scholarly journals The role of tolloid/mini fin in dorsoventral pattern formation of the zebrafish embryo

Development ◽  
1999 ◽  
Vol 126 (14) ◽  
pp. 3119-3130 ◽  
Author(s):  
S.A. Connors ◽  
J. Trout ◽  
M. Ekker ◽  
M.C. Mullins
Keyword(s):  
Gene Expression ◽  
Neural Development ◽  
Zebrafish Embryo ◽  
Bmp Signaling ◽  
Mutant Phenotype ◽  
Chromosomal Mapping ◽  
Activity Levels ◽  
Dorsoventral Axis ◽  
Gene Characterization

A highly conserved TGF-β signaling pathway is involved in the establishment of the dorsoventral axis of the vertebrate embryo. Specifically, Bone Morphogenetic Proteins (Bmps) pattern ventral tissues of the embryo while inhibitors of Bmps, such as Chordin, Noggin and Follistatin, are implicated in dorsal mesodermal and neural development. We investigated the role of Tolloid, a metalloprotease that can cleave Chordin and increase Bmp activity, in patterning the dorsoventral axis of the zebrafish embryo. Injection of tolloid mRNA into six dorsalized mutants rescued only one of these mutants, mini fin. Through chromosomal mapping, linkage and cDNA sequence analysis of several mini fin alleles, we demonstrate that mini fin encodes the tolloid gene. Characterization of the mini fin mutant phenotype reveals that Mini fin/Tolloid activity is required for patterning ventral tissues of the tail: the ventral fin, and the ventroposterior somites and vasculature. Gene expression studies show that mfn mutants exhibit reduced expression of ventrally restricted markers at the end of gastrulation, suggesting that the loss of ventral tail tissues is caused by a dorsalization occurring at the end of gastrulation. Based on the mini fin mutant phenotype and the expression of tolloid, we propose that Mini fin/Tolloid modifes the Bmp activity gradient at the end of gastrulation, when the ventralmost marginal cells of the embryo are in close proximity to the dorsal Chordin-expressing cells. At this time, unimpeded Chordin may diffuse to the most ventral marginal regions and inhibit high Bmp activity levels. In the presence of Mini fin/Tolloid, however, Chordin activity would be negatively modulated through proteolytic cleavage, thereby increasing Bmp signaling activity. This extracellular mechanism is amplified by an autoregulatory loop for bmp gene expression.

Lost-a-fin encodes a type I BMP receptor, Alk8, acting maternally and zygotically in dorsoventral pattern formation

Development ◽  
2001 ◽  
Vol 128 (6) ◽  
pp. 859-869 ◽  
Author(s):  
K.A. Mintzer ◽  
M.A. Lee ◽  
G. Runke ◽  
J. Trout ◽  
M. Whitman ◽  
...  
Keyword(s):  
Pattern Formation ◽  
Cell Types ◽  
Bmp Signaling ◽  
Mutant Phenotype ◽  
Chromosomal Mapping ◽  
Growth Defect ◽  
Type I ◽  
Cell Fates ◽  
Bmp Receptor

TGFbeta signaling pathways of the bone morphogenetic protein (BMP) subclass are essential for dorsoventral pattern formation of both vertebrate and invertebrate embryos. Here we determine by chromosomal mapping, linkage analysis, cDNA sequencing and mRNA rescue that the dorsalized zebrafish mutant lost-a-fin (laf) is defective in the gene activin receptor-like kinase 8 (alk8), which encodes a novel type I TGFbeta receptor. The alk8 mRNA is expressed both maternally and zygotically. Embyros that lack zygotic, but retain maternal Laf/Alk8 activity, display a weak dorsalization restricted to the tail and die by 3 days postfertilization. We rescued the laf dorsalized mutant phenotype by alk8 mRNA injection and generated homozygous laf/alk8 mothers to investigate the maternal role of Laf/Alk8 activity. Adult fish lacking Laf/Alk8 activity are fertile, exhibit a growth defect and are significantly smaller than their siblings. Embryos derived from homozygous females, which lack both maternal and zygotic Laf/Alk8 activity, display a strongly dorsalized mutant phenotype, no longer limited to the tail. These mutant embryos lack almost all gastrula ventral cell fates, with a concomitant expansion of dorsal cell types. During later stages, most of the somitic mesoderm and neural tissue circumscribe the dorsoventral axis of the embryo. Zygotic laf/alk8 mutants can be rescued by overexpression of the BMP signal transducer Smad5, but not the Bmp2b or Bmp7 ligands, consistent with the Laf/Alk8 receptor acting within a BMP signaling pathway, downstream of a Bmp2b/Bmp7 signal. Antibodies specific for the phosphorylated, activated form of Smad1/5, show that BMP signaling is nearly absent in gastrula lacking both maternal and zygotic Laf/Alk8 activity, providing further evidence that Laf/Alk8 transduces a BMP signal. In total, our work strongly supports the role of Laf/Alk8 as a type I BMP receptor required for the specification of ventral cell fates.

scholarly journals MicroRNA-125b Promotes Neuronal Differentiation in Human Cells by Repressing Multiple Targets

2009 ◽  
Vol 29 (19) ◽  
pp. 5290-5305 ◽  
Author(s):  
Minh T. N. Le ◽  
Huangming Xie ◽  
Beiyan Zhou ◽  
Poh Hui Chia ◽  
Pamela Rizk ◽  
...  
Keyword(s):  
Gene Expression ◽  
Neurite Outgrowth ◽  
Neuronal Differentiation ◽  
Neural Development ◽  
Ectopic Expression ◽  
Global Changes ◽  
Human Neuroblastoma Cell ◽  
Human Neuroblastoma ◽  
Mrna Targets

ABSTRACT MicroRNAs (miRNAs) are a class of small noncoding RNAs that regulate gene expression at the posttranscriptional level. Research on miRNAs has highlighted their importance in neural development, but the specific functions of neurally enriched miRNAs remain poorly understood. We report here the expression profile of miRNAs during neuronal differentiation in the human neuroblastoma cell line SH-SY5Y. Six miRNAs were significantly upregulated during differentiation induced by all-trans-retinoic acid and brain-derived neurotrophic factor. We demonstrated that the ectopic expression of either miR-124a or miR-125b increases the percentage of differentiated SH-SY5Y cells with neurite outgrowth. Subsequently, we focused our functional analysis on miR-125b and demonstrated the important role of this miRNA in both the spontaneous and induced differentiations of SH-SH5Y cells. miR-125b is also upregulated during the differentiation of human neural progenitor ReNcell VM cells, and miR-125b ectopic expression significantly promotes the neurite outgrowth of these cells. To identify the targets of miR-125b regulation, we profiled the global changes in gene expression following miR-125b ectopic expression in SH-SY5Y cells. miR-125b represses 164 genes that contain the seed match sequence of the miRNA and/or that are predicted to be direct targets of miR-125b by conventional methods. Pathway analysis suggests that a subset of miR-125b-repressed targets antagonizes neuronal genes in several neurogenic pathways, thereby mediating the positive effect of miR-125b on neuronal differentiation. We have further validated the binding of miR-125b to the miRNA response elements of 10 selected mRNA targets. Together, we report here for the first time the important role of miR-125b in human neuronal differentiation.

Equivalent genetic roles for bmp7/snailhouse and bmp2b/swirl in dorsoventral pattern formation

Development ◽  
2000 ◽  
Vol 127 (5) ◽  
pp. 957-967 ◽  
Author(s):  
B. Schmid ◽  
M. Furthauer ◽  
S.A. Connors ◽  
J. Trout ◽  
B. Thisse ◽  
...  
Keyword(s):  
Pattern Formation ◽  
Zebrafish Embryo ◽  
Bmp Signaling ◽  
Mutant Phenotype ◽  
Null Mutant ◽  
Cell Fates ◽  
Hypomorphic Mutation ◽  
Morphogenetic Protein ◽  
A Cell

A bone morphogenetic protein (BMP) signaling pathway acts in the establishment of the dorsoventral axis of the vertebrate embryo. Here we demonstrate the genetic requirement for two different Bmp ligand subclass genes for dorsoventral pattern formation of the zebrafish embryo. From the relative efficiencies observed in Bmp ligand rescue experiments, conserved chromosomal synteny, and isolation of the zebrafish bmp7 gene, we determined that the strongly dorsalized snailhouse mutant phenotype is caused by a mutation in the bmp7 gene. We show that the original snailhouse allele is a hypomorphic mutation and we identify a snailhouse/bmp7 null mutant. We demonstrate that the snailhouse/bmp7 null mutant phenotype is identical to the presumptive null mutant phenotype of the strongest dorsalized zebrafish mutant swirl/bmp2b, revealing equivalent genetic roles for these two Bmp ligands. Double mutant snailhouse/bmp7; swirl/bmp2b embryos do not exhibit additional or stronger dorsalized phenotypes, indicating that these Bmp ligands do not function redundantly in early embryonic development. Furthermore, overexpression experiments reveal that Bmp2b and Bmp7 synergize in the ventralization of wild-type embryos through a cell-autonomous mechanism, suggesting that Bmp2b/Bmp7 heterodimers may act in vivo to specify ventral cell fates in the zebrafish embryo.

Role of small nuclear RNAs in eukaryotic gene expression

2013 ◽  
Vol 54 ◽  
pp. 79-90 ◽  
Author(s):  
Saba Valadkhan ◽  
Lalith S. Gunawardane
Keyword(s):  
Gene Expression ◽  
Protein Interactions ◽  
Rna Stability ◽  
Splice Sites ◽  
Branch Site ◽  
Small Nuclear Rnas ◽  
Eukaryotic Gene Expression ◽  
Eukaryotic Gene ◽  
Rna Biogenesis

Eukaryotic cells contain small, highly abundant, nuclear-localized non-coding RNAs [snRNAs (small nuclear RNAs)] which play important roles in splicing of introns from primary genomic transcripts. Through a combination of RNA–RNA and RNA–protein interactions, two of the snRNPs, U1 and U2, recognize the splice sites and the branch site of introns. A complex remodelling of RNA–RNA and protein-based interactions follows, resulting in the assembly of catalytically competent spliceosomes, in which the snRNAs and their bound proteins play central roles. This process involves formation of extensive base-pairing interactions between U2 and U6, U6 and the 5′ splice site, and U5 and the exonic sequences immediately adjacent to the 5′ and 3′ splice sites. Thus RNA–RNA interactions involving U2, U5 and U6 help position the reacting groups of the first and second steps of splicing. In addition, U6 is also thought to participate in formation of the spliceosomal active site. Furthermore, emerging evidence suggests additional roles for snRNAs in regulation of various aspects of RNA biogenesis, from transcription to polyadenylation and RNA stability. These snRNP-mediated regulatory roles probably serve to ensure the co-ordination of the different processes involved in biogenesis of RNAs and point to the central importance of snRNAs in eukaryotic gene expression.

Cell-specific regulation of IRS-1 gene expression: role of E box and C/EBP binding site in HepG2 cells and CHO cells

Diabetes ◽  
1997 ◽  
Vol 46 (3) ◽  
pp. 354-362 ◽  
Author(s):  
K. Matsuda ◽  
E. Araki ◽  
R. Yoshimura ◽  
K. Tsuruzoe ◽  
N. Furukawa ◽  
...  
Keyword(s):  
Gene Expression ◽  
Binding Site ◽  
Cho Cells ◽  
Hepg2 Cells ◽  
E Box ◽  
Specific Regulation
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