Mutational analysis establishes a critical role for the N terminus of fragile X mental retardation protein FMRP.
Fragile X syndrome is the most common form of heritable mental retardation caused by the loss of function of the fragile X mental retardation protein FMRP. FMRP is a multidomain, RNA-binding protein involved in RNA transport and/or translational regulation. However, the binding specificity between FMRP and its various partners including interacting proteins and mRNA targets is essentially unknown. Previous work demonstrated that dFMRP, the Drosophila homolog of human FMRP, is structurally and functionally conserved with its mammalian counterparts. Here, we perform a forward genetic screen and isolate 26 missense mutations at 13 amino acid residues in the dFMRP coding dfmr1. Interestingly, all missense mutations identified affect highly conserved residues in the N terminal of dFMRP. Loss- and gain-of-function analyses reveal altered axonal and synaptic elaborations in mutants. Yeast two-hybrid assays and in vivo analyses of interaction with CYFIP (cytoplasmic FMR1 interacting protein) in the nervous system demonstrate that some of the mutations disrupt specific protein-protein interactions. Thus, our mutational analyses establish that the N terminus of FMRP is critical for its neuronal function.
Reeve
Simon P
SP
Laboratory of Neurogenetics, Department of Molecular and Developmental Genetics, Flanders Institute for Biotechnology, 3000 Leuven, Belgium.
Lin
Xinda
X
Sahin
Bahar H
BH
Jiang
Fangfang
F
Yao
Aiyu
A
Liu
Zhihua
Z
Zhi
Hui
H
Broadie
Kendal
K
Li
Wei
W
Giangrande
Angela
A
Hassan
Bassem A
BA
Zhang
Yong Q
YQ
D000595:Amino Acid Sequence; D000818:Animals; D030801:Animals, Genetically Modified; D001483:Base Sequence; D002490:Central Nervous System / Q000378:metabolism; D017124:Conserved Sequence; D004252:DNA Mutational Analysis / Q000379:methods*; D004330:Drosophila; D029721:Drosophila Proteins / Q000235:genetics; D051860:Fragile X Messenger Ribonucleoprotein 1 / Q000737:chemistry* / Q000235:genetics*; D005786:Gene Expression Regulation; D008969:Molecular Sequence Data; D009154:Mutation / Q000502:physiology*; D009469:Neuromuscular Junction / Q000378:metabolism; D009474:Neurons / Q000378:metabolism; D010525:Peripheral Nerves / Q000166:cytology; D017434:Protein Structure, Tertiary; D020798:Two-Hybrid System Techniques
D029721:Drosophila Proteins; D051860:Fragile X Messenger Ribonucleoprotein 1