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  • Author: Patrice Mollard x
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Norbert Chauvet, Taoufik El-Yandouzi, Marie-Noëlle Mathieu, Audrey Schlernitzauer, Evelyne Galibert, Chrystel Lafont, Paul Le Tissier, Iain C Robinson, Patrice Mollard and Nathalie Coutry

Our view of anterior pituitary organization has been altered with the recognition that folliculo-stellate (FS) and somatotroph cell populations form large-scale three-dimensional homotypic networks. This morphological cellular organization may optimize communication within the pituitary gland promoting coordinated pulsatile secretion adapted to physiological needs. The aim of this study was to identify the molecules involved in the formation and potential functional organization and/or signaling within these cell–cell networks. Here, we have focused on one class of cell adhesion molecules, the cadherins, since β-catenin has been detected in the GH cell network. We have characterized, by qPCR and immunohistochemistry, their cellular expression and distribution. We have also examined whether their expression could be modulated during pituitary tissue remodeling. The mouse anterior pituitary has a restricted and cell-type specific repertoire of cadherin expression: cadherin-11 is exclusively expressed in TSH cells; N-cadherin displays a ubiquitous expression pattern but with different levels of expression between endocrine cell types; E-cadherin is restricted to homotypic contacts between FS cells; while cadherin-18 is expressed both in somatotrophs and FS cells. Thus, each cell type presents a defined combinatorial expression of different subsets of cadherins. This cell-type specific cadherin expression profile emerges early during development and undergoes major changes during postnatal development. These results suggest the existence within the anterior pituitary of cell–cell contact signaling based on a defined pattern of cadherin expression, which may play a crucial role in cellular recognition during the formation and fate of pituitary cell homotypic networks.

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Thomas M Braxton, Dionne E A Sarpong, Janine L Dovey, Anne Guillou, Bronwen A J Evans, Juan M Castellano, Bethany E Keenan, Saja Baraghithy, Sam L Evans, Manuel Tena-Sempere, Patrice Mollard, Joseph Tam and Timothy Wells

Human Prader–Willi syndrome (PWS) is characterised by impairments of multiple systems including the growth hormone (GH) axis and skeletal growth. To address our lack of knowledge of the influence of PWS on skeletal integrity in mice, we have characterised the endocrine and skeletal phenotype of the PWS-ICdel mouse model for ‘full’ PWS and determined the impact of thermoneutrality. Tibial length, epiphyseal plate width and marrow adiposity were reduced by 6, 18 and 79% in male PWS-ICdel mice, with osteoclast density being unaffected. Similar reductions in femoral length accompanied a 32% reduction in mid-diaphyseal cortical diameter. Distal femoral Tb.N was reduced by 62%, with individual trabeculae being less plate-like and the lattice being more fragmented (Tb.Pf increased by 63%). Cortical strength (ultimate moment) was reduced by 26% as a result of reductions in calcified tissue strength and the geometric contribution. GH and prolactin contents in PWS-ICdel pituitaries were reduced in proportion to their smaller pituitary size, with circulating IGF-1 concentration reduced by 37–47%. Conversely, while pituitary luteinising hormone content was halved, circulating gonadotropin concentrations were unaffected. Although longitudinal growth, marrow adiposity and femoral geometry were unaffected by thermoneutrality, strengthened calcified tissue reversed the weakened cortex of PWS-ICdel femora. While underactivity of the GH axis may be due to loss of Snord116 expression and impaired limb bone geometry and strength due to loss of Magel2 expression, comprehensive analysis of skeletal integrity in the single gene deletion models is required. Our data imply that thermoneutrality may ameliorate the elevated fracture risk associated with PWS.