| Year | 2002 | Journal | J Bone Miner Res |
| Volume | 17 Suppl 1 | Pages | S125-541 |
| PubMed ID | 12236227 | Mgi Jnum | J:92983 |
| Mgi Id | MGI:3055439 | Citation | Laplace C, et al. (2002) (Homozygous deletion of the murine calcitonin receptor gene is an embryonic lethal). Abstracts of the 24th Annual Meeting of the American Society for Bone and Mineral Research. San Antonio, Texas, USA. September 20-24, 2002. J Bone Miner Res 17 Suppl 1:S125-541 (S143) |
| abstractText | Full text of Abstract: Homozygous Deletion of the Murine Calcitonin Receptor Gene Is an Embryonic Lethal. Presentation Time: Tuesday, 9:30 a.m. - 9:45 a.m. C. Laplace*, X. Li*, S.R. Goldring, D.L. Galson. NEB Bone & Joint Institute, Dept. of Medicine, Beth Israel Deaconess Medical Center & Harvard Medical School, Boston, MA, USA. Presentation Number: 1175 The calcitonin receptor (CTR) has multiple ligands. It is the receptor for both calcitonin (CT) and amylin (requiring in the latter case, a RAMP accessory protein). CTR is expressed in a variety of tissues at different times during development from embryonic through adult, suggesting a role in morphogenesis. To study the consequences during development of a complete ablation of the murine CTR (mCTR) gene, we generated two ES cell lines that have a targeted deletion of exons E6 and E7 in one allele of the mCTR gene. Deletion of these exons should effectively disable all mCTR isoforms as splicing of exon E5 to exon E8a is out of phase. Therefore, any protein that could be generated would encode no more than a portion of the first extracellular domain. Although we have generated 17 chimeric mice from the two ES cell lines, only one male chimera has sired mCTR (-/+) heterozygous mice. Our heterozygous breeding pairs have produced 69 mCTR (+/+) wild type mice (29%), 170 mCTR (-/+) heterozygous mice (71%) and no mCTR (-/-) homozygous mice (0%). These results indicate that, although CTR is known to be expressed in sperm at various stages of differentiation, male heterozygous CTR knock-out mice are not sterile and do produce CTR-negative sperm. Therefore, expression of CTR is not necessary for sperm differentiation or function. However, the absence of CTR knock-out mice suggests that lack of CTR expression results in a lethal embryonic defect. Pregnant females from mCTR (-/+) heterozygous intercrosses were sacrificed at different times of gestation and the embryos genotyped by PCR. Analysis of 25 embryos at 9.5 days post coitum (dpc) shows that there is a concordance between the observed (7:12:6; +/+, -/+, -/-, respectively) and expected (1:2:1) distributions. These data indicate that there is no deleterious effect of the homozygous CTR deletion up to this point of development. Therefore, these data exclude the possible theory that blastocyst expression of CTR is necessary for implantation. This is a critical observation as uterine CT has been suggested to have a key regulatory role during blastocyst implantation and CTR has been demonstrated on mouse preimplantation embryos. The observed ratio of embryos at 10.5 dpc (11:38:5) suggests that some homozygous null embryos are dying between 9.5 and 10.5 dpc. We have not observed any homozygous null embryos after 10.5 dpc. The 66 embryos analyzed from 11.5 through 14.5 dpc have an observed ratio of 1:2.7:0. We have not observed any obvious differences in gross anatomy between the homozygous null and heterozygous or wildtype embryos. Further analysis of the lethal developmental defect due to ablation of the CTR gene is underway. |
