title: Claudin gene expression patterns do not associate with interspecific differences in paracellular nutrient absorption.
abstract: Bats exhibit higher paracellular absorption of glucose-sized molecules than non-flying mammals, a phenomenon that may be driven by higher permeability of the intestinal tight junctions. The various claudins, occludin, and other proteins making up the tight junctions are thought to determine their permeability properties. Here we show that absorption of the paracellular probe l-arabinose is higher in a bat (Eptesicus fuscus) than in a vole (Microtus pennsylvanicus) or a hedgehog (Atelerix albiventris). Furthermore, histological measurements demonstrated that hedgehogs have many more enterocytes in their intestines, suggesting that bats cannot have higher absorption of arabinose simply by having more tight junctions. We therefore investigated the mRNA levels of several claudins and occludin, because these proteins may affect permeability of tight junctions to macronutrients. To assess the expression levels of claudins per tight junction, we normalized the mRNA levels of the claudins to the constitutively expressed tight junction protein ZO-1, and combined these with measurements previously made in a bat and a rodent to determine if there were among-species differences. Although expression ratios of several genes varied among species, there was not a consistent difference between bats and non-flyers in the expression ratio of any particular gene. Protein expression patterns may differ from mRNA expression patterns, and might better explain differences among species in arabinose absorption.
authors.affiliation: Department of Forest and Wildlife Ecology, University of Wisconsin-Madison, Madison, WI 53706, USA. Electronic address: Edwin.price@unt.edu.
authors.forename: Edwin R
authors.initials: ER
authors.lastname: Price
authors.affiliation: Department of Forest and Wildlife Ecology, University of Wisconsin-Madison, Madison, WI 53706, USA.
authors.forename: Katherine H
authors.initials: KH
authors.lastname: Rott
authors.affiliation: Departamento de Bioquímica y Ciencias Biológicas y Laboratorio de Biología "Profesor E. Caviedes Codelia", Universidad Nacional de San Luis, 5700 San Luis, Argentina; Laboratorio de Biología Integrativa, Instituto Multidisciplinario de Investigaciones Biológicas de San Luis, Consejo Nacional de Investigaciones Científicas y Técnicas, 5700 San Luis, Argentina.
authors.forename: Enrique
authors.initials: E
authors.lastname: Caviedes-Vidal
authors.affiliation: Department of Forest and Wildlife Ecology, University of Wisconsin-Madison, Madison, WI 53706, USA.
authors.forename: William H
authors.initials: WH
authors.lastname: Karasov
mesh_terms: D000818:Animals; D003411:Arvicolinae / Q000235:genetics / Q000378:metabolism; D002685:Chiroptera / Q000235:genetics / Q000378:metabolism; D057167:Claudins / Q000235:genetics*; D005786:Gene Expression Regulation; D006364:Hedgehogs / Q000235:genetics / Q000378:metabolism; D007408:Intestinal Absorption; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000166:cytology*; D013045:Species Specificity
chemical_list: D057167:Claudins
keywords: Comparative transcriptomics; Intestine; Occludin; Paracellular absorption; Tight junction