“…This results from the predominant localization of TbR-I and TbR-II in lipid rafts/caveolae in these cells [Ren et al, 2011]. We hypothesize that high-level accumulation (10-2,000-fold normal) of 7-DHC, which varies in severity in SLOS patients and SLOS tissues, results in lipid raft/caveolae dysfunction, turnover, and down-regulation of the many resident membrane proteins in lipid rafts/caveolae, including TGF-b receptors [Huang and Huang, 2005;Chen et al, 2007Chen et al, , 2008Chen et al, , 2009Chen et al, , 2011, neurotrophin receptors [Sebastião et al, 2011;Zhang et al, 2013;Gou-F abregas et al, 2016], G protein-coupled receptors (GPCRs) (neurological receptors) [Bj€ ork and Svenningsson, 2011], ion channels [Jaffr es et al, 2016], receptor protein kinases (RTKs) (e.g., growth factor receptors) [Basu et al, 2008] and growth hormone receptor [Yang et al, 2004]. Down-regulation of these important membrane proteins in tissues during embryonic development may result in prenatal and postnatal growth retardation, microcephaly, intellectual disability, multiple external malformations (e.g., cleft palate), internal anomalies, and mental retardation characteristic of SLOS.…”