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Deletion of the pluripotency-associated Tex19.1 gene causes activation of endogenous retroviruses and defective spermatogenesis in mice.

Ollinger R, Childs AJ, Burgess HM, Speed RM, Lundegaard PR, Reynolds N, Gray NK, Cooke HJ, Adams IR - PLoS Genet. (2008)

Bottom Line: Immunostaining and histological analysis revealed defects in meiotic chromosome synapsis, the persistence of DNA double-strand breaks during meiosis, and a loss of post-meiotic germ cells in the testis.Furthermore, expression of a class of endogenous retroviruses is upregulated during meiosis in the Tex19.1(-/-) testes.Our results suggest that Tex19.1 is part of a specialised mechanism that operates in the germline to repress transposable genetic elements and maintain genomic stability through successive generations.

View Article: PubMed Central - PubMed

Affiliation: MRC Human Genetics Unit, Western General Hospital, Edinburgh, United Kingdom.

ABSTRACT
As genetic information is transmitted through successive generations, it passes between pluripotent cells in the early embryo and germ cells in the developing foetus and adult animal. Tex19.1 encodes a protein of unknown function, whose expression is restricted to germ cells and pluripotent cells. During male spermatogenesis, Tex19.1 expression is highest in mitotic spermatogonia and diminishes as these cells differentiate and progress through meiosis. In pluripotent stem cells, Tex19.1 expression is also downregulated upon differentiation. However, it is not clear whether Tex19.1 has an essential function in germ cells or pluripotent stem cells, or what that function might be. To analyse the potential role of Tex19.1 in pluripotency or germ cell function we have generated Tex19.1(-/-) knockout mice and analysed the Tex19.1(-/-) mutant phenotype. Adult Tex19.1(-/-) knockout males exhibit impaired spermatogenesis. Immunostaining and histological analysis revealed defects in meiotic chromosome synapsis, the persistence of DNA double-strand breaks during meiosis, and a loss of post-meiotic germ cells in the testis. Furthermore, expression of a class of endogenous retroviruses is upregulated during meiosis in the Tex19.1(-/-) testes. Increased transposition of endogenous retroviruses in the germline of Tex19.1(-/-) mutant mice, and the concomitant increase in DNA damage, may be sufficient to disrupt the normal processes of recombination and chromosome synapsis during meiosis and cause defects in spermatogenesis. Our results suggest that Tex19.1 is part of a specialised mechanism that operates in the germline to repress transposable genetic elements and maintain genomic stability through successive generations.

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Expression of the endogenous retrovirus MMERVK10C is upregulated in Tex19.1−/−  testes.(A) Quantitative PCR showing relative expression of retrotransposons and marker genes in testes from 16 dpp Tex19.1−/− knockout animals relative to their Tex19.1+/+ wild-type littermates. Expression levels in cDNAs prepared from different animals were normalised to Sdmg1, animals represented in the first and third columns were littermates, and those in the second and fourth columns were littermates. Error bars indicate standard error. (B) Northern blot probed for MMERVK10C env transcripts in Tex19.1+/+ wild-type and Tex19.1−/− knockout testes at 16 dpp. A schematic diagram showing the organisation of the 8.5 kb full-length MMERVK10C element and the predicted size and organisation of the env-containing transcripts (∼8.5 kb and ∼3.3 kb, [39]) is shown above the Northern blot. Littermates are indicated with a black bar. 28S rRNA is shown as a loading control. (C–L) In situ hybridisation with an antisense MMERVK10C probe (purple precipitate) in Tex19.1+/+, Tex19.1+/− and Tex19.1−/− testes. Nuclei are counterstained with nuclear fast red. (C, D, G, H) Low-level expression of MMERVK10C can be seen in some seminiferous tubules in Tex19.1+/+ and Tex19.1+/− testes. However, MMERVK10C transcripts are more abundant in testes from 16 dpp Tex19.1−/− animals than those from heterozygous or wild-type littermates. (K, L) MMERVK10C transcripts are upregulated in meiotic spermatocytes in 16 dpp Tex19.1−/− mutant testes. (E, F, I, J) MMERVK10C transcripts are upregulated in meiotic spermatocytes in testes from adult Tex19.1−/− knockout animals relative to their Tex19.1+/− heterozygous littermates. (M, N) Control in situ hybridisation with a sense MMERVK10C probe shows no staining in adult Tex19.1+/− or Tex19.1−/− testes.
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pgen-1000199-g006: Expression of the endogenous retrovirus MMERVK10C is upregulated in Tex19.1−/− testes.(A) Quantitative PCR showing relative expression of retrotransposons and marker genes in testes from 16 dpp Tex19.1−/− knockout animals relative to their Tex19.1+/+ wild-type littermates. Expression levels in cDNAs prepared from different animals were normalised to Sdmg1, animals represented in the first and third columns were littermates, and those in the second and fourth columns were littermates. Error bars indicate standard error. (B) Northern blot probed for MMERVK10C env transcripts in Tex19.1+/+ wild-type and Tex19.1−/− knockout testes at 16 dpp. A schematic diagram showing the organisation of the 8.5 kb full-length MMERVK10C element and the predicted size and organisation of the env-containing transcripts (∼8.5 kb and ∼3.3 kb, [39]) is shown above the Northern blot. Littermates are indicated with a black bar. 28S rRNA is shown as a loading control. (C–L) In situ hybridisation with an antisense MMERVK10C probe (purple precipitate) in Tex19.1+/+, Tex19.1+/− and Tex19.1−/− testes. Nuclei are counterstained with nuclear fast red. (C, D, G, H) Low-level expression of MMERVK10C can be seen in some seminiferous tubules in Tex19.1+/+ and Tex19.1+/− testes. However, MMERVK10C transcripts are more abundant in testes from 16 dpp Tex19.1−/− animals than those from heterozygous or wild-type littermates. (K, L) MMERVK10C transcripts are upregulated in meiotic spermatocytes in 16 dpp Tex19.1−/− mutant testes. (E, F, I, J) MMERVK10C transcripts are upregulated in meiotic spermatocytes in testes from adult Tex19.1−/− knockout animals relative to their Tex19.1+/− heterozygous littermates. (M, N) Control in situ hybridisation with a sense MMERVK10C probe shows no staining in adult Tex19.1+/− or Tex19.1−/− testes.

Mentions: The levels of MMERVK10C expression in testis cDNA from two Tex19.1−/− knockout animals relative to their Tex19.1+/+ wild-type littermates were each tested by quantitative PCR (Figure 6A). The Sertoli cell marker Sdmg1[22] was used to normalise cDNAs from different animals. Although there was no significant change in the expression of the ubiquitously expressed β-actin gene, or the germ cell marker Dazl[38], expression of the MMERVK10C endogenous retrovirus was increased by a factor of approximately four-fold in both Tex19.1−/− knockout animals (Student's t-test, p<0.01) (Figure 6A). Expression of LINE, SINE or IAP retrotransposons showed no significant change in the absence of Tex19.1 (Figure 6A).


Deletion of the pluripotency-associated Tex19.1 gene causes activation of endogenous retroviruses and defective spermatogenesis in mice.

Ollinger R, Childs AJ, Burgess HM, Speed RM, Lundegaard PR, Reynolds N, Gray NK, Cooke HJ, Adams IR - PLoS Genet. (2008)

Expression of the endogenous retrovirus MMERVK10C is upregulated in Tex19.1−/−  testes.(A) Quantitative PCR showing relative expression of retrotransposons and marker genes in testes from 16 dpp Tex19.1−/− knockout animals relative to their Tex19.1+/+ wild-type littermates. Expression levels in cDNAs prepared from different animals were normalised to Sdmg1, animals represented in the first and third columns were littermates, and those in the second and fourth columns were littermates. Error bars indicate standard error. (B) Northern blot probed for MMERVK10C env transcripts in Tex19.1+/+ wild-type and Tex19.1−/− knockout testes at 16 dpp. A schematic diagram showing the organisation of the 8.5 kb full-length MMERVK10C element and the predicted size and organisation of the env-containing transcripts (∼8.5 kb and ∼3.3 kb, [39]) is shown above the Northern blot. Littermates are indicated with a black bar. 28S rRNA is shown as a loading control. (C–L) In situ hybridisation with an antisense MMERVK10C probe (purple precipitate) in Tex19.1+/+, Tex19.1+/− and Tex19.1−/− testes. Nuclei are counterstained with nuclear fast red. (C, D, G, H) Low-level expression of MMERVK10C can be seen in some seminiferous tubules in Tex19.1+/+ and Tex19.1+/− testes. However, MMERVK10C transcripts are more abundant in testes from 16 dpp Tex19.1−/− animals than those from heterozygous or wild-type littermates. (K, L) MMERVK10C transcripts are upregulated in meiotic spermatocytes in 16 dpp Tex19.1−/− mutant testes. (E, F, I, J) MMERVK10C transcripts are upregulated in meiotic spermatocytes in testes from adult Tex19.1−/− knockout animals relative to their Tex19.1+/− heterozygous littermates. (M, N) Control in situ hybridisation with a sense MMERVK10C probe shows no staining in adult Tex19.1+/− or Tex19.1−/− testes.
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Related In: Results  -  Collection

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Show All Figures
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pgen-1000199-g006: Expression of the endogenous retrovirus MMERVK10C is upregulated in Tex19.1−/− testes.(A) Quantitative PCR showing relative expression of retrotransposons and marker genes in testes from 16 dpp Tex19.1−/− knockout animals relative to their Tex19.1+/+ wild-type littermates. Expression levels in cDNAs prepared from different animals were normalised to Sdmg1, animals represented in the first and third columns were littermates, and those in the second and fourth columns were littermates. Error bars indicate standard error. (B) Northern blot probed for MMERVK10C env transcripts in Tex19.1+/+ wild-type and Tex19.1−/− knockout testes at 16 dpp. A schematic diagram showing the organisation of the 8.5 kb full-length MMERVK10C element and the predicted size and organisation of the env-containing transcripts (∼8.5 kb and ∼3.3 kb, [39]) is shown above the Northern blot. Littermates are indicated with a black bar. 28S rRNA is shown as a loading control. (C–L) In situ hybridisation with an antisense MMERVK10C probe (purple precipitate) in Tex19.1+/+, Tex19.1+/− and Tex19.1−/− testes. Nuclei are counterstained with nuclear fast red. (C, D, G, H) Low-level expression of MMERVK10C can be seen in some seminiferous tubules in Tex19.1+/+ and Tex19.1+/− testes. However, MMERVK10C transcripts are more abundant in testes from 16 dpp Tex19.1−/− animals than those from heterozygous or wild-type littermates. (K, L) MMERVK10C transcripts are upregulated in meiotic spermatocytes in 16 dpp Tex19.1−/− mutant testes. (E, F, I, J) MMERVK10C transcripts are upregulated in meiotic spermatocytes in testes from adult Tex19.1−/− knockout animals relative to their Tex19.1+/− heterozygous littermates. (M, N) Control in situ hybridisation with a sense MMERVK10C probe shows no staining in adult Tex19.1+/− or Tex19.1−/− testes.
Mentions: The levels of MMERVK10C expression in testis cDNA from two Tex19.1−/− knockout animals relative to their Tex19.1+/+ wild-type littermates were each tested by quantitative PCR (Figure 6A). The Sertoli cell marker Sdmg1[22] was used to normalise cDNAs from different animals. Although there was no significant change in the expression of the ubiquitously expressed β-actin gene, or the germ cell marker Dazl[38], expression of the MMERVK10C endogenous retrovirus was increased by a factor of approximately four-fold in both Tex19.1−/− knockout animals (Student's t-test, p<0.01) (Figure 6A). Expression of LINE, SINE or IAP retrotransposons showed no significant change in the absence of Tex19.1 (Figure 6A).

Bottom Line: Immunostaining and histological analysis revealed defects in meiotic chromosome synapsis, the persistence of DNA double-strand breaks during meiosis, and a loss of post-meiotic germ cells in the testis.Furthermore, expression of a class of endogenous retroviruses is upregulated during meiosis in the Tex19.1(-/-) testes.Our results suggest that Tex19.1 is part of a specialised mechanism that operates in the germline to repress transposable genetic elements and maintain genomic stability through successive generations.

View Article: PubMed Central - PubMed

Affiliation: MRC Human Genetics Unit, Western General Hospital, Edinburgh, United Kingdom.

ABSTRACT
As genetic information is transmitted through successive generations, it passes between pluripotent cells in the early embryo and germ cells in the developing foetus and adult animal. Tex19.1 encodes a protein of unknown function, whose expression is restricted to germ cells and pluripotent cells. During male spermatogenesis, Tex19.1 expression is highest in mitotic spermatogonia and diminishes as these cells differentiate and progress through meiosis. In pluripotent stem cells, Tex19.1 expression is also downregulated upon differentiation. However, it is not clear whether Tex19.1 has an essential function in germ cells or pluripotent stem cells, or what that function might be. To analyse the potential role of Tex19.1 in pluripotency or germ cell function we have generated Tex19.1(-/-) knockout mice and analysed the Tex19.1(-/-) mutant phenotype. Adult Tex19.1(-/-) knockout males exhibit impaired spermatogenesis. Immunostaining and histological analysis revealed defects in meiotic chromosome synapsis, the persistence of DNA double-strand breaks during meiosis, and a loss of post-meiotic germ cells in the testis. Furthermore, expression of a class of endogenous retroviruses is upregulated during meiosis in the Tex19.1(-/-) testes. Increased transposition of endogenous retroviruses in the germline of Tex19.1(-/-) mutant mice, and the concomitant increase in DNA damage, may be sufficient to disrupt the normal processes of recombination and chromosome synapsis during meiosis and cause defects in spermatogenesis. Our results suggest that Tex19.1 is part of a specialised mechanism that operates in the germline to repress transposable genetic elements and maintain genomic stability through successive generations.

Show MeSH
Related in: MedlinePlus