Mutations In Fukutin-related Protein Gene Research Articles

Phenotype Genotype Characterization of FKRP-related Muscular Dystrophy among Indian Patients.

The phenotypic spectrum of Fukutin-related protein (FKRP) mutations is highly variable and comprises of limb girdle muscular dystrophy (LGMD) R9 (previously LGMD 2I) and FKRP related congenital muscular dystrophies. To identify the distinct genotype phenotype pattern in Indian patients with FKRP gene mutations. We retrospectively reviewed the case files of patients with muscular dystrophy having a genetically confirmed FKRP mutation. All patients had undergone genetic testing using next-generation sequencing. Our patients included five males and four females presenting between 1.5 years and seven years of age (median age - 3 years). The initial symptom was a delayed acquisition of gross motor developmental milestones in seven patients and recurrent falls and poor sucking in one patient each. Two patients had a language delay, with both having abnormalities on the brain MRI. Macroglossia, scapular winging, and facial weakness were noted in one, three and four patients respectively. Calf muscle hypertrophy was seen in eight patients and ankle contractures in six. At the last follow-up, three patients had lost ambulation (median age - 7 years; range 6.5-9 years) and three patients had not attained independent ambulation. Creatine kinase levels ranged between 2793 and 32,396 U/L (mean 12,120 U/L). A common mutation - c.1343C>T was noted in 5 patients in our cohort. Additionally, four novel mutations were identified. Overall, six patients had an LGMD R9 phenotype, and three had a congenital muscular dystrophy phenotype. Patients with FKRP mutations can have varied presentations. A Duchenne-like phenotype was the most commonly encountered pattern in our cohort, with c.1343C>T being the most common mutation.

Eye and Brain Abnormalities in Congenital Muscular Dystrophies Caused by Fukutin-Related Protein Gene (FKRP) Mutations

Mutations in the fukutin-related protein gene account for a broad spectrum of phenotypes ranging from severe congenital muscular dystrophies to a much milder limb-girdle muscular dystrophy 2I. The involvement of the eyes is variable, with most patients having normal eye examination. We describe eye and brain abnormalities in a 16 month-old-boy with Walker-Warburg syndrome phenotype resulting from a novel fukutin-related protein gene mutation in exon 4 and compare these with other reported patients with fukutin-related protein gene mutation. All patients with reported fukutin-related protein gene mutations who had eye involvement were included. Their clinical features, brain magnetic resonance imaging, and eye findings were compared with our patient. Patients with fukutin-related protein gene mutation tend to have no or mild eye involvement (generally strabismus), with very few cases reported of moderate to severe eye involvement. Our patient with a novel mutation c.558dupC(p.Ala187fs) represents one of the most severe phenotypes described in regard to eye involvement.

Zebrafish models for human FKRP muscular dystrophies

Various muscular dystrophies are associated with the defective glycosylation of α-dystroglycan and are known to result from mutations in genes encoding glycosyltransferases. Fukutin-related protein (FKRP) was identified as a homolog of fukutin, the defective protein in Fukuyama-type congenital muscular dystrophy (FCMD), that is thought to function as a glycosyltransferase. Mutations in FKRP have been linked to a variety of phenotypes including Walker–Warburg syndrome (WWS), limb girdle muscular dystrophy (LGMD) 2I and congenital muscular dystrophy 1C (MDC1C). Zebrafish are a useful animal model to reveal the mechanism of these diseases caused by mutations in FKRP gene. Downregulating FKRP expression in zebrafish by two different morpholinos resulted in embryos which had developmental defects similar to those observed in human muscular dystrophies associated with mutations in FKRP. The FKRP morphants showed phenotypes involving alterations in somitic structure and muscle fiber organization, as well as defects in developing eye morphology. Additionally, they were found to have a reduction in α-dystroglycan glycosylation and a shortened myofiber length. Moreover, co-injection of fish or human FKRP mRNA along with the morpholino restored normal development, α-dystroglycan glycosylation and laminin binding activity of α-dystroglycan in the morphants. Co-injection of the human FKRP mRNA containing causative mutations found in human patients of WWS, MDC1C and LGMD2I could not restore their phenotypes significantly. Interestingly, these morphant fish having human FKRP mutations showed a wide phenotypic range similar to that seen in humans.

Variable Cardiac Involvement in Tunisian Siblings Harboring FKRP Gene Mutations

Mutations in the gene encoding fukutin-related protein (FKRP) cause limb-girdle muscular dystrophy 2I (LGMD2I) and congenital muscular dystrophy (MDC1C). Cardiac involvement was frequently reported with numerous mutations including C826A and 1364C > A mutations. The original Tunisian family with LGMD2I included 12 patients sharing the LGMD phenotype and homozygous to the 1486T > A mutation but who did not display any cardiac involvement. In this study, we report the clinical data, cardiac assessment and mutation analysis in four sibs belonging to a second Tunisian LGMD2I family. All patients showed the LGMD phenotype, the oldest brother and sister had mild cardiac involvement, whereas two twin sisters displayed severe cardiomyopathy leading to death. The patients shared the compound heterozygous 1486T > A, 1364C > A mutation in the FKRP gene suggesting that the association of a compound heterozygous state of mutation responsible for LGMD2I and the MDC1C phenotype could lead to cardiac involvement.

Heart transplantation in a child with LGMD2I presenting as isolated dilated cardiomyopathy

Limb-girdle muscle dystrophy type 2I is associated with mutations in the gene encoding Fukutin-related protein. Clinical phenotypes are heterogeneous, ranging from isolated hyperCkemia to severe congenital muscular dystrophy. Affected patients frequently develop dilated cardiomyopathy, depending on evolution of their skeletal myopathy. We report on an 8 years-old boy presenting a severe dilated cardiomyopathy requiring heart transplantation. The child harbored a homozygous p.Leu276Ile mutation in Fukutin-related protein gene ( FKRP). At the current age of 20 years, the patient shows persistent hyperCKemia but no clinical muscle weakness, CT scan showing very mild features of muscle involvement. Our findings add to the array of clinical presentations of FKRP mutations.

C.P.3.09 Ultrastructural approach to molecularly defined FKRP-related muscular dystrophy

MDC1C and LGMD2I are two allelic conditions due to mutations in Fukutin-related protein gene, FKRP, encoding for a putative glycosyltransferase involved in α-dystroglycan processing. Defects in the dystroglycan–dystrophin complex play a crucial role in both basement membrane organization and link with intracellular actin. FKRP locates possibly in a subcompartment of the ER closely associated to the nuclear envelope in normal and regenerating muscle. The retention of mutant FKRP in the ER has recently been suggested as a possible mechanism of disease in MDC1C and LGMD2I suggesting an aberrant post-traslational modification of protein.