Mutations that impair Eyes absent tyrosine phosphatase activity in vitro reduce robustness of retinal determination gene network output in Drosophila

The Eyes Absent proteins in development and in developmental disorders

The Eyes Absent (EYA) transactivator-phosphatase proteins are important contributors to cell-fate determination processes and to the development of multiple organs. The transcriptional regulatory activity as well as the protein tyrosine phosphatase activities of the EYA proteins can independently contribute to proliferation, differentiation, morphogenesis and tissue homeostasis in different contexts. Aberrant EYA levels or activity are associated with numerous syndromic and non-syndromic developmental disorders, as well as cancers. Commensurate with the multiplicity of biochemical activities carried out by the EYA proteins, they impact upon a range of cellular signaling pathways. Here, we provide a broad overview of the roles played by EYA proteins in development, and highlight the molecular signaling pathways known to be linked with EYA-associated organ development and developmental disorders.

The Eyes Absent Proteins: Unusual HAD Family Tyrosine Phosphatases

Here, we review the haloacid dehalogenase (HAD) class of protein phosphatases, with a particular emphasis on an unusual group of enzymes, the eyes absent (EYA) family. EYA proteins have the unique distinction of being structurally and mechanistically classified as HAD enzymes, yet, unlike other HAD phosphatases, they are protein tyrosine phosphatases (PTPs). Further, the EYA proteins are unique among the 107 classical PTPs in the human genome because they do not use a Cysteine residue as a nucleophile in the dephosphorylation reaction. We will provide an overview of HAD phosphatase structure-function, describe unique features of the EYA family and their tyrosine phosphatase activity, provide a brief summary of the known substrates and cellular functions of the EYA proteins, and speculate about the evolutionary origins of the EYA family of proteins.

Up-regulation of circRNA_0068481 promotes right ventricular hypertrophy in PAH patients via regulating miR-646/miR-570/miR-885

CircRNA‐0068481 and several miRNAs are important in the pathogenesis of right ventricular hypertrophy (VH), while the inhibition of eye absent transcriptional coactivator and phosphatase 3 (EYA3) was proved to reverse vascular remodelling in rats. In this study, we tried to study the diagnostic value and mechanistic role of circRNA_0068481 in the diagnosis of RVH in PAH patients. qPCR was done to measure circRNA‐0068481, miR‐646, miR‐750, miR‐885 and EYA3 mRNA expression. Luciferase assay was done to explore the regulatory relationship between circRNA‐0068481/EYA3 and the miRNAs. Western blot was done to measure EYA3 expression in AC16 cells. The expression of circRNA‐0068481, miR‐646 and miR‐570 showed a considerable capability to diagnose RVH in PAH patients. The luciferase activity of circRNA‐0068481 was remarkably suppressed by miR‐646, miR‐570 or miR‐885. The luciferase signal of EYA3 was also inhibited by miR‐646, miR‐570 and miR‐885. Up‐regulation of circRNA‐0068481 expression in AC16 significantly decreased miR‐646, miR‐570 and miR‐885 expression, and up‐regulated EYA3 expression, whereas circRNA‐0068481 down‐regulation significantly increased miR‐646, miR‐570 and miR‐885 expression, and repressed EYA3 expression. CircRNA_0068481 sponged several miRNAs including miR‐646, miR‐570 and miR‐885. These miRNAs were all found to target the expression of EYA3 mRNA, which is involved in the onset of right ventricular hypertrophy. Therefore, it can be concluded that the up‐regulation of circRNA_0068481 can predict the diagnosis of right ventricular hypertrophy in pulmonary arterial hypertension patients.

The Eya1 Phosphatase Mediates Shh-Driven Symmetric Cell Division of Cerebellar Granule Cell Precursors

During neural development, stem and precursor cells can divide either symmetrically or asymmetrically. The transition between symmetric and asymmetric cell divisions is a major determinant of precursor cell expansion and neural differentiation, but the underlying mechanisms that regulate this transition are not well understood. Here, we identify the Sonic hedgehog (Shh) pathway as a critical determinant regulating the mode of division of cerebellar granule cell precursors (GCPs). Using partial gain and loss of function mutations within the Shh pathway, we show that pathway activation determines spindle orientation of GCPs, and that mitotic spindle orientation correlates with the mode of division. Mechanistically, we show that the phosphatase Eya1 is essential for implementing Shh-dependent GCP spindle orientation. We identify atypical protein kinase C (aPKC) as a direct target of Eya1 activity and show that Eya1 dephosphorylates a critical threonine (T410) in the activation loop. Thus, Eya1 inactivates aPKC, resulting in reduced phosphorylation of Numb and other components that regulate the mode of division. This Eya1-dependent cascade is critical in linking spindle orientation, cell cycle exit and terminal differentiation. Together these findings demonstrate that a Shh-Eya1 regulatory axis selectively promotes symmetric cell divisions during cerebellar development by coordinating spindle orientation and cell fate determinants.

Tuned polymerization of the transcription factor Yan limits off-DNA sequestration to confer context-specific repression

During development, transcriptional complexes at enhancers regulate gene expression in complex spatiotemporal patterns. To achieve robust expression without spurious activation, the affinity and specificity of transcription factor–DNA interactions must be precisely balanced. Protein–protein interactions among transcription factors are also critical, yet how their affinities impact enhancer output is not understood. The Drosophila transcription factor Yan provides a well-suited model to address this, as its function depends on the coordinated activities of two independent and essential domains: the DNA-binding ETS domain and the self-associating SAM domain. To explore how protein–protein affinity influences Yan function, we engineered mutants that increase SAM affinity over four orders of magnitude. This produced a dramatic subcellular redistribution of Yan into punctate structures, reduced repressive output and compromised survival. Cell-type specification and genetic interaction defects suggest distinct requirements for polymerization in different regulatory decisions. We conclude that tuned protein–protein interactions enable the dynamic spectrum of complexes that are required for proper regulation.