Genetics and Molecular Medicine, Haukeland University Hospital, Bergen, Norway Mutations in the FKRP gene are associated with a variety of phe- notypes including LGMD2I, MDC1C and rare cases displaying mental retardation, cerebral malformations and eye involvement. The muta- tion c.826C > A (p.Leu276Ile) is a frequent cause of LGMD in several European populations. However, data on the prevalence of FKRP associated disease appear to be lacking. Here we present data from a 2 year experience with a nation wide diagnostic testing of FKRP asso- ciated disease at the Department of Medical Genetics and Neuromus- cular Centre in Tromsø as well as additional data from Department of Medical Genetics, Bergen. The entire coding region (exon 4) of FKRP was subjected to DNA sequencing (Tromsø) or c.826C > A testing (Bergen). Only cases harbouring 2 disease causing mutations were included in assessment of prevalence. Immunohistochemistry and Wes- tern blot analysis were carried out according to standard methods with antibodies towards a-dystroglycan, laminin-a2 and calpain3. Forty-six patients from 36 families were found to be homozygous for c.826C > A. Even within the same sib-ship they presented with variable disease severity, including age of onset, CK level, muscular weakness and cardiac and respiratory involvement. Some presented episodes of rhabdomyolysis. Five patients (four families) were compound hetero- zygous – all of them harbouring c.826C > A in combination with either c.962C > A (p.A321E), c.899T > C (p.V300A) or c.913C > T (p.P305S). Four patients remained heterozygous for c.826C > A after mutation analysis. Patients with c.826CA in combination with either c.962C > A or 913C > T had a severe phenotype whereas the patient with the c.826C > A/c.899T > C genotype showed a LGMD2I pheno- type, comparable with c.826A homozygotes. The muscle biopsies (total 32) showed chronic, unspecific myopathic changes, some with signs of inflammation and necrotic fibres. Immunohistochemistry showed partial defects of a-dystroglycan, ranging from 40% to 90% positive fibres in all, and five with partial loss of laminin-a2. Western blot demonstrated 5 with reduced calpain3 levels. FKRP associated muscular disease is frequent also in Norway. The number of molec- ularly confirmed cases is 51; corresponding to a minimum prevalence of approximately 1/90,000 affected in the general population, and a carrier frequency of 1/150. In accordance with previous reports, com- pound heterozygotes tend to be more severely affected than c.826C > A homozygotes. doi:10.1016/j.nmd.2006.05.126 P.P.4 10 Galectin-1 and -3 expression in patients with mutations in the FKRP gene L.U. Yamamoto 1,* , R. Chammas 2 , M. Zatz 1 , M. Vainzof 1 1 Human Genome Research Center, IBUSP, Sa ˜o Paulo, Brazil; 2 Laboratory of Oncology, Center of Cellular Therapy, FMUSP, Sa ˜o Paulo, Brazil Neuromuscular disorders caused by deficient post-translational modification of proteins have been recently linked to mutations in several genes that encode known or putative glycosylation enzymes. The galectins are a large group of conserved proteins that recognize specific carbohydrates, and are defined by their affinity for b-galacto- sides. Cross-linking of galectin ligands can result in cell–cell interac- tions, signal transduction or formation of galectin-glycoconjugate lattices. Galectins are therefore implicated in many biological pro- cesses such as morphogenesis, control of cell death and cell prolifer- ation, playing a role in cancers and in the development of immune responses. Besides, an additional important role of the galectins in the organization of membrane complexes is suggested, mainly involv- ing the interactions between laminins and their cell surface receptors. Here, we studied the distribution and quantity of galectins-1 and -3, through immunofluorescence and Western blot methodologies, in muscle biopsies from patients with muscular dystrophies due to mutations in the FKRP gene. A correlation between the deficiency of a-dystroglycan in the muscle and the expression of galectin 1 was observed, while galectin 3 presented a normal expression in the majority of the studied patients. Galectin-1 is abundantly synthesized in adult skeletal muscles and has been associated with basement membranes of myofibers. After muscle injury, galectin-1 is present in high quantity in the cytoplasm of activated satellite cells, and has been considered as a novel factor that promotes myoblast fusion. Therefore, galectin-1 seems to play an important role in the regula- tion of myotube growth in regenerating skeletal muscles. If secondary deficiency of galectin-1 occurs as a consequence of a defect of glyco- sylation in FKRP mutated patients, this can have important implica- tion in their mechanism of muscle regeneration. FAPESP-CEPID, CNPq, ABDIM. doi:10.1016/j.nmd.2006.05.127 PATHOGENESIS OF THE MUSCULAR DYSTROPHIES; INVITED LECTURES P.I.1 Molecular basis of facioscapulohumeral muscular dystrophy S.M. van der Maarel * Leiden University Medical Center, Department of Human Genetics, Leiden, Netherlands Facioscapulohumeral muscular dystrophy (FSHD) is one of the most common muscular dystrophies characterized by progressive and often asymmetric weakness and wasting of the facial, shoulder and upper arm muscles. FSHD is caused by contraction of the poly- morphic D4Z4 repeat in the subtelomere of chromosome 4q. Each unit is 3.3 kb in size and in controls this repeat may vary between 11 and 100 units. Ninety-five percent of FSHD patients carry one repeat of 1–10 units. The insight in FSHD pathogenesis is increasing steadily but so far FSHD has been refractory to therapy. It is becoming increasingly evident that D4Z4 contraction causes a cas- cade of epigenetic events resulting in the transcriptional deregulation of yet poorly defined genes. FSHD alleles are hypomethylated at D4Z4 and patients phenotypically identical to FSHD but without D4Z4 contraction also show hypomethylation at D4Z4. This dem- onstrates that in these patients the pathogenic mechanism also acts through 4qter. Current focus is on the precise characterization of the chromatin structure at 4qter in health and disease and the immediate secondary effects of altered chromatin structure. Central to this debate is whether the effects are local (in cis), global (gen- ome-wide) or both and evidence is presented arguing for all possibil- ities. A repressor complex was identified to bind to D4Z4 and loss of this complex in cell culture causes transcriptional upregulation of 4qter genes. Although transcriptional upregulation of 4qter genes in FSHD muscle remains controversial, transgenic mice muscle-specifi- cally overexpressing one of the 4qter candidate genes, FRG1, pres- ent with muscular dystrophy. Corroborating on earlier observations that FRG1 encodes a spliceosomal protein, in muscle of these mice and in muscle cell cultures of FSHD patients, missplicing of specific mRNAs is observed. This intriguing observation may suggest that FSHD is mechanistically related to myotonic dystrophy. Evidence for genome-wide effects comes from transcriptome and nuclear orga- nization studies. The 4q chromosome end occupies a unique position in the nucleus primarily being localized in the nuclear rim. This may suggest that FSHD is mechanistically related to the nuclear envelope Abstracts / Neuromuscular Disorders 16 (2006) 644–726 681