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The Tnfrh1 (Tnfrsf23) gene is weakly imprinted in several organs and expressed at the trophoblast-decidua interface.

Clark L, Wei M, Cattoretti G, Mendelsohn C, Tycko B - BMC Genet. (2002)

Bottom Line: Genes preferentially expressed in the placenta are predicted to evolve rapidly, and Tnfrh1 appears to be an example of this phenomenon.In view of its strong expression in cells at the fetal-maternal boundary, Tnfrh1 warrants further study as a gene that might modulate immune or trophic interactions between the invasive placental trophoblast and the maternal decidua.The preferential expression of Tnfrh1 from the maternal allele indicates weak functional imprinting of this locus in some tissues.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute for Cancer Genetics, Columbia University College of Physicians and Surgeons, New York, NY, USA. lc654@columbia.edu

ABSTRACT

Background: The Tnfrh1 gene (gene symbol Tnfrsf23) is located near one end of a megabase-scale imprinted region on mouse distal chromosome 7, about 350 kb distant from the nearest known imprinting control element. Within 20 kb of Tnfrh1 is a related gene called Tnfrh2 (Tnfrsf22) These duplicated genes encode putative decoy receptors in the tumor necrosis factor (TNF) receptor family. Although other genes in this chromosomal region show conserved synteny with genes on human Chr11p15.5, there are no obvious human orthologues of Tnfrh1 or Tnfrh2.

Results: We analyzed Tnfrh1 for evidence of parental imprinting, and characterized its tissue-specific expression. Tnfrh1 mRNA is detectable in multiple adult and fetal tissues, with highest expression in placenta, where in situ hybridization reveals a distinctive population of Tnfrh1-positive cells in maternal decidua, directly beneath the trophoblast giant cells. In offspring of interspecific mouse crosses, Tnfrh1 shows a consistent parent-of-origin-dependent allelic expression bias, with relative repression, but not silencing, of the paternal allele in several organs including fetal liver and adult spleen.

Conclusions: Genes preferentially expressed in the placenta are predicted to evolve rapidly, and Tnfrh1 appears to be an example of this phenomenon. In view of its strong expression in cells at the fetal-maternal boundary, Tnfrh1 warrants further study as a gene that might modulate immune or trophic interactions between the invasive placental trophoblast and the maternal decidua. The preferential expression of Tnfrh1 from the maternal allele indicates weak functional imprinting of this locus in some tissues.

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Preferential expression of the maternal allele of Tnfrh1 in fetal liver from CAST × BL/6 reciprocal crosses.A, Analysis of the MboII RFLP, in which the BL/6 allele is undigested and the CAST allele yields two fragments. There is a strong maternal allele bias in placenta, and a weaker but still obvious parent-of-origin dependent biases in fetal liver. This imprinting effect is superimposed on a non-imprinted bias for higher expression of the BL/6 allele. The allelic bias in placenta reflects expression from maternal cells, but the bias in fetal liver reflects parental imprinting. Similar results were obtained with multiple aliquots of cDNA (not shown). B=BL/6, C=CAST. (Note that only the internal comparisons of alleles in single PCR reactions are valid; the stronger band obtained from the CAST maternal kidney should not be compared to that from the BL/6 maternal kidney for intensity of expression, since these were separate RT-PCR reactions). B, Direct sequencing of RT-PCR products. This shows an allelic expression bias that depends on the direction of the cross, consistent with the RFLP results.
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Figure 7: Preferential expression of the maternal allele of Tnfrh1 in fetal liver from CAST × BL/6 reciprocal crosses.A, Analysis of the MboII RFLP, in which the BL/6 allele is undigested and the CAST allele yields two fragments. There is a strong maternal allele bias in placenta, and a weaker but still obvious parent-of-origin dependent biases in fetal liver. This imprinting effect is superimposed on a non-imprinted bias for higher expression of the BL/6 allele. The allelic bias in placenta reflects expression from maternal cells, but the bias in fetal liver reflects parental imprinting. Similar results were obtained with multiple aliquots of cDNA (not shown). B=BL/6, C=CAST. (Note that only the internal comparisons of alleles in single PCR reactions are valid; the stronger band obtained from the CAST maternal kidney should not be compared to that from the BL/6 maternal kidney for intensity of expression, since these were separate RT-PCR reactions). B, Direct sequencing of RT-PCR products. This shows an allelic expression bias that depends on the direction of the cross, consistent with the RFLP results.

Mentions: To investigate potential imprinting of Tnfrh1 and Tnfrh2, we next searched for genetic polymorphisms in these genes that would allow us to distinguish maternal from paternal alleles in interspecific mouse crosses. We failed to identify polymorphisms in Tnfrh2, but we found multiple single-nucleotide polymorphisms (SNPs) in the Tnfrh1 gene (Table 2). Using cDNAs from fetal and adult tissues derived from interspecific crosses, we amplified a region of Tnfrh1 containing several of these SNPs. The PCR strategies generated products that crossed either 4 or 5 exon-exon boundaries, thereby eliminating the possibility of genomic contamination (Fig.1b). Since one of the SNPs that distinguished the standard C57BL/6 laboratory strain from the divergent strain M. m. castaneus (CAST) created an MboII restriction site in the CAST sequence, we used RFLP analysis to assess allelic representation in cDNAs from F1 progeny of BL/6 × CAST and CAST × BL/6 reciprocal crosses. This indicated an obvious but partial maternal bias in the fetal liver, and a nearly complete bias towards the maternal allele in placenta (Fig.7). This was confirmed by direct sequencing of the cDNAs, and the parent-of-origin dependence of this effect was emphasized by the opposite patterns observed in the reciprocal crosses (Fig.7). The bias in fetal liver must reflect parental imprinting of Tnfrh1, but based on the information from Northern blotting and ISH, the pattern seen in the placental cDNAs in these experiments reflects expression from maternal cells, not imprinting.


The Tnfrh1 (Tnfrsf23) gene is weakly imprinted in several organs and expressed at the trophoblast-decidua interface.

Clark L, Wei M, Cattoretti G, Mendelsohn C, Tycko B - BMC Genet. (2002)

Preferential expression of the maternal allele of Tnfrh1 in fetal liver from CAST × BL/6 reciprocal crosses.A, Analysis of the MboII RFLP, in which the BL/6 allele is undigested and the CAST allele yields two fragments. There is a strong maternal allele bias in placenta, and a weaker but still obvious parent-of-origin dependent biases in fetal liver. This imprinting effect is superimposed on a non-imprinted bias for higher expression of the BL/6 allele. The allelic bias in placenta reflects expression from maternal cells, but the bias in fetal liver reflects parental imprinting. Similar results were obtained with multiple aliquots of cDNA (not shown). B=BL/6, C=CAST. (Note that only the internal comparisons of alleles in single PCR reactions are valid; the stronger band obtained from the CAST maternal kidney should not be compared to that from the BL/6 maternal kidney for intensity of expression, since these were separate RT-PCR reactions). B, Direct sequencing of RT-PCR products. This shows an allelic expression bias that depends on the direction of the cross, consistent with the RFLP results.
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Related In: Results  -  Collection

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Figure 7: Preferential expression of the maternal allele of Tnfrh1 in fetal liver from CAST × BL/6 reciprocal crosses.A, Analysis of the MboII RFLP, in which the BL/6 allele is undigested and the CAST allele yields two fragments. There is a strong maternal allele bias in placenta, and a weaker but still obvious parent-of-origin dependent biases in fetal liver. This imprinting effect is superimposed on a non-imprinted bias for higher expression of the BL/6 allele. The allelic bias in placenta reflects expression from maternal cells, but the bias in fetal liver reflects parental imprinting. Similar results were obtained with multiple aliquots of cDNA (not shown). B=BL/6, C=CAST. (Note that only the internal comparisons of alleles in single PCR reactions are valid; the stronger band obtained from the CAST maternal kidney should not be compared to that from the BL/6 maternal kidney for intensity of expression, since these were separate RT-PCR reactions). B, Direct sequencing of RT-PCR products. This shows an allelic expression bias that depends on the direction of the cross, consistent with the RFLP results.
Mentions: To investigate potential imprinting of Tnfrh1 and Tnfrh2, we next searched for genetic polymorphisms in these genes that would allow us to distinguish maternal from paternal alleles in interspecific mouse crosses. We failed to identify polymorphisms in Tnfrh2, but we found multiple single-nucleotide polymorphisms (SNPs) in the Tnfrh1 gene (Table 2). Using cDNAs from fetal and adult tissues derived from interspecific crosses, we amplified a region of Tnfrh1 containing several of these SNPs. The PCR strategies generated products that crossed either 4 or 5 exon-exon boundaries, thereby eliminating the possibility of genomic contamination (Fig.1b). Since one of the SNPs that distinguished the standard C57BL/6 laboratory strain from the divergent strain M. m. castaneus (CAST) created an MboII restriction site in the CAST sequence, we used RFLP analysis to assess allelic representation in cDNAs from F1 progeny of BL/6 × CAST and CAST × BL/6 reciprocal crosses. This indicated an obvious but partial maternal bias in the fetal liver, and a nearly complete bias towards the maternal allele in placenta (Fig.7). This was confirmed by direct sequencing of the cDNAs, and the parent-of-origin dependence of this effect was emphasized by the opposite patterns observed in the reciprocal crosses (Fig.7). The bias in fetal liver must reflect parental imprinting of Tnfrh1, but based on the information from Northern blotting and ISH, the pattern seen in the placental cDNAs in these experiments reflects expression from maternal cells, not imprinting.

Bottom Line: Genes preferentially expressed in the placenta are predicted to evolve rapidly, and Tnfrh1 appears to be an example of this phenomenon.In view of its strong expression in cells at the fetal-maternal boundary, Tnfrh1 warrants further study as a gene that might modulate immune or trophic interactions between the invasive placental trophoblast and the maternal decidua.The preferential expression of Tnfrh1 from the maternal allele indicates weak functional imprinting of this locus in some tissues.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute for Cancer Genetics, Columbia University College of Physicians and Surgeons, New York, NY, USA. lc654@columbia.edu

ABSTRACT

Background: The Tnfrh1 gene (gene symbol Tnfrsf23) is located near one end of a megabase-scale imprinted region on mouse distal chromosome 7, about 350 kb distant from the nearest known imprinting control element. Within 20 kb of Tnfrh1 is a related gene called Tnfrh2 (Tnfrsf22) These duplicated genes encode putative decoy receptors in the tumor necrosis factor (TNF) receptor family. Although other genes in this chromosomal region show conserved synteny with genes on human Chr11p15.5, there are no obvious human orthologues of Tnfrh1 or Tnfrh2.

Results: We analyzed Tnfrh1 for evidence of parental imprinting, and characterized its tissue-specific expression. Tnfrh1 mRNA is detectable in multiple adult and fetal tissues, with highest expression in placenta, where in situ hybridization reveals a distinctive population of Tnfrh1-positive cells in maternal decidua, directly beneath the trophoblast giant cells. In offspring of interspecific mouse crosses, Tnfrh1 shows a consistent parent-of-origin-dependent allelic expression bias, with relative repression, but not silencing, of the paternal allele in several organs including fetal liver and adult spleen.

Conclusions: Genes preferentially expressed in the placenta are predicted to evolve rapidly, and Tnfrh1 appears to be an example of this phenomenon. In view of its strong expression in cells at the fetal-maternal boundary, Tnfrh1 warrants further study as a gene that might modulate immune or trophic interactions between the invasive placental trophoblast and the maternal decidua. The preferential expression of Tnfrh1 from the maternal allele indicates weak functional imprinting of this locus in some tissues.

Show MeSH
Related in: MedlinePlus