Biomedical subjects

Yasuhide Furuta

Publications and source records attributed to Yasuhide Furuta.

10 recordsLinked to original sources

PubMed2006

Essential pro-Bmp roles of crossveinless 2 in mouse organogenesis.

We here report essential roles of the Bmp-binding protein crossveinless 2 (Cv2; Bmper) in mouse organogenesis. In the null Cv2 mutant mouse, gastrulation occurs normally, but a number of defects are found in Cv2-expressing tissues such as the skeleton. Cartilage differentiation by Bmp4 treatment is reduced in cultured Cv2(-/-) fibroblasts. Moreover, the defects in the vertebral column and eyes of the Cv2(-/-) mouse are substantially enhanced by deleting one copy of the Bmp4 gene, suggesting a pro-Bmp role of Cv2 in the development of these organs. In addition, the Cv2(-/-) mutant exhibits substantial defects in Bmp-dependent processes of internal organ formation, such as nephron generation in the kidney. This kidney hypoplasia is synergistically enhanced by the additional deletion of Kcp (Crim2) which encodes a pro-Bmp protein structurally related to Cv2. This study demonstrates essential pro-Bmp functions of Cv2 for locally restricted signal enhancement in multiple aspects of mammalian organogenesis.

Animals↗

PubMed2006

Novel lethal mouse mutants produced in balancer chromosome screens.

Mutagenesis screens are a valuable method to identify genes that are required for normal development. Previous mouse mutagenesis screens for lethal mutations were targeted at specific time points or for developmental processes. Here we present the results of lethal mutant isolation from two mutagenesis screens that use balancer chromosomes. One screen was localized to mouse chromosome 4, between the STS markers D4Mit281 and D4Mit51. The second screen covered the region between Trp53 and Wnt3 on mouse chromosome 11. These screens identified all lethal mutations in the balancer regions, without bias towards any phenotype or stage of death. We have isolated 19 lethal lines on mouse chromosome 4, and 59 lethal lines on chromosome 11, many of which are distinct from previous mutants that map to these regions of the genome. We have characterized the mutant lines to determine the time of death, and performed a pair-wise complementation cross to determine if the mutations are allelic. Our data suggest that the majority of mouse lethal mutations die during mid-gestation, after uterine implantation, with a variety of defects in gastrulation, heart, neural tube, vascular, or placental development. This initial group of mutants provides a functional annotation of mouse chromosomes 4 and 11, and indicates that many novel developmental phenotypes can be quickly isolated in defined genomic intervals through balancer chromosome mutagenesis screens.

Animals↗

PubMed2006

Tissue-specific RNAi reveals that WT1 expression in nurse cells controls germ cell survival and spermatogenesis.

Using a novel tissue-specific RNA interference (RNAi) approach that mimics the principle by which naturally occurring microRNAs (miRNA) are made, we demonstrate that the Wilms' tumor 1 (WT1) transcription factor has an essential role in spermatogenesis. Mice depleted of WT1 in Sertoli nurse cells suffered from increased germ cell apoptosis, loss of adherens junctions, disregulation of adherence junction-associated genes, and impaired fertility. These effects were recapitulated in transgenic mice expressing a dominant-negative form of WT1 in Sertoli cells, demonstrating the validity of our RNAi approach. Our results indicate that the tumor suppressor WT1 promotes Sertoli cell-germ cell signaling events driving spermatogenesis.

Adherens Junctions↗

PubMed2005

Threshold-specific requirements for Bmp4 in mandibular development.

Mandibular development is regulated by an interplay between a specified branchial arch ectoderm and a plastic mesenchyme. Moreover, signaling from the pharyngeal endoderm has been shown to be important for mandibular morphogenesis. To gain insight into the mechanisms regulating mandibular pattern, it is important to investigate the function of the epithelial-derived signals. Bmp4 is expressed in both distal, mandibular arch ectoderm and pharyngeal endoderm. Here, we show that deletion of Bmp4 in the mandibular ectoderm and to a lesser extent in the pharyngeal endoderm, resulted in severe defects in mandibular development. Furthermore, our data uncovered different Bmp4 thresholds for expression of the Bmp-dependent Msx1 and Msx2 genes in mandibular mesenchyme. We also found that ectodermal Fgf8 expression was both activated and repressed by Bmp4 in a dosage-dependent fashion indicating a novel Bmp4 function in threshold-specific regulation of Fgf8 transcription. Lastly, we provide evidence that Prx homeobox genes repress expression of an Msx2 transgene, previously shown to be Bmp4-responsive, revealing a mechanism for differential regulation of Msx1 and Msx2 by Bmp signaling.

Animals↗

PubMed2005

AP-2alpha selectively regulates fragile X mental retardation-1 gene transcription during embryonic development.

Fragile X syndrome (FXS) is almost always caused by silencing of the FMR1 gene. The defects observed in FXS indicate that the normal FMR1 gene has a range of functions and plays a particularly prominent role during development. However, the mechanisms regulating FMR1 expression in vivo are not known. Here, we have tested the role of the transcription factor AP-2alpha in regulating Fmr1 expression. Chromatin immunoprecipitation showed that AP-2alpha associates with the Fmr1 promoter in vivo. Furthermore, Fmr1 transcript levels are reduced >4-fold in homozygous null AP-2alpha mutant mice at embryonic day 18.5 when compared with normal littermates. Notably, AP-2alpha exhibits a strong gene dosage effect, with heterozygous mice showing approximately 2-fold reduction in Fmr1 levels. Examination of conditional AP-2alpha mutant mice indicates that this transcription factor plays a major role in regulating Fmr1 expression in embryos, but not in adults. We further investigated the role of AP-2alpha in the developmental regulation of Fmr1 expression using the Xenopus animal cap assay. Over-expression of a dominant-negative AP-2alpha in Xenopus embryos led to reduced Fmr1 levels. Moreover, exogenous wild-type AP-2alpha rescued Fmr1 expression in embryos where endogenous AP-2alpha had been suppressed. We conclude that AP-2alpha associates with the Fmr1 promoter in vivo and selectively regulates Fmr1 transcription during embryonic development.

Animals↗

PubMed2005

Distinct developmental programs require different levels of Bmp signaling during mouse retinal development.

The Bmp family of secreted signaling molecules is implicated in multiple aspects of embryonic development. However, the cell-type-specific requirements for this signaling pathway are often obscure in the context of complex embryonic tissue interactions. To define the cell-autonomous requirements for Bmp signaling, we have used a Cre-loxP strategy to delete Bmp receptor function specifically within the developing mouse retina. Disruption of a Bmp type I receptor gene, Bmpr1a, leads to no detectable eye abnormality. Further reduction of Bmp receptor activity by removing one functional copy of another Bmp type I receptor gene, Bmpr1b, in the retina-specific Bmpr1a mutant background, results in abnormal retinal dorsoventral patterning. Double mutants completely lacking both of these genes exhibit severe eye defects characterized by reduced growth of embryonic retina and failure of retinal neurogenesis. These studies provide direct genetic evidence that Bmpr1a and Bmpr1b play redundant roles during retinal development, and that different threshold levels of Bmp signaling regulate distinct developmental programs such as patterning, growth and differentiation of the retina.

Animals↗

PubMed2005

Recent innovations in tissue-specific gene modifications in the mouse.

Annotating the functions of individual genes in in vivo contexts has become the primary task of mouse genetics in the post-genome era. In addition to conventional approaches using transgenic technologies and gene targeting, the recent development of conditional gene modification techniques has opened novel opportunities for elucidating gene function at the level of the whole mouse to individual tissues or cell types. Tissue-specific gene modifications in the mouse have been made possible using site-specific DNA recombinases and conditional alleles. Recent innovations in this basic technology have facilitated new types of experiments, revealing novel insights into mammalian embryology. In this review, we focus on these recent innovations and new technical issues that impact the success of these conditional gene modification approaches.

Animals↗

PubMed2005

Fgf15 is required for proper morphogenesis of the mouse cardiac outflow tract.

Evidence in animal models indicates that signaling networks functioning in the developing pharyngeal arches regulate stereotyped processes critical for proper development of the aortic arch and cardiac outflow tract. Here, we describe the phenotype of mice lacking fibroblast growth factor 15 (Fgf15), which encodes a secreted signaling molecule expressed within the developing pharyngeal arches. Homozygous Fgf15 mutants present heart defects consistent with malalignment of the aorta and pulmonary trunk. These defects correlate with early morphological defects of the outflow tract due to aberrant behavior of the cardiac neural crest. We demonstrate that Fgf15 expression within the pharyngeal arches is unaltered by a loss of Tbx1, a key regulator of pharyngeal arch development implicated in DiGeorge syndrome. In addition, Fgf15 and Tbx1 do not interact genetically, suggesting that Fgf15 operates through a pathway independent of Tbx1. These studies reveal a novel role of Fgf15 during development of the cardiac outflow tract.

Animals↗

PubMed2005

Tbx1 expression in pharyngeal epithelia is necessary for pharyngeal arch artery development.

During embryonic life, the initially paired pharyngeal arch arteries (PAAs) follow a precisely orchestrated program of persistence and regression that leads to the formation of the mature aortic arch and great vessels. When this program fails, specific cardiovascular defects arise that may be life threatening or mild, according to the identity of the affected artery. Fourth PAA-derived cardiovascular defects occur commonly in DiGeorge syndrome and velocardiofacial syndrome (22q11DS), and in Tbx1(+/-) mice that model the 22q11DS cardiovascular phenotype. Tbx1 is expressed in pharyngeal mesoderm, endoderm and ectoderm, and, in addition, we show that it is expressed in precursors of the endothelial cells that line the PAAs, thus expanding the number of tissues in which Tbx1 is potentially required for fourth PAA development. In this study, we have used cell fate mapping and tissue-specific gene deletion, driven by six different Cre lines, to explore Tbx1 gene-dosage requirements in the embryonic pharynx for fourth PAA development. Through this approach, we have resolved the spatial requirements for Tbx1 in this process, and we show pharyngeal epithelia to be a critical tissue. We also thereby demonstrate conclusively that the role of Tbx1 in fourth PAA development is cell non-autonomous.

Animals↗

PubMed2004

BMP signaling through ACVRI is required for left-right patterning in the early mouse embryo.

Vertebrate organisms are characterized by dorsal-ventral and left-right asymmetry. The process that establishes left-right asymmetry during vertebrate development involves bone morphogenetic protein (BMP)-dependent signaling, but the molecular details of this signaling pathway remain poorly defined. This study tests the role of the BMP type I receptor ACVRI in establishing left-right asymmetry in chimeric mouse embryos. Mouse embryonic stem (ES) cells with a homozygous deletion at Acvr1 were used to generate chimeric embryos. Chimeric embryos were rescued from the gastrulation defect of Acvr1 null embryos but exhibited abnormal heart looping and embryonic turning. High mutant contribution chimeras expressed left-side markers such as nodal bilaterally in the lateral plate mesoderm (LPM), indicating that loss of ACVRI signaling leads to left isomerism. Expression of lefty1 was absent in the midline of chimeric embryos, but shh, a midline marker, was expressed normally, suggesting that, despite formation of midline, its barrier function was abolished. High-contribution chimeras also lacked asymmetric expression of nodal in the node. These data suggest that ACVRI signaling negatively regulates left-side determinants such as nodal and positively regulates lefty1. These functions maintain the midline, restrict expression of left-side markers, and are required for left-right pattern formation during embryogenesis in the mouse.

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