, and notably, markedly distorted mitochondrial morphology. Importantly, the same mitochondrial gene-expression signature was observed in human AMLs harboring GATA2 aberrations. Similar to the observations in mice, non-leukemic bone marrows from children with germline GATA2 mutation demonstrated marked mitochondrial abnormalities. Thus, we observed the tumor suppressive effects of GATA2 in two germline Gata2 genetic mouse models. As oncogenic mutations often accumulate with age, Gata2 deficiency mediated priming of hematopoietic cells for oncogenic transformation may explain the earlier occurrence of MDS/AML in patients with GATA2 germline mutation. The mitochondrial phenotype is a potential therapeutic opportunity for prevention of leukemic transformation in these patients