The Tnfrh1 (Tnfrsf23) gene is weakly imprinted in several organs and expressed at the trophoblast-decidua interface.
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.
Clark
Lorraine
L
Institute for Cancer Genetics, Columbia University College of Physicians and Surgeons, New York, NY, USA. lc654@columbia.edu
Wei
Michelle
M
Cattoretti
Giorgio
G
Mendelsohn
Cathy
C
Tycko
Benjamin
B
D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D003656:Decidua / Q000378:metabolism*; D005260:Female; D005333:Fetus / Q000378:metabolism; D014644:Genetic Variation; D018392:Genomic Imprinting; D008099:Liver / Q000196:embryology / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D010920:Placenta / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis; D018124:Receptors, Tumor Necrosis Factor / Q000096:biosynthesis* / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution; D014158:Transcription, Genetic; D014327:Trophoblasts / Q000378:metabolism*
D012333:RNA, Messenger; D018124:Receptors, Tumor Necrosis Factor; C469948:Tnfrh2 protein, mouse; C469947:Tnfrsf23 protein, mouse