<i>Sim1</i>and<i>Sim2</i>are required for the correct targeting of mammillary body axons

Marion, Jean-François; Yang, Chun; Caqueret, Aurore; Boucher, Francine; Michaud, Jacques L.

doi:10.1242/dev.02142

Cited by 47 publications

(57 citation statements)

References 45 publications

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“…This roughly conserved sim1 mRNA expression pattern suggests an important role for sim1 in posterior diencephalon and midbrain development. Although no specific defects were reported in these areas of Sim1 knockout mice, Sim1/ Sim2 double knockout mice have significant defects in axon targeting of mammillary body axons (Marion et al, 2005). Given the conserved expression patterns between zebrafish sim1 and mouse Sim1, the role of zebrafish sim1 in axonal development in the posterior diencephalon may also be conserved.…”

Section: Discussionmentioning

confidence: 96%

The zebrafish bHLH PAS transcriptional regulator, single‐minded 1 (sim1), is required for isotocin cell development

Eaton

Glasgow

2006

Developmental Dynamics

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A wide range of physiological and behavioral processes, such as social, sexual, and maternal behaviors, learning and memory, and osmotic homeostasis are influenced by the neurohypophysial peptides oxytocin and vasopressin. Disruptions of these hormone systems have been linked to several neurobehavioral disorders, including autism, Prader-Willi syndrome, affective disorders, and obsessive-compulsive disorder. Studies in zebrafish promise to reveal the complex network of regulatory genes and signaling pathways that direct the development of oxytocin-and vasopressin-like neurons, and provide insight into factors involved in brain disorders associated with disruption of these systems. Isotocin, which is homologous to oxytocin, is expressed early, in a simple pattern in the developing zebrafish brain. Single-minded 1 (sim1), a member of the bHLH-PAS family of transcriptional regulatory genes, is required for terminal differentiation of mammalian oxytocin cells and is a master regulator of neurogenesis in Drosophila. Here we show that sim1 is expressed in the zebrafish forebrain and is required for isotocin cell development. The expression pattern of sim1 mRNA in the embryonic forebrain is dynamic and complex, and overlaps with isotocin expression in the preoptic area. We provide evidence that the role of sim1 in zebrafish neuroendocrine cell development is evolutionarily conserved with that of mammals.

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Section: Discussionmentioning

confidence: 96%

The zebrafish bHLH PAS transcriptional regulator, single‐minded 1 (sim1), is required for isotocin cell development

Eaton

Glasgow

2006

Developmental Dynamics

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“…Interestingly, mammillary axons are rerouted toward the midline in Sim1/Sim2 null mice, possibly because of abnormal Robo3 expression (Marion et al, 2005).…”

Section: Transcriptional Regulationmentioning

confidence: 99%

“…Robo3 expression is also upregulated in a subset of mammillary neurons of the hypothalamus of mouse embryos deficient for the basic helix-loop-helix (bHLH) transcription factors Sim1 and Sim2 (Marion et al, 2005). Interestingly, mammillary axons are rerouted toward the midline in Sim1/Sim2 null mice, possibly because of abnormal Robo3 expression (Marion et al, 2005).…”

Section: Transcriptional Regulationmentioning

confidence: 99%

“…Robo3 was discovered as a gene that is upregulated in retinoblastoma (Rb)-deficient mice (Yuan et al, 1999). It was later confirmed that Rb represses Robo3 promoter activity in vitro but also that Pax2 activates Robo3 transcription by binding to Rb and thereby inhibiting its repressor function on Robo3 (Yuan et al, 2002).Robo3 expression is also upregulated in a subset of mammillary neurons of the hypothalamus of mouse embryos deficient for the basic helix-loop-helix (bHLH) transcription factors Sim1 and Sim2 (Marion et al, 2005). Interestingly, mammillary axons are rerouted toward the midline in Sim1/Sim2 null mice, possibly because of abnormal Robo3 expression (Marion et al, 2005).…”

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confidence: 99%

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Moving away from the midline: new developments for Slit and Robo

2010

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SummaryIn most tissues, the precise control of cell migration and cellcell interaction is of paramount importance to the development of a functional structure. Several families of secreted molecules have been implicated in regulating these aspects of development, including the Slits and their Robo receptors. These proteins have well described roles in axon guidance but by influencing cell polarity and adhesion, they participate in many developmental processes in diverse cell types. We review recent progress in understanding both the molecular mechanisms that modulate Slit/Robo expression and their functions in neural and non-neural tissue. Key words: Axon guidance, Cell migration, Cell-cell interaction IntroductionIn most organisms, the central nervous system (CNS) develops along a bilateral axis of symmetry located at the midline (Placzek and Briscoe, 2005). During development, the ventral midline or floor plate acts as an organiser through the secretion of diffusible proteins (Placzek and Briscoe, 2005;Gore et al., 2008), which control the growth of axons and dendrites and the migration of neurons across the midline. In the forebrain, glial or neuronal cells delineate the midline (see Glossary, Box 1) and also control axon guidance. For more than two decades, many developmental neurobiologists have tried to understand the mechanisms that control midline crossing in the CNS and to answer some key questions. Firstly, how are commissural axons (see Glossary, Box 1) attracted to the midline and how do their growth cones (see Glossary, Box1) receive and integrate the multiple and contrasting signals released by midline cells? Secondly, what are the molecular and signalling changes that enable commissural axons to leave the midline and often to switch to a longitudinal growth mode? All midline-derived axon guidance factors are expressed at other locations in many developing and mature tissues, where they control a wide range of biological processes.Roundabout receptors (Robo) and their Slit ligands form one of the most crucial ligand-receptor pairings among the axon guidance molecules. Robos were identified in Drosophila in a mutant screen for genes that control the midline crossing of commissural axons (Kidd et al., 1998;Seeger et al., 1993). Similarly, Slit was discovered in Drosophila as a protein secreted by midline glia (Rothberg et al., 1988;Rothberg et al., 1990). Homologues of both proteins have since been discovered in many species (for a review, see . However, the Slit/Robo couple not only functions in axon guidance but also in a variety of developmental Development 137, 1939Development 137, -1952Development 137, (2010 Commissural axons Axons with cell bodies (somata) located on one side of the central nervous system (CNS) that project axons across the midline to contact target cells on the opposite side. Growth cone A specialised bulbous enlargement at the end of growing axons that is characterised by dynamic filamentous extensions, known as filopodia. They sense the environment and respond to adhesi...

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“…Sim mutant analysis showed that Sim1 acts upstream of Sim2 and partially compensates for the loss of Sim2 in PVN embryonic development (Michaud et al, 1998, Goshu et al, 2002, Goshu et al, 2004. However, mSim1 and mSim2 act along compensatory pathways in mammillary body axonal development (Marion et al, 2005).…”

Section: Limb Sim1 Expression In Chick and Mouse Embryosmentioning

confidence: 99%

Sim1 and Sim2 expression during chick and mouse limb development

Coumailleau¹,

Duprez²

2009

Int. J. Dev. Biol.

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The Drosophila Single minded (Sim) transcription factor is a master regulator of cell fate during midline development. The homolog mouse Sim1 and Sim2 genes are important for central nervous system development. Loss of mSim1 activity leads to an absence of specific neuroendocrine lineages within the hypothalamus, while overexpression of mSim2 leads to behavioural defects. We now provide evidence that vertebrate Sim genes might be important for limb muscle formation. We have examined by in situ hybridisation the expression of the Sim1 and Sim2 genes during limb development in chick and mouse embryos. The expression of both Sim genes is mainly associated with limb muscle formation. We found that each Sim gene has a similar temporal and spatial expression pattern in chick and mouse embryonic limbs, although with some differences for the Sim2 gene between species. In chick or mouse embryonic limbs, Sim1 and Sim2 display non-overlapping expression domains, suggesting an involvement for Sim1 and Sim2 proteins at different steps of limb muscle formation. Sim1 gene expression is associated with the early step of muscle progenitor cell migration in chick and mouse, while the Sim2 gene is expressed just after the migration process. In addition, chick and mouse Sim2 gene expression is enhanced in limb ventral muscle masses versus dorsal ventral muscle masses. Our results provide a basis for further functional analysis of the Sim genes in limb muscle formation.

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Sim1andSim2are required for the correct targeting of mammillary body axons

Cited by 47 publications

References 45 publications

The zebrafish bHLH PAS transcriptional regulator, single‐minded 1 (sim1), is required for isotocin cell development

The zebrafish bHLH PAS transcriptional regulator, single‐minded 1 (sim1), is required for isotocin cell development

Moving away from the midline: new developments for Slit and Robo

Sim1 and Sim2 expression during chick and mouse limb development

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