SummaryFragile X-associated tremor/ataxia syndrome (FXTAS) is a neurodegenerative disorder caused by a limited expansion of CGG repeats in the 5′ UTR of FMR1. Two mechanisms are proposed to cause FXTAS: RNA gain-of-function, where CGG RNA sequesters specific proteins, and translation of CGG repeats into a polyglycine-containing protein, FMRpolyG. Here we developed transgenic mice expressing CGG repeat RNA with or without FMRpolyG. Expression of FMRpolyG is pathogenic, while the sole expression of CGG RNA is not. FMRpolyG interacts with the nuclear lamina protein LAP2β and disorganizes the nuclear lamina architecture in neurons differentiated from FXTAS iPS cells. Finally, expression of LAP2β rescues neuronal death induced by FMRpolyG. Overall, these results suggest that translation of expanded CGG repeats into FMRpolyG alters nuclear lamina architecture and drives pathogenesis in FXTAS.

Trudel, L., C. Tomasetto, M. C. Rio, M. Bouin M, V. Plourde, P. Eberling, and P. Poitras. Ghrelin/motilinrelated peptide is a potent prokinetic to reverse gastric postoperative ileus in rat. Am J Physiol Gastrointest Liver Physiol 282: G948-G952, 2002; 10.1152/ajpgi.00339.2001.-A novel peptide called ghrelin or motilin-related-peptide (MTLRP) was found in the stomach of various mammals. We studied its effect on the motor function of the rat gastrointestinal tract. In normal, conscious unoperated animals, ghrelin/MTLRP (5 or 20 g/kg iv) significantly accelerated the gastric emptying of a methylcellulose liquid solution (gastric residue after 15 min: 57 Ϯ 7, 42 Ϯ 11, 17 Ϯ 4, and 9 Ϯ 3% of the ingested meal with doses of 0, 1, 5, and 20 g/kg iv, respectively) Transit of the methylcellulose liquid solution was also accelerated by ghrelin/MTLRP in the small intestine but not in the colon. Des- [Gln 14 ]ghrelin, also found in the mammalian stomach, was as potent as ghrelin in emptying the stomach (gastric residue after 15 min: 12 Ϯ 3% at a dose of 20 g/kg iv). In rats in which postoperative gastrointestinal ileus had been experimentally induced, ghrelin/MTLRP (20 g/kg iv) reversed the delayed gastric evacuation (gastric residue after 15 min: 28 Ϯ 7% of the ingested meal vs. 82 Ϯ 9% with saline). In comparison, the gastric ileus was not modified by high doses of motilin (77 Ϯ 7%) or erythromycin (82 Ϯ 6%) and was only partially improved by calcitonin gene-related peptide (CGRP) 8-37 antagonist (59 Ϯ 7%). Ghrelin/MTLRP, therefore, accelerates the gastric emptying and small intestinal transit of a liquid meal and is a strong prokinetic agent capable of reversing the postoperative gastric ileus in rat. regulatory peptides; gastrointestinal hormones; gastrointestinal motility A NOVEL PEPTIDE WAS IDENTIFIED recently in endocrine cells of the gastric mucosa of mouse, rat, dog, and human (9,20,22). It was discovered simultaneously by two research teams who named it, respectively, motilin-related peptide (MTLRP) and ghrelin. Tomasetto et al. (21) used molecular biology to look for new proteins of the gastric epithelium that could provide insight to the differentiation and function of the gastric unit. They discovered a protein expressed in secretory granules of the mouse stomach endocrine cells in which chromogranin A, serotinin, and somatostatin also colocalized. The protein has sequence similarity (47%) with prepromotilin, and the secreted peptide was, therefore, tentatively named motilin-related peptide. At the same time, Japanese researchers (9), looking for an endogenous ligand for growth hormone secretagoge receptor, purified and identified from rat stomach a peptide of 28 amino acids they called ghrelin (ghre is the proto-IndoEuropean root of the word grow). Ghrelin is now most often used to identify the peptide.Because it interacts with the growth hormone secretagoge receptor of the pituitary, ghrelin has definite actions on the release of growth hormone (9,18,20,24), but also on appetite stimulation (counterbalancin...