title: Genetic background influences embryonic lethality and the occurrence of neural tube defects in Men1 null mice: relevance to genetic modifiers.
abstract: Germline mutations of the multiple endocrine neoplasia type 1 (MEN1) gene cause parathyroid, pancreatic and pituitary tumours in man. MEN1 mutations also cause familial isolated primary hyperparathyroidism (FIHP) and the same MEN1 mutations, in different families, can cause either FIHP or MEN1. This suggests a role for genetic background and modifier genes in altering the expression of a mutation. We investigated the effects of genetic background on the phenotype of embryonic lethality that occurs in a mouse model for MEN1. Men1(+/-) mice were backcrossed to generate C57BL/6 and 129S6/SvEv incipient congenic strains, and used to obtain homozygous Men1(-/-) mice. No viable Men1(-/-) mice were obtained. The analysis of 411 live embryos obtained at 9.5-16.5 days post-coitum (dpc) revealed that significant deviations from the expected Mendelian 1:2:1 genotype ratio were first observed at 12.5 and 14.5 dpc in the 129S6/SvEv and C57BL/6 strains respectively (P<0.05). Moreover, live Men1(-/-) embryos were absent by 13.5 and 15.5 dpc in the 129S6/SvEv and C57BL/6 strains respectively thereby indicating an earlier lethality by 2 days in the 129S6/SvEv strain (P<0.01). Men1(-/-) embryos had macroscopic haemorrhages, and histology and optical projection tomography revealed them to have internal haemorrhages, myocardial hypotrophy, pericardial effusion, hepatic abnormalities and neural tube defects. The neural tube defects occurred exclusively in 129S6/SvEv embryos (21 vs 0%, P<0.01). Thus, our findings demonstrate the importance of genetic background in influencing the phenotypes of embryonic lethality and neural tube defects in Men1(-/-) mice, and implicate a role for genetic modifiers.
authors: Academic Endocrine Unit, Nuffield Department of Clinical Medicine, Oxford Centre for Diabetes, Endocrinology and Metabolism, Churchill Hospital, University of Oxford, Headington, Oxford OX3 7LJ, UK.
authors: Manuel C
authors: MC
authors: Lemos
authors: Brian
authors: B
authors: Harding
authors: Anita A C
authors: AA
authors: Reed
authors: Jeshmi
authors: J
authors: Jeyabalan
authors: Gerard V
authors: GV
authors: Walls
authors: Michael R
authors: MR
authors: Bowl
authors: James
authors: J
authors: Sharpe
authors: Sarah
authors: S
authors: Wedden
authors: Julie E
authors: JE
authors: Moss
authors: Allyson
authors: A
authors: Ross
authors: Duncan
authors: D
authors: Davidson
authors: Rajesh V
authors: RV
authors: Thakker
mesh_terms: D000818:Animals; D004622:Embryo, Mammalian / Q000473:pathology*; D005260:Female; D005804:Genes, Lethal; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009436:Neural Tube Defects / Q000235:genetics* / Q000473:pathology; D010641:Phenotype; D011247:Pregnancy; D011518:Proto-Oncogene Proteins / Q000235:genetics*
chemical_list: C484898:Men1 protein, mouse; D011518:Proto-Oncogene Proteins