Fragile X mental retardation protein: A paradigm for translational control by RNA-binding proteins

The Family ◽

The Brain

Chapter 8 discusses how Fragile X syndrome (FXS) is caused by the absence of the RNA-binding protein fragile X mental retardation protein (FMRP). FMRP is highly expressed in the brain and gonads, the two organs mainly affected in patients with the syndrome. Functionally, FMRP belongs to the family of RNA-binding proteins, shuttling from the nucleus to the cytoplasm, and, as shown for other RNA-binding proteins, forms large messenger ribonucleoparticles.

Dicer-Derived MicroRNAs Are Utilized by the Fragile X Mental Retardation Protein for Assembly on Target RNAs

Journal of Biomedicine and Biotechnology ◽

10.1155/jbb/2006/64347 ◽

2006 ◽

Vol 2006 ◽

pp. 1-12 ◽

Cited By ~ 36

Author(s):

Isabelle Plante ◽

Laetitia Davidovic ◽

Dominique L. Ouellet ◽

Lise-Andrée Gobeil ◽

Sandra Tremblay ◽

...

Keyword(s):

Mental Retardation ◽

Translational Control ◽

Mammalian Cells ◽

Rna Binding ◽

Fragile X ◽

Rna Sequences ◽

Rnp Complex

In mammalian cells, fragile X mental retardation protein (FMRP) has been reported to be part of a microRNA (miRNA)-containing effector ribonucleoprotien (RNP) complex believed to mediate translational control of specific mRNAs. Here, using recombinant proteins, we demonstrate that human FMRP can act as a miRNA acceptor protein for the ribonuclease Dicer and facilitate the assembly of miRNAs on specific target RNA sequences. The miRNA assembler property of FMRP was abrogated upon deletion of its single-stranded (ss) RNA binding K-homology domains. The requirement of FMRP for efficient RNA interference (RNAi) in vivo was unveiled by reporter gene silencing assays using various small RNA inducers, which also supports its involvement in an ss small interfering RNA (siRNA)-containing RNP (siRNP) effector complex in mammalian cells. Our results define a possible role for FMRP in RNA silencing and may provide further insight into the molecular defects in patients with the fragile X syndrome.

Expression of fragile X mental retardation protein and Fmr1 mRNA during folliculogenesis in the rat

Reproduction ◽

10.1530/rep-12-0305 ◽

2013 ◽

Vol 145 (4) ◽

pp. 335-343 ◽

Cited By ~ 14

Author(s):

Ianina Ferder ◽

Fernanda Parborell ◽

Victoria Sundblad ◽

Violeta Chiauzzi ◽

Karina Gómez ◽

...

Keyword(s):

Mental Retardation ◽

Rna Binding ◽

Rna Binding Proteins ◽

Fragile X ◽

Expression Patterns ◽

Follicular Development ◽

Mrna Levels ◽

Germline Development ◽

Fragile X mental retardation protein (FMRP) belongs to a small family of RNA-binding proteins. Its absence or inactivity is responsible for fragile X syndrome, the most common cause of inherited mental retardation. Despite its ubiquitous expression, FMRP function and expression remain almost understudied in non-neuronal tissues, though previous studies on germline development during oogenesis may suggest a special function of this protein also in ovarian tissue. In addition, the well-documented association ofFMR1premutation state with fragile X-related premature ovarian insufficiency adds interest to the role of FMRP in ovarian physiology. The aim of the present work was to investigate the expression ofFmr1mRNA and its protein, FMRP, at different stages of rat follicular development. By immunohistochemical studies we demonstrated FMRP expression in granulosa, theca and germ cells in all stages of follicular development. In addition, changes inFmr1expression, both at the protein and mRNA levels, were observed. FMRP levels increased upon follicular development while preantral and early antral follicles presented similar levels ofFmr1transcripts with decreased expression in preovulatory follicles. These observations suggest thatFmr1expression in the ovary is regulated at different and perhaps independent levels. In addition, our results show expression of at least four different isoforms of FMRP during all stages of follicular growth with expression patterns that differ from those observed in brain and testis. Our study shows a regulated expression ofFmr1, both at mRNA and protein levels, during rat follicular development.

RNA-Binding Specificity of the Human Fragile X Mental Retardation Protein

Journal of Molecular Biology ◽

10.1016/j.jmb.2020.04.021 ◽

2020 ◽

Vol 432 (13) ◽

pp. 3851-3868 ◽

Cited By ~ 4

Author(s):

Youssi M. Athar ◽

Simpson Joseph

Keyword(s):

Mental Retardation ◽

Rna Binding ◽

Fragile X ◽

Binding Specificity ◽

The RNA-binding fragile-X mental retardation protein and its role beyond the brain

Biophysical Reviews ◽

10.1007/s12551-020-00730-4 ◽

2020 ◽

Vol 12 (4) ◽

pp. 903-916 ◽

Cited By ~ 1

Author(s):

Cassandra Malecki ◽

Brett D. Hambly ◽

Richmond W. Jeremy ◽

Elizabeth N. Robertson

Keyword(s):

Mental Retardation ◽

Rna Binding ◽

Fragile X ◽

The Brain

Kinase pathway inhibition restores PSD95 induction in neurons lacking fragile X mental retardation protein

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1812056116 ◽

2019 ◽

pp. 201812056

Author(s):

Ying Yang ◽

Yang Geng ◽

Dongyun Jiang ◽

Lin Ning ◽

Hyung Joon Kim ◽

...

Keyword(s):

Protein Synthesis ◽

Mental Retardation ◽

Rna Binding ◽

Fragile X ◽

Alternative Pathways ◽

Mrna Targets ◽

Pathway Inhibition

Fragile X syndrome (FXS) is the leading monogenic cause of autism and intellectual disability. FXS is caused by loss of expression of fragile X mental retardation protein (FMRP), an RNA-binding protein that regulates translation of numerous mRNA targets, some of which are present at synapses. While protein synthesis deficits have long been postulated as an etiology of FXS, how FMRP loss affects distributions of newly synthesized proteins is unknown. Here we investigated the role of FMRP in regulating expression of new copies of the synaptic protein PSD95 in an in vitro model of synaptic plasticity. We find that local BDNF application promotes persistent accumulation of new PSD95 at stimulated synapses and dendrites of cultured neurons, and that this accumulation is absent in FMRP-deficient mouse neurons. New PSD95 accumulation at sites of BDNF stimulation does not require known mechanisms regulating FMRP–mRNA interactions but instead requires the PI3K-mTORC1-S6K1 pathway. Surprisingly, in FMRP-deficient neurons, BDNF induction of new PSD95 accumulation can be restored by mTORC1-S6K1 blockade, suggesting that constitutively high mTORC1-S6K1 activity occludes PSD95 regulation by BDNF and that alternative pathways exist to mediate induction when mTORC1-S6K1 is inhibited. This study provides direct evidence for deficits in local protein synthesis and accumulation of newly synthesized protein in response to local stimulation in FXS, and supports mTORC1-S6K1 pathway inhibition as a potential therapeutic approach for FXS.

Fragile X Mental Retardation Protein FMRP Binds mRNAs in the Nucleus

Molecular and Cellular Biology ◽

10.1128/mcb.01377-08 ◽

2008 ◽

Vol 29 (1) ◽

pp. 214-228 ◽

Cited By ~ 67

Author(s):

Miri Kim ◽

Michel Bellini ◽

Stephanie Ceman

Keyword(s):

Mental Retardation ◽

Nuclear Export ◽

Rna Binding ◽

Fragile X ◽

Simian Virus 40 ◽

Nuclear Localization Sequence ◽

Dependent Manner ◽

Nuclear Export Sequence ◽

ABSTRACT The fragile X mental retardation protein FMRP is an RNA binding protein that associates with a large collection of mRNAs. Since FMRP was previously shown to be a nucleocytoplasmic shuttling protein, we examined the hypothesis that FMRP binds its cargo mRNAs in the nucleus. The enhanced green fluorescent protein-tagged FMRP construct (EGFP-FMRP) expressed in Cos-7 cells was efficiently exported from the nucleus in the absence of its nuclear export sequence and in the presence of a strong nuclear localization sequence (the simian virus 40 [SV40] NLS), suggesting an efficient mechanism for nuclear export. We hypothesized that nuclear FMRP exits the nucleus through its bound mRNAs. Using silencing RNAs to the bulk mRNA exporter Tap/NXF1, we observed a significantly increased number of cells containing EGFP-FMRP in the nucleus, which was further augmented by removal of FMRP's nuclear export sequence. Nuclear-retained SV40-FMRP could be released upon treatment with RNase. Further, Tap/NXF1 coimmunoprecipitated with EGFP-FMRP in an RNA-dependent manner and contained the FMR1 mRNA. To determine whether FMRP binds pre-mRNAs cotranscriptionally, we expressed hemagglutinin-SV40 FMRP in amphibian oocytes and found it, as well as endogenous Xenopus FMRP, on the active transcription units of lampbrush chromosomes. Collectively, our data provide the first lines of evidence that FMRP binds mRNA in the nucleus.

Temporal-specific roles of fragile X mental retardation protein in the development of the hindbrain auditory circuit

Development ◽

10.1242/dev.188797 ◽

2020 ◽

Vol 147 (21) ◽

pp. dev188797

Author(s):

Xiaoyu Wang ◽

Ayelet Kohl ◽

Xiaoyan Yu ◽

Diego A. R. Zorio ◽

Avihu Klar ◽

...

Keyword(s):

Mental Retardation ◽

Rna Binding ◽

Fragile X ◽

Neuronal Cell ◽

High Specificity ◽

Midline Crossing ◽

Axonal Targeting

ABSTRACTFragile X mental retardation protein (FMRP) is an RNA-binding protein abundant in the nervous system. Functional loss of FMRP leads to sensory dysfunction and severe intellectual disabilities. In the auditory system, FMRP deficiency alters neuronal function and synaptic connectivity and results in perturbed processing of sound information. Nevertheless, roles of FMRP in embryonic development of the auditory hindbrain have not been identified. Here, we developed high-specificity approaches to genetically track and manipulate throughout development of the Atoh1+ neuronal cell type, which is highly conserved in vertebrates, in the cochlear nucleus of chicken embryos. We identified distinct FMRP-containing granules in the growing axons of Atoh1+ neurons and post-migrating NM cells. FMRP downregulation induced by CRISPR/Cas9 and shRNA techniques resulted in perturbed axonal pathfinding, delay in midline crossing, excess branching of neurites, and axonal targeting errors during the period of circuit development. Together, these results provide the first in vivo identification of FMRP localization and actions in developing axons of auditory neurons, and demonstrate the importance of investigating early embryonic alterations toward understanding the pathogenesis of neurodevelopmental disorders.

Conformational-Dependent and Independent RNA Binding to the Fragile X Mental Retardation Protein

Journal of Nucleic Acids ◽

10.4061/2011/246127 ◽

2011 ◽

Vol 2011 ◽

pp. 1-14 ◽

Cited By ~ 1

Author(s):

Xin Yan ◽

Robert B. Denman

Keyword(s):

Mental Retardation ◽

Rna Binding ◽

Fragile X ◽

In Vitro Transcription ◽

Rna Transcripts ◽

Arginine Residues ◽

Rnase Digestion

The interaction between the fragile X mental retardation protein (FMRP) and BC1 RNA has been the subject of controversy. We probed the parameters of RNA binding to FMRP in several ways. Nondenaturing agarose gel analysis showed that BC1 RNA transcripts produced by in vitro transcription contain a population of conformers, which can be modulated by preannealing. Accordingly, FMRP differentially binds to the annealed and unannealed conformer populations. Using partial RNase digestion, we demonstrate that annealed BC1 RNA contains a unique conformer that FMRP likely binds. We further demonstrate that this interaction is 100-fold weaker than that the binding of eEF-1A mRNA and FMRP, and that preannealing is not a general requirement for FMRP's interaction with RNA. In addition, binding does not require the N-terminal 204 amino acids of FMRP, methylated arginine residues and can be recapitulated by both fragile X paralogs. Altogether, our data continue to support a model in which BC1 RNA functions independently of FMRP.

Cells Lacking the Fragile X Mental Retardation Protein (FMRP) have Normal RISC Activity but Exhibit Altered Stress Granule Assembly

Molecular Biology of the Cell ◽

10.1091/mbc.e08-07-0737 ◽

2009 ◽

Vol 20 (1) ◽

pp. 428-437 ◽

Cited By ~ 53

Author(s):

Marie-Cécile Didiot ◽

Murugan Subramanian ◽

Eric Flatter ◽

Jean-Louis Mandel ◽

Hervé Moine

Keyword(s):

Mental Retardation ◽

Molecular Mechanisms ◽

Rna Binding ◽

Fragile X ◽

Stress Granule ◽

Translation Regulation ◽

Positive Role ◽

Granule Formation ◽

The fragile X mental retardation protein (FMRP) is an RNA-binding protein involved in the mRNA metabolism. The absence of FMRP in neurons leads to alterations of the synaptic plasticity, probably as a result of translation regulation defects. The exact molecular mechanisms by which FMRP plays a role in translation regulation have remained elusive. The finding of an interaction between FMRP and the RNA interference silencing complex (RISC), a master of translation regulation, has suggested that both regulators could be functionally linked. We investigated here this link, and we show that FMRP exhibits little overlap both physically and functionally with the RISC machinery, excluding a direct impact of FMRP on RISC function. Our data indicate that FMRP and RISC are associated to distinct pools of mRNAs. FMRP, unlike RISC machinery, associates with the pool of mRNAs that eventually goes into stress granules upon cellular stress. Furthermore, we show that FMRP plays a positive role in this process as the lack of FMRP or a point mutant causing a severe fragile X alter stress granule formation. Our data support the proposal that FMRP plays a role in controlling the fate of mRNAs after translation arrest.