TY - JOUR
T1 - Co-segregation of DM2 with a recessive CLCN1 mutation in juvenile onset of myotonic dystrophy type 2
AU - Cardani, Rosanna
AU - Giagnacovo, Marzia
AU - Botta, Annalisa
AU - Rinaldi, Fabrizio
AU - Morgante, Alessandra
AU - Udd, Bjarne
AU - Raheem, Olayinka
AU - Penttilä, Sini
AU - Suominen, Tiina
AU - Renna, Laura V.
AU - Sansone, Valeria
AU - Bugiardini, Enrico
AU - Novelli, Giuseppe
AU - Meola, Giovanni
PY - 2012/10
Y1 - 2012/10
N2 - Myotonic dystrophy type 2 (DM2) is a common adult onset muscular dystrophy caused by a dominantly transmitted (CCTG)n expansion in intron 1 of the CNBP gene. In DM2 there is no obvious evidence for an intergenerational increase of expansion size, and no congenital cases have been confirmed. We describe the clinical and histopathological features, and provide the genetic and molecular explanation for juvenile onset of myotonia in a 14-year-old female with DM2 and her affected mother presenting with a more severe phenotype despite a later onset of symptoms. Histological and immunohistochemical findings correlated with disease severity or age at onset in both patients. Southern blot on both muscle and blood samples revealed only a small increase in the CCTG repeat number through maternal transmission. Fluorescence in situ hybridization, in combination with MBNL1 immunofluorescence on muscle sections, showed the presence of mutant mRNA and MBNL1 in nuclear foci; the fluorescence intensity and its area appeared to be similar in the two patients. Splicing analysis of the INSR, CLCN1 and MBNL1 genes in muscle tissue demonstrates that the level of aberrant splicing isoforms was lower in the daughter than in the mother. However, in the CLCN1 gene, a heterozygous mutation c.501C>G p.F167L was present in the daughter's DNA and found to be maternally inherited. Biomolecular findings did not explain the unusual young onset in the daughter. The co-segregation of DM2 with a recessive CLCN1 mutation provided the explanation for the unusual clinical findings.
AB - Myotonic dystrophy type 2 (DM2) is a common adult onset muscular dystrophy caused by a dominantly transmitted (CCTG)n expansion in intron 1 of the CNBP gene. In DM2 there is no obvious evidence for an intergenerational increase of expansion size, and no congenital cases have been confirmed. We describe the clinical and histopathological features, and provide the genetic and molecular explanation for juvenile onset of myotonia in a 14-year-old female with DM2 and her affected mother presenting with a more severe phenotype despite a later onset of symptoms. Histological and immunohistochemical findings correlated with disease severity or age at onset in both patients. Southern blot on both muscle and blood samples revealed only a small increase in the CCTG repeat number through maternal transmission. Fluorescence in situ hybridization, in combination with MBNL1 immunofluorescence on muscle sections, showed the presence of mutant mRNA and MBNL1 in nuclear foci; the fluorescence intensity and its area appeared to be similar in the two patients. Splicing analysis of the INSR, CLCN1 and MBNL1 genes in muscle tissue demonstrates that the level of aberrant splicing isoforms was lower in the daughter than in the mother. However, in the CLCN1 gene, a heterozygous mutation c.501C>G p.F167L was present in the daughter's DNA and found to be maternally inherited. Biomolecular findings did not explain the unusual young onset in the daughter. The co-segregation of DM2 with a recessive CLCN1 mutation provided the explanation for the unusual clinical findings.
KW - CLCN1
KW - Juvenile case
KW - Muscle pathology
KW - Myotonia congenital
KW - Myotonic dystrophy type 2
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U2 - 10.1007/s00415-012-6462-1
DO - 10.1007/s00415-012-6462-1
M3 - Article
C2 - 22407275
AN - SCOPUS:84867332225
VL - 259
SP - 2090
EP - 2099
JO - Journal of Neurology
JF - Journal of Neurology
SN - 0340-5354
IS - 10
ER -