Functional role of transporter Slc4a11 (BTR1/NaBC1) in the cornea

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DESCRIPTION (provided by applicant): Congenital hereditary endothelial dystrophy (CHED) causes impaired vision resulting from opacification of the cornea. The recessive form of CHED (CHED2) as well as some types of Fuch's endothelial dystrophy and Harboyan syndrome were recently shown to be associated with mutations in the SLC4A11 gene that encodes BTR1/NaBC1, a member of the bicarbonate transporter family. The function and subcellular location of this protein in cornea are unknown, and there is currently no adequate animal model for the study of CHED caused by SLC4A11 mutations. The goals of the proposed experiments are to determine the molecular function of SLC4A11 and its localization in the cornea, and to generate a mouse model for CHED2. The available functional information suggests that SLC4A11 transports Na+ and borate [B(OH)4- ], although no boron transport experiments with this protein have been performed. Specific Aim 1A is to use HEK293 cells and a corneal endothelial cell line, with mass-spectrometry, to determine whether mammalian (mouse, human) SLC4A11 cotransports Na+ and boron. Specific Aim 1B is to use Xenopus oocytes, with ion-selective microelectrodes, to determine whether SLC4A11 cotransports Na+ and HCO3-. In Specific Aim 2 we will perform immunohistochemistry to determine whether Slc4a11 is located in the basolateral or apical membrane of the mouse corneal endothelium. In Specific Aim 3 we will generate and evaluate the phenotype of a mouse model of CHED2 prepared by introducing, to mouse Slc4a11, a point mutation (in the position of human R755Q) that is known to cause CHED2 in humans. PUBLIC HEALTH RELEVANCE: Maintenance of transparency of the cornea is essential for good vision. A variety of conditions can cause the cornea to become cloudy, including an inherited condition known as congenital hereditary endothelial dystrophy (CHED). Some forms of CHED are a result of mutations in a transport protein known as SLC4A11, the function of which has not been well established. The goals of this project are to determine the function of SLC4A11 and to establish a mouse model of CHED.