Laminin alpha2 muscular dystrophy: genotype/phenotype studies of 22 patients.
OBJECTIVE
To determine the number of primary laminin alpha2 gene mutations and to conduct genotype/phenotype correlation in a cohort of laminin alpha2-deficient congenital muscular dystrophy patients.


BACKGROUND
Congenital muscular dystrophies (CMD) are a heterogeneous group of muscle disorders characterized by early onset muscular dystrophy and a variable involvement of the CNS. Laminin alpha2 deficiency has been reported in about 40 to 50% of cases of the occidental, classic type of CMD. Laminin alpha2 is a muscle specific isoform of laminin localized to the basal lamina of muscle fibers, where it is thought to interact with myofiber membrane receptor, such as integrins, and possibly dystrophin-associated glycoproteins.


METHODS
Seventy-five CMD patients were tested for laminin alpha2 expression by immunofluorescence and immunoblot. The entire 10 kb laminin alpha2 coding sequence of 22 completely laminin alpha2-deficient patients was screened for causative mutations by reverse transcription (RT)-PCR/single strand conformational polymorphisms (SSCP) analysis and protein truncation test (PTT) analysis followed by automatic sequencing of patient cDNA. Clinical data from the laminin alpha2-deficient patients were collected.


RESULTS
Thirty laminin alpha2-negative patients were identified (40% of CMD patients tested) and 22 of them were screened for laminin alpha2 mutations. Clinical features of laminin alpha2-deficient patients were similar, with severe floppiness at birth, delay in achievement of motor milestones, and MRI findings of white matter changes with normal intelligence. Loss-of-function mutations were identified in 95% (21/22) of the patients studied. SSCP analysis detected laminin alpha2 gene mutations in about 50% of the mutant chromosomes; PTT successfully identified 75% of the mutations. A two base pair deletion mutation at position 2,096-2,097 bp was present in 23% of the patients analyzed.


CONCLUSIONS
Our data suggest that the large majority of laminin alpha2-deficient patients show laminin alpha2 gene mutations.
Department of Molecular Genetics and Biochemistry, University of Pittsburgh School of Medicine, PA 15261, USA.
E
E
Pegoraro
H
H
Marks
C A
CA
Garcia
T
T
Crawford
P
P
Mancias
A M
AM
Connolly
M
M
Fanin
F
F
Martinello
C P
CP
Trevisan
C
C
Angelini
A
A
Stella
M
M
Scavina
R L
RL
Munk
S
S
Servidei
C C
CC
Bönnemann
T
T
Bertorini
G
G
Acsadi
C E
CE
Thompson
D
D
Gagnon
G
G
Hoganson
V
V
Carver
R A
RA
Zimmerman
E P
EP
Hoffman
D001483:Base Sequence; D001706:Biopsy; D002648:Child; D002675:Child, Preschool; D004252:DNA Mutational Analysis; D005260:Female; D005455:Fluorescent Antibody Technique; D017353:Gene Deletion; D005838:Genotype; D006801:Humans; D007223:Infant; D007797:Laminin / Q000032:analysis / Q000235:genetics*; D008297:Male; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000737:chemistry / Q000473:pathology; D009136:Muscular Dystrophies / Q000151:congenital* / Q000235:genetics* / Q000473:pathology; D009154:Mutation; D010641:Phenotype; D011110:Polymorphism, Genetic
D007797:Laminin; C102645:laminin alpha 2