article 384 nature genetics • volume 32 • november 2002 The K–Cl cotransporter KCC3 is mutant in a severe peripheral neuropathy associated with agenesis of the corpus callosum Heidi C. Howard 1 *, David B. Mount 2,3 *, Daniel Rochefort 1 , Nellie Byun 4 , Nicolas Dupré 1 , Jianming Lu 4 , Xuemo Fan 5 , Luyan Song 3 , Jean-Baptiste Rivière 1 , Claude Prévost 6 , Jürgen Horst 7 , Alessandro Simonati 8 , Beate Lemcke 8 , Rick Welch 3 , Roger England 4 , Frank Q. Zhan 4 , Adriana Mercado 2,3 , William B. Siesser 9 , Alfred L. George, Jr. 3 , Michael P. McDonald 9–11 , Jean-Pierre Bouchard 12 , Jean Mathieu 6 , Eric Delpire 4,9,11 & Guy A. Rouleau 1 *These authors contributed equally to this work Published online 7 October 2002; corrected 21 October 2002 (details online); doi:10.1038/ng1002 Peripheral neuropathy associated with agenesis of the corpus callosum (ACCPN) is a severe sensorimotor neuropa- thy associated with mental retardation, dysmorphic features and complete or partial agenesis of the corpus callo- sum. ACCPN is transmitted in an autosomal recessive fashion and is found at a high frequency in the province of Quebec, Canada. ACCPN has been previously mapped to chromosome 15q. The gene SLC12A6 (solute carrier fam- ily 12, member 6), which encodes the K + –Cl – transporter KCC3 and maps within the ACCPN candidate region, was screened for mutations in individuals with ACCPN. Four distinct protein-truncating mutations were found: two in the French Canadian population and two in non–French Canadian families. The functional consequence of the pre- dominant French Canadian mutation (2436delG, Thr813fsX813) was examined by heterologous expression of wildtype and mutant KCC3 in Xenopus laevis oocytes; the truncated mutant is appropriately glycosylated and expressed at the cellular membrane, where it is non-functional. Mice generated with a targeted deletion of Slc12a6 have a locomotor deficit, peripheral neuropathy and a sensorimotor gating deficit, similar to the human disease. Our findings identify mutations in SLC12A6 as the genetic lesion underlying ACCPN and suggest a critical role for SLC12A6 in the development and maintenance of the nervous system. 1 Centre for Research in Neuroscience, McGill University and the Montreal General Hospital Research Institute, 1650 Cedar Ave., Montreal, Quebec H3G 1A4, Canada. 2 Renal Division, West Roxbury VA Medical Center and Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA. 3 Departments of Medicine, 4 Anesthesiology and 5 Pathology, Vanderbilt University Medical Center, Nashville, Tennessee, USA. 6 Complexe hospitalier de la Sagamie, Chicoutimi, Quebec, Canada. 7 Institut für Humangenetik, Universität Münster, Münster, Germany. 8 Department of Neurological and Visual Sciences, Section of Neurology, University of Verona, Verona, Italy. 9 Center for Molecular Neuroscience, 10 Department of Pharmacology and 11 John F. Kennedy Center for Research on Human Development, Vanderbilt University Medical Center, Nashville, Tennessee, USA. 12 Department of Neurology, Hôpital de l’Enfant Jesus, Quebec, Quebec, Canada. Correspondence should be addressed to G.A.R. (human studies; e-mail: guy.rouleau@mcgill.ca) or E.D. (mouse studies; e-mail: eric.delpire@vanderbilt.edu). Introduction Peripheral neuropathy associated with agenesis of the corpus cal- losum (ACCPN) is an autosomal recessive disease characterized by progressive sensorimotor neuropathy, mental retardation, dysmorphic features (high arched palate, hypertelorism and syn- dactyly) and complete or partial agenesis of the corpus callo- sum 1 . Neither the significance nor the causes of the variable corpus callosum involvement are known, but the natural course of the peripheral neuropathy does not vary significantly between individuals with partial and complete agenesis of the corpus cal- losum 1,2 . Generalized hypotonia and delays in developmental motor milestones are evident during the first year of life. Individ- uals with ACCPN are able to stand or walk with support at 4–6 years of age 3 and often develop scoliosis. Physical and mental abilities deteriorate over time, and by adolescence, all motor movements are severely impaired and most individuals are con- fined to a wheelchair or bedridden 4 . Individuals with ACCPN have frequent convulsions, and many develop persistent halluci- natory psychosis during adolescence 5 . The average life expectancy is 33 years of age (C.P., unpublished data); death commonly results from complications stemming from respira- tory infections. In the Charlevoix and Saguenay–Lac-St-Jean regions of the province of Quebec, ACCPN is found at a frequency of 1 in 2,117 live births 6 . Although rare elsewhere, ACCPN has also been reported in Austria 7 , Italy 8 , Spain 9 , Oman 10 and Algeria 11 . The ACCPN locus has been mapped to a region of 4 cM on chromo- some 15 by linkage analysis 12 . Linkage disequilibrium analysis and recombination mapping have further refined the ACCPN candidate region to approximately 1,000 kilobases between microsatellite markers D15S1040 and ACTC 13 . The gene encod- ing the gap-junction protein connexin-36 (Cx36) is situated © 2002 Nature Publishing Group http://www.nature.com/naturegenetics