Journal Article

Interaction of survival of motor neuron (SMN) and HuD proteins with mRNA cpg15 rescues motor neuron axonal deficits

Kye, Min Jeong, Merianda, Tanuja T, Singh, Sasha, Twiss, Jeffery L, Hao, Le T, Wertz, Mary H, Nie, Duyu, Beattie, Christine E, Steen, Judith A.J, Huang, Jia, Akten, Bikem, Sahin, Mustafa

2011

Overview

Spinal muscular atrophy (SMA), caused by the deletion of the SMN1 gene, is the leading genetic cause of infant mortality. SMN protein is present at high levels in both axons and growth cones, and loss of its function disrupts axonal extension and pathfinding. SMN is known to associate with the RNA-binding protein hnRNP-R, and together they are responsible for the transport and/or local translation of β-actin mRNA in the growth cones of motor neurons. However, the full complement of SMN-interacting proteins in neurons remains unknown. Here we used mass spectrometry to identify HuD as a novel neuronal SMN-interacting partner. HuD is a neuron-specific RNA-binding protein that interacts with mRNAs, including candidate plasticity-related gene 15 (cpg15). We show that SMN and HuD form a complex in spinal motor axons, and that both interact with cpg15 mRNA in neurons. CPG15 is highly expressed in the developing ventral spinal cord and can promote motor axon branching and neuromuscular synapse formation, suggesting a crucial role in the development of motor axons and neuromuscular junctions. Cpg15 mRNA previously has been shown to localize into axonal processes. Here we show that SMN deficiency reduces cpg15 mRNA levels in neurons, and, more importantly, cpg15 overexpression partially rescues the SMN-deficiency phenotype in zebrafish. Our results provide insight into the function of SMN protein in axons and also identify potential targets for the study of mechanisms that lead to the SMA pathology and related neuromuscular diseases.

• Publisher: National Academy of Sciences,National Academy of Sciences Issue,National Acad Sciences
• Subject: Actin / Animals / Animals, Genetically Modified / Antibodies / Axon guidance / Axonogenesis / Axons / Axons - metabolism / Axons - pathology / Biological Sciences / branching / Cell survival / Cells, Cultured / Danio rerio / ELAV Proteins - genetics / ELAV Proteins - metabolism / ELAV-Like Protein 4 / Embryo, Mammalian - anatomy & histology / Embryo, Mammalian - physiology / Gene deletion / Gene expression regulation / gene overexpression / genes / Genotype & phenotype / GPI-Linked Proteins - genetics / GPI-Linked Proteins - metabolism / Growth cones / HuD protein / Humans / Infant mortality / Infants / Mass spectrometry / Mass spectroscopy / Mental disorders / Messenger RNA / Mice / Mortality / motor development / Motor neurons / Motor Neurons - cytology / Motor Neurons - metabolism / muscular atrophy / Nerve Tissue Proteins - genetics / Nerve Tissue Proteins - metabolism / Neuromuscular diseases / Neuromuscular junctions / Neurons / Neuropeptides - genetics / Neuropeptides - metabolism / Neuroscience / Pathology / phenotype / Proteins / Recombinant Fusion Proteins - genetics / Recombinant Fusion Proteins - metabolism / Ribonucleic acid / RNA / RNA, Messenger - genetics / RNA, Messenger - metabolism / RNA-binding protein / RNA-binding proteins / SMN complex proteins / SMN protein / Spinal cord / spinal muscular atrophy / survival / Survival of Motor Neuron 1 Protein - genetics / Survival of Motor Neuron 1 Protein - metabolism / synapse / Translation / translation (genetics) / Zebrafish / Zebrafish - embryology / Zebrafish - physiology