ECHO-liveFISH: in vivo RNA labeling reveals dynamic regulation of nuclear RNA foci in living tissues.

Elucidating the dynamic organization of nuclear RNA foci is important for understanding and manipulating these functional sites of gene expression in both physiological and pathological states. However, such studies have been difficult to establish in vivo as a result of the absence of suitable RNA imaging methods. Here, we describe a high-resolution fluorescence RNA imaging method, ECHO-liveFISH, to label endogenous nuclear RNA in living mice and chicks.

A SINE-derived element constitutes a unique modular enhancer for mammalian diencephalic Fgf8.

Transposable elements, including short interspersed repetitive elements (SINEs), comprise nearly half the mammalian genome. Moreover, they are a major source of conserved non-coding elements (CNEs), which play important functional roles in regulating development-related genes, such as enhancing and silencing, serving for the diversification of morphological and physiological features among species. We previously reported a novel SINE family, AmnSINE1, as part of mammalian-specific CNEs.

Dynamic spatiotemporal gene expression in embryonic mouse thalamus.

The anatomy of the mammalian thalamus is characterized by nuclei, which can be readily identified in postnatal animals. However, the molecular mechanisms that guide specification and differentiation of neurons in specific thalamic nuclei are still largely unknown, and few molecular markers are available for most of these thalamic subregions at early stages of development. We therefore searched for patterned gene expression restricted to specific mouse thalamic regions by in situ hybridization during the onset of thalamic neurogenesis (embryonic [E] days E10.

FGF8 acts as a classic diffusible morphogen to pattern the neocortex.

Gain- and loss-of-function experiments have demonstrated that a source of fibroblast growth factor (FGF) 8 regulates anterior to posterior (A/P) patterning in the neocortical area map. Whether FGF8 controls patterning as a classic diffusible morphogen has not been directly tested. We report evidence that FGF8 diffuses through the mouse neocortical primordium from a discrete source in the anterior telencephalon, forms a protein gradient across the entire A/P extent of the primordium, and acts directly at a distance from its source to determine area identity.

Activation of Ras-ERK pathway by Fgf8 and its downregulation by Sprouty2 for the isthmus organizing activity.

In the previous studies, we showed that strong Fgf8 signaling activates the Ras-ERK pathway to induce cerebellum. Here, we show importance of negative regulation following activation of this pathway for proper regionalization of mesencephalon and metencephalon in chick embryos. 'Prolonged' activation of ERK by misexpression of Fgf8b and dominant-negative Sprouty2 (dnSprouty2) did not change the fate of the mesencephalic alar plate.

The role of Fgf8 in telencephalic and diencephalic patterning.

Correct patterning of the developing brain is crucial importance for accurate wiring and function. Although the adult brain contains many complex structures, it begins with a simple structure-the neural tube. As it develops, the neural tube is divided into several regions, including the telencephalon, diencephalon, midbrain, and hindbrain.

Isthmus organizer for mesencephalon and metencephalon.

The vertebrate central nervous system is elaborated from a simple neural tube. Brain vesicles formation is the first sign of regionalization. Classical transplantation using quail and chick embryos revealed that the mesencephalon-metencephalon boundary (isthmus) functions as an organizer of the mesencephalon and metencephalon.

Regulation of isthmic Fgf8 signal by sprouty2.

Fgf8 functions as an organizer at the mes/metencephalic boundary (isthmus). We showed that a strong Fgf8 signal activates the Ras-ERK signaling pathway to organize cerebellar differentiation. Sprouty2 is expressed in an overlapping manner to Fgf8, and is induced by Fgf8.