Genetic modifiers of upper limb function in Duchenne muscular dystrophy.

Area of Science:

• Genetics
• Neuromuscular Disorders
• Disease Modifiers

Background:

• Genetic modifiers influence Duchenne muscular dystrophy (DMD) onset and progression.
• Previous studies focused on ambulatory function, neglecting upper limb function's impact on quality of life for non-ambulatory patients.

Purpose of the Study:

• To investigate the effect of known genetic modifier loci (SPP1, LTBP4, CD40, ACTN3) on upper limb function in Duchenne muscular dystrophy.
• To assess the association of specific genotypes with upper limb function scores in Italian and international DMD cohorts.

Main Methods:

• Genotyping at known modifier loci (SPP1, LTBP4, CD40, ACTN3).
• Association analysis with Performance Upper Limb (PUL) version 1.2 scores in an Italian cohort.
• Association analysis with Brooke scale scores in the Cooperative International Neuromuscular Group Duchenne Natural History Study (CINRG-DNHS).
• Longitudinal data analysis using generalized estimating equation (GEE) models, controlling for age and glucocorticoid treatment.

Main Results:

• The CD40 rs1883832 variant was identified as a significant modifier of upper limb function.
• This variant negatively impacted shoulder and distal domains of the PUL score (p=0.023 and p=0.018) in the Italian cohort.
• The CD40 rs1883832 variant also negatively affected the Brooke scale score (p=0.018) in the CINRG-DNHS cohort.

Conclusions:

• The CD40 rs1883832 variant is a key genetic modifier of upper limb function in Duchenne muscular dystrophy.
• These findings are crucial for designing and interpreting clinical trials, particularly for non-ambulatory DMD populations.
• Understanding genetic modifiers can lead to personalized treatment strategies and improved quality of life for DMD patients.