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Spag16, an axonemal central apparatus gene, encodes a male germ cell nuclear speckle protein that regulates SPAG16 mRNA expression.

Nagarkatti-Gude DR, Jaimez R, Henderson SC, Teves ME, Zhang Z, Strauss JF - PLoS ONE (2011)

Bottom Line: 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.This is a unique example of a highly conserved axonemal protein gene that encodes two protein products with different functions.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, Virginia, United States of America.

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 PF20 gene 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 Spag16L promoter 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.

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SPAG16S co-localizes with SC35 in nuclear speckles of mouse male germ cells.(A) Mixed male germ cells immunolabeled for SC35 (green) or SPAG16 (red), with DAPI as a nuclear marker. (B) Co-localization analysis of SC35 + SPAG16, n = 43.
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pone-0020625-g005: SPAG16S co-localizes with SC35 in nuclear speckles of mouse male germ cells.(A) Mixed male germ cells immunolabeled for SC35 (green) or SPAG16 (red), with DAPI as a nuclear marker. (B) Co-localization analysis of SC35 + SPAG16, n = 43.

Mentions: In order to characterize the discrete nuclear structures identified by immunohistochemical analysis of SPAG16S localization, wild-type germ cells were co-immunolabeled with both the C-terminal SPAG16 antibody and a monoclonal antibody directed against SC35, a marker for nuclear speckles. SC35 and SPAG16S signals strongly overlapped (Fig. 5A). They were determined to have a significant co-localization (Fig. 5B – Pearson's coefficient = 0.40). Analysis demonstrated that 79% of SC35 signal co-localized with SPAG16S, while 44% of SPAG16S signal co-localized with SC35; in other words, most SC35-containing domains also contained SPAG16S, but SPAG16S had a wider distribution as well.


Spag16, an axonemal central apparatus gene, encodes a male germ cell nuclear speckle protein that regulates SPAG16 mRNA expression.

Nagarkatti-Gude DR, Jaimez R, Henderson SC, Teves ME, Zhang Z, Strauss JF - PLoS ONE (2011)

SPAG16S co-localizes with SC35 in nuclear speckles of mouse male germ cells.(A) Mixed male germ cells immunolabeled for SC35 (green) or SPAG16 (red), with DAPI as a nuclear marker. (B) Co-localization analysis of SC35 + SPAG16, n = 43.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3105110&req=5

pone-0020625-g005: SPAG16S co-localizes with SC35 in nuclear speckles of mouse male germ cells.(A) Mixed male germ cells immunolabeled for SC35 (green) or SPAG16 (red), with DAPI as a nuclear marker. (B) Co-localization analysis of SC35 + SPAG16, n = 43.
Mentions: In order to characterize the discrete nuclear structures identified by immunohistochemical analysis of SPAG16S localization, wild-type germ cells were co-immunolabeled with both the C-terminal SPAG16 antibody and a monoclonal antibody directed against SC35, a marker for nuclear speckles. SC35 and SPAG16S signals strongly overlapped (Fig. 5A). They were determined to have a significant co-localization (Fig. 5B – Pearson's coefficient = 0.40). Analysis demonstrated that 79% of SC35 signal co-localized with SPAG16S, while 44% of SPAG16S signal co-localized with SC35; in other words, most SC35-containing domains also contained SPAG16S, but SPAG16S had a wider distribution as well.

Bottom Line: 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.This is a unique example of a highly conserved axonemal protein gene that encodes two protein products with different functions.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, Virginia, United States of America.

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 PF20 gene 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 Spag16L promoter 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.

Show MeSH
Related in: MedlinePlus