ZPR1 Is Essential for Survival and Is Required for Localization of the Survival Motor Neurons (SMN) Protein to Cajal Bodies

Abstract

Mutation of the survival motor neurons 1 (SMN1) gene causes motor neuron apoptosis and represents the major cause of spinal muscular atrophy in humans. Biochemical studies have established that the SMN protein plays an important role in spliceosomal small nuclear ribonucleoprotein (snRNP) biogenesis and that the SMN complex can interact with the zinc finger protein ZPR1. Here we report that targeted ablation of the Zpr1 gene in mice disrupts the subcellular localization of both SMN and spliceosomal snRNPs. Specifically, SMN localization to Cajal bodies and gems was not observed in cells derived from Zpr1^−/− embryos and the amount of cytoplasmic snRNP detected in Zpr1^−/− embryos was reduced compared with that in wild-type embryos. We found that Zpr1^−/− mice die during early embryonic development, with reduced proliferation and increased apoptosis. These effects of Zpr1 gene disruption were confirmed and extended in studies of cultured motor neuron-like cells using small interfering RNA-mediated Zpr1 gene suppression; ZPR1 deficiency caused growth cone retraction, axonal defects, and apoptosis. Together, these data indicate that ZPR1 contributes to the regulation of SMN complexes and that it is essential for cell survival.

SUPPLEMENTAL MATERIAL

Supplemental material for this article may be found at http://mcb.asm.org/.

ACKNOWLEDGMENTS

We thank Neil Cashman for providing motor neurons, Eng Tan for providing the coilin antibody, Gideon Dreyfuss for providing the SMN antibody, Linda Evalgelista for performing the ES cell culture, John Nunnari and Greg Hendricks for performing electron microscopy, Stephen Jones for performing blastocyst injections, Brooke Barbara for contributing expert technical assistance, and Kathy Gemme for providing administrative assistance.

This work was supported, in part, by the Muscular Dystrophy Association (to L.G.), The Families of SMA (to L.G.), NIH/NINDS (to R.J.D.), and the Diabetes and Endocrinology Research Center (DERC) of the University of Massachusetts (NIH/NIDDK). R.A.F. and R.J.D. are investigators of the Howard Hughes Medical Institute.