Spag16, an Axonemal Central Apparatus Gene, Encodes a Male Germ Cell Nuclear Speckle Protein that Regulates SPAG16 mRNA Expression

Authors

David R. Nagarkatti-Gude, Virginia Commonwealth UniversityFollow
Ruth Jaimez, University of Pennsylvania
Scott C. Henderson, Virginia Commonwealth UniversityFollow
Maria E. Teves, Virginia Commonwealth UniversityFollow
Zhibing Zhang, Virginia Commonwealth UniversityFollow
Jerome F. Strauss III, Virginia Commonwealth UniversityFollow

Document Type

Article

Original Publication Date

2011

Journal/Book/Conference Title

PLOS ONE

Volume

6

DOI of Original Publication

10.1371/journal.pone.0020625

Comments

Originally published at http://dx.doi.org/10.1371/journal.pone.0020625

Date of Submission

November 2014

Abstract

Spag16 is the murine orthologue of Chlamydomonas reinhardtii PF20, a protein known to be essential to the structure and function of the “9+2” axoneme. In Chlamydomonas, the PF20gene encodes a single protein present in the central pair of the axoneme. Loss of PF20 prevents central pair assembly/integrity and results in flagellar paralysis. Here we demonstrate that the murine Spag16 gene encodes two proteins: 71 kDa SPAG16L, which is found in all murine cells with motile cilia or flagella, and 35 kDa SPAG16S, representing the C terminus of SPAG16L, which is expressed only in male germ cells, and is predominantly found in specific regions within the nucleus that also contain SC35, a known marker of nuclear speckles enriched in pre-mRNA splicing factors. SPAG16S expression precedes expression of SPAG16L. Mice homozygous for a knockout of SPAG16L alone are infertile, but show no abnormalities in spermatogenesis. Mice chimeric for a mutation deleting the transcripts for both SPAG16L and SPAG16S have a profound defect in spermatogenesis. We show here that transduction of SPAG16S into cultured dispersed mouse male germ cells and BEAS-2B human bronchial epithelial cells increases SPAG16L expression, but has no effect on the expression of several other axoneme components. We also demonstrate that the Spag16Lpromoter shows increased activity in the presence of SPAG16S. The distinct nuclear localization of SPAG16S and its ability to modulate Spag16L mRNA expression suggest that SPAG16S plays an important role in the gene expression machinery of male germ cells. This is a unique example of a highly conserved axonemal protein gene that encodes two protein products with different functions.

Rights

© 2011 Nagarkatti-Gude et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Is Part Of

VCU Biochemistry and Molecular Biology Publications