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Bethlem myopathy: clinical aspects
S14
BO1
CIS 1
EXON-SPECIFIC MONOCLONAL ANTIBODIES AGAINST DYSTROPHIN FOR DIAGNOSIS AND GENETIC DELETION ANALYSIS IN MUSCULAR DYSTROPHY.
PHENOTYPE.-GENOTYPE CORRELATION WITH ATICIPATION ASSISTS DNA MODELS, GENE SEARCH AND CLINICAL APPLICATION FOR FSH DYSTROPHY (FSIID)
Nguyen thi Man, Le Thiet Thanh 1 and G. E. Morris. MRIC Biotechnology Group, N.E. Wales Institute, Deeside, Clwyd, CH5 4BR, U.K. 1present address: Dept. of Neurology, Ohio State University, Columbus, Ohio, U.S.A.
Lunt PW I, Rogers M 2, Hill H 3, Harper PS 2, Upadhyaya M 2. tBristol Children's Hosp., Bristol UK; 2Univ. Wales Coll.Med., Cardiff UK;3Soathmead Hasp., Bristol UK
Duchenne muscular dystrophy (DMD) diagnosis can be confirmed by the absence of dystrophin in a muscle biopsy, particularly the the absence of the C-terminal domiaos. DNA tests for genetic deletions (Southern blotting or PCR) are less decisive, since some DMD patients have point mutations. In Becker muscular dystrophy (BMD), dystrophin immunostaining in muscle biopsies is still present, though often much reduced, and confirmation of BMD by DNA tests (or Western blotting) may be needed. The availability of exon-specific dystrophin would allow precise identification of BMD deletions during routine immunostaining of muscle biopsy sections. We shall describe the preparation of mAbs against two regions of dystrophin encoded by exons 45-50 and exons 4-16, which include the two deletion hotspots in the dystrophin gene. The mAbs were mapped to specific exons, enabling their use as probes for specific genetic deletions. This approach is illustrated by recent work on identification of BMD deletions (Le Thiet Thanh et al, Am. J. Med. Genet. [1995] 58:177-186) and they can also be used to identify deletions in some DMD patients, though less precisely and only when "revertant" fibres are present in the biopsy (Le Thiet Thanh et al, Am. J. Hum. Genet. [1995] 56:725-731). If biopsies are already available, the method is more rapid and less expensive than DNA tests.
Deletion of multiple 3.2kb homeobox-containing repeats at D4FI04S1 is presumed to cause 4q35-FSHD in over 80% of families, and provides a diagnostic test in new mutation cases (10%). Severity of presentation measured by age at onset or to wheelchair correlates inversely with the residual D4F104S1 EcoR1 fragment size, and within a family suggests clinicalanticipation despite a consistent fragment size. Cross hybridisatiun of D4FI04S1 with a similar polymorphic 3.2kb tandem repeat at 10q26 currently restricts clinical genetic use to families of new mutation cases, or families with sufficient scorable meioses to confirm 4q35-cosegregation. With no evidence for transcription of the homeobox-like sequence, current hypotheses favour a positional or other regulatory effect of the deletion on the expression of postulatexl muscle gene, probably adjacent on 4(t35. Current efforts are aimed at isolating possible candidate mRNA or muscle proteins encodexl by genes from this region. Additional regulatory factors must be postulated for clinical anticipation. The unusually high frequency of D4F104SI fragments of <40kb in normal parents of isolated cases who show no denovo fragment, and the cosegregatiun with 4q35 of a small fragment in some apparent FSHD-recombinant families, may be clues to other genetic interaction affecting expression of the true FSHD gene.
CIS2
CIS3
"MOLECULAR MECHANISM OF DNA REARRANGEMENTS IMPLICATED IN FSH DYSTROPHY AND APPLICATIONS TO THE DIAGNOSIS OF THE DISEASE"
Bethlem myopathy: clinical aspects
S. Caeurril, G. Deiddal, N. Piazzol, I. La Cesal, G. Galluzzil, E. Ricci2 and L. Felieettil 1 Istituto di Biologia Cellulare, CN-R; 2 Istituto di Neurologia, Univ. Cattolica, Policlinico Gemelli, Rome, Italy. In both sporadic and familial cases of FSH , pl3E-11 probe detects DNA rextrrangements due to the deletion of a definite number of KpnI tandem repeat units in the 4q subtelomerie region .The diagnostic use of this probe has been hampered by the fact that it reveals two pairs of alleles, one 4q35 specific, the other derived from 10qter. In some cases the small 4q35 rearrangements related to the disease display on Southern blots a size similar to that of polymorphic 10qter fragments. We have found that the restriction enzyme Bin/ six,ideally cleaves the KpnI repeat units derived from 10qter in Italian FSH families, leaving unmodified the 4q35 alleles. The extension of Bin/ restriction to a larger sample of FSH patients and to the general population will establish the univocal correlation between 4q35 rearrangements and the disease and will shed light on the molecular mechanism involved in the deletion of KpnI repeats. In addition the direct detection of 4q35 rearrangements by Bin/will facilitate the molecular diagnosis and genetic counseling of FSH avoiding linkage analysis with 4qter and 10qter polymorphic markers, particularly in small pedigrees and isolated cases.
M. de Visser, GJ Jbbsis, PG Barth, JM Beers Dept. of Neurology, Academic Medical Center, Amsterdam, The Netherlands Bethlem myopathy is a rare early-onset autosomal dominant myopathy characterized by slowly progressive weakness and wasting, and multiple joint contractures. Onset is either in the neonatal period presenting with hypotonia or contractures, or in early childhood, weakness being the first symptom. Muscle involvement is generalized, proximal more than distal. Contractures bear no relationship to the severity of weakness. Nearly all patients have flexion contractures of the interghalangcal joints of the last four fingers, elbows and ankles, but contractures of other joints, and rarely rigidity of the spine also occur. Although weakness is slowly progressive, nearly half of the patients above 50 years is dependent on a wheelchair for out-of-doors ambulation. There is intra-familial and interfamiliar variability. Cardiac involvement is shown to be absent. Life expectancy is unaffected. All hitherto described pedigrees show autosomal dominant mode of inheritance and complete penetranee. Ancillary investigations axe usually non--contributory. Serum CK activity is normal or slightly elevated. Electromyography is compatible with myopathy and muscle biopsy reveals non-specific myopathic changes with occasional necrotic and regenerating muscle fibers indicating that we are dealing with a muscular
dystrophy. Differential diagnosis is very limited, including Emery-Dreifnss muscular dystrophy and rigid spine syndrome.
BO1
CIS 1
EXON-SPECIFIC MONOCLONAL ANTIBODIES AGAINST DYSTROPHIN FOR DIAGNOSIS AND GENETIC DELETION ANALYSIS IN MUSCULAR DYSTROPHY.
PHENOTYPE.-GENOTYPE CORRELATION WITH ATICIPATION ASSISTS DNA MODELS, GENE SEARCH AND CLINICAL APPLICATION FOR FSH DYSTROPHY (FSIID)
Nguyen thi Man, Le Thiet Thanh 1 and G. E. Morris. MRIC Biotechnology Group, N.E. Wales Institute, Deeside, Clwyd, CH5 4BR, U.K. 1present address: Dept. of Neurology, Ohio State University, Columbus, Ohio, U.S.A.
Lunt PW I, Rogers M 2, Hill H 3, Harper PS 2, Upadhyaya M 2. tBristol Children's Hosp., Bristol UK; 2Univ. Wales Coll.Med., Cardiff UK;3Soathmead Hasp., Bristol UK
Duchenne muscular dystrophy (DMD) diagnosis can be confirmed by the absence of dystrophin in a muscle biopsy, particularly the the absence of the C-terminal domiaos. DNA tests for genetic deletions (Southern blotting or PCR) are less decisive, since some DMD patients have point mutations. In Becker muscular dystrophy (BMD), dystrophin immunostaining in muscle biopsies is still present, though often much reduced, and confirmation of BMD by DNA tests (or Western blotting) may be needed. The availability of exon-specific dystrophin would allow precise identification of BMD deletions during routine immunostaining of muscle biopsy sections. We shall describe the preparation of mAbs against two regions of dystrophin encoded by exons 45-50 and exons 4-16, which include the two deletion hotspots in the dystrophin gene. The mAbs were mapped to specific exons, enabling their use as probes for specific genetic deletions. This approach is illustrated by recent work on identification of BMD deletions (Le Thiet Thanh et al, Am. J. Med. Genet. [1995] 58:177-186) and they can also be used to identify deletions in some DMD patients, though less precisely and only when "revertant" fibres are present in the biopsy (Le Thiet Thanh et al, Am. J. Hum. Genet. [1995] 56:725-731). If biopsies are already available, the method is more rapid and less expensive than DNA tests.
Deletion of multiple 3.2kb homeobox-containing repeats at D4FI04S1 is presumed to cause 4q35-FSHD in over 80% of families, and provides a diagnostic test in new mutation cases (10%). Severity of presentation measured by age at onset or to wheelchair correlates inversely with the residual D4F104S1 EcoR1 fragment size, and within a family suggests clinicalanticipation despite a consistent fragment size. Cross hybridisatiun of D4FI04S1 with a similar polymorphic 3.2kb tandem repeat at 10q26 currently restricts clinical genetic use to families of new mutation cases, or families with sufficient scorable meioses to confirm 4q35-cosegregation. With no evidence for transcription of the homeobox-like sequence, current hypotheses favour a positional or other regulatory effect of the deletion on the expression of postulatexl muscle gene, probably adjacent on 4(t35. Current efforts are aimed at isolating possible candidate mRNA or muscle proteins encodexl by genes from this region. Additional regulatory factors must be postulated for clinical anticipation. The unusually high frequency of D4F104SI fragments of <40kb in normal parents of isolated cases who show no denovo fragment, and the cosegregatiun with 4q35 of a small fragment in some apparent FSHD-recombinant families, may be clues to other genetic interaction affecting expression of the true FSHD gene.
CIS2
CIS3
"MOLECULAR MECHANISM OF DNA REARRANGEMENTS IMPLICATED IN FSH DYSTROPHY AND APPLICATIONS TO THE DIAGNOSIS OF THE DISEASE"
Bethlem myopathy: clinical aspects
S. Caeurril, G. Deiddal, N. Piazzol, I. La Cesal, G. Galluzzil, E. Ricci2 and L. Felieettil 1 Istituto di Biologia Cellulare, CN-R; 2 Istituto di Neurologia, Univ. Cattolica, Policlinico Gemelli, Rome, Italy. In both sporadic and familial cases of FSH , pl3E-11 probe detects DNA rextrrangements due to the deletion of a definite number of KpnI tandem repeat units in the 4q subtelomerie region .The diagnostic use of this probe has been hampered by the fact that it reveals two pairs of alleles, one 4q35 specific, the other derived from 10qter. In some cases the small 4q35 rearrangements related to the disease display on Southern blots a size similar to that of polymorphic 10qter fragments. We have found that the restriction enzyme Bin/ six,ideally cleaves the KpnI repeat units derived from 10qter in Italian FSH families, leaving unmodified the 4q35 alleles. The extension of Bin/ restriction to a larger sample of FSH patients and to the general population will establish the univocal correlation between 4q35 rearrangements and the disease and will shed light on the molecular mechanism involved in the deletion of KpnI repeats. In addition the direct detection of 4q35 rearrangements by Bin/will facilitate the molecular diagnosis and genetic counseling of FSH avoiding linkage analysis with 4qter and 10qter polymorphic markers, particularly in small pedigrees and isolated cases.
M. de Visser, GJ Jbbsis, PG Barth, JM Beers Dept. of Neurology, Academic Medical Center, Amsterdam, The Netherlands Bethlem myopathy is a rare early-onset autosomal dominant myopathy characterized by slowly progressive weakness and wasting, and multiple joint contractures. Onset is either in the neonatal period presenting with hypotonia or contractures, or in early childhood, weakness being the first symptom. Muscle involvement is generalized, proximal more than distal. Contractures bear no relationship to the severity of weakness. Nearly all patients have flexion contractures of the interghalangcal joints of the last four fingers, elbows and ankles, but contractures of other joints, and rarely rigidity of the spine also occur. Although weakness is slowly progressive, nearly half of the patients above 50 years is dependent on a wheelchair for out-of-doors ambulation. There is intra-familial and interfamiliar variability. Cardiac involvement is shown to be absent. Life expectancy is unaffected. All hitherto described pedigrees show autosomal dominant mode of inheritance and complete penetranee. Ancillary investigations axe usually non--contributory. Serum CK activity is normal or slightly elevated. Electromyography is compatible with myopathy and muscle biopsy reveals non-specific myopathic changes with occasional necrotic and regenerating muscle fibers indicating that we are dealing with a muscular
dystrophy. Differential diagnosis is very limited, including Emery-Dreifnss muscular dystrophy and rigid spine syndrome.