'Howard Hughes Medical Institute and Department of Physiologyand Biophysics, The University of Iowa College ojMedicine, Iowa City, Iowa 52242, USA 2FondationJean- Dausset-CEPH, 7501 0 Paris, France 3Git~&thon, 91 000 Evry, France University of Texas, Howard Hughes Medical Institute, Biopolymer Facility, Dallas, Texas 75235, USA jINSERM U153, 75005 Paris, France 6~enry Ford Hospital, Division of Clinical and Molecular Genetics, C.F.P.407, Detroit, Michigan 48202, USA Correspondence should be addressed to K.P.C. and J.S.B. +Thefirstthree authors contributed equally to this work. P-sarcoglycan: characterization and role in limb-girdle muscular dystrophy linked to 4q12 Leland E. Liml*, Franck ~uclos'",Odile Broux3*, Nathalie our^^, Yoshihide Sunadal, Valerie Allamand3, Jon ~ e~erl, Isabelle ~ i c h a r d ~ , Carolyn Moomaw4, Clive Slaughter4,Fernando M.S. Tome5, Michel Fardeau5, Charles E. Jackson6,Jacques S. ~eckmann~>~ & Kevin P. Campbell1 P-sarcoglycan, a 43 kDa dystrophin-associated glycoprotein, is an integral component of the dystrophin-glycoprotein complex. We have cloned human P-sarcoglycan cDlVA and mapped the P-sarcoglycan gene to chromosome 4q12. Pericentromeric markers and an intragenic polymorphic CA repeat cosegregated perfectly with autosomal recessive limb- girdle muscular dystrophy in several Amish families. A Thr-to-Arg missense mutation was identified within the P-sarcoglycan gene that leads to a dramatically reduced expression of P-sarcoglycan in the sarcolemma and a concomitant loss of adhalin and 35 DAG, which may represent a disruption of a functional subcomplex within the dystrophin- glycoprotein complex. Thus, the P-sarcoglycan gene is the fifth locus identified (LGMD2E)that is involved in autosomal recessive limb-girdle muscular dystrophy. The dystrophin-glycoprotein complex (DGC)1-4is a large oligomeric complex of sarcolemmal proteins and glycoproteins, consisting of dystrophin, a large F-actin binding intracellular syntrophin, a 59 kDa intracellular proteins,9; adhalin, a 50 kDa transmem- brane glycoproteinlO; a 43 kDa transmembrane glyco- protein doublet (P-dystroglycan and A3b)2,3,"; a 35 kDa transmembrane glycoprotein; a 25 kDa trans- membrane protein; and a-dystroglycan, a large extra- cellular laminin-binding gly~oprotein"-'~. Together, the dystrophin-glycoprotein complex acts as a struc- tural link between the cytoskeleton and the extracellu- lar matrix, and is believed to confer stability to the sarcolemma and protect muscle cells from contrac- tion-induced damage and necrosis15. The DGC has been implicated in several forms of muscular dystrophy. In Duchenne muscular dystrophy (DMD), mutations in the dystrophin gene cause the complete absence of dystrophin and a dramatic reduc- tion of its associated glycoproteins at the sarcolemma resulting in severe muscular dystrophy2,5. In the milder Becker muscular dystrophy, mutations in dystrophin result in the ~roduction of a dvsfunctional vrotein16. More recently, some cases of severe childhood autoso- ma1 recessive muscular dystrophy (SCARMD or LGMD2D) were shown to be caused by missense and null mutations in the adhalin genel7>l8, which result in the reduction or absence of adhalin at the sarcolem- ma19. Non-Fukuyama congenital muscular dystrophy (CMD) has recently been linked close to the merosin locus on chromosome 6q20,21, which is likely to be responsible for this disease. Thus, in these muscular dystrophies, mutations in one component of the DGC cause the disruption of the complex and consequently lead to the dystrophic process. The limb-girdle muscular dystrophies (LGMDs) represent a clinically heterogeneous group of diseases which are characterized by progressive weakness of the pelvic and shoulder girdle m u ~ c l e s ~ ~ , ~ ~ . These disor- ders may be inherited as an autosomal dominant or recessive trait, the latter being more common with an estimated prevalence of I in 100,000 indi~idua1.s~~. Several genes have been implicated in the aetiology of these disorders. The autosomal dominant form, LGMDlA, was mapped to 5q22-q34 (ref. 25), while four genes involved in the autosomal recessive forms were mapped to chromosomes 2~13-p16 (LGMD2B)26, 13q12 (LGMD2C)27,28, 15915.1 (LGMD2A)29, and 17q12-q21.33 (LGMD~D)". The genes responsible for LGMD2D and LGMD2A have been identified: adhalin17 and muscle-specific calpain (cANP~)~~, respectively. Cases of autosomal recessive limb-girdle muscular dystrophy among members of the old order of Amish of northern and-southern Indiana were described by Iackson and Carev31 and Tackson and Strehler32. Most of the families of these communities are interrelated by multiple consanguineous links and common ancestry which can be traced to the 18th and 19th century in the canton of Bern. Switzerland31. In view of the high u degree of consanguinity and the similar clinical pre- sentation of all Amish LGMD patients, the demonstra- tion of genetic heterogeneity within this community was unexpected33. Although families from northern Indiana were shown to carry the same R769Q calpain 3 mutation30, involvement of this locus was excluded in nature genetics volume 11 november 1995 257