Uncoupled Embryonic and Extra-Embryonic Tissues Compromise Blastocyst Development after Somatic Cell Nuclear Transfer

Somatic cell nuclear transfer (SCNT) is the most efficient cell reprogramming technique available, especially when working with bovine species. Although SCNT blastocysts performed equally well or better than controls in the weeks following embryo transfer at Day 7, elongation and gastrulation defects were observed prior to implantation. To understand the developmental implications of embryonic/extra-embryonic interactions, the morphological and molecular features of elongating and gastrulating tissues were analysed. At Day 18, 30 SCNT conceptuses were compared to 20 controls (AI and IVP: 10 conceptuses each); one-half of the SCNT conceptuses appeared normal while the other half showed signs of atypical elongation and gastrulation. SCNT was also associated with a high incidence of discordance in embryonic and extra-embryonic patterns, as evidenced by morphological and molecular “uncoupling”. Elongation appeared to be secondarily affected; only 3 of 30 conceptuses had abnormally elongated shapes and there were very few differences in gene expression when they were compared to the controls. However, some of these differences could be linked to defects in microvilli formation or extracellular matrix composition and could thus impact extra-embryonic functions. In contrast to elongation, gastrulation stages included embryonic defects that likely affected the hypoblast, the epiblast, or the early stages of their differentiation. When taking into account SCNT conceptus somatic origin, i.e. the reprogramming efficiency of each bovine ear fibroblast (Low: 0029, Med: 7711, High: 5538), we found that embryonic abnormalities or severe embryonic/extra-embryonic uncoupling were more tightly correlated to embryo loss at implantation than were elongation defects. Alternatively, extra-embryonic differences between SCNT and control conceptuses at Day 18 were related to molecular plasticity (high efficiency/high plasticity) and subsequent pregnancy loss. Finally, because it alters re-differentiation processes in vivo, SCNT reprogramming highlights temporally and spatially restricted interactions among cells and tissues in a unique way

L'expressivité inter- et intrafamiliale de la dysostose cléido-crânienne

La dysostose cléido-crânienne est une affection osseuse, définie par le retard d'ossification des fontanelles et des sutures, l'hypoplasie ou l'aplasie claviculaire et l'hyperdontie. Au sein de trois familles porteuses de la malformation, nous avons cherché à définir les mutations du gène CBFA1 et à observer le retentissement phénotypique associé. Nous avons constaté que la mutation R 225Q s'accompagnait d'un phénotype similaire au sein d'une même famille, alors que la mutation G146R située dans le même domaine était d'une expression différente pour deux membres de la même famille. Une troisième mutation R190Q était responsable d'une expression non caractéristique pour le syndrome. Ces manifestations craniofaciales variées sont conformes aux nombreuses descriptions de la littérature. Cette étude met l'accent sur l'importante variabilité phénotypique de la dysostose cléido-crânienne qui rend difficile un diagnostic certain à partir uniquement d'observations cliniques

Buffet and buffeting control in transonic flow

Communication to : ODAS 2003 Toulouse (France), June 04-06, 2003Available from INIST (FR), Document Supply Service, under shelf-number : 22419, issue : a.2003 n.74 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc