RESUMEN
BACKGROUND: Scarb2 or Limp2 belong to a subfamily of Scavenger receptors described as lysosomal transmembrane glycosylated receptors, that are mutated in the human syndrome AMRF (action myoclonus-renal failure). The zebrafish insertional mutant scarb2a(hi1463Tg) has notochord defects, the notochord is a defining feature of chordates running along the center of the longitudinal axis and it is essential for forming the spinal column in all vertebrates. RESULTS: There are three paralogous scarb2 genes in zebrafish; scarb2a, scarb2b, and scarb2c. Both Scarb2a and Scarb2b proteins lack the classical di-leucine motif. We found that scarb2a(hi1463Tg) homozygous zebrafish embryos have a null mutation impairing vacuole formation in the notochord and simultaneously disrupting proper formation of the basement membrane resulting in its thickening at the ventral side of the notochord, which may be the cause for the anomalous upward bending observed in the trunk. Through whole-mount in situ hybridization, we detected scarb2a mRNA expression in the notochord and in the brain early in development. However, it is puzzling that scarb2a notochord mRNA expression is short-lived in the presumptive notochord and precedes the complete differentiation of the notochord. CONCLUSIONS: This work describes a novel function for the Scarb2 receptor as an essential glycoprotein for notochord development.
Asunto(s)
Regulación del Desarrollo de la Expresión Génica , Proteínas de Membrana de los Lisosomas/metabolismo , Mutagénesis Insercional , Notocorda/embriología , Proteínas de Pez Cebra/metabolismo , Pez Cebra/embriología , Secuencias de Aminoácidos , Animales , Humanos , Proteínas de Membrana de los Lisosomas/genética , Pez Cebra/genética , Proteínas de Pez Cebra/genéticaRESUMEN
ATP-dependent SWI/SNF-like BAF chromatin remodeling complexes are emerging as key regulators of embryonic and adult stem cell function. Particularly intriguing are the findings that specialized assemblies of BAF complexes are required for establishing and maintaining pluripotent and multipotent states in cells. However, little is known on the importance of these complexes in normal and leukemic hemopoiesis. Here we provide the first evidence that the actin-related protein BAF53a, a subunit of BAF complexes preferentially expressed in long-term repopulating stem cells, is essential for adult hemopoiesis. Conditional deletion of BAF53a resulted in multilineage BM failure, aplastic anemia, and rapid lethality. These severe hemopoietic defects originate from a proliferative impairment of BM HSCs and progenitors and decreased progenitor survival. Using hemopoietic chimeras, we show that the impaired function of BAF53a-deficient HSCs is cell-autonomous and independent of the BM microenvironment. Altogether, our studies highlight an unsuspected role for BAF chromatin remodeling complexes in the maintenance of HSC and progenitor cell properties.
Asunto(s)
Actinas/genética , Proteínas Cromosómicas no Histona/genética , Proteínas de Unión al ADN/genética , Células Madre Hematopoyéticas/metabolismo , Sistema Hematopoyético/metabolismo , Transcriptoma , Actinas/metabolismo , Anemia Aplásica/genética , Anemia Aplásica/metabolismo , Animales , Apoptosis/genética , Apoptosis/fisiología , Células de la Médula Ósea/metabolismo , Células de la Médula Ósea/fisiología , Proteínas de Ciclo Celular/genética , Proliferación Celular , Supervivencia Celular/genética , Supervivencia Celular/fisiología , Células Cultivadas , Proteínas Cromosómicas no Histona/metabolismo , Proteínas de Unión al ADN/metabolismo , Femenino , Feto , Citometría de Flujo , Regulación del Desarrollo de la Expresión Génica , Células Madre Hematopoyéticas/fisiología , Sistema Hematopoyético/crecimiento & desarrollo , Hígado , Masculino , Ratones , Ratones de la Cepa 129 , Ratones Endogámicos C57BL , Ratones Noqueados , Embarazo , Reacción en Cadena de la Polimerasa de Transcriptasa InversaRESUMEN
Stress granules are cytoplasmic foci that directly respond to the protein synthesis status of the cell. Various environmental insults, such as oxidative stress or extreme heat, block protein synthesis; consequently, mRNA will stall in translation, and stress granules will immediately form and become enriched with mRNAs. P54 DEAD box RNA helicases are components of RNA granules such as P-bodies and stress granules. We studied the expression, in cytoplasmic foci, of both zebrafish P54 RNA helicases (P54a and P54b) during development and found that they are expressed in cytoplasmic granules under both normal conditions and stress conditions. In zebrafish embryos exposed to heat shock, some proportion of P54a and P54b helicases move to larger granules that exhibit the properties of genuine stress granules. Knockdown of P54a and/or P54b in zebrafish embryos produces developmental abnormalities restricted to the posterior trunk; further, these embryos do not form stress granules, and their survival upon exposure to heat-shock conditions is compromised. Our observations fit the model that cells lacking stress granules have no resilience or ability to recover once the stress has ended, indicating that stress granules play an essential role in the way organisms adapt to a changing environment.