Axis formation in annual killifish: Nodal and ß-catenin regulate morphogenesis without Huluwa prepatterning.

Axis formation in fish and amphibians typically begins with a prepattern of maternal gene products. Annual killifish embryogenesis, however, challenges prepatterning models as blastomeres disperse and then aggregate to form the germ layers and body axes. We show that huluwa, a prepatterning factor thought to break symmetry by stabilizing ß-catenin, is truncated and inactive in Nothobranchius furzeri. Nuclear ß-catenin is not selectively stabilized on one side of the blastula but accumulates in cells forming the aggregate. Blocking ß-catenin activity or Nodal signaling disrupts aggregate formation and germ layer specification. Nodal signaling coordinates cell migration, establishing an early role for this signaling pathway. These results reveal a surprising departure from established mechanisms of axis formation: Huluwa-mediated prepatterning is dispensable, and ß-catenin and Nodal regulate morphogenesis.

BET activity plays an essential role in control of stem cell attributes in Xenopus.

Neural crest cells are a stem cell population unique to vertebrate embryos that retains broad multi-germ layer developmental potential through neurulation. Much remains to be learned about the genetic and epigenetic mechanisms that control the potency of neural crest cells. Here, we examine the role that epigenetic readers of the BET (bromodomain and extra terminal) family play in controlling the potential of pluripotent blastula and neural crest cells. We find that inhibiting BET activity leads to loss of pluripotency at blastula stages and a loss of neural crest at neurula stages. We compare the effects of HDAC (an eraser of acetylation marks) and BET (a reader of acetylation) inhibition and find that they lead to similar cellular outcomes through distinct effects on the transcriptome. Interestingly, loss of BET activity in cells undergoing lineage restriction is coupled to increased expression of genes linked to pluripotency and prolongs the competence of initially pluripotent cells to transit to a neural progenitor state. Together these findings advance our understanding of the epigenetic control of pluripotency and the formation of the vertebrate neural crest.

SoxB1 transcription factors are essential for initiating and maintaining neural plate border gene expression.

SoxB1 transcription factors (Sox2/3) are well known for their role in early neural fate specification in the embryo, but little is known about functional roles for SoxB1 factors in non-neural ectodermal cell types, such as the neural plate border (NPB). Using Xenopus laevis, we set out to determine whether SoxB1 transcription factors have a regulatory function in NPB formation. Here, we show that SoxB1 factors are necessary for NPB formation, and that prolonged SoxB1 factor activity blocks the transition from a NPB to a neural crest state. Using ChIP-seq, we demonstrate that Sox3 is enriched upstream of NPB genes in early NPB cells and in blastula stem cells. Depletion of SoxB1 factors in blastula stem cells results in downregulation of NPB genes. Finally, we identify Pou5f3 factors as potential Sox3 partners in regulating the formation of the NPB and show that their combined activity is needed for normal NPB gene expression. Together, these data identify a role for SoxB1 factors in the establishment and maintenance of the NPB, in part through partnership with Pou5f3 factors.

Changes in repair pathways of radiation-induced DNA double-strand breaks at the midblastula transition in Xenopus embryo.

Ionizing radiation (IR) causes DNA damage, particularly DNA double-strand breaks (DSBs), which have significant implications for genome stability. The major pathways of repairing DSBs are homologous recombination (HR) and nonhomologous end joining (NHEJ). However, the repair mechanism of IR-induced DSBs in embryos is not well understood, despite extensive research in somatic cells. The externally developing aquatic organism, Xenopus tropicalis, serves as a valuable model for studying embryo development. A significant increase in zygotic transcription occurs at the midblastula transition (MBT), resulting in a longer cell cycle and asynchronous cell divisions. This study examines the impact of X-ray irradiation on Xenopus embryos before and after the MBT. The findings reveal a heightened X-ray sensitivity in embryos prior to the MBT, indicating a distinct shift in the DNA repair pathway during embryo development. Importantly, we show a transition in the dominant DSB repair pathway from NHEJ to HR before and after the MBT. These results suggest that the MBT plays a crucial role in altering DSB repair mechanisms, thereby influencing the IR sensitivity of developing embryos.

Small molecule-mediated reprogramming of Xenopus blastula stem cells to a neural crest state.

Neural crest cells are a stem cell population unique to vertebrates that give rise to a diverse array of derivatives, including much of the peripheral nervous system, pigment cells, cartilage, mesenchyme, and bone. Acquisition of these cells drove the evolution of vertebrates and defects in their development underlies a broad set of neurocristopathies. Moreover, studies of neural crest can inform differentiation protocols for pluripotent stem cells and regenerative medicine applications. Xenopus embryos are an important system for studies of the neural crest and have provided numerous insights into the signals and transcription factors that control the formation and later lineage diversification of these stem cells. Pluripotent animal pole explants are a particularly powerful tool in this system as they can be cultured in simple salt solution and instructed to give rise to any cell type including the neural crest. Here we report a protocol for small molecule-mediated induction of the neural crest state from blastula stem cells and validate it using transcriptome analysis and grafting experiments. This is an powerful new tool for generating this important cell type that will facilitate future studies of neural crest development and mutations and variants linked to neurocristopathies.

Depression help-seeking attitudes and behaviors among an Internet-based sample of Spanish-speaking perinatal women / Actitudes y comportamientos de búsqueda de ayuda para la depresión en una muestra basada en internet de mujeres de habla hispana en período perinatal

OBJECTIVE: To examine attitudes and beliefs related to help-seeking for depression among an international sample of pregnant women, a majority of whom were Spanish-speakers residing in Latin America. METHODS: More than 6 000 (n = 6 672) pregnant women met eligibility criteria and consented to participate between 15 January 2009-12 August 2011. Of these, 1 760 with a Latino/Hispanic background completed a baseline survey as part of a larger study. Group comparisons analyzed attitudes and behaviors related to seeking help for depression, while a logistic regression was conducted to identify demographic characteristics related to help-seeking support. RESULTS: Of the participants, three-fourths reported experiencing depression during or after their current or past pregnancies. The majority of participants did not seek help, and generally reported ambivalence about their depressive symptoms and uncertainty as to the helpfulness of others. However, 44.8% did seek help, mostly by speaking to family or partners and reported feeling fear, shame, and embarrassment about their symptoms. A current major depressive episode and an income less than or equal to US$ 10 000 were significant predictors of help-seeking behaviors. CONCLUSIONS: Data from this study suggest that when feeling sad or depressed, perinatal Latinas tend to seek emotional support first from family and friends and may underutilize mental health services when needed. The Internet is an effective means for reaching perinatal women, especially those in areas of the world where there may be barriers to accessing psychological resources.

OBJETIVO: Analizar las actitudes y las creencias relacionadas con la búsqueda de ayuda para la depresión en una muestra internacional de mujeres embarazadas, la mayor parte de ellas hispanohablantes y residentes en América Latina. MÉTODOS: Más de 6 000 mujeres embarazadas (n = 6 672) cumplieron los criterios de selección y aceptaron participar entre el 15 de enero del 2009 y el 12 de agosto del 2011. De estas, 1 760 de origen latino o hispano completaron una encuesta básica que formaba parte de un estudio más amplio. Mediante comparaciones de grupo, se analizaron las actitudes y los comportamientos relacionados con la búsqueda de ayuda para la depresión, mientras que, mediante regresión logística, se determinaron las características demográficas relacionadas con la búsqueda de ayuda o apoyo. RESULTADOS: De todas las participantes, tres cuartas partes notificaron sentimientos de depresión durante o después de los embarazos actuales o pasados. La mayor parte de ellas no buscaron ayuda, y en general manifestaron ambivalencia acerca de sus síntomas depresivos e incertidumbre en cuanto a la capacidad de ayuda de otras personas. Sin embargo, 44,8% buscaron ayuda, principalmente hablando con familiares o compañeros, y notificaron sentimientos de temor, culpabilidad y vergüenza acerca de sus síntomas. Un episodio depresivo mayor actual y unos ingresos iguales o inferiores a US$ 10 000 fueron factores predictivos significativos de comportamientos de búsqueda de ayuda. CONCLUSIONES: Los datos de este estudio indican que, cuando se sienten tristes o deprimidas, las mujeres latinas en período perinatal tienden a buscar en primer lugar el apoyo emocional de la familia y los amigos, y podrían subutilizar los servicios de salud mental cuando son necesarios. La internet es un medio eficaz para llegar a las mujeres en período perinatal, especialmente a las que viven en zonas del mundo donde pueden existir barreras para el acceso a los recursos psicológicos.