Use of an allelic series in mouse to study the role of epidermal growth factor receptor in placental development and pregnancy

Epidermal growth factor receptor (EGFR) is a member of the ERBB family of receptor tyrosine kinases that has been shown to play an important developmental and physiological role in many aspects of pregnancy. Using genetically engineered mice our lab and others have demonstrated that Egfrtm1Mag nullizygous placentas exhibit strain-specific defects ranging from mild reductions in spongiotrophoblasts to severe labyrinth dysmorphogenesis that results in mid-gestational embryonic lethality. Experiments included in this dissertation show that Egfrtm1Mag nullizygous placentas have reduced numbers of proliferating trophoblast. However, intercrosses with mice deficient for cell cycle checkpoint genes did not rescue Egfrtm1Mag embryo viability suggesting that reduced proliferation in the placenta is not a primary cause of embryonic lethality. We characterized an Egfr allelic series on several genetic backgrounds in mice to assess the effects of reduced as well as increased EGFR signaling on placental and embryonic growth. Congenic strains homozygous for the hypomorphic Egfrwa2 allele exhibited strain-dependent placental and embryonic growth restriction at 15.5 dpc while heterozygotes for the antimorphic EgfrWa5 allele had placentas were only slightly reduced in size with no effect on embryonic growth. At the histological level Egfrwa2 homozygous placentas had a reduced layer of spongiotrophoblast and in some strains spongiotrophoblasts and glycogen cells were almost completely absent. The placentas of embryos heterozygous or homozygous for the hypermorphic EgfrDsk5 allele were enlarged with a more prominent spongiotrophoblast layer and increased expression of glycogen cell-specific genes. There were no effects on growth of EgfrDsk5 embryos at 15.5 dpc. We also observed strain-specific sub-fertility in EgfrDsk5 heterozygous adult females that may be due deferred embryo implantation beyond the normal window of uterine receptivity. Our results demonstrate that EGFR plays a fundamental role in development of the placental spongiotrophoblast layer in mice and suggest that reduced proliferation in EGFR-deficient placentas primarily affects the spongiotrophoblast compartment. We have also shown that aberrant levels of EGFR signaling result in an extensive level of genetic background-dependent phenotypic variability and that EGFR expressed in the uterine stroma may function in preparation of the uterus for embryo implantation

A genome-wide association study of anorexia nervosa

Anorexia nervosa (AN) is a complex and heritable eating disorder characterized by dangerously low body weight. Neither candidate gene studies nor an initial genome wide association study (GWAS) have yielded significant and replicated results. We performed a GWAS in 2,907 cases with AN from 14 countries (15 sites) and 14,860 ancestrally matched controls as part of the Genetic Consortium for AN (GCAN) and the Wellcome Trust Case Control Consortium 3 (WTCCC3). Individual association analyses were conducted in each stratum and meta-analyzed across all 15 discovery datasets. Seventy-six (72 independent) SNPs were taken forward for in silico (two datasets) or de novo (13 datasets) replication genotyping in 2,677 independent AN cases and 8,629 European ancestry controls along with 458 AN cases and 421 controls from Japan. The final global meta-analysis across discovery and replication datasets comprised 5,551 AN cases and 21,080 controls. AN subtype analyses (1,606 AN restricting; 1,445 AN binge-purge) were performed. No findings reached genome-wide significance. Two intronic variants were suggestively associated: rs9839776 (P=3.01×10−7) in SOX2OT and rs17030795 (P=5.84×10−6) in PPP3CA. Two additional signals were specific to Europeans: rs1523921 (P=5.76×10−6) between CUL3 and FAM124B and rs1886797 (P=8.05×10−6) near SPATA13. Comparing discovery to replication results, 76% of the effects were in the same direction, an observation highly unlikely to be due to chance (P= 4×10−6), strongly suggesting that true findings exist but that our sample, the largest yet reported, was underpowered for their detection. The accrual of large genotyped AN case-control samples should be an immediate priority for the field

A genome-wide association study of anorexia nervosa.

Anorexia nervosa (AN) is a complex and heritable eating disorder characterized by dangerously low body weight. Neither candidate gene studies nor an initial genome-wide association study (GWAS) have yielded significant and replicated results. We performed a GWAS in 2907 cases with AN from 14 countries (15 sites) and 14 860 ancestrally matched controls as part of the Genetic Consortium for AN (GCAN) and the Wellcome Trust Case Control Consortium 3 (WTCCC3). Individual association analyses were conducted in each stratum and meta-analyzed across all 15 discovery data sets. Seventy-six (72 independent) single nucleotide polymorphisms were taken forward for in silico (two data sets) or de novo (13 data sets) replication genotyping in 2677 independent AN cases and 8629 European ancestry controls along with 458 AN cases and 421 controls from Japan. The final global meta-analysis across discovery and replication data sets comprised 5551 AN cases and 21 080 controls. AN subtype analyses (1606 AN restricting; 1445 AN binge-purge) were performed. No findings reached genome-wide significance. Two intronic variants were suggestively associated: rs9839776 (P=3.01 × 10(-7)) in SOX2OT and rs17030795 (P=5.84 × 10(-6)) in PPP3CA. Two additional signals were specific to Europeans: rs1523921 (P=5.76 × 10(-)(6)) between CUL3 and FAM124B and rs1886797 (P=8.05 × 10(-)(6)) near SPATA13. Comparing discovery with replication results, 76% of the effects were in the same direction, an observation highly unlikely to be due to chance (P=4 × 10(-6)), strongly suggesting that true findings exist but our sample, the largest yet reported, was underpowered for their detection. The accrual of large genotyped AN case-control samples should be an immediate priority for the field

Placental and Embryonic Growth Restriction in Mice With Reduced Function Epidermal Growth Factor Receptor Alleles

Embryos lacking an epidermal growth factor receptor (EGFR) exhibit strain-specific defects in placental development that can result in mid-gestational embryonic lethality. To determine the level of EGFR signaling required for normal placental development, we characterized congenic strains homozygous for the hypomorphic Egfrwa2 allele or heterozygous for the antimorphic EgfrWa5 allele. Egfrwa2 homozygous embryos and placentas exhibit strain-dependent growth restriction at 15.5 days post-coitus while EgfrWa5 heterozygous placentas are only slightly reduced in size with no effect on embryonic growth. Egfrwa2 homozygous placentas have a reduced spongiotrophoblast layer in some strains, while spongiotrophoblasts and glycogen cells are almost completely absent in others. Our results demonstrate that more EGFR signaling occurs in EgfrWa5 heterozygotes than in Egfrwa2 homozygotes and suggest that Egfrwa2 homozygous embryos model EGFR-mediated intrauterine growth restriction in humans. We also consistently observed differences between strains in wild-type placenta and embryo size as well as in the cellular composition and expression of trophoblast cell subtype markers and propose that differential expression in the placenta of Glut3, a glucose transporter essential for normal embryonic growth, may contribute to strain-dependent differences in intrauterine growth restriction caused by reduced EGFR activity

Using ancestry-informative markers to identify fine structure across 15 populations of European origin

J. Kaprio, A. Keski-Rahkonen, A. Raevuori, A. Palotie ja S. Ripatti työryhmien jäseniä, joita yhteensä 219.Peer reviewe